Refine
Year of publication
Language
- English (272)
Has Fulltext
- yes (272) (remove)
Is part of the Bibliography
- no (272)
Keywords
- BESIII (13)
- Branching fraction (9)
- e +-e − Experiments (9)
- Particle and Resonance Production (5)
- Quarkonium (5)
- Hadronic decays (4)
- Lepton colliders (4)
- Branching fractions (3)
- Charm Physics (3)
- Charmed mesons (3)
- Charmonium (3)
- Elastic scattering (3)
- Electroweak interaction (3)
- Exotics (3)
- Initial state radiation (3)
- Polarization (3)
- Spectroscopy (3)
- e+-e− Experiments (3)
- ALICE experiment (2)
- Bhabha (2)
- Charm physics (2)
- Collectivity (2)
- Correlation (2)
- Cross section (2)
- Diffraction (2)
- Electroweak Interaction (2)
- Elliptic flow (2)
- Hadronic cross section (2)
- LHC (2)
- Leptonic, semileptonic & radiative decays (2)
- Muon anomaly (2)
- Particle decays (2)
- Pion form factor (2)
- QCD (2)
- RHIC (2)
- Shear viscosity (2)
- Angular distribution (1)
- Annihilation (1)
- B-slope (1)
- BESIII detector (1)
- Beauty production (1)
- Born cross section measurement (1)
- CP violation (1)
- Charged-particle multiplicity (1)
- Charm quark spatial diffusion coefficient (1)
- Charmonia (1)
- Charmonium (-like) (1)
- Coalescence (1)
- Cold nuclear matter effects (1)
- Covariance matrix (1)
- Critical point (1)
- Cross section measurements (1)
- D meson (1)
- D0 and D+ mesons (1)
- Dalitz decay (1)
- Dark photon (1)
- Dark sector (1)
- Deuteron production (1)
- Di-hadron correlations (1)
- Electromagnetic form factor (1)
- Electromagnetic form factors (1)
- Experimental nuclear physics (1)
- Experimental particle physics (1)
- FOS: Physical sciences (1)
- Flavor changing neutral currents (1)
- Flavor symmetries (1)
- Flavour Physics (1)
- Flow (1)
- Form factors (1)
- Groomed jet radius (1)
- Hadrons (1)
- Heavy Ion Experiments (1)
- Heavy Ions (1)
- Heavy Quark Production (1)
- Heavy-Ion Collision (1)
- Heavy-flavor decay electron (1)
- Heavy-flavour decay muons (1)
- Heavy-flavour production (1)
- Heavy-ion (1)
- Heavy-ion collisions (1)
- High Energy Physics - Experiment (hep-ex) (1)
- Higher moments (1)
- Hyperons (1)
- Interference fragmentation function (1)
- Invisible decays (1)
- J/ψ suppression (1)
- Jet substructure (1)
- Jets (1)
- Multiple parton interactions (1)
- Neutrinos (1)
- Nonflow (1)
- Particle and resonance production (1)
- Particle phenomena (1)
- Pb–Pb collisions (1)
- Proton (1)
- Proton-proton collisions (1)
- Proton–proton collisions (1)
- Quantum chromodynamics (1)
- R value (1)
- Radiative decay (1)
- Rare decays (1)
- STAR (1)
- Semi-leptonic decays (1)
- Single electrons (1)
- SoftDrop (1)
- Spin alignment (1)
- Splitting function (1)
- Techniques Electromagnetic calorimeters (1)
- Thermal model (1)
- Transversity (1)
- Triple quarkonia (1)
- Y (4260) (1)
- Y states (1)
- center-of-mass energy (1)
- charmonium-like states (1)
- dimuon (1)
- diphoton (1)
- e+e − annihilation (1)
- e+e⁻ − Experiments (1)
- e+e− Experiments (1)
- e+e− annihilation (1)
- electron-positron collision (1)
- hadron spectroscopy (1)
- hadronic events (1)
- helicity amplitude analysis (1)
- inclusive J/ψ decays (1)
- luminosity (1)
- number of J/ψ events (1)
- p+p collisions (1)
- pp collisions (1)
- tetraquark (1)
- trigger efficiency (1)
- Λ+c baryon (1)
- Σ hyperon (1)
Institute
- Physik (240)
- Frankfurt Institute for Advanced Studies (FIAS) (46)
- Informatik (14)
The elliptic (v2) and triangular (v3) azimuthal anisotropy coefficients in central 3He+Au, d+Au, and p+Au collisions at sNN−−−√ = 200 GeV are measured as a function of transverse momentum (pT) at mid-rapidity (|η|<0.9), via the azimuthal angular correlation between two particles both at |η|<0.9. While the v2(pT) values depend on the colliding systems, the v3(pT) values are system-independent within the uncertainties, suggesting an influence on eccentricity from sub-nucleonic fluctuations in these small-sized systems. These results also provide stringent constraints for the hydrodynamic modeling of these systems.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5 fb -1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e− (γISR/FSR)µ -> +µ-, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-collection period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44~GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fb−1 of e+e− collision data at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data samples are primarily used for the study of excited charmonium and charmoniumlike states. By analyzing the di-muon process e+e−→(γISR/FSR)μ+μ−, we measure the center-of-mass energies of the data samples with a precision of 0.6 MeV. Through a run-by-run study, we find that the center-of-mass energies were stable throughout most of the data-taking period.
Based on (2712.4±14.3)×106 ψ(3686) events, we investigate four hadronic decay modes of the P-wave charmonium spin-singlet state hc(1P1)→h+h−π0/η (h=π or K) via the process ψ(3686)→π0hc at BESIII. The hc→π+π−π0 decay is observed with a significance of 9.6σ after taking into account systematic uncertainties. Evidences for hc→K+K−π0 and hc→K+K−η are found with significances of 3.5σ and 3.3σ, respectively, after considering the systematic uncertainties. The branching fractions of these decays are measured to be B(hc→π+π−π0)=(1.36±0.16±0.14)×10−3, B(hc→K+K−π0)=(3.26±0.84±0.36)×10−4, and B(hc→K+K−η)=(3.13±1.08±0.38)×10−4, where the first uncertainties are statistical and the second are systematic. No significant signal of hc→π+π−η is found, and the upper limit of its decay branching fraction is determined to be B(hc→π+π−η)<4.0×10−4 at 90% confidence level.
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.
By analyzing an electron-positron collision data sample corresponding to an integrated luminosity of 2.93 fb−1 taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, we obtain for the first time the absolute branching fractions for seven 𝐷0 and 𝐷+ hadronic decay modes and search for the hadronic decay 𝐷0→𝐾0𝑆𝐾0𝑆𝜋0 with much improved sensitivity. The results are ℬ(𝐷0→𝐾0𝑆𝜋0𝜋0𝜋0)=(7.64±0.30±0.29)×10−3, (𝐷0→𝐾−𝜋+𝜋0𝜋0𝜋0)=9.54±0.30±0.31)×10−3, ℬ(𝐷0→𝐾0𝑆𝜋+𝜋−𝜋0𝜋0)=(12.66±0.45±0.43)×10−3, ℬ(𝐷+→𝐾0𝑆𝜋+𝜋0𝜋0)=(29.04±0.62±0.87)×10−3, ℬ(𝐷+→𝐾0𝑆𝜋+𝜋+𝜋−𝜋0)=(15.28±0.57±0.60)×10−3, ℬ(𝐷+→𝐾0𝑆𝜋+𝜋0𝜋0𝜋0)=(5.54±0.44±0.32)×10−3, ℬ(𝐷+→𝐾−𝜋+𝜋+𝜋0𝜋0)=(4.95±0.26±0.19)×10−3, and ℬ(𝐷0→𝐾0𝑆𝐾0𝑆𝜋0)<1.45×10−4 at the 90% confidence level. Here, the first uncertainties are statistical, and the second ones are systematic. The newly studied decays greatly enrich the knowledge of the 𝐷→¯𝐾𝜋𝜋𝜋 and 𝐷→¯𝐾𝜋𝜋𝜋𝜋 hadronic decays and open a bridge to access more two-body hadronic 𝐷 decays containing scalar, vector, axial, and tensor mesons in the charm sector.
Using data samples collected with the BESIII detector operating at the BEPCII storage ring, the cross section of the inclusive process e+e−→η+X, normalized by the total cross section of e+e−→hadrons, is measured at eight center-of-mass energy points from 2.0000 GeV to 3.6710 GeV. These are the first measurements with momentum dependence in this energy region. Our measurement shows a significant discrepancy from calculations with the existing fragmentation functions. To address this discrepancy, a new QCD analysis is performed at the next-to-next-to-leading order with hadron mass corrections and higher twist effects, which can explain both the established high-energy data and our measurements reasonably well.
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%.
Using 2.93 fb−1 of 𝑒+𝑒− collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector, we report the first measurements of the absolute branching fractions of 14 hadronic 𝐷0(+) decays to exclusive final states with an 𝜂, e.g., 𝐷0→𝐾−𝜋+𝜂, 𝐾0𝑆𝜋0𝜂, 𝐾+𝐾−𝜂, 𝐾0𝑆𝐾0𝑆𝜂, 𝐾−𝜋+𝜋0𝜂, 𝐾0𝑆𝜋+𝜋−𝜂, 𝐾0𝑆𝜋0𝜋0𝜂, and 𝜋+𝜋−𝜋0𝜂; 𝐷+→𝐾0𝑆𝜋+𝜂, 𝐾0𝑆𝐾+𝜂, 𝐾−𝜋+𝜋+𝜂, 𝐾0𝑆𝜋+𝜋0𝜂, 𝜋+𝜋+𝜋−𝜂, and 𝜋+𝜋0𝜋0𝜂. Among these decays, the 𝐷0→𝐾−𝜋+𝜂 and 𝐷+→𝐾0 𝑆𝜋+𝜂 decays have the largest branching fractions, which are ℬ(𝐷0→𝐾−𝜋+𝜂) = (1.853±0.025stat±0.031syst)% and ℬ(𝐷+→𝐾0𝑆𝜋+𝜂) = (1.309±0.037stat±0.031syst)%, respectively. The charge-parity asymmetries for the six decays with highest event yields are determined, and no statistically significant charge-parity violation is found.
We report the first measurements of the absolute branching fractions of D0 → K0 Lϕ, D0 → K0Lη, D0 → K0Lω, and D0 → K0Lη0, by analyzing 2.93 fb−1 of eþe− collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector. Taking the world averages of the branching fractions of D0 → K0Sϕ, D0 → K0Sη, D0 → K0Sω, and D0 → K0Sη0, the K0S − K0L asymmetries RðD0; XÞ in these decay modes are obtained. The CP asymmetries in these decays are also determined. No significant CP violation is observed
With data samples collected with the BESIII detector at seven energy points at √s = 3.68 − 3.71 GeV, corresponding to an integrated luminosity of 333 pb−1, we present a study of the Λ transverse polarization in the e+e− → ΛΛ¯ reaction. The signifcance of polarization by combining the seven energy points is found to be 2.6σ including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the ΛΛ¯ helicity states. The modulus ratio and the relative phase of EM-psionic form factors combined with all energy points are measured to be RΨ = 0.71+0.10−0.10 ± 0.03 and ∆ΦΨ = 23+8.8−8.0 ± 1.6◦, where the frst uncertainties are statistical and the second systematic.
Using e+e− annihilation data sets collected with the BESIII detector, we measure the cross sections of the processes e+e−→e+e− and e+e−→μ+μ− at fifteen center-of-mass energy points in the vicinity of the J/ψ resonance. By a simultaneous fit to the measured, center-of-mass energy dependent cross sections of the two processes, the combined quantities ΓeeΓee/Γtot and ΓeeΓμμ/Γtot are determined to be (0.346±0.009) and (0.335±0.006) keV, respectively, where Γee, Γμμ, and Γtot are the electronic, muonic, and total decay widths of the J/ψ resonance, respectively. Using the resultant ΓeeΓμμ/Γtot and ΓeeΓee/Γtot, the ratio Γee/Γμμ is calculated to be 1.031±0.015, which is consistent with the expectation of lepton universality within about two standard deviations. Assuming lepton universality and using the branching fraction of the J/ψ leptonic decay measured by BESIII in 2013, Γtot and Γll are determined to be (93.0±2.1) and (5.56±0.11) keV, respectively, where Γll is the average leptonic decay width of the J/ψ resonance.
We report new STAR measurements of the single-spin asymmetries 𝐴𝐿 for 𝑊+ and 𝑊− bosons produced in polarized proton-proton collisions at √𝑠=510 GeV as a function of the decay-positron and decay-electron pseudorapidity. The data were obtained in 2013 and correspond to an integrated luminosity of 250 pb−1. The results are combined with previous results obtained with 86 pb−1. A comparison with theoretical expectations based on polarized lepton-nucleon deep-inelastic scattering and prior polarized proton-proton data suggests a difference between the ¯𝑢 and ¯𝑑 quark helicity distributions for 0.05<𝑥<0.25. In addition, we report new results for the double-spin asymmetries 𝐴𝐿𝐿 for 𝑊±, as well as 𝐴𝐿 for 𝑍/𝛾* production and subsequent decay into electron-positron pairs.
We report a measurement of the cross section for the process e+e−→π+π−J/ψ around the X(3872) mass in search for the direct formation of e+e−→X(3872) through the two-photon fusion process. No enhancement of the cross section is observed at the X(3872) peak and an upper limit on the product of electronic width and branching fraction of X(3872)→π+π−J/ψ is determined to be Γee×B(X(3872)→π+π−J/ψ)<7.5×10−3eV at 90% confidence level under an assumption of total width of 1.19±0.21 MeV. This is an improvement of a factor of about 17 compared to the previous limit. Furthermore, using the latest result of B(X(3872)→π+π−J/ψ), an upper limit on the electronic width Γee of X(3872) is obtained to be <0.32eV at the 90% confidence level.
Based on e+e− collision data collected at center-of-mass energies from 2.000 to 3.080 GeV by the BESIII detector at the BEPCII collider, a partial wave analysis isperformed for the process e+e− → K0SK0Lπ0. The results allow the Born cross sections of the process e+e− → K0SK0Lπ0, as well as its subprocesses e+e− → K∗(892)0K¯ 0 and K∗2(1430)0K¯ 0 to be measured. The Born cross sections for e+e− → K0SK0 Lπ 0 are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the process e+e − → K∗(892)0K¯ 0 is consistent with a vector meson state around 2.2 GeV with a signifcance of 3.2σ. A Breit-Wigner ft determines its mass as MY = (2164.7 ± 9.1 ± 3.1) MeV/c2 and its width as ΓY = (32.4 ± 21.0 ± 1.8) MeV.
The process e+e−→pp¯π0 is studied at 20 center-of-mass energies ranging from 2.1000 to 3.0800 GeV using 636.8 pb−1 of data collected with the BESIII detector operating at the BEPCII collider. The Born cross sections for e+e−→pp¯π0 are measured with high precision. Since the lowest center-of-mass energy, 2.1000 GeV, is less than 90 MeV above the pp¯π0 energy threshold, we can probe the threshold behavior for this reaction. However, no anomalous threshold enhancement is found in the cross sections for e+e−→pp¯π0.
Measurement of the e+e−→π+π− cross section between 600 and 900 MeV using initial state radiation
(2016)
We extract the e+e− →π+π− cross section in the energy range between 600 and 900 MeV, exploiting the method of initial state radiation. A data set with an integrated luminosity of 2.93 fb−1 taken at a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider is used. The cross section is measured with a systematic uncertainty of 0.9%. We extract the pion form factor |Fπ|2 as well as the contribution of the measured cross section to the leading-order hadronic vacuum polarization contribution to (g−2)μ. We find this value to be aππ,LO μ (600–900 MeV) = (368.2 ±2.5stat±3.3sys) ·10−10, which is between the corresponding values using the BaBar or KLOE data.
The decays D → K−π+π+π− and D → K−π+π 0 are studied in a sample of quantum-correlated DD¯ pairs produced through the process e+e− → ψ(3770) → DD¯, exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fb−1 . Here D indicates a quantum superposition of a D0 and a D¯ 0 meson. By reconstructing one neutral charm meson in a signal decay, and the other in the same or a different final state, observables are measured that contain information on the coherence factors and average strong-phase differences of each of the signal modes. These parameters are critical inputs in the measurement of the angle γ of the Unitarity Triangle in B− → DK− decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3π = 0.52+0.12−0.10 and RKππ0 = 0.78 ± 0.04, with values for the average strong-phase differences that are δ K3π D = (167+31−19)◦ and δKππ0D = (196+14−15◦ , where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D → K−π+π+π− to yield results that will allow for a more sensitive measurement of γ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6◦.
A measurement of the 𝐶𝑃-even fraction of the decay 𝐷0→𝜋+𝜋−𝜋+𝜋− is performed with a quantum-correlated 𝜓(3770)→𝐷¯𝐷 data sample collected by the BESIII experiment, corresponding to an integrated luminosity of 2.93 fb−1. Using a combination of 𝐶𝑃 eigenstates, 𝐷→𝜋+𝜋−𝜋0 and 𝐷→𝐾0𝑆,𝐿𝜋+𝜋− as tagging modes, the 𝐶𝑃-even fraction is measured to be 𝐹4𝜋+=0.735±0.015±0.005, where the first uncertainty is statistical and the second is systematic. This is the most precise determination of this quantity to date. It provides valuable model-independent input for the measurement of the angle 𝛾 of the Cabibbo-Kobayashi-Maskawa matrix with 𝐵±→𝐷𝐾± decays, and for time-dependent studies of 𝐶𝑃 violation and mixing in the 𝐷0−¯𝐷0 system.
A measurement of the CP-even fraction of the decay D0→π+π−π+π− is performed with a quantum-correlated ψ(3770)→DD¯ data sample collected by the BESIII experiment, corresponding to an integrated luminosity of 2.93 fb−1. Using a combination of CP eigenstates, D→π+π−π0 and D→K0S,Lπ+π− as tagging modes, the CP-even fraction is measured to be F4π+=0.735±0.015±0.005, where the first uncertainty is statistical and the second is systematic. This is the most precise determination of this quantity to date. It provides valuable model-independent input for the measurement of the CKM angle γ with B±→DK± decays, and for time-dependent studies of CP violation and mixing in the D0-D¯0 system.
By analyzing 6.32 fb − 1 of e+ e− annihilation data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we determine the branching fraction of the leptonic decay D + s → τ + ντ, with τ+ → π + π0¯ντ, to be B D + s → τ + ν τ = (5.29 ± 0.25 stat ± 0.20 syst) %. We estimate the product of the Cabibbo-Kobayashi-Maskawa matrix element |Vcs|and the D + s decay constant f D + s to be f D + s|Vcs| = (244.8 ± 5.8 stat ± 4.8syst) MeV, using the known values of the τ + and D + s masses as well as the D + s lifetime, together with our branching fraction measurement. Combining the value of |Vcs| obtained from a global fit in the standard model and f D + s from lattice quantum chromodynamics, we obtain f D + s = (251.6 ± 5.9 stat ± 4.9syst) MeV and |Vcs| = 0.980 ± 0.023 stat ± 0.019 syst. Using the branching fraction of B D + s → μ + νμ = (5.35±0.21)×10−3, we obtain the ratio of the branching fractions B D + s → τ + ντ/B D +s → μ+νμ = 9.89±0.71, which is consistent with the standard model prediction of lepton flavor universality.
The rare decay 𝜂′→𝜋+𝜋−𝑒+𝑒− is studied using a sample of 1.3×109 𝐽/𝜓 events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be (2.42±0.05stat±0.08syst)×10−3. Due to the inclusion of new data, this result supersedes the last BESIII result on this branching fraction. In addition, the 𝐶𝑃-violating asymmetry in the angle between the decay planes of the 𝜋+𝜋−-pair and the 𝑒+𝑒−-pair is investigated. A measurable value would indicate physics beyond the standard model; the result is 𝒜𝐶𝑃=(2.9±3.7stat±1.1syst)%, which is consistent with the standard model expectation of no 𝐶𝑃-violation. The precision is comparable to the asymmetry measurement in the 𝐾0𝐿→𝜋+𝜋−𝑒+𝑒− decay where the observed (14±2)% effect is driven by a standard model mechanism.
The radiative hyperon decay Λ→nγ is studied using (10087±44)×106 J/ψ events collected with the BESIII detector operating at BEPCII. The absolute branching fraction of the decay Λ→nγ is determined with a significance of 5.6σ to be [0.832±0.038(stat.)±0.054(syst.)]×10−3, which lies significantly below the current PDG value. By analyzing the joint angular distribution of the decay products, the first determination of the decay asymmetry αγ is reported with a value of −0.16±0.10(stat.)±0.05(syst.).
The Born cross sections for the process e+e−→η′π+π− at different center-of-mass energies between 2.00 and 3.08~GeV are reported with improved precision from an analysis of data samples collected with the BESIII detector operating at the BEPCII storage ring. An obvious structure is observed in the Born cross section line shape. Fit as a Breit-Wigner resonance, it has a statistical significance of 6.3σ and a mass and width of M=(2108±46±25)~MeV/c2 and Γ=(138±36±30)~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in e+e−→η′π+π− and BESIII in e+e−→ωπ0 within two standard deviations.
The Born cross sections for the process e+e−→η′π+π− at different center-of-mass energies between 2.00 and 3.08~GeV are reported with improved precision from an analysis of data samples collected with the BESIII detector operating at the BEPCII storage ring. An obvious structure is observed in the Born cross section line shape. Fit as a Breit-Wigner resonance, it has a statistical significance of 6.3σ and a mass and width of M=(2108±46±25)~MeV/c2 and Γ=(138±36±30)~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in e+e−→η′π+π− and BESIII in e+e−→ωπ0 within two standard deviations.
The Born cross sections for the process e+e−→η′π+π− at different center-of-mass energies between 2.00 and 3.08 GeV are reported with improved precision from an analysis of data samples collected with the BESIII detector operating at the BEPCII storage ring. An obvious structure is observed in the Born cross section line shape. Fit as a Breit-Wigner resonance, it has a statistical significance of 6.3σ and a mass and width of M=(2111±43±25)~MeV/c2 and Γ=(135±34±30)~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in e+e−→η′π+π− and BESIII in e+e−→ωπ0 within two standard deviations.
he Born cross sections for the process 𝑒+𝑒−→𝜂′𝜋+𝜋− at different center-of-mass energies between 2.00 and 3.08 GeV are reported with improved precision from an analysis of data samples collected with the BESIII detector operating at the BEPCII storage ring. An obvious structure is observed in the Born cross section line shape. Fit as a Breit-Wigner resonance, it has a statistical significance of 6.3𝜎 and a mass and width of 𝑀=(2111±43±25) MeV/𝑐2 and Γ=(135±34±30) MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in 𝑒+𝑒−→𝜂′𝜋+𝜋− and BESIII in 𝑒+𝑒−→𝜔𝜋0 within two standard deviations.
The processes 𝑒+𝑒−→𝐷+ 𝑠𝐷𝑠1(2460)−+c.c. and 𝑒+𝑒−→𝐷*+ 𝑠𝐷𝑠1(2460)−+c.c. are studied for the first time using data samples collected with the BESIII detector at the BEPCII collider. The Born cross sections of 𝑒+𝑒−→𝐷+ 𝑠𝐷𝑠1(2460)−+c.c. at nine center-of-mass energies between 4.467 GeV and 4.600 GeV and those of 𝑒+𝑒−→𝐷*+ 𝑠𝐷𝑠1(2460)−+c.c. at √𝑠=4.590 GeV and 4.600 GeV are measured. No obvious charmonium or charmoniumlike structure is seen in the measured cross sections.
We measure the Born cross section for the reaction e+e−→ηhc from s√=4.129 to 4.600~GeV using data sets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross section line shape near 4.200~GeV is observed with a statistical significance of 7σ. The parameters of this resonance are measured to be \MeasMass\ and \MeasWidth, where the first uncertainties are statistical and the second systematic.
We report new measurements of the branching fraction ℬ(𝐷+𝑠→ℓ+𝜈), where ℓ+ is either 𝜇+ or 𝜏+(→𝜋+¯𝜈𝜏), based on 6.32 fb−1 of electron-positron annihilation data collected by the BESIII experiment at six center-of-mass energy points between 4.178 and 4.226 GeV. Simultaneously floating the 𝐷+𝑠→𝜇+𝜈𝜇 and 𝐷+𝑠→𝜏+𝜈𝜏 components yields ℬ(𝐷+𝑠→𝜏+𝜈𝜏)=(5.21±0.25±0.17)×10−2, ℬ(𝐷+𝑠→𝜇+𝜈𝜇)=(5.35±0.13±0.16)×10−3, and the ratio of decay widths 𝑅=Γ(𝐷+𝑠→𝜏+𝜈𝜏)Γ(𝐷+𝑠→𝜇+𝜈𝜇)=9.73+0.61−0.58±0.36, where the first uncertainties are statistical and the second systematic. No evidence of 𝐶𝑃 asymmetry is observed in the decay rates 𝐷±𝑠→𝜇±𝜈𝜇 and 𝐷±𝑠→𝜏±𝜈𝜏: 𝐴𝐶𝑃(𝜇±𝜈)=(−1.2±2.5±1.0)% and 𝐴𝐶𝑃(𝜏±𝜈)=(+2.9±4.8±1.0)%. Constraining our measurement to the Standard Model expectation of lepton universality (𝑅=9.75), we find the more precise results ℬ(𝐷+𝑠→𝜏+𝜈𝜏)=(5.22±0.10±0.14)×10−2 and 𝐴𝐶𝑃(𝜏±𝜈𝜏)=(−0.1±1.9±1.0)%. Combining our results with inputs external to our analysis, we determine the 𝑐→¯𝑠 quark mixing matrix element, 𝐷+𝑠 decay constant, and ratio of the decay constants to be |𝑉𝑐𝑠|=0.973±0.009±0.014, 𝑓𝐷+𝑠=249.9±2.4±3.5 MeV, and 𝑓𝐷+𝑠/𝑓𝐷+=1.232±0.035, respectively.
The Cabbibo-favored decay Λ+c→Ξ0K+π0 is studied for the first time using 6.1 fb−1 of e+e− collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay Λ+c→Ξ0K+π0 is measured to be (7.79±1.46±0.71)×10−3, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Λ+c→Ξ(1530)0K+ is (5.99±1.04±0.29)×10−3, which is consistent with the previous result of (5.02±0.99±0.31)×10−3. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Λ+c→nK+π0 is 7.1×10−4 at the 90% confidence level. The upper limits on the branching fractions of Λ+c→Σ0K+π0 and ΛK+π0 are also determined to be 1.8×10−3 and 2.0×10−3, respectively.
The Cabbibo-favored decay Λ+c→Ξ0K+π0 is studied for the first time using 6.1 fb−1 of e+e− collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay Λ+c→Ξ0K+π0 is measured to be (7.79±1.46±0.71)×10−3, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Λ+c→Ξ(1530)0K+ is (5.99±1.04±0.29)×10−3, which is consistent with the previous result of (5.02±0.99±0.31)×10−3. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Λ+c→nK+π0 is 7.1×10−4 at the 90% confidence level. The upper limits on the branching fractions of Λ+c→Σ0K+π0 and ΛK+π0 are also determined to be 1.8×10−3 and 2.0×10−3, respectively.
The Cabbibo-favored decay Λ+c→Ξ0K+π0 is studied for the first time using 6.1 fb−1 of e+e− collision data at center-of-mass energies between 4.600 and 4.840 GeV, collected with the BESIII detector at the BEPCII collider. With a double-tag method, the branching fraction of the three-body decay Λ+c→Ξ0K+π0 is measured to be (7.79±1.46±0.71)×10−3, where the first and second uncertainties are statistical and systematic, respectively. The branching fraction of the two-body decay Λ+c→Ξ(1530)0K+ is (5.99±1.04±0.29)×10−3, which is consistent with the previous result of (5.02±0.99±0.31)×10−3. In addition, the upper limit on the branching fraction of the doubly Cabbibo-suppressed decay Λ+c→nK+π0 is 7.1×10−4 at the 90% confidence level. The upper limits on the branching fractions of Λ+c→Σ0K+π0 and ΛK+π0 are also determined to be 1.8×10−3 and 2.0×10−3, respectively.
We measure the inclusive semielectronic decay branching fraction of the D+s meson. A double-tag technique is applied to e+e− annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range 4.178–4.230 GeV. We select positrons fromD+s→Xe+νe with momenta greater than 200 MeV/c and determine the laboratory momentum spectrum, accounting for the effects of detector efficiency and resolution. The total positron yield and semielectronic branching fraction are determined by extrapolating this spectrum below the momentum cutoff. We measure the D+s semielectronic branching fraction to be(6.30±0.13(stat.)±0.09(syst.)±0.04(ext.))%, showing no evidence for unobserved exclusive semielectronic modes. We combine this result with external data taken from literature to determine the ratio of the D+s and D0 semielectronic widths, Γ(D+s→Xe+νe)Γ(D0→Xe+νe)=0.790±0.016(stat.)±0.011(syst.)±0.016(ext.). Our results are consistent with and more precise than previous measurements.
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).
Using 2.93 fb−1 of 𝑒+𝑒− collision data taken at a center-of-mass energy of 3.773 GeV by the BESIII detector at the BEPCII, we measure the branching fractions of the singly Cabibbo-suppressed decays 𝐷→𝜔𝜋𝜋 to be ℬ(𝐷0→𝜔𝜋+𝜋−)=(1.33±0.16±0.12)×10−3 and ℬ(𝐷+→𝜔𝜋+𝜋0)=(3.87±0.83±0.25)×10−3, where the first uncertainties are statistical and the second ones systematic. The statistical significances are 12.9𝜎 and 7.7𝜎, respectively. The precision of ℬ(𝐷0→𝜔𝜋+𝜋−) is improved by a factor of 2.1 over prior measurements, and ℬ(𝐷+→𝜔𝜋+𝜋0) is measured for the first time. No significant signal for 𝐷0→𝜔𝜋0𝜋0 is observed, and the upper limit on the branching fraction is ℬ(𝐷0→𝜔𝜋0𝜋0)<1.10×10−3 at the 90% confidence level. The branching fractions of 𝐷→𝜂𝜋𝜋 are also measured and consistent with existing results.
The electromagnetic process is studied with the initial-state-radiation technique using 7.5 fb−1 of data collected by the BESIII experiment at seven energy points from 3.773 to 4.600 GeV. The Born cross section and the effective form factor of the proton are measured from the production threshold to 3.0 GeV/ using the invariant-mass spectrum. The ratio of electric and magnetic form factors of the proton is determined from the analysis of the proton-helicity angular distribution.
The transverse momentum (pT) spectrum and nuclear modification factor (RAA) of reconstructed jets in 0–10% and 10–30% central Pb–Pb collisions at √sNN = 2.76 TeV were measured. Jets were reconstructed using the anti-kT jet algorithm with a resolution parameter of R = 0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet pT spectra are reported in the pseudorapidity interval of |ηjet| < 0.5 for 40 < pT, jet < 120 GeV/c in 0–10% and for 30 < pT, jet < 100 GeV/c in 10–30% collisions. Reconstructed jets were required to contain a leading charged particle with pT > 5 GeV/c to suppress jets constructed from the combinatorial background in Pb–Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb–Pb collisions had a negligible effect on the RAA. The nuclear modification factor RAA was found to be 0.28 ± 0.04 in 0–10% and 0.35 ± 0.04 in 10–30% collisions, independent of pT, jet within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching.
The integrated luminosities of data samples collected in the BESIII experiment in 2016–2017 at center-of-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events. The integrated luminosities of old datasets collected in 2010–2014 are updated by considering corrections related to detector performance, offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter, which can haphazardly occur.
The integrated luminosities of the data samples collected in the BESIII experiment in 2016--2017 at center-of-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events. The integrated luminosities of the old data sets collected in 2010--2014 are updated by considering correction related to the detector performance, offsettting the effect of newly discovered readout errors in the electromagnetic calorimeter that happen haphazardly.
Measurement of inclusive J/ψ polarization in p + p collisions at √s=200 GeV by the STAR experiment
(2020)
We report on new measurements of inclusive 𝐽/𝜓 polarization at midrapidity in 𝑝+𝑝 collisions at √𝑠=200 GeV by the STAR experiment at the Relativistic Heavy Ion Collider. The polarization parameters, 𝜆𝜃, 𝜆𝜙, and 𝜆𝜃𝜙, are measured as a function of transverse momentum (𝑝T) in both the helicity and Collins-Soper (CS) reference frames within 𝑝T<10 GeV/𝑐. Except for 𝜆𝜃 in the CS frame at the highest measured 𝑝T, all three polarization parameters are consistent with 0 in both reference frames without any strong 𝑝T dependence. Several model calculations are compared with data, and the one using the Color Glass Condensate effective field theory coupled with nonrelativistic QCD gives the best overall description of the experimental results, even though other models cannot be ruled out due to experimental uncertainties.
Measurement of groomed jet substructure observables in p+p collisions at √s = 200 GeV with STAR
(2020)
In this letter, measurements of the shared momentum fraction (zg) and the groomed jet radius (Rg), as defined in the SoftDrop algorithm, are reported in p+p collisions at √s = 200 GeV collected by the STAR experiment. These substructure observables are differentially measured for jets of varying resolution parameters from R = 0.2 − 0.6 in the transverse momentum range 15 < pT,jet < 60 GeV/c. These studies show that, in the pT,jet range accessible at √s = 200 GeV and with increasing jet resolution parameter and jet transverse momentum, the zg distribution asymptotically converges to the DGLAP splitting kernel for a quark radiating a gluon. The groomed jet radius measurements reflect a momentum-dependent narrowing of the jet structure for jets of a given resolution parameter, i.e., the larger the pT,jet, the narrower the first splitting. For the first time, these fully corrected measurements are compared to Monte Carlo generators with leading order QCD matrix elements and leading log in the parton shower, and to state-of-the-art theoretical calculations at next-to-leading-log accuracy. We observe that PYTHIA 6 with parameters tuned to reproduce RHIC measurements is able to quantitatively describe data, whereas PYTHIA 8 and HERWIG 7, tuned to reproduce LHC data, are unable to provide a simultaneous description of both zg and Rg, resulting in opportunities for fine parameter tuning of these models for p+p collisions at RHIC energies. We also find that the theoretical calculations without non-perturbative corrections are able to qualitatively describe the trend in data for jets of large resolution parameters at high pT,jet, but fail at small jet resolution parameters and low jet transverse momenta.
The cross sections of the 𝑒+𝑒−→𝜙𝜂′ process at center-of-mass energies from 3.508 to 4.951 GeV are measured with high precision using 26.1 fb−1 data collected with the BESIII detector operating at the BEPCII storage ring. The cross sections are of the order of a few picobarn and decrease as the center-of-mass energy increases as 𝑠−𝑛/2 with 𝑛=4.35±0.14. This result is in agreement with the Nambu-Jona-Lasinio model prediction of 𝑛=3.5±0.9. In addition, the charmless decay 𝜓(3770)→𝜙𝜂′ is searched for by fitting the measured cross sections, yet no significant signal is observed. The upper limit of ℬ(𝜓(3770)→𝜙𝜂′) at the 90% confidence level is determined to be 2.3×10−5.
The Born cross sections for the process e+e−→ωη′ are measured at 22 center-of-mass energies from 2.000 to 3.080 GeV using data collected with the BESIII detector at the BEPCII collider. A resonant structure is observed with a statistical significance of 9.6σ. A Breit-Wigner fit determines its mass to be MR=(2153±30±31) MeV/c2 and its width to be ΓR=(167±77±7) MeV, where the first uncertainties are statistical and the second are systematic.
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.
We report a new measurement of the production of electrons from open heavy-flavor hadron decays (HFEs) at mid-rapidity (|y| < 0.7) in Au+Au collisions at √sNN = 200 GeV. Invariant yields of HFEs are measured for the transverse momentum range of 3.5 < pT < 9 GeV/c in various configurations of the collision geometry. The HFE yields in head-on Au+Au collisions are suppressed by approximately a factor of 2 compared to that in p + p collisions scaled by the average number of binary collisions, indicating strong interactions between heavy quarks and the hot and dense medium created in heavy-ion collisions. Comparison of these results with models provides additional tests of theoretical calculations of heavy quark energy loss in the quark-gluon plasma.