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By analyzing the large-angle Bhabha scattering events e+e− → (γ)e+e− and diphoton events e+e− → (γ)γγ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. The results are important inputs for the R value and J/ψ resonance parameter measurements.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 20 times larger than that of χc2→ρ(770)±π∓, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 10 times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
Using a data sample of 448.1×106 𝜓(3686) events collected with the BESIII detector operating at the BEPCII, we perform search for the hadronic transition ℎ𝑐→𝜋+𝜋−𝐽/𝜓 via 𝜓(3686)→𝜋0ℎ𝑐. No signals of the transition are observed, and the upper limit on the product branching fraction ℬ(𝜓(3686)→𝜋0ℎ𝑐)ℬ(ℎ𝑐→𝜋+𝜋−𝐽/𝜓) at the 90% confidence level (C.L.) is determined to be 2.0×10−6. This is the most stringent upper limit to date.
The decay 𝐽/𝜓→𝛾𝛾𝜙 is studied using a sample of 1.31×109 𝐽/𝜓 events collected with the BESIII detector. Two structures around 1475 MeV/𝑐2 and 1835 MeV/𝑐2 are observed in the 𝛾𝜙 invariant mass spectrum for the first time. With a fit on the 𝛾𝜙 invariant mass, which takes into account the interference between the two structures, and a simple analysis of the angular distribution, the structure around 1475 MeV/𝑐2 is found to favor an assignment as the 𝜂(1475) and the mass and width for the structure around 1835 MeV/𝑐2 are consistent with the 𝑋(1835). The statistical significances of the two structures are 13.5𝜎 and 6.3𝜎, respectively. The results indicate that both 𝜂(1475) and 𝑋(1835) contain a sizeable 𝑠¯𝑠 component.
Using a low background data sample of 9.7×105 𝐽/𝜓→𝛾𝜂′, 𝜂′→𝛾𝜋+𝜋− events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of 𝜂′→𝛾𝜋+𝜋− are studied with both model-dependent and model-independent approaches. The contributions of 𝜔 and the 𝜌(770)−𝜔 interference are observed for the first time in the decays 𝜂′→𝛾𝜋+𝜋− in both approaches. Additionally, a contribution from the box anomaly or the 𝜌(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 10 times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 20 times larger than that of χc2→ρ(770)±π∓, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
The ALICE Collaboration at the LHC reports measurement of the inclusive production cross section of electrons from semi-leptonic decays of beauty hadrons with rapidity |y| < 0.8 and transverse momentum 1 < pT < 10 GeV/c, in pp collisions at √s = 2.76 TeV. Electrons not originating from semi-electronic decay of beauty hadrons are suppressed using the impact parameter of the corresponding tracks. The production cross section of beauty decay electrons is compared to the result obtained with an alternative method which uses the distribution of the azimuthal angle between heavy-flavour decay electrons and charged hadrons. Perturbative QCD predictions agree with the measured cross section within the experimental and theoretical uncertainties. The integrated visible cross section, σb→e = 3.47 ± 0.40(stat) +1.12 −1.33(sys) ± 0.07(norm) μb, was extrapolated to full phase space using Fixed Order plus Next-to-Leading Log (FONLL) calculations to obtain the total bb production ¯ cross section, σbb¯ = 130 ± 15.1(stat) +42.1 −49.8(sys) +3.4 −3.1(extr) ± 2.5(norm) ± 4.4(BR) μb.
Transverse momentum spectra of π±, K± and p(p¯) up to pT = 20 GeV/c at mid-rapidity in pp, peripheral (60–80%) and central (0–5%) Pb–Pb collisions at √sNN = 2.76 TeV have been measured using the ALICE detector at the Large Hadron Collider. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at pT ≈ 3 GeV/c in central Pb–Pb collisions. Below the peak, pT < 3 GeV/c, both ratios are in good agreement with hydrodynamical calculations, suggesting that the peak itself is dominantly the result of radial flow rather than anomalous hadronization processes. For pT > 10 GeV/c particle ratios in pp and Pb–Pb collisions are in agreement and the nuclear modification factors for π±, K± and p(p¯) indicate that, within the systematic and statistical uncertainties, the suppression is the same. This suggests that the chemical composition of leading particles from jets in the medium is similar to that of vacuum jets.
Freeze-out radii extracted from three-pion cumulants in pp, p–Pb and Pb–Pb collisions at the LHC
(2014)
In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose–Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p–Pb and Pb–Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p–Pb collisions are found to be 5–15% larger than those in pp, while those in Pb–Pb are 35–55% larger than those in p–Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p–Pb as compared to pp collisions at similar multiplicity.
The production of prompt Λc+ baryons at midrapidity (|y|<0.5) was measured in central (0–10%) and mid-central (30–50%) Pb–Pb collisions at the center-of-mass energy per nucleon–nucleon pair √sNN=5.02 TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum (pT=1 GeV/c) with respect to previous measurements performed by the ALICE, STAR, and CMS Collaborations in nucleus–nucleus collisions, allowing for an extrapolation down to pT=0. The pT-differential Λc+/D0 ratio is enhanced with respect to the pp measurement for 4<pT<8 GeV/c by 3.7 standard deviations (σ), while the pT-integrated ratios are compatible within 1σ. The observed trend is similar to that observed in the strange sector for the Λ/KS0 ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data.
Using data samples collected with the BESIII detector at the BEPCII collider at six center-of-mass energies between 4.008 and 4.600 GeV, we observe the processes e+e− → φφω and e+e− → φφφ. The Born cross sections are measured and the ratio of the cross sections σ(e+e− → φφω)/σ(e+e− → φφφ) is estimated to be 1.75 ± 0.22 ± 0.19 averaged over six energy points, where the first uncertainty is statistical and the second is systematic. The results represent first measurements of these interactions.
Measurements of cross section of e⁺e⁻ → pp¯π⁰ at center-of-mass energies between 4.008 and 4.600 GeV
(2017)
Based on e+e− annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center-of-mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of e+e− → pp¯π0 are performed. No significant resonant structure is observed in the measured energy dependence of the cross section. The upper limit on the Born cross section of e+e− → Y (4260) → pp¯π0 at the 90% C.L. is determined to be 0.01 pb. The upper limit on the ratio of the branching fractions B(Y (4260)→pp¯π0) B(Y (4260)→π+π− J/ψ) at the 90% C.L. is determined to be 0.02%.
We report the first measurement of the absolute branching fraction for Λ+c→Λμ+νμ. This measurement is based on a sample of e+e− annihilation data at a center-of-mass energy of s√=4.6 GeV collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb−1. The branching fraction is determined to be B(Λ+c→Λμ+νμ)=(3.49±0.46(stat)±0.27(syst))%. In addition, we calculate the ratio B(Λ+c→Λμ+νμ)/B(Λ+c→Λe+νe) to be 0.96±0.16(stat)±0.04(syst).
We study the decays of J/ψ and ψ(3686) to the final states Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0 based on a single baryon tag method using data samples of (1310.6±7.0)×106 J/ψ and (447.9±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider. The decays to Σ(1385)0Σ¯(1385)0 are observed for the first time. The measured branching fractions of J/ψ and ψ(3686)→Ξ0Ξ¯0 are in good agreement with, and much more precise, than the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J/ψ→Σ(1385)0Σ¯(1385)0, α=−0.64±0.03±0.10, is found to be negative, different to the other decay processes in this measurement. In addition, the "12\% rule" and isospin symmetry in the J/ψ and ψ(3686)→ΞΞ¯ and Σ(1385)Σ¯(1385) systems are tested.
By analyzing 2.93 fb−1 of data taken at the ψ(3770) resonance peak with the BESIII detector, we measure the branching fractions for the hadronic decays D+ → K0S K0S K +, D+ → K0S K0Sπ+, D0 → K0S K0S and D0 → K0S K0S K0S . They are determined to be B(D+ → K0S K0S K +) = (2.54 ± 0.05stat. ± 0.12sys.) × 10−3, B(D+ → K0S K0Sπ+) = (2.70 ± 0.05stat. ± 0.12sys.) × 10−3, B(D0 → K0S K0S ) = (1.67 ± 0.11stat. ± 0.11sys.) × 10−4 and B(D0 → K0S K0S K0S ) = (7.21 ± 0.33stat. ± 0.44sys.) × 10−4, where the second one is measured for the first time and the others are measured with significantly improved precision over the previous measurements.
A measurement of the transverse momentum spectra of jets in Pb-Pb collisions at sNN−−−√=2.76 TeV is reported. Jets are reconstructed from charged particles using the anti-kT jet algorithm with jet resolution parameters R of 0.2 and 0.3 in pseudo-rapidity |η|<0.5. The transverse momentum pT of charged particles is measured down to 0.15 GeV/c which gives access to the low pT fragments of the jet. Jets found in heavy-ion collisions are corrected event-by-event for average background density and on an inclusive basis (via unfolding) for residual background fluctuations and detector effects. A strong suppression of jet production in central events with respect to peripheral events is observed. The suppression is found to be similar to the suppression of charged hadrons, which suggests that substantial energy is radiated at angles larger than the jet resolution parameter R=0.3 considered in the analysis. The fragmentation bias introduced by selecting jets with a high pT leading particle, which rejects jets with a soft fragmentation pattern, has a similar effect on the jet yield for central and peripheral events. The ratio of jet spectra with R=0.2 and R=0.3 is found to be similar in Pb-Pb and simulated PYTHIA pp events, indicating no strong broadening of the radial jet structure in the reconstructed jets with R<0.3.
New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN)1,2,3,4. However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region5,6. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.
A fundamental question in evolutionary genetics concerns the extent to which adaptive phenotypic convergence is attributable to convergent or parallel changes at the molecular sequence level. Here we report a comparative analysis of hemoglobin (Hb) function in eight phylogenetically replicated pairs of high- and low-altitude waterfowl taxa to test for convergence in the oxygenation properties of Hb, and to assess the extent to which convergence in biochemical phenotype is attributable to repeated amino acid replacements. Functional experiments on native Hb variants and protein engineering experiments based on site-directed mutagenesis revealed the phenotypic effects of specific amino acid replacements that were responsible for convergent increases in Hb-O2 affinity in multiple high-altitude taxa. In six of the eight taxon pairs, high-altitude taxa evolved derived increases in Hb-O2 affinity that were caused by a combination of unique replacements, parallel replacements (involving identical-by-state variants with independent mutational origins in different lineages), and collateral replacements (involving shared, identical-by-descent variants derived via introgressive hybridization). In genome scans of nucleotide differentiation involving high- and low-altitude populations of three separate species, function-altering amino acid polymorphisms in the globin genes emerged as highly significant outliers, providing independent evidence for adaptive divergence in Hb function. The experimental results demonstrate that convergent changes in protein function can occur through multiple historical paths, and can involve multiple possible mutations. Most cases of convergence in Hb function did not involve parallel substitutions and most parallel substitutions did not affect Hb-O2 affinity, indicating that the repeatability of phenotypic evolution does not require parallelism at the molecular level.
The highly infectious disease COVID-19 caused by the Betacoronavirus SARS-CoV-2 poses a severe threat to humanity and demands the redirection of scientific efforts and criteria to organized research projects. The international COVID19-NMR consortium seeks to provide such new approaches by gathering scientific expertise worldwide. In particular, making available viral proteins and RNAs will pave the way to understanding the SARS-CoV-2 molecular components in detail. The research in COVID19-NMR and the resources provided through the consortium are fully disclosed to accelerate access and exploitation. NMR investigations of the viral molecular components are designated to provide the essential basis for further work, including macromolecular interaction studies and high-throughput drug screening. Here, we present the extensive catalog of a holistic SARS-CoV-2 protein preparation approach based on the consortium’s collective efforts. We provide protocols for the large-scale production of more than 80% of all SARS-CoV-2 proteins or essential parts of them. Several of the proteins were produced in more than one laboratory, demonstrating the high interoperability between NMR groups worldwide. For the majority of proteins, we can produce isotope-labeled samples of HSQC-grade. Together with several NMR chemical shift assignments made publicly available on covid19-nmr.com, we here provide highly valuable resources for the production of SARS-CoV-2 proteins in isotope-labeled form.
In quantum scattering processes between two particles, aspects characterizing the strong and Coulomb forces can be observed in kinematic distributions of the particle pairs. The sensitivity to the interaction potential reaches a maximum at low relative momentum and vanishing distance between the two particles. Ultrarelativistic heavy-ion collisions at the LHC provide an abundant source of many hadron species and can be employed as a measurement method of scattering parameters that is complementary to scattering experiments. This study confirms that momentum correlations of particles produced in Pb–Pb collisions at the LHC provide an accurate measurement of kaon–proton scattering parameters at low relative momentum, allowing precise access to the K−p→K−p process. This work also validates the femtoscopic measurement in ultrarelativistic heavy-ion collisions as an alternative to scattering experiments and a complementary tool to the study of exotic atoms with comparable precision. In this work, the first femtoscopic measurement of momentum correlations of K−p(K+p‾) and K+p(K−p‾) pairs in Pb–Pb collisions at centre-of-mass energy per nucleon pair of sNN=5.02 TeV registered by the ALICE experiment is reported. The components of the K−p complex scattering length are extracted and found to be ℜf0=−0.91±0.03(stat)−0.03+0.17(syst) and ℑf0=0.92±0.05(stat)−0.33+0.12(syst). The results are compared with chiral effective field theory predictions as well as with existing data from dedicated scattering and exotic kaonic atom experiments.
The production of prompt D0, Ds+, and Λc+ hadrons, and their ratios, Ds+/D0 and Λc+/D0, are measured in proton–proton collisions at √s=13 TeV at midrapidity (|y|<0.5) with the ALICE detector at the LHC. The measurements are performed as a function of the charm-hadron transverse momentum (pT) in intervals of charged-particle multiplicity, measured with two multiplicity estimators covering different pseudorapidity regions. While the strange to non-strange Ds+/D0 ratio indicates no significant multiplicity dependence, the baryon-to-meson pT-differential Λc+/D0 ratio shows a multiplicity-dependent enhancement, with a significance of 5.3σ for 1<pT<12 GeV/c, comparing the highest multiplicity interval with respect to the lowest one. The measurements are compared with a theoretical model that explains the multiplicity dependence by a canonical treatment of quantum charges in the statistical hadronisation approach, and with predictions from event generators that implement colour reconnection mechanisms beyond the leading colour approximation to model the hadronisation process. The Λc+/D0 ratios as a function of pT present a similar shape and magnitude as the Λ/KS0 ratios in comparable multiplicity intervals, suggesting a potential common mechanism for light- and charm-hadron formation, with analogous multiplicity dependence. The pT-integrated ratios, extrapolated down to pT=0, do not show a significant dependence on multiplicity within the uncertainties.
We report a measurement of the observed cross sections of e+ e− → J/ψX based on 3.21 fb − 1 of data accumulated at energies from 3.645 to 3.891 GeV with the BESIII detector operated at the BEPCII collider. In analysis of the cross sections, we measured the decay branching fractions of B(ψ(3686) → J/ψX) = (64.4 ± 0.6 ± 1.6)% and B(ψ(3770) → J/ψX) = (0.5 ± 0.2 ± 0.1)% for the first time. The energy-dependent line shape of these cross sections cannot be well described by two Breit-Wigner (BW) amplitudes of the expected decays ψ (3686) → J/ψX and ψ(3770) → J/ψX. Instead, it can be better described with one more BW amplitude of the decay R(3760)→ J/ψX. Under this assumption, we extracted the R (3760) mass M R (3760 ) = 3766.2 ± 3.8 ± 0.4 MeV/c2, total width Γ tot R ( 3760 ) = 22.2 ± 5.9 ± 1.4 MeV, and product of leptonic width and decay branching fraction
ΓeeR(3760) B[R(3760) → J/ψX] = (79.4 ± 85.5 ± 11.7) eV. The significance of the R(3760) is 5.3σ. The first uncertainties of these measured quantities are from fits to the cross sections and second systematic.
Using a data sample of e+e− collision data corresponding to an integrated luminosity of 2.93 fb−1 collected with the BESIII detector at a center-of-mass energy of s=3.773GeV, we search for the singly Cabibbo-suppressed decays D0→π0π0π0, π0π0η, π0ηη and ηηη using the double tag method. The absolute branching fractions are measured to be B(D0→π0π0π0)=(2.0±0.4±0.3)×10−4, B(D0→π0π0η)=(3.8±1.1±0.7)×10−4 and B(D0→π0ηη)=(7.3±1.6±1.5)×10−4 with the statistical significances of 4.8σ, 3.8σ and 5.5σ, respectively, where the first uncertainties are statistical and the second ones systematic. No significant signal of D0→ηηη is found, and the upper limit on its decay branching fraction is set to be B(D0→ηηη)<1.3×10−4 at the 90% confidence level.
This article presents the first measurement of the interaction between charm hadrons and nucleons. The two-particle momentum correlations of pD− and ¯pD+ pairs are measured by the ALICE Collaboration in high-multiplicity pp collisions at √s=13 TeV. The data are compatible with the Coulomb-only interaction hypothesis within (1.1–1.5)σ. The level of agreement slightly improves if an attractive nucleon (N)¯D strong interaction is considered, in contrast to most model predictions which suggest an overall repulsive interaction. This measurement allows for the first time an estimation of the 68% confidence level interval for the isospin I=0 inverse scattering length of the N¯D state f−10, I=0∈[−0.4,0.9] fm−1, assuming negligible interaction for the isospin I=1 channel.
The Born cross sections of the e+e− → +¯ − and e+e− → −¯ + processes are determined for centerof-mass energy from 2.3864 to 3.0200 GeV with the BESIII detector. The cross section lineshapes can be described properly by a pQCD function and the resulting ratio of effective form factors for the + and − is consistent with 3. In addition, ratios of the + electric and magnetic form factors, |GE /GM |, are obtained at three center-of-mass energies through an analysis of the angular distributions. These measurements, which are studied for the first time in the off-resonance region, provide precision experimental input for understanding baryonic structure. The observed new features of the ± form factors require more theoretical discussions for the hyperons.
Using 16 energy points of e+e− annihilation data collected in the vicinity of the J/ψ resonance with the BESIII detector and with a total integrated luminosity of around 100 pb−1, we study the relative phase between the strong and electromagnetic amplitudes of J/ψ decays. The relative phase between J/ψ electromagnetic decay and the continuum process (e+e− annihilation without the J/ψ resonance) is confirmed to be zero by studying the cross section lineshape of μ+μ− production. The relative phase between J/ψ strong and electromagnetic decays is then measured to be (84.9 ± 3.6)◦ or (−84.7 ± 3.1)◦ for the 2(π+π−)π0 final state by investigating the interference pattern between the J/ψ decay and the continuum process. This is the first measurement of the relative phase between J/ψ strong and electromagnetic decays into a multihadron final state using the lineshape of the production cross section. We also study the production lineshape of the multihadron final state ηπ+π− with η → π+π−π0, which provides additional information about the phase between the J/ψ electromagnetic decay amplitude and the continuum process. Additionally, the branching fraction of J/ψ → 2(π+π−)π0 is measured to be (4.73 ± 0.44)% or (4.85 ± 0.45)%, and the branching fraction of J/ψ → ηπ+π− is measured to be (3.78 ± 0.68) × 10−4. Both of them are consistent with the world average values. The quoted uncertainties include both statistical and systematic uncertainties, which are mainly caused by the low statistics.
We report the first measurements of absolute branching fractions for the W -exchange-only processes + c → 0K + and + c → (1530)0K + with the double-tag technique, by analyzing an e+e− collision data sample, that corresponds to an integrated luminosity of 567 pb−1 collected at a center-of-mass energy of 4.6 GeV by the BESIII detector. The branching fractions are measured to be B(+c → 0K +) = (5.90 ± 0.86 ± 0.39) × 10−3 and B(+c → (1530)0K +) = (5.02 ± 0.99 ± 0.31) × 10−3, where the first uncertainties are statistical and the second systematic. Our results are more precise than the previous relative measurements.
Using a data sample of 448.1 × 106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay ψ(3686) → η e+e−, with significances of 7.0σ and 6.3σ when reconstructing the η meson via its decay modes η → γπ+π− and η → π+π−η (η → γγ ), respectively. The weighted average branching fraction is determined to be B(ψ(3686) → η e+e−) = (1.90 ± 0.25 ± 0.11) × 10−6, where the first uncertainty is statistical and the second systematic.
Born cross sections for the processes e+e− → ωη and e+e− → ωπ0 have been determined for centerof-mass energies between 2.00 and 3.08 GeV with the BESIII detector at the BEPCII collider. The results obtained in this work are consistent with previous measurements but with improved precision. Two resonant structures are observed. In the e+e− → ωη cross sections, a resonance with a mass of (2176 ± 24 ± 3) MeV/c2 and a width of (89 ± 50 ± 5) MeV is observed with a significance of 6.2σ. Its properties are consistent with the φ(2170). In the e+e− → ωπ0 cross sections, a resonance denoted Y (2040) is observed with a significance of more than 10σ. Its mass and width are determined to be (2034 ± 13 ± 9) MeV/c2 and (234 ± 30 ± 25) MeV, respectively, where the first uncertainties are statistical and the second ones are systematic.
We report the first observation of the decay Λ+c→Σ−π+π+π0, based on data obtained in e+e− annihilations with an integrated luminosity of 567~pb−1 at s√=4.6~GeV. The data were collected with the BESIII detector at the BEPCII storage rings. The absolute branching fraction B(Λ+c→Σ−π+π+π0) is determined to be (2.11±0.33(stat.)±0.14(syst.))%. In addition, an improved measurement of B(Λ+c→Σ−π+π+) is determined as (1.81±0.17(stat.)±0.09(syst.))%.
Based on an 𝑒+𝑒− collision data sample corresponding to an integrated luminosity of 567 pb−1 taken at the center-of-mass energy of √𝑠=4.6 GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay Λ+𝑐→Λ+𝑋 to be ℬ(Λ+𝑐→Λ+𝑋)=(38.2+2.8−2.2±0.9)% using the double-tag method, where 𝑋 refers to any possible final state particles. In addition, we search for direct 𝐶𝑃 violation in the charge asymmetry of this inclusive decay for the first time, and obtain 𝒜𝐶𝑃≡[ℬ(Λ+𝑐→Λ+𝑋)−ℬ(¯Λ−𝑐 → ¯Λ+𝑋)]/[ℬ(Λ+𝑐→Λ+𝑋)+ℬ(¯Λ−𝑐 → ¯Λ+𝑋)]=(2.1+7.0−6.6±1.6)%, a statistically limited result with no evidence of 𝐶𝑃 violation.
Using an 𝑒+𝑒− collision data sample of 2.93 fb−1 collected at a center-of-mass energy of 3.773 GeV by the BESIII detector at BEPCII, we report the observation of 𝐷0→𝑎0(980)−𝑒+𝜈𝑒 and evidence for 𝐷+→𝑎0(980)0𝑒+𝜈𝑒 with significances of 6.4𝜎 and 2.9𝜎, respectively. The absolute branching fractions are determined to be ℬ(𝐷0→𝑎0(980)−𝑒+𝜈𝑒)×ℬ(𝑎0(980)−→𝜂𝜋−) = [1.33+0.33−0.29(stat)±0.09(syst)]×10−4 and ℬ(𝐷+→𝑎0(980)0𝑒+𝜈𝑒)×ℬ(𝑎0(980)0→𝜂𝜋0)=[1.66+0.81
−0.66(stat)±0.11(syst)]×10−4. This is the first time the 𝑎0(980) meson has been measured in a 𝐷0 semileptonic decay, which would open one more interesting page in the investigation of the nature of the puzzling 𝑎0(980) states.
Using a sample of 4.48×108 ψ(3686) events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons π0, η, η′, η(1405), η(1475), η(1760), and X(1835) in J/ψ radiative decays using ψ(3686)→π+π−J/ψ events. The π0, η and η′ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be B(J/ψ→γπ0→3γ)=(3.57±0.12±0.16)×10−5, B(J/ψ→γη→3γ)=(4.42±0.04±0.18)×10−4, and B(J/ψ→γη′→3γ)=(1.26±0.02±0.05)×10−4, where the first errors are statistical and the second systematic. No clear signal for η(1405), η(1475), η(1760) or X(1835) is observed in the two-photon mass spectra, and upper limits at the 90% confidence level on the product branching fractions are obtained.
Measurement of cross sections for e⁺e⁻ → μ⁺μ⁻ at center-of-mass energies from 3.80 to 4.60 GeV
(2020)
The observed cross sections for 𝑒+𝑒−→𝜇+𝜇− at energies from 3.8 to 4.6 GeV are measured using data samples taken with the BESIII detector operated at the BEPCII collider. We measure the muonic widths and determine the branching fractions of the charmonium states 𝜓(4040), 𝜓(4160), and 𝜓(4415) decaying to 𝜇+𝜇−, as well as making a first determination of the phase of the amplitudes. In addition, we observe evidence for a structure in the dimuon cross section near 4.220 GeV/𝑐2, which we denote as 𝑆(4220). Analyzing a coherent sum of amplitudes yields eight solutions, one of which gives a mass of 𝑀𝑆(4220) = 4216.7±8.9±4.1 MeV/𝑐2, a total width of Γtot S(4220) = 47.2±22.8±10.5 MeV, and a muonic width of Γ𝜇𝜇 𝑆(4220) = 1.53±1.26±0.54 keV, where the first uncertainties are statistical and the second systematic. The eight solutions give the central values of the mass, total width, muonic width to be, respectively, in the range from 4212.8 to 4219.4 MeV/𝑐2, from 36.4 to 49.6 MeV, and from 1.09 to 1.53 keV. The statistical significance of the 𝑆(4220) signal is 3.9𝜎. Correcting the total dimuon cross section for radiative effects yields a statistical significance for this structure of 8.1𝜎.
Using a sample of 106 million 𝜓(3686) decays, 𝜓(3686)→𝛾𝜒𝑐𝐽(𝐽=0,1,2) and 𝜓(3686)→𝛾𝜒𝑐𝐽,𝜒𝑐𝐽→𝛾𝐽/𝜓(𝐽=1,2) events are utilized to study inclusive 𝜒𝑐𝐽→anything, 𝜒𝑐𝐽→hadrons, and 𝐽/𝜓→anything distributions, including distributions of the number of charged tracks, electromagnetic calorimeter showers, and 𝜋0s, and to compare them with distributions obtained from the BESIII Monte Carlo simulation. Information from each Monte Carlo simulated decay event is used to construct matrices connecting the detected distributions to the input predetection “produced” distributions. Assuming these matrices also apply to data, they are used to predict the analogous produced distributions of the decay events. Using these, the charged particle multiplicities are compared with results from MARK I. Further, comparison of the distributions of the number of photons in data with those in Monte Carlo simulation indicates that G-parity conservation should be taken into consideration in the simulation.
We report the first observation of the semimuonic decay 𝐷+→𝜔𝜇+𝜈𝜇 using an 𝑒+𝑒− collision data sample corresponding to an integrated luminosity of 2.93 fb−1 collected with the BESIII detector at a center-of-mass energy of 3.773 GeV. The absolute branching fraction of the 𝐷+→𝜔𝜇+𝜈𝜇 decay is measured to be ℬ𝐷+→𝜔𝜇+𝜈𝜇=(17.7±1.8stat±1.1syst)×10−4. Its ratio with the world average value of the branching fraction of the 𝐷+→𝜔𝑒+𝜈𝑒 decay probes lepton flavor universality and it is determined to be ℬ𝐷+→𝜔𝜇+𝜈𝜇/ℬPDG 𝐷+→𝜔𝑒+𝜈𝑒=1.05±0.14, in agreement with the standard model expectation within one standard deviation.
The cross section of the process e+e−→K+K− is measured at a number of center-of-mass energies s√ from 2.00 to 3.08 GeV with the BESIII detector at the Beijing Electron Positron Collider (BEPCII). The results provide the best precision achieved so far. A resonant structure around 2.2 GeV is observed in the cross section line shape. A Breit-Wigner fit yields a mass of M=2239.2±7.1±11.3~and a width of Γ=139.8±12.3±20.6 MeV, where the first uncertainties are statistical and the second ones are systematic. In addition, the time-like electromagnetic form factor of the kaon is determined at the individual center-of-mass energy points.
We report on new measurements of Cabibbo-suppressed semileptonic D+s decays using 3.19 fb−1 of e+e− annihilation data sample collected at a center-of-mass energy of 4.178~GeV with the BESIII detector at the BEPCII collider. Our results include branching fractions B(D+s→K0e+νe)=(3.25±0.38(stat.)±0.16(syst.))×10−3 and B(D+s→K∗0e+νe)=(2.37±0.26(stat.)±0.20(syst.))×10−3 which are much improved relative to previous measurements, and the first measurements of the hadronic form-factor parameters for these decays. For D+s→K0e+νe, we obtain f+(0)=0.720±0.084(stat.)±0.013(syst.), and for D+s→K∗0e+νe, we find form-factor ratios rV=V(0)/A1(0)=1.67±0.34(stat.)±0.16(syst.) and r2=A2(0)/A1(0)=0.77±0.28(stat.)±0.07(syst.).
We study the electromagnetic Dalitz decay 𝐽/𝜓→𝑒+𝑒−𝜂 and search for dielectron decays of a dark gauge boson (𝛾′) in 𝐽/𝜓→𝛾′𝜂 with the two 𝜂 decay modes 𝜂→𝛾𝛾 and 𝜂→𝜋+𝜋−𝜋0 using (1310.6±7.0)×106 𝐽/𝜓 events collected with the BESIII detector. The branching fraction of 𝐽/𝜓→𝑒+𝑒−𝜂 is measured to be (1.43±0.04(stat)±0.06(syst))×10−5, with a precision that is improved by a factor of 1.5 over the previous BESIII measurement. The corresponding dielectron invariant mass dependent modulus square of the transition form factor is explored for the first time, and the pole mass is determined to be Λ=2.84±0.11(stat)±0.08(syst) GeV/𝑐2. We find no evidence of 𝛾′ production and set 90% confidence level upper limits on the product branching fraction ℬ(𝐽/𝜓→𝛾′𝜂)×ℬ(𝛾′→𝑒+𝑒−) as well as the kinetic mixing strength between the standard model photon and 𝛾′ in the mass range of 0.01≤𝑚𝛾′≤2.4 GeV/𝑐2.
An amplitude analysis of the 𝐾𝑆𝐾𝑆 system produced in radiative 𝐽/𝜓 decays is performed using the (1310.6±7.0)×106 𝐽/𝜓 decays collected by the BESIII detector. Two approaches are presented. A mass-dependent analysis is performed by parametrizing the 𝐾𝑆𝐾𝑆 invariant mass spectrum as a sum of Breit-Wigner line shapes. Additionally, a mass-independent analysis is performed to extract a piecewise function that describes the dynamics of the 𝐾𝑆𝐾𝑆 system while making minimal assumptions about the properties and number of poles in the amplitude. The dominant amplitudes in the mass-dependent analysis include the 𝑓0(1710), 𝑓0(2200), and 𝑓′2(1525). The mass-independent results, which are made available as input for further studies, are consistent with those of the mass-dependent analysis and are useful for a systematic study of hadronic interactions. The branching fraction of radiative 𝐽/𝜓 decays to 𝐾𝑆𝐾𝑆 is measured to be (8.1±0.4)×10−4, where the uncertainty is systematic and the statistical uncertainty is negligible.
he process e+e−→pK0Sn¯K−+c.c. and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb−1. The Born cross section of e+e−→pK0Sn¯K−+c.c. is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the pK−, nK0S, pK0S, nK+, pn¯, or K0SK− invariant mass distributions except for Λ(1520). The Born cross sections of e+e−→Λ(1520)n¯K0S+c.c. and e+e−→Λ(1520)p¯K++c.c. are measured, and the 90\% confidence level upper limits on the Born cross sections of e+e−→Λ(1520)Λ¯(1520) are determined at the seven center-of-mass energies.
We report new measurements of the cross sections for the production of Dbar D final states at the ψ(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fb−1 of e+e− annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D0 and six D+ hadronic decay modes and use the ratio of the yield of fully reconstructed Dbar D events ("double tags") to the yield of all reconstructed D or bar D mesons ("single tags") to determine the number of D0bar D0 and D+D− events, benefiting from the cancellation of many systematic uncertainties. Combining these yields with an independent determination of the integrated luminosity of the data sample, we find the cross sections to be σ(e+e− → D0bar D0) nb and σ(e+e− → D+D−) = (2.830 ± 0.011 ± 0.026) nb, where the uncertainties are statistical and systematic, respectively.
Using a data sample of 𝑒+𝑒− collisions corresponding to an integrated luminosity of 567 pb−1 collected at a center-of-mass energy of √𝑠=4.6 GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive semileptonic Λ+𝑐 decay with a double-tag method. We obtain ℬ(Λ+𝑐→𝑋𝑒+𝜈𝑒)=(3.95±0.34±0.09)%, where the first uncertainty is statistical and the second systematic. Using the known Λ+𝑐 lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons (𝐷0 and 𝐷+), we obtain the ratio of the inclusive semileptonic decay widths Γ(Λ+𝑐→𝑋𝑒+𝜈𝑒)/¯Γ(𝐷→𝑋𝑒+𝜈𝑒)=1.26±0.12.
Using a data sample with an integrated luminosity of 2.93 fb−1 taken at the center-of-mass energy of 3.773 GeV, we search for the Majorana neutrino (𝜈𝑚) in the lepton number violating decays 𝐷→𝐾𝜋𝑒+𝑒+. No significant signal is observed, and the upper limits on the branching fraction at the 90% confidence level are set to be ℬ(𝐷0→𝐾−𝜋−𝑒+𝑒+)<2.8×10−6, ℬ(𝐷+→𝐾0𝑆𝜋−𝑒+𝑒+)<3.3×10−6 and ℬ(𝐷+→𝐾−𝜋0𝑒+𝑒+)<8.5×10−6. The Majorana neutrino is searched for with different mass assumptions ranging from 0.25 to 1.0 GeV/𝑐2 in the decays 𝐷0→𝐾−𝑒+𝜈𝑚,𝜈𝑚→𝜋−𝑒+ and 𝐷+→𝐾0𝑆𝑒+𝜈𝑚,𝜈𝑚→𝜋−𝑒+, and the upper limits on the branching fraction at the 90% confidence level are at the level of 10−7∼10−6, depending on the mass of the Majorana neutrino. The constraints on the mixing matrix element |𝑉𝑒𝜈𝑚|2 are also evaluated.
Using a data sample of 448.1×106 𝜓(3686) events collected at √𝑠=3.686 GeV with the BESIII detector at the Beijing Electron-Positron Collider II, we search for the rare decay 𝐽/𝜓→𝜙𝑒+𝑒− via 𝜓(3686)→𝜋+𝜋−𝐽/𝜓. No signal events are observed and the upper limit on the branching fraction is set to be ℬ(𝐽/𝜓→𝜙𝑒+𝑒−)<1.2×10−7 at the 90% confidence level, which is still about one order of magnitude higher than the Standard Model prediction.
Using a data sample of 448.1×106 ψ(3686) events collected at s√= 3.686 GeV with the BESIII detector at the BEPCII, we search for the rare decay J/ψ→ϕe+e− via ψ(3686)→π+π−J/ψ. No signal events are observed and the upper limit on the branching fraction is set to be B(J/ψ→ϕe+e−)<1.2×10−7 at the 90\% confidence level, which is still about one order of magnitude higher than the Standard Model prediction.
The production of the Λ(1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s√ = 7 TeV and in p-Pb collisions at sNN−−−√ = 5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Λ(1520) → pK− and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p-Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (π, K, K0S, p, Λ) describes the shape of the Λ(1520) transverse momentum distribution up to 3.5 GeV/c in p-Pb collisions. In the framework of this model, this observation suggests that the Λ(1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Λ(1520) to the yield of the ground state particle Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p-Pb collisions on the Λ(1520) yield.
The production of the Λ(1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s√ = 7 TeV and in p-Pb collisions at sNN−−−√ = 5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Λ(1520) → pK− and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p-Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (π, K, K0S, p, Λ) describes the shape of the Λ(1520) transverse momentum distribution up to 3.5 GeV/c in p-Pb collisions. In the framework of this model, this observation suggests that the Λ(1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Λ(1520) to the yield of the ground state particle Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p-Pb collisions on the Λ(1520) yield.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p–Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.
The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at s√=13 TeV. After applying all corrections, the achieved mass resolution of π0 and η mesons for pT>1.7 GeV/c is σπ0m=4.56±0.03 MeV/c2 and σηm=15.3±1.0 MeV/c2.
The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at s√ = 13 TeV. After applying all corrections, the achieved mass resolutions for π0 and η mesons for pT>1.7 GeV/c are σπ0m=4.56±0.03 MeV/c2 and σηm=15.3±1.0 MeV/c2, respectively.
The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at s√= 7 TeV and central Pb-Pb collisions at sNN−−−√ = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the zg, and its dependence on the opening angle, in both pp and Pb-Pb collisions. We also present the first measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb-Pb collisions, we observe a suppression of symmetric splittings at large opening angles and an enhancement of splittings at small opening angles relative to pp collisions, with no significant modification of the number of splittings. The results are compared to predictions from various Monte Carlo event generators to test the role of important concepts in the evolution of the jet in the medium such as color coherence.
The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at s√= 7 TeV and central Pb-Pb collisions at sNN−−−√ = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the zg, and its dependence on the opening angle, in both pp and Pb-Pb collisions. We also present the first measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb-Pb collisions, we observe a suppression of symmetric splittings at large opening angles and an enhancement of splittings at small opening angles relative to pp collisions, with no significant modification of the number of splittings. The results are compared to predictions from various Monte Carlo event generators to test the role of important concepts in the evolution of the jet in the medium such as color coherence.
Transverse momentum (pT ) spectra of charged particles at mid-pseudorapidity in Xe–Xe collisions at √sNN=5.44TeV measured with the ALICE apparatus at the Large Hadron Collider are reported. The kinematic range 0.15<pT<50GeV/c and |η|<0.8 is covered. Results are presented in nine classes of collision centrality in the 0–80% range. For comparison, a pp reference at the collision energy of √s=5.44 TeV is obtained by interpolating between existing pp measurements at √s=5.02 and 7 TeV. The nuclear modification factors in central Xe–Xe collisions and Pb–Pb collisions at a similar center-of-mass energy of √sNN=5.02 TeV, and in addition at 2.76 TeV, at analogous ranges of charged particle multiplicity density 〈dNch/dη〉 show a remarkable similarity at pT>10 GeV/c. The centrality dependence of the ratio of the average transverse momentum 〈pT〉 in Xe–Xe collisions over Pb–Pb collision at √s=5.02 TeV is compared to hydrodynamical model calculations.
The elliptic flow (v2) of (anti-)3He is measured in Pb–Pb collisions at √sNN=5.02TeV in the transverse-momentum (pT) range of 2–6 GeV/c for the centrality classes 0–20%, 20–40%, and 40–60% using the event-plane method. This measurement is compared to that of pions, kaons, and protons at the same center-of-mass energy. A clear mass ordering is observed at low pT, as expected from relativistic hydrodynamics. The violation of the scaling of v2 with the number of constituent quarks at low pT, already observed for identified hadrons and deuterons at LHC energies, is confirmed also for (anti-)3He. The elliptic flow of (anti-)3He is underestimated by the Blast-Wave model and overestimated by a simple coalescence approach based on nucleon scaling. The elliptic flow of (anti-)3He measured in the centrality classes 0–20% and 20–40% is well described by a more sophisticated coalescence model where the phase-space distributions of protons and neutrons are generated using the iEBE-VISHNU hybrid model with AMPT initial conditions.
The relaxation of hot nuclear matter to an equilibrated state in the central zone of heavy-ion collisions at energies from AGS to RHIC is studied within the microscopic UrQMD model. It is found that the system reaches the (quasi)equilibrium stage for the period of 10-15 fm/c. Within this time the matter in the cell expands nearly isentropically with the entropy to baryon ratio S/A = 150 - 170. Thermodynamic characteristics of the system at AGS and at SPS energies at the endpoints of this stage are very close to the parameters of chemical and thermal freeze-out extracted from the thermal fit to experimental data. Predictions are made for the full RHIC energy square root s = 200$ AGeV. The formation of a resonance-rich state at RHIC energies is discussed.
Relativistic hadron-hadron collisions in the ultra-relativistic quantum molecular dynamics model
(1999)
Hadron-hadron collisions at high energies are investigated in the Ultra- relativistic-Quantum-Molecular-Dynamics approach. This microscopic trans- port model describes the phenomenology of hadronic interactions at low and intermediate energies ( s < 5 GeV) in terms of interactions between known hadrons and their resonances. At higher energies, s > 5 GeV, the excitation of color strings and their subsequent fragmentation into hadrons dominates the multiple production of particles in the UrQMD model. The model shows a fair overall agreement with a large body of experimental h-h data over a wide range of h-h center-of-mass energies. Hadronic reaction data with higher precision would be useful to support the use of the UrQMD model for relativistic heavy ion collisions.
Local equilibrium in heavy ion collisions. Microscopic model versus statistical model analysis
(1999)
The assumption of local equilibrium in relativistic heavy ion collisions at energies from 10.7 AGeV (AGS) up to 160 AGeV (SPS) is checked in the microscopic transport model. Dynamical calculations performed for a central cell in the reaction are compared to the predictions of the thermal statistical model. We find that kinetic, thermal and chemical equilibration of the expanding hadronic matter are nearly approached late in central collisions at AGS energy for t >= 10 fm/c in a central cell. At these times the equation of state may be approximated by a simple dependence P ~= (0.12-0.15) epsilon. Increasing deviations of the yields and the energy spectra of hadrons from statistical model values are observed for increasing energy, 40 AGeV and 160 AGeV. These violations of local equilibrium indicate that a fully equilibrated state is not reached, not even in the central cell of heavy ion collisions at energies above 10 AGeV. The origin of these findings is traced to the multiparticle decays of strings and many-body decays of resonances.
Abstract: Local thermal and chemical equilibration is studied for central AqA collisions at 10.7 160 AGeV in the Ultrarelativis- . tic Quantum Molecular Dynamics model UrQMD . The UrQMD model exhibits strong deviations from local equilibrium at the high density hadron string phase formed during the early stage of the collision. Equilibration of the hadron resonance matter is established in the central cell of volume Vs125 fm3 at later stages, tG10 fmrc, of the resulting quasi-isentropic expansion. The thermodynamical functions in the cell and their time evolution are presented. Deviations of the UrQMD quasi-equilibrium state from the statistical mechanics equilibrium are found. They increase with energy per baryon and lead to a strong enhancement of the pion number density as compared to statistical mechanics estimates at SPS energies. PACS: 25.75.-q; 24.10.Lx; 24.10.Pa; 64.30.qt
The hypothesis of local equilibrium (LE) in relativistic heavy ion collisions at energies from AGS to RHIC is checked in the microscopic transport model. We find that kinetic, thermal, and chemical equilibration of the expanding hadronic matter is nearly reached in central collisions at AGS energy for t >_ fm/c in a central cell. At these times the equation of state may be approximated by a simple dependence P ~= (0.12-0.15) epsilon. Increasing deviations of the yields and the energy spectra of hadrons from statistical model values are observed for increasing bombarding energies. The origin of these deviations is traced to the irreversible multiparticle decays of strings and many-body (N >_ 3) decays of resonances. The violations of LE indicate that the matter in the cell reaches a steady state instead of idealized equilibrium. The entropy density in the cell is only about 6% smaller than that of the equilibrium state.
We present the first measurement of event-by-event fluctuations in the kaon sector in Pb – Pb collisions at √sNN = 2.76 TeV with the ALICE detector at the LHC. The robust fluctuation correlator νdyn is used to evaluate the magnitude of fluctuations of the relative yields of neutral and charged kaons, as well as the relative yields of charged kaons, as a function of collision centrality and selected kinematic ranges. While the correlator νdyn[K+,K−] exhibits a scaling approximately in inverse proportion of the charged particle multiplicity, νdyn[K0 S ,K±] features a significant deviation from such scaling. Within uncertainties, the value of νdyn[K0 S ,K±] is independent of the selected transverse momentum interval, while it exhibits a pseudorapidity dependence. The results are compared with HIJING, AMPT and EPOS–LHC predictions, and are further discussed in the context of the possible production of disoriented chiral condensates in central Pb – Pb collisions.
Spleen injuries are among the most frequent trauma-related injuries. At present, they are classified according to the anatomy of the injury. The optimal treatment strategy, however, should keep into consideration the hemodynamic status, the anatomic derangement, and the associated injuries. The management of splenic trauma patients aims to restore the homeostasis and the normal physiopathology especially considering the modern tools for bleeding management. Thus, the management of splenic trauma should be ultimately multidisciplinary and based on the physiology of the patient, the anatomy of the injury, and the associated lesions. Lastly, as the management of adults and children must be different, children should always be treated in dedicated pediatric trauma centers. In fact, the vast majority of pediatric patients with blunt splenic trauma can be managed non-operatively. This paper presents the World Society of Emergency Surgery (WSES) classification of splenic trauma and the management guidelines.
Damage control resuscitation may lead to postoperative intra-abdominal hypertension or abdominal compartment syndrome. These conditions may result in a vicious, self-perpetuating cycle leading to severe physiologic derangements and multiorgan failure unless interrupted by abdominal (surgical or other) decompression. Further, in some clinical situations, the abdomen cannot be closed due to the visceral edema, the inability to control the compelling source of infection or the necessity to re-explore (as a “planned second-look” laparotomy) or complete previously initiated damage control procedures or in cases of abdominal wall disruption. The open abdomen in trauma and non-trauma patients has been proposed to be effective in preventing or treating deranged physiology in patients with severe injuries or critical illness when no other perceived options exist. Its use, however, remains controversial as it is resource consuming and represents a non-anatomic situation with the potential for severe adverse effects. Its use, therefore, should only be considered in patients who would most benefit from it. Abdominal fascia-to-fascia closure should be done as soon as the patient can physiologically tolerate it. All precautions to minimize complications should be implemented.
Acute calculus cholecystitis is a very common disease with several area of uncertainty. The World Society of Emergency Surgery developed extensive guidelines in order to cover grey areas. The diagnostic criteria, the antimicrobial therapy, the evaluation of associated common bile duct stones, the identification of “high risk” patients, the surgical timing, the type of surgery, and the alternatives to surgery are discussed. Moreover the algorithm is proposed: as soon as diagnosis is made and after the evaluation of choledocholitiasis risk, laparoscopic cholecystectomy should be offered to all patients exception of those with high risk of morbidity or mortality. These Guidelines must be considered as an adjunctive tool for decision but they are not substitute of the clinical judgement for the individual patient.
Schriftenschau
(2008)
Die Vegetationsverhältnisse der Hase, eines 174 km langen Nebenflusses der Ems, wurden im Sommer 1975 von der Quelle an auf einer Strecke von 93,3 km an 77 Probeabschnitten untersucht. Die Analysen konzentrierten sich dabei auf die Gefäßpflanzen des Wassers und der Böschungen in ihrer Abhängigkeit von den natürlichen und anthropogenen Standortsbedingungen. - Im Zusammenhang mit der Beschreibung der Pflanzengesellschaften werden die morphologische und ökologische Plastizität der vorkommenden Arten und die dadurch gegebenen Probleme für die syntaxonomische Zuordnung amphibischer Gesellschaften behandelt. Die Arten werden je nach dem Grad ihrer Polymorphie, ihrer Amphibie und ihres Standortoptimums in verschiedene Typen eingeteilt. - Von den zahlreichen Pflanzen.gesellschaften der Hase sind die wichtigsten: 1) als Hydrophytengesellschaft das Sparganio-Potametum pectinati Ass. nov. Als einzige in der Hase vorhandene gleichzeitig strömungs- und verschmutzungstolerante Gesellschaft ist sie vor allem im Mittellauf verbreitet. 2) Als Helophytengesellschaft begleitet das Sagittario-Sparganietum emersi TX. bis auf den quell nahen Oberlauf den Fluß zu beiden Seiten bis zur Mündung. 3) Als nur periodisch überflutete Epigeophytengesellschaft ist das Phalaridetum arundinaceae LIBB. parallel dazu an den Böschungen verbreitet. Ein Vergleich der Hydrophytenflora von der Quelle bis Quakenbrück zeigt nach einer arten armen quellnahen Strecke eine große Zunahme der Artenmannigfaltigkeit bis Osnabrück, dann ein starkes Absinken und später bis Quakenbrück wieder eine allmähliche Zunahme. Einige früher nachweislich auch unterhalb von Osnabrück verbreitete Arten haben sich heute nur noch im Oberlauf halten können. - Es wird gezeigt, daß zwischen der Diversität der Hydrophytenflora und den jeweiligen Saprobieverhältnissen eine enge Abhängigkeit besteht. Dabei werden die Ursachen für das Absterben der Arten diskutiert. Die vegetationskundlichen Befunde ergeben an den fünf Punkten, für die langfristige hydrobiologische und chemische Analysen aus dem Zeitraum 1966-69 vorliegen (NEUMANN 1975 u. a.) noch im Jahr 1975 eine vollständige Koinzidenz. Die Diversität der Hydrophytenvegetation erweist sich somit als deutlicher Indikator für die ökologische Beurteilung von Fließgewässern und erlaubt die Einordnung punktueller mikrobiologischer und chemischer Meßstationen in ein Gesamtgefüge, denn wegen der raschen Erkennbarkeit der Makrophyten und ihres Zeigerwerts für langfristig wirksame Bedingungen kann ein Fließgewässer an allen Punkten seiner gesamten Strecke leicht und ohne mehrfache Analysen ökologisch beurteilt werden. Der untersuchte Haselauf von der Quelle bis Quakenbrück ist auf dieser Grundlage in unterschiedliche Abschnitte mit verschiedener Gewässergüte zu gliedern, die oberhalb von Osnabrück zunächst die Klasse I, dann die Klasse II durchläuft. Diese reicht noch bis in die Stadt hinein, sinkt dann durch verschiedene Belastungen bis auf III ab und bessert sich erst allmählich wieder (etwa von der Dütemündung an) bis auf II, wobei hinter der Stadt Bramsche noch einmal eine vorübergehende Verschlechterung der Saprobieverhältnisse zu beobachten ist. Das 1975 erfaßte Floreninventar der Hase ist in einem abschließenden Verzeichnis mit 322 Gefäßpflanzen zusammengestellt.
Der Fischbestand der Hase. eines 174 km langen Nebenflusses der Ems, wird (im wesentlichen durch Umfrage bei den Fischereiberechtigten) für die insgesamt 93,2 km lange Strecke von der Quelle bis Quakenbrück ermittelt. Von den (mindestens) 28 ehemals vorhandenen einheimischen Arten sind 7 inzwischen verschollen oder nachweislich ausgestorben, fast ebenso viele sind nur noch in Restbeständen erhalten. Die Gründe für den Rückgang werden diskutiert. 5 Arten sind zusätzlich eingesetzt oder verwildert. Die fischereilich wichtigen Arten können sich heute im Fluß nicht ausreichend vermehren und werden planmäßig eingesetzt. Die Arten sind in charakteristischer Weise auf die natürlichen Flußregionen verteilt und spiegeln andererseits auch die unterschiedlichen Saprobieverhältnisse wider. Der noch um 1900 in der Hase und überhaupt im Raum Osnabrück häufige Flußkrebs ist heute anscheinend bis auf eine einzige. unter Schutz zu stellende Reliktpopulation an der oberen Wierau ausgestorben.
Zur Nomenklatur der Brombeeren in Norddeutschland (Gattung Rubus L. sect. Corylifolii, Rosaceae)
(1990)
Auf der Basis der Regeln des International Code of Botanical Nomenclature (ICBN) wird die Gültigkeit der Veröffentlichungen von Namen für Brombeeren der Sektion Corylifolii (Gattung Rubus L.) bei FRIDERICHSEN & GELERT (1887) und KRAUSE (1888, 1890) diskutiert. Hierbei wird deutlich, daß, wie bei der Anwendung von Gesetzesparagraphen auf konkrete Rechtsfälle, in bestimmten Fällen ein Ermessensspielraum gegeben ist, ob ein Name als gültig oder als nicht gültig veröffentlicht anzusehen ist.
Vier in Deutschland neu nachgewiesene Brombeerarten (Rubus L. Rosaceae), von denen zwei neu beschrieben sind, werden behandelt: (1) Rubus laetus Beek (Sect. Rubus subsect. Rubus), nachgewiesen im mittleren Westfalen; (2) R. discors Beek (Sect. Rubus ser. Sylvatici [P.J. Müller] Focke), im westlichen Niedersachsen und Westfalen; (3) R. hilsianus H. E. Weber spec. nov. (Sect. Rubus ser. Glandulosi Wimmer & Grab.), im südöstlichen Niedersachsen, in Hessen (Taunus) und im Saarland; (4) R. loosii H. E. Weber spec. nov. (Sect. Corylifolii Lindley ser. Subthyrsoidei Focke), stellenweise häufig im mittleren Westfalen. Die Arten sind detailliert beschrieben und durch Fotos von Herbarexemplaren abgebildet. Ihre Ökologie und Verbreitung sind behandelt.
Anlässlich des Jubiläums des Naturwissenschaftlichen Vereins Osnabrück und des heutigen Museums am Schölerberg werden deren Geschichte und Aufgaben dargestellt; es werden bedeutende Wissenschaftler, die hier tätig waren, kurz besprochen sowie die heutigen Arbeitsgemeinschaften des Vereins vorgestellt.
Rubus pottianus H. E. Weber wird als neue Brombeerart der Serie Pallidi W. C. R. Watson (Sektion Rubus) beschrieben. Ihr Verbreitungsgebiet umfasst Teile Nordhessens und Südniedersachsens. Die neue Art ist illustriert durch Fotos des Holotypus und der lebenden Pflanze am locus typicus. Ihre Verbreitung und Ökologie sind erläutert, und eine Liste von Herbarexemplaren ist beigefügt.
In Ergänzung zu früheren Veröffentlichungen (z. B. Pedersen & Weber 1993) wird eine aktualisierte Übersicht über die Brombeerflora (Rubus L. subgen. Rubus) von Niedersachsen und Bremen gegeben. Bis jetzt sind 169 Arten der Sektionen Rubus und Corylifolii in diesem Gebiet nachgewiesen. Davon gehören 117 zur Sektion Rubus und 52 zur Sektion Corylifolii. Fünf Arten der Sektion Rubus sind Gartenflüchtlinge und inzwischen völlig eingebürgert: Rubus allegheniensis, R. armeniacus, R. canadensis und R. laciniatus. Selten und zufällig eingeschleppt wurden Rubus bifrons und R. ulmifolius. Somit besteht die Brombeerflora in Niedersachsen und Bremen aus 162 einheimischen Arten, von denen 52 (= 32%) zur Sektion Corylifolii gehören.
Zwei Brombeerarten der Sektion Rubus ser. Glandulosi (Wimmer & Grabowski) Fokke werden neu beschrieben. Beide sind in Thüringen und Nordbayern verbreitet: Rubus exarmatus H. E. Weber & W. Jansen spec. nov. und Rubus perlongus H.E. Weber & W. Jansen spec. nov. Die Arten sind durch Fotos ihrer Holotypen abgebildet, ihre bekannte Verbreitung ist durch Rasterkarten dargestellt.
Limodorum abortivum (L.) Sw. (Orchidaceae) wurde 1932 auf dem Silberberg bei Natrup-Hagen (Landkreis Osnabrück) gefunden. Das Belegstück ging leider verloren, aber die Angabe stammt von dem zuverlässigen Pflanzenkenner Wilhelm Meyer (Direktor des Botanischen Gartens in Oldenburg), und das Exemplar wurde nach einer Zeitungsnotiz von Hunderten von Besuchern, darunter von zahlreichen Botanikern besichtigt. Der Silberberg ist der weitaus nördlichste Fundort dieser thermophilen Orchidee.
Der Beitrag behandelt die in Europa nachgewiesenen Zwergformen der Gattung Rubus L. Sechzehn Arten (alle nur Sekt. Rubus) bilden solche offensichtlich genetisch fixierten Abwandlungen aus, die als Varietäten der betreffenden Arten eingestuft werden. Neu beschrieben werden R. marssonianus H. E. WEBER var. pusillus H. E. WEBER, R. muenteri T. MARSS. var. pusillus H. E. WEBER und R. senticosus KÖHLER ex WEIHE var. pusillus H. E. WEBER & KIESEWETTER. Einen status novus erhalten R. gracilis J. & C. PRESL var. parvulus (HÜLSEN) H. E. WEBER, R. pyramidalis KALT. var. parvifolius (K. FRID. & GELERT) H. E. WEBER und R. silvaticus WEIHE & NEES var. microphyllus (K. FRID. ex ERICHSEN) H. E. WEBER. – Zwergformen sind meist etwa nur halb so groß wie die Normalform und weisen weitere charakteristische Merkmale auf. Ihre Häufigkeit nimmt von Norden nach Süden ab. Die meisten Zwergformen wachsen in Dänemark (13), es folgen Norddeutschland (9) und Mitteleuropa bis zur Donau (4). Weiter südlich und in Südeuropa fehlen sie. Von den Britischen Inseln sind vier Zwergformen bekannt.
Das bislang kaum dokumentierte, im nordwestdeutschen Tiefland sehr häufige Rubetum grati Tx. & NEUM.ex WEBER 76 ist in einer Tabelle mit Aufnahmen aus dem westlichen und mittleren Niedersachsen dargestellt. Die Assoziation ist kennzeichnend für die ärmsten Standorte im potentiell natürlichen Wuchsbereich des Querco-Betuletum molinietosum. Rubus silvaticus und die übrigen Arten des Rubenion silvatici fehlen hier vollständig. Als zweites sind Besenginstergebüsche (Rubo plicati-Sarothamnetum ass. nov., Rubion plicati) behandelt. Sarothamnus scoparius wurde früher meist zu den Borstgras- und Heidegesellschaften gestell
t. Dieser Auffassung liegen Nardo-Callunetea-Gesellschaften zugrunde, die mit einzelnen Besenginsterexemplaren durchsetzt sind, ähnlich wie auch Birken sich zunächst in Einzelexemplaren auf solchen Standorten ansiedeln. Auch das Cytiso-Callunetum Malc. 29 (Calluno- Sarothamnetum auct.) beruht nach den Originalaufnahmen ebenso wie der hierdurch typisierte Verband Sarothamnion auf der Vermengung zweier Gesellschaften (meist Sarothamno-Calluno-Sigmetum). Der Besenginster ist jedoch nicht Kennart von Rasen- und Zwergstrauchgesellschaften, sondern von Gebüschen, wie sie hier in einer Tabelle mit Aufnahmen aus dem nordwestdeutschen Tiefland dargestellt sind. Die im Tiefland vorhandene Ausbildung quercetosum roboris subass. nov. wird der im Bergland verbreiteten Form teucrietosum scorodoniae subass. nov. gegenübergestellt. Schließlich ist eine Rubus armeniacus-Gesellschaft beschrieben. Sie wird von der im vorigen Jahrhundert nach Mitteleuropa eingeführten Gartenbrombeere Rubus armeniacus gebildet, die auf Ruderalstandorten häufig verwildert ist und ausgedehnte Gebüsche bildet.
Mimulus moschatus wurde vor etwa 160 Jahren von Nordamerika nach Europa importiert und als Zierpflanze kultiviert. Verwilderungen sind seit mindestens 1872 bekannt. Für Niedersachsen liegen sieben Nachweise vor, von denen zwei unsichere Angaben zum Fundort oder Status enthalten. In drei Fällen konnte eine jahrelange Einbürgerung nachgewiesen werden (einmal über mindestens 17 Jahre). Damit hat die Art in Niedersachsen den Status eines „eingebürgerten Neophyten". Das Fehlen des früher intensiven Moschusgeruchs der Pflanzen wird diskutiert. Unterscheidungsmerkmale zu dem in Niedersachsen wesentlich häufigeren Mimulus guttatus werden herausgestellt. Die Soziologie von Mimulus moschatus ist in einer Vegetationstabelle veranschaulicht. Die Art ist auf Calthion-Standorten (besonders im Crepido-Juncetum acutiflori) eingebürgert und verhält sich somit anders als Mimulus guttatus, der in Niedersachsen vorzugsweise in Chenopodion fluviatilis- und Rumici-Phalaridion-Gesellschaften vorkommt.
Es wird ein Schlüssel zur nomenklatorischen Überprüfung der Namen von Syntaxa als Hilfe geliefert, um die oft komplizierten Regeln des Codes der pflanzensoziologischen Nomenklatur korrekt und konsequent anzuwenden. Außerdem werden Vorschläge zur Verbesserung des Codes unterbreitet. Im Interesse der nomenklatorischen Stabilität wird dafür plädiert, für bestimmte Syntaxa allgemein eingebürgerte, aber nach den Regeln zu verwerfende Namen als nomina conservanda beibehalten zu können, sowie die "Assoziationen" der skandinavischen Schule grundsätzlich nicht in das heutige syntaxonomische System zu überführen. Auf die Gefahr der immer noch zu beobachtenden Publikation von überflüssigen Namen (nomina superflua) ist besonders hingewiesen.
Entsprechend dem von ELLENBERG (1974) entwickelten Verfahren werden Zeigerwerte für Rubus-Arten in Mitteleuropa angegeben. Sie basieren auf pflanzensoziologischen und arealgeographischen Untersuchungen. Die Daten müssen zum Teil durch weitere Untersuchungen noch ergänzt und verbessert werden. Einige ökologische und soziologische Besonderheiten der Gattung Rubus sind diskutiert.
Senecio inaequidens De., ein in Natal und Transvaal beheimateter, sich im westlichen Europa zunehmend ausbreitender Neophyt, ist seit 1985 auch bei Osnabrück nachgewiesen. Die pflanzensoziologische Situation des 1986 noch vorhandenen Standorts in einem fragmentarischen Echino-Melilotatum Tx. 42 bei Bramsche-Achmer ist durch eine Vegetationstabelle veranschaulicht.
Buchbesprechungen
(1979)
Rubus ferocior WEBER 1977 (= R. ferox WEIHE non VEST) und Rubus placidus WEBER nov. spec. (= R. milliformis var. roseus FRID. & GELERT) werden als weitverbreitete zentraleuropäische Arten der Rubi sect. Corylifolii erstmals genauer beschrieben und in typischen Exemplaren (specimina normalia) abgebildet. Die zum Teil verwickelte Nomenklatur wird ausführlich diskutiert. Die Verbreitung ist durch eine Auflistung von Fundorten und in Rasterkarten angegeben. Durch einen Bestimmungsschlüssel, der auch die nächstverwandten Taxa enthält, soll einer Verwechslung mit ähnlichen Arten vorgebeugt werden.
Drei Arten der Rubi sect. Corylifolii sind behandelt. Rubus hadroacanthos G. Br., eine bislang unbeachtete Art, ist erstmals detailliert beschrieben. Sie ist stellenweise häufig verbreitet in NW-Deutschland (vom Harz bis ins westliche Westfalen). R. tuberculatiformis Weber nov. spec. wächst ziemlich häufig in Teilen von SW-Niedersachsen und NO-Westfalen. R. parahebecarpus Weber nov. spec. (= R. hebecarpus ssu. auct. div. p.p. non P. J. M.) ist bislang nachgewiesen im unteren Rheingebiet (Bergisches Land bis Aachen und Kleve) und in den südlichen Niederlanden. Die Arten sind durch Photos abgebildet, und ihre Verbreitung ist durch Fundortslisten und Rasterkarten dargestellt.
Im Zusammenhang mit einer Revision der Rubus-Flora von Mitteleuropa werden fünf neue Rubus-Arten beschrieben: Rubus hastiferus H. E. WEBER(sect. Rubus ser. Micantes), R. hirsutior FITSCHEN ex H. E. WEBER(= R. pallidus subsp. hirsutior FITSCHEN 1914, nom. prov.- Sect. Rubus ssr. Radulae), R. contractipes H. E. WEBER,R. rhytidophyllus H. E. WEBER(beide sect. Corylifolii ser. Subsilvatici) sowie R. visurgianus H. E. WEBER(sect. Corylifolii sero Subcanescentes). Die Arten sind gebietsweise häufig in Niedersachsen und kommen teilweise auch in Westfalen und Hessen vor.
Drei neue Rubus-Arten (sect. Corylifolii) des nordwestlichen Mitteleuropas werden beschrieben: Rubus calvus, nachgewiesen von der Niedereibe bis zum Niederrhein und in den Niederlanden, R. calviformis, gefunden in Westfalen und dem benachbarten Niedersachsen, und R. incisior, der früher als eine Form von R. orthostachys G. BRAUN betrachtet wurde, als streckenweise häufige Art in Westfalen, den Niederlanden und Belgien. Photographien der Holotypen, Raster-Verbreitungskarten und ein Bestimmungsschlüssel zu diesen und ähnlichen Arten sind beigefügt. Zusätzlich ist eine Kombination publiziert: R. pruinosus f. heteracanthus (FRID.) H. E. WEBER (= R. pruinosus f. warmingii).
Der früher in oligotrophen Heidegewässern verbreitete, heute vom Aussterben bedrohte Reinweiße Wasserhahnenfuß ist heute noch von vier Fundpunkten in Mitteleuropa bekannt. Die einstige und heutige, sich westlich der Linie Hamburg - Osnabrück - Krefeld erstreckende Verbreitung ist in einer Liste aller bekannten Fundorte mit Meßtischblatt-Rasterangaben wiedergegeben. Die Situation in Niedersachen und im benachbarten Westfalen ist zusätzlich in einer Karte dargestellt. Ranunculus ololeucos bildet in nährstoffarmen Klarwasserbereichen eine der Ufervegetation vorgelagerte eigene Schwimmblatt-Gesellschaft. Diese ist hier auf der Grundlage von Aufnahmen aus Niedersachsen und Westfalen als eine zum Verband Hydrocolylo- Baldellion (Klasse Littorelletea) gehörende Assoziation Ranunculetum ololeuci ass. nov. beschrieben.
Die früher im Osnabrücker Raum fehlende Erzengelwurz (Angelica archangelica L.) hat sich im Zuge einer allgemeinen Ausbreitung in den letzten beiden Jahrzehnten am Mittelland- und Stich kanal angesiedelt. Sie tritt hier in der ssp. archangelica auf. Das am noch unverbauten Westufer des Stichkanals zwischen Osnabrück und Pente besonders reichlich entwikkelte Calystegio-Archangelietum PASS. 64 ist durch eine Vegetationstabelle dokumentiert. Die Ufer der parallel zum Kanal verlaufenden Hase werden von der Art nicht besiedelt.
Am 16. Mai 1980 verstarb in Rinteln-Todenmann das Ehrenmitglied des Naturwissenschaftlichen Vereins Osnabrück, Prof. Dr. Drs. h.c. REINHOLD TÜXEN, wenige Tage vor der Vollendung seines 81. Lebensjahres. Mit ihm verliert ein ganzer Wissenschaftszweig einen seiner wichtigsten Begründer und Bahnbrecher. Ohne REINHOLD TÜXEN wäre die Pflanzensoziologie in der Art, wie sie heute weltweit als Forschungsrichtung praktiziert wird, nicht denkbar.
Rubus ehrnsbergeri H. E. Weber spec. nov. wird als neue Art der Sektion Corylifolii Lindley serie Suberectigeni H. E. Weber beschrieben. Ihr bislang bekanntes Verbreitungsgebiet umfasst die Gegend um Mennighüffen (in Westfalen gelegenes Gebiet, in dem K. E. A.Weihe in der ersten Hälfte des 19. Jahrhunderts die Brombeerforschung in Europa begründete) und erstreckt sich bis östlich von Stadthagen in Niedersachsen. Fotos (auch des Holotypus) und eine Liste der Herbarbelege sind beigefügt.
Rubus wittigianus spec. nov., eine sich ausbreitende Brombeerart in Westfalen und bei Osnabrück
(2002)
Rubus wittigianus H. E.Weber spec. nov. wird als neue Art der Sektion Rubus serie Sylvatici (P. J. Müller) Focke beschrieben. Ihr bislang bekanntes Verbreitungsgebiet erstreckt sich von Wellendorf (Landkreis Osnabrück) durch Westfalen bis Bad Lippspringe.Die Art ist durch Fotos (auch des Holotypus) abgebildet, und eine Liste der bisherigen Fundorte ist beigefügt.
Vier neue Rubus-Arten sind beschrieben: (1) Rubus immodicus A. SCHUMACHER ex H. E. WEBER (sect. Rubus ser. Sylvatici), bislang bekannt aus dem Rheinland und aus Belgien, (2) Rubus pseudargenteus H. E. WEBER (sect. Rubus ser. Discolores, = R. argenteus sensu SUDRE pro parte, non WEIHE & NEES nec GMELIN), nachgewiesen in Westdeutschland (Rheinland), (3) Rubus norvegicus H. E. WEBER & A. PEDERSEN (sect. Corylifolii ser. Sepincoli, = R. rosanthus var. leiocarpus LINDEBERG, R. mortensenii auct. div., non E. H. L. KRAUSE quoad typum), häufig in Südnorwegen, außerdem in Schweden (Bohuslän) und zerstreut in Dänemark, (4) Rubus martensenii H. E. WEBER (sect. Corylifolii ser. Sepincoli), gefunden in Dänemark und in Nordwestdeutschland (besonders in Schleswiq-Hotstein). Die Arten sind abgebildet, und exemplarische Herbarbelege sind angegeben. Als Nachtrag zu SCHOLZ & WEBER (1990) ist außerdem die Nomenklatur einiger von E. H. L. KRAUSE (1888, 1890) benannter Arten der Sektion Corylifolii behandelt.