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Based on e+e− collision data corresponding to an integrated luminosity of 4.5 fb−1 collected at the center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII, the absolute branching fraction of the inclusive decay Λ+c→n+X, where X refers to any possible final state particles, is measured. The absolute branching fraction is determined to be B(Λ+c→n+X)=(32.4±0.7±1.5)%, where the first uncertainty is statistical and the second systematic. Assuming CP symmetry, the measurement indicates that about one-fourth of Λ+c (Λ¯−c) decay modes with a neutron (an anti-neutron) in the final state have not been observed.
Measurement of e⁺e⁻ → ϕη′ cross sections at center-of-mass energies
between 3.508 and 4.600 GeV
(2023)
We present a measurement of the dressed cross sections for e+e−→ϕη′ at different center-of-mass energies between 3.508 and 4.600 GeV based on 15.1 fb−1 of e+e− annihilation data collected with the BESIII detector operating at the BEPCII collider. In addition, a search for the decay Y(4230)→ϕη′ is performed. No clear signal is observed and the corresponding upper limit is provided.
A search has been performed for the semileptonic decays D0→K0SK−e+νe, D+→K0SK0Se+νe and D+→K+K−e+νe, using 7.9 fb−1 of e+e− annihilation data collected at the center-of-mass energy s√=3.773 GeV by the BESIII detector operating at the BEPCII collider. No significant signals are observed, and upper limits are set at the 90\% confidence level of 2.13×10−5, 1.54×10−5 and 2.10×10−5 for the branching fractions of D0→K0SK−e+νe, D+→K0SK0Se+νe and D+→K+K−e+νe, respectively.
We perform a study of the X(3872) lineshape using the data samples of e+e−→γX(3872), X(3872)→D0D¯0π0 and π+π−J/ψ collected with the BESIII detector. The effects of the coupled-channels and the off-shell D∗0 are included in the parameterization of the lineshape. The lineshape mass parameter is obtained to be MX=(3871.63±0.13+0.06−0.05) MeV. Two poles are found on the first and second Riemann sheets corresponding to the D∗0D¯0 branch cut. The pole location on the first sheet is much closer to the D∗0D¯0 threshold than the other, and is determined to be 7.04±0.15+0.07−0.08 MeV above the D0D¯0π0 threshold with an imaginary part −0.19±0.08+0.14−0.19 MeV.
This paper reports the study of D+s→τ+ν via τ+→π+ν¯τ using a boosted decision tree method, with 7.33 fb−1 of e+e− collision data collected by the BESIII detector at center-of-mass energies between 4.128 and 4.226~GeV. The branching fraction of D+s→τ+ντ is determined to be (5.44±0.17stat±0.13syst)%. The product of the D+s decay constant fD+s and the CKM matrix element |Vcs| is fD+s|Vcs| =(248.3±3.9stat±3.1syst±1.0input) MeV. Combining with the |Vcs| value obtained from the Standard Model global fit or the fD+s from the lattice quantum chromodynamics, we determine |Vcs| = 0.993±0.015stat±0.012syst±0.004input and fD+s =(255.0±4.0stat±3.2syst±1.0input) MeV. The first uncertainty is statistical, the second one is systematic and the third one is due to the input parameters, mainly the lifetime of D+s. All results obtained in this work supersede the BESIII previous results based on 6.32 fb−1 of e+e− collision data taken at center-of-mass energies between 4.178 and 4.226~GeV.
Precise measurement of the branching fractions of of J/ψ → Λ¯π⁺Σ⁻ + c.c. and J/ψ → Λ¯π⁻Σ⁺ + c.c.
(2023)
Based on a data sample of (10087±44)×106 J/ψ events collected with the BESIII detector, the branching fraction of J/ψ→Λ¯π+Σ−+c.c. is measured to be (1.221±0.002±0.038)×10−3, and the branching fraction of its isospin partner mode J/ψ→Λ¯π−Σ++c.c. is measured to be (1.244±0.002±0.045)×10−3 with improved precision. Here the first uncertainties are statistical and the second ones systematic. The isospin symmetry of the Σ baryon in charmonium hadronic decay and the "12% rule" are tested, and no violation is found. The potential of using these channels as Σ baryon sources for nuclear physics research is studied, and the momentum and angular distributions of these sources are provided.
We report the measurement of the cross sections for e+e−→{nOCH} (nOCH stands for non-open charm hadrons) with improved precision at center-of-mass energies from 3.645 to 3.871 GeV. We observe for the first time a three-resonance structure in the energy-dependent lineshape of the cross sections, which are R(3760), R(3780) and R(3810) with significances of 9.4σ, 15.7σ, and 9.8σ, respectively. The R(3810) is observed for the first time. We found two solutions in analysis of the cross sections. For solution I [solution II], we measure the mass, the total width and the product of electronic width and nOCH decay branching fraction to be (3805.8±1.1±2.7) [(3805.8±1.1±2.7)] MeV/c2, (11.6±2.6±1.9) [(11.5±2.5±1.8)] MeV, and (10.8±3.2±2.3) [(11.0±2.9±2.4)] eV for the R(3810), respectively. In addition, we measure the branching fractions B(R(3760)→{nOCH})=(24.5±13.4±27.4)%[(6.8±5.4±7.6)%] for the first time, and B(R(3780)→{nOCH})=(11.6±5.8±7.8)%[(10.3±4.5±6.9)%]. Moreover, we determine the open-charm (OC) branching fraction B(R(3760)→{OC})=(75.5±13.4±27.4)%[(93.2±5.4±7.6)%], which supports the interpretation of R(3760) as an OC pair molecular state, but contained a simple four-quark state component. The first uncertainties are from fits to the cross sections, and the second are systematic.
Using a sample of (10087±44)×106 J/ψ events, which is about fifty times larger than that was previously analyzed, a further investigation on the J/ψ→γ3(π+π−) decay is performed. A significant distortion at 1.84 GeV/c2 in the line-shape of the 3(π+π−) invariant mass spectrum is observed for the first time, which is analogous to the behavior of X(1835) and could be resolved by two overlapping resonant structures, X(1840) and X(1880). The new state X(1880) is observed with a statistical significance of 14.7σ. The mass and width of X(1880) are determined to be 1882.1±1.7±0.7 MeV/c2 and 30.7±5.5±2.4 MeV, respectively, which indicates the existence of a pp¯ bound state.
The process e+e−→D∗+sD∗−s is studied with a semi-inclusive method using data samples at center-of-mass energies from threshold to 4.95 GeV collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections of the process are measured for the first time with high precision in this energy region. Two resonance structures are observed in the energy-dependent cross sections around 4.2 and 4.4 GeV. By fitting the cross sections with a coherent sum of three Breit-Wigner amplitudes and one phase-space amplitude, the two significant structures are assigned masses of (4186.5±9.0±30) MeV/c2 and (4414.5±3.2±6.0) MeV/c2, widths of (55±17±53) MeV and (122.6±7.0±8.2) MeV, where the first errors are statistical and the second ones are systematic. The inclusion of a third Breit-Wigner amplitude is necessary to describe a structure around 4.79 GeV.
Using e+e− collision data corresponding to a total integrated luminosity of 12.9 fb−1 collected with the BESIII detector at the BEPCII collider, the exclusive Born cross sections and the effective form factors of the reaction e+e−→Ξ−Ξ¯+ are measured via the single baryon-tag method at 23 center-of-mass energies between 3.510 and 4.843 GeV. Evidence for the decay ψ(3770)→Ξ−Ξ¯+ is observed with a significance of 4.5σ by analyzing the measured cross sections together with earlier BESIII results. For the other charmonium(-like) states ψ(4040), ψ(4160), Y(4230), Y(4360), ψ(4415), and Y(4660), no significant signal of their decay to Ξ−Ξ¯+ is found. For these states, upper limits of the products of the branching fraction and the electronic partial width at the 90% confidence level are provided.
The process e+e−→D∗+sD∗−s is studied with a semi-inclusive method using data samples at center-of-mass energies from threshold to 4.95 GeV collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections of the process are measured for the first time with high precision in this energy region. Two resonance structures are observed in the energy-dependent cross sections around 4.2 and 4.4 GeV. By fitting the cross sections with a coherent sum of three Breit-Wigner amplitudes and one phase-space amplitude, the two significant structures are assigned masses of (4186.5±9.0±30) MeV/c2 and (4414.5±3.2±6.0) MeV/c2, widths of (55±17±53) MeV and (122.6±7.0±8.2) MeV, where the first errors are statistical and the second ones are systematic. The inclusion of a third Breit-Wigner amplitude is necessary to describe a structure around 4.79 GeV.
The singly Cabibbo-suppressed decay Λ+c→Σ−K+π+ is observed for the first time with a statistical significance of 6.4σ by using 4.5 fb−1 of e+e− collision data collected at center-of-mass energies between 4.600 and 4.699 GeV with the BESIII detector at BEPCII. The absolute branching fraction of Λ+c→Σ−K+π+ is measured to be (3.8±1.3stat±0.2syst)×10−4 in a model-independent approach. This is the first observation of a Cabibbo-suppressed Λ+c decay involving Σ− in the final state. The ratio of branching fractions between Λ+c→Σ−K+π+ and the Cabibbo-favored decay Λ+c→Σ−π+π+ is calculated to be (0.4±0.1)s2c, where sc≡sinθc=0.2248 with θc the Cabibbo mixing angle. This ratio significantly deviates from 1.0s2c and provides important information for the understanding of nonfactorization contributions in Λ+c decays.
Using (447.9 ± 2.3) million ψ(3686) events collected with the BESIII detector, the decays of χcJ→ϕϕ (J=0, 1, 2) have been studied via the decay ψ(3686)→γχcJ. The branching fractions of the decays χcJ→ϕϕ (J=0, 1, 2) are determined to be (8.48±0.26±0.27)×10−4, (4.36±0.13±0.18)×10−4, and (13.36±0.29±0.49)×10−4, respectively, which are the most precise measurements to date. From a helicity amplitude analysis of the process ψ(3686)→γχcJ,χcJ→ϕϕ,ϕ→K+K−, the polarization parameters of the χcJ→ϕϕ decays are determined for the first time.
Based on electron positron collision data collected with the BESIII detector operating at the BEPCII storage rings, the differential cross sections of inclusive π0 and K0S production as a function of hadron momentum, normalized by the total cross section of the e+e−→ hadrons process, are measured at six center-of-mass energies from 2.2324 to 3.6710 GeV. Our results with a relative hadron energy coverage from 0.1 to 0.9 significantly deviate from several theoretical calculations based on existing fragmentation functions, especially at lower energies.
Based on a sample of (448.1±2.9)×106 ψ(3686) events collected with the BESIII detector at BEPCII, the decays of ψ(3686)→K−ΛΞ¯¯¯¯++c.c. with Ξ¯¯¯¯+→Λ¯¯¯¯π+, Λ¯¯¯¯→p¯¯¯π+ are this http URL excited hyperons, Ξ(1690)− and Ξ(1820)−, are observed with large significance (≫10σ) in the K−Λ invariant mass distributions. A partial wave analysis is performed, and the spin-parities of Ξ(1690)− and Ξ(1820)− are determined to be 12− and 32−, respectively. The masses, widths, and product branching fractions of Ξ(1690)− and Ξ(1820)− are also measured.
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.
We report on the measurements of directed flow v1 and elliptic flow v2 for hadrons (π±, K ±, K0 S , p, φ, Λ and ) from Au+Au collisions at √sN N = 3 GeV and v2 for (π±, K ±, p and p) at 27 and 54.4 GeV with the STAR experiment. While at the two higher energy midcentral collisions the numberof-constituent-quark (NCQ) scaling holds, at 3 GeV the v2 at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the v1 slopes at midrapidity for almost all observed hadrons are found to be positive, implying dominant repulsive baryonic interactions. The features of negative v2 and positive v1 slope at 3 GeV can be reproduced with a baryonic mean-field in transport model calculations. These results imply that the medium in such collisions is likely characterized by baryonic interactions.
In high-energy heavy-ion collisions, partonic collectivity is evidenced by the constituent quark number scaling of elliptic flow anisotropy for identified hadrons. A breaking of this scaling and dominance of baryonic interactions is found for identified hadron collective flow measurements in √sNN = 3 GeV Au+Au collisions. In this paper, we report measurements of the first- and second-order azimuthal anisotropic parameters, v1 and v2, of light nuclei (d, t, 3He, 4He) produced in √sNN = 3 GeV Au+Au collisions at the STAR experiment. An atomic mass number scaling is found in the measured v1 slopes of light nuclei at mid-rapidity. For the measured v2 magnitude, a strong rapidity dependence is observed. Unlike v2 at higher collision energies, the v2 values at mid-rapidity for all light nuclei are negative and no scaling is observed with the atomic mass number. Calculations by the Jet AA Microscopic Transport Model (JAM), with baryonic mean-field plus nucleon coalescence, are in good agreement with our observations, implying baryonic interactions dominate the collective dynamics in 3 GeV Au+Au collisions at RHIC.
Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b – Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345.