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By using 6.32 fbโ1 of data collected with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, we perform an amplitude analysis of the decay D+s ! K0S +โ0 and determine the relative fractions and phase differences of different intermediate processes, which include K0S (770)+, K0S (1450)+, Kโ(892)0โ+, Kโ(892)+โ0, and Kโ(1410)0โ+. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be B(D+s ! K0S +โ0) = (5.43 ยฑ 0.30stat ยฑ 0.15syst) ร 10โ3.
Using 10.1 ร 109 J/ฯ events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy โs = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/ฯ โ Dโe+ฮฝe + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction B(J/ฯ โ Dโe +ฮฝe + c.c.) < 7.1 ร 10โ8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.
Based on an e+eโ collision data sample corresponding to an integrated luminosity of 2.93 fbโ1 collected with the BESIII detector at โs=3.773 GeV, the first amplitude analysis of the singly Cabibbo-suppressed decay D+โK+K0Sฯ0 is performed. From the amplitude analysis, the Kโ(892)+K0S component is found to be dominant with a fraction of (57.1ยฑ2.6ยฑ4.2)%, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction B(D+โK+K0Sฯ0) measured by BESIII, we obtain B(D+โKโ(892)+K0S)=(8.69ยฑ0.40ยฑ0.64ยฑ0.51)ร10โ3, where the third uncertainty is due to the branching fraction B(D+โK+K0Sฯ0). The precision of this result is significantly improved compared to the previous measurement. This result also differs from most of theoretical predictions by about 4ฯ, which may help to improve the understanding of the dynamics behind.
Using a sample of (10.09ยฑ0.04)ร109 J/ฯ events collected with the BESIII detector, a partial wave analysis of J/ฯโฮณฮทโฒฮทโฒ is performed.The masses and widths of the observed resonances and their branching fractions are reported. The main contribution is from J/ฯโฮณf0(2020) with f0(2020)โฮทโฒฮทโฒ, which is found with a significance of greater than 25ฯ. The product branching fraction B(J/ฯ โ ฮณf0(2020))โ
B(f0(2020) โ ฮทโฒฮทโฒ is measured to be (2.63ยฑ0.06(stat.) + 0.31โ0.46(syst.))ร10โ4.
We present the first experimental search for the rare charm decay D0โฯ0ฮฝยฏฮฝ. It is based on an e+eโ collision sample consisting of 10.6ร10^6 pairs of D0ยฏD0 mesons collected by the BESIII detector at โs=3.773 GeV, corresponding to an integrated luminosity of 2.93 fb^โ1. A data-driven method is used to ensure the reliability of the background modeling. No significant D0โฯ0ฮฝยฏฮฝ signal is observed in data and an upper limit of the branching fraction is set to be 2.1ร10^-4 at the 90% confidence level. This is the first experimental constraint on charmed-hadron decays into dineutrino final states.
Study of the process eโบeโปโโโฯโฐฯโฐJ/ฯ and neutral charmoniumlike state Zc(3900)โฐ
(2020)
Cross sections of the process ๐+โข๐โโ๐0โข๐0โข๐ฝ/๐ at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4โโfbโ1 of data samples collected with the BESIII detector operating at the BEPCII collider facility. A fit to the measured energy-dependent cross sections confirms the existence of the charmoniumlike state ๐โก(4220). The mass and width of the ๐โก(4220) are determined to be (4220.4ยฑ2.4ยฑ2.3) MeV/๐2 and (46.2ยฑ4.7ยฑ2.1)โโMeV, respectively, where the first uncertainties are statistical and the second systematic. The mass and width are consistent with those measured in the process ๐+โข๐โโ๐+โข๐โโข๐ฝ/๐. The neutral charmonium-like state ๐๐โข(3900)0 is observed prominently in the ๐0โข๐ฝ/๐ invariant-mass spectrum, and, for the first time, an amplitude analysis is performed to study its properties. The spin-parity of ๐๐โข(3900)0 is determined to be ๐ฝ๐=1+, and the pole position is (3893.1ยฑ2.2ยฑ3.0)โ๐โข(22.2ยฑ2.6ยฑ7.0)โโMeV/๐2, which is consistent with previous studies of electrically charged ๐๐โข(3900)ยฑ. In addition, cross sections of ๐+โข๐โ โ ๐0โข๐๐โข(3900)0 โ ๐0โข๐0โข๐ฝ/๐ are extracted, and the corresponding line shape is found to agree with that of the ๐โก(4220).
We report the first observation of the semimuonic decay ๐ท+โ๐โข๐+โข๐๐ using an ๐+โข๐โ collision data sample corresponding to an integrated luminosity of 2.93โโfbโ1 collected with the BESIII detector at a center-of-mass energy of 3.773 GeV. The absolute branching fraction of the ๐ท+โ๐โข๐+โข๐๐ decay is measured to be โฌ๐ท+โ๐โข๐+โข๐๐=(17.7ยฑ1.โข8statยฑ1.โข1syst)ร10โ4. Its ratio with the world average value of the branching fraction of the ๐ท+โ๐โข๐+โข๐๐ decay probes lepton flavor universality and it is determined to be โฌ๐ท+โ๐โข๐+โข๐๐/โฌPDG ๐ท+โ๐โข๐+โข๐๐=1.05ยฑ0.14, in agreement with the standard model expectation within one standard deviation.
Using 2.93โโfbโ1 of ๐+โข๐โ collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay ๐ท+โ๐พ+โข๐+โข๐โโข๐0 is reported. After removing decays that contain narrow intermediate resonances, including ๐ท+โ๐พ+โข๐, ๐ท+โ๐พ+โข๐, and ๐ท+โ๐พ+โข๐, the branching fraction of the decay ๐ท+โ๐พ+โข๐+โข๐โโข๐0 is measured to be (1.13ยฑ0.0โข8statยฑ0.0โข3syst)ร10โ3. The ratio of branching fractions of ๐ท+โ๐พ+โข๐+โข๐โโข๐0 over ๐ท+โ๐พโโข๐+โข๐+โข๐0 is found to be (1.81ยฑ0.15)%, which corresponds to (6.28ยฑ0.52)โขtan4โก๐๐ถ, where ๐๐ถ is the Cabibbo mixing angle. This ratio is significantly larger than the corresponding ratios for other doubly Cabibbo-suppressed decays. The asymmetry of the branching fractions of charge-conjugated decays ๐ทยฑโ๐พยฑโข๐ยฑโข๐โโข๐0 is also determined, and no evidence for ๐ถโข๐ violation is found. In addition, the first evidence for the ๐ท+โ๐พ+โข๐ decay, with a statistical significance of 3.3โข๐, is presented and the branching fraction is measured to be โฌโก(๐ท+โ๐พ+โข๐) = (5.โข7+2.5โ2.1statยฑ0.โข2syst)ร10โ5.
The processes ๐+โข๐โโ๐ท+ ๐ โข๐ท๐ โข1โข(2460)โ+c.c. and ๐+โข๐โโ๐ท*+ ๐ โข๐ท๐ โข1โข(2460)โ+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 ๐+โข๐โโ๐ท+ ๐ โข๐ท๐ โข1โข(2460)โ+c.c. at nine center-of-mass energies between 4.467 GeV and 4.600 GeV and those of ๐+โข๐โโ๐ท*+ ๐ โข๐ท๐ โข1โข(2460)โ+c.c. at โ๐ =4.590โโGeV and 4.600 GeV are measured. No obvious charmonium or charmoniumlike structure is seen in the measured cross sections.
By analyzing a data sample corresponding to an integrated luminosity of 2.93โโfbโ1 collected at a center-of-mass energy of 3.773 GeV with By analyzing a data sample corresponding to an integrated luminosity of 2.93โโfbโ1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure for the first time the absolute branching fraction of the ๐ท+โ๐โข๐+โข๐๐ decay to be โฌ๐ท+โ๐โข๐+โข๐๐=(10.4ยฑ1.โข0statยฑ0.โข5syst)ร10โ4. Using the world averaged value of โฌ๐ท+โ๐โข๐+โข๐๐, the ratio of the two branching fractions is determined to be โฌ๐ท+โ๐โข๐+โข๐๐/โฌ๐ท+โ๐โข๐+โข๐๐=0.91ยฑ0.13(stat+syst), which agrees with the theoretical expectation of lepton flavor universality within uncertainty. By studying the differential decay rates in five four-momentum transfer intervals, we obtain the product of the hadronic form factor ๐๐+โก(0) and the ๐โ๐ Cabibbo-Kobayashi-Maskawa matrix element |๐๐โข๐| to be ๐๐+โก(0)โข|๐๐โข๐|=0.087ยฑ0.00โข8statยฑ0.00โข2syst. Taking the input of |๐๐โข๐| from the global fit in the standard model, we determine ๐๐+โก(0)=0.39ยฑ0.0โข4statยฑ0.0โข1syst. On the other hand, using the value of ๐๐+โก(0) calculated in theory, we find |๐๐โข๐| = 0.242ยฑ0.02โข2statยฑ0.00โข6systยฑ0.03โข3theory.
By analyzing an electron-positron collision data sample corresponding to an integrated luminosity of 2.93โโfbโ1 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 ๐ท0 and ๐ท+ hadronic decay modes and search for the hadronic decay ๐ท0โ๐พ0๐โข๐พ0๐โข๐0 with much improved sensitivity. The results are โฌโก(๐ท0โ๐พ0๐โข๐0โข๐0โข๐0)=(7.64ยฑ0.30ยฑ0.29)ร10โ3, โก(๐ท0โ๐พโโข๐+โข๐0โข๐0โข๐0)=9.54ยฑ0.30ยฑ0.31)ร10โ3, โฌโก(๐ท0โ๐พ0๐โข๐+โข๐โโข๐0โข๐0)=(12.66ยฑ0.45ยฑ0.43)ร10โ3, โฌโก(๐ท+โ๐พ0๐โข๐+โข๐0โข๐0)=(29.04ยฑ0.62ยฑ0.87)ร10โ3, โฌโก(๐ท+โ๐พ0๐โข๐+โข๐+โข๐โโข๐0)=(15.28ยฑ0.57ยฑ0.60)ร10โ3, โฌโก(๐ท+โ๐พ0๐โข๐+โข๐0โข๐0โข๐0)=(5.54ยฑ0.44ยฑ0.32)ร10โ3, โฌโก(๐ท+โ๐พโโข๐+โข๐+โข๐0โข๐0)=(4.95ยฑ0.26ยฑ0.19)ร10โ3, and โฌโก(๐ท0โ๐พ0๐โข๐พ0๐โข๐0)<1.45ร10โ4 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 ๐ทโยฏ๐พโข๐โข๐โข๐ and ๐ทโยฏ๐พโข๐โข๐โข๐โข๐ hadronic decays and open a bridge to access more two-body hadronic ๐ท decays containing scalar, vector, axial, and tensor mesons in the charm sector.
The process e+eโโฯฮท is studied at 22 center-of-mass energy points (โs) between 2.00 and 3.08 GeV using 715โโpbโ1 of data collected with the BESIII detector. The measured Born cross section of e+eโโฯฮท is found to be consistent with BABAR measurements, but with improved precision. A resonant structure around 2.175 GeV is observed with a significance of 6.9ฯ with mass (2163.5ยฑ6.2ยฑ3.0)โโMeV/c2 and width (31.1+21.1โ11.6ยฑ1.1)โโMeV, where the first uncertainties are statistical and the second are systematic.
The electromagnetic process is studied with the initial-state-radiation technique using 7.5 fbโ1 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.
Measurement of the branching fraction of leptonic decay D+s โ ฯ+ฮฝฯ via ฯ+ โ ฯ+ฯ0ยฏฮฝฯ
(2021)
By analyzing 6.32 fb โ 1 of e+ eโ 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 โ ฯ + ฮฝฯ, with ฯ+ โ ฯ + ฯ0ยฏฮฝฯ, to be B D + s โ ฯ + ฮฝ ฯ = (5.29 ยฑ 0.25 stat ยฑ 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 ยฑ 5.8 stat ยฑ 4.8syst) MeV, using the known values of the ฯ + 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 ยฑ 5.9 stat ยฑ 4.9syst) MeV and |Vcs| = 0.980 ยฑ 0.023 stat ยฑ 0.019 syst. Using the branching fraction of B D + s โ ฮผ + ฮฝฮผ = (5.35ยฑ0.21)ร10โ3, we obtain the ratio of the branching fractions B D + s โ ฯ + ฮฝฯ/B D +s โ ฮผ+ฮฝฮผ = 9.89ยฑ0.71, which is consistent with the standard model prediction of lepton flavor universality.
We report an amplitude analysis and branching fraction measurement of ๐ท+
๐ โ๐พ+โข๐พโโข๐+ decay using a data sample of 3.19โโfbโ1 recorded with BESIII detector at a center-of-mass energy of 4.178 GeV. We perform a model-independent partial wave analysis in the low ๐พ+โข๐พโ mass region to determine the ๐พ+โข๐พโ S-wave line shape, followed by an amplitude analysis of our very pure high-statistics sample. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be โฌโก(๐ท+๐ โ๐พ+โข๐พโโข๐+)=(5.47ยฑ0.0โข8statยฑ0.1โข3sys)%.
Using 2.93โโfbโ1 of ๐+โข๐โ 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 ๐ทโ๐โข๐โข๐ to be โฌโก(๐ท0โ๐โข๐+โข๐โ)=(1.33ยฑ0.16ยฑ0.12)ร10โ3 and โฌโก(๐ท+โ๐โข๐+โข๐0)=(3.87ยฑ0.83ยฑ0.25)ร10โ3, where the first uncertainties are statistical and the second ones systematic. The statistical significances are 12.9โข๐ and 7.7โข๐, respectively. The precision of โฌโก(๐ท0โ๐โข๐+โข๐โ) is improved by a factor of 2.1 over prior measurements, and โฌโก(๐ท+โ๐โข๐+โข๐0) is measured for the first time. No significant signal for ๐ท0โ๐โข๐0โข๐0 is observed, and the upper limit on the branching fraction is โฌโก(๐ท0โ๐โข๐0โข๐0)<1.10ร10โ3 at the 90% confidence level. The branching fractions of ๐ทโ๐โข๐โข๐ are also measured and consistent with existing results.
Study of the process eโบeโปโโโฯโฐฯโฐJ/ฯ and neutral charmoniumlike state Zc(3900)โฐ
(2020)
Cross sections of the process ๐+โข๐โโ๐0โข๐0โข๐ฝ/๐ at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4โโfbโ1 of data samples collected with the BESIII detector operating at the BEPCII collider facility. A fit to the measured energy-dependent cross sections confirms the existence of the charmoniumlike state ๐โก(4220). The mass and width of the ๐โก(4220) are determined to be (4220.4ยฑ2.4ยฑ2.3) MeV/๐2 and (46.2ยฑ4.7ยฑ2.1)โโMeV, respectively, where the first uncertainties are statistical and the second systematic. The mass and width are consistent with those measured in the process ๐+โข๐โโ๐+โข๐โโข๐ฝ/๐. The neutral charmonium-like state ๐๐โข(3900)0 is observed prominently in the ๐0โข๐ฝ/๐ invariant-mass spectrum, and, for the first time, an amplitude analysis is performed to study its properties. The spin-parity of ๐๐โข(3900)0 is determined to be ๐ฝ๐=1+, and the pole position is (3893.1ยฑ2.2ยฑ3.0)โ๐โข(22.2ยฑ2.6ยฑ7.0)โโMeV/๐2, which is consistent with previous studies of electrically charged ๐๐โข(3900)ยฑ. In addition, cross sections of ๐+โข๐โ โ ๐0โข๐๐โข(3900)0 โ ๐0โข๐0โข๐ฝ/๐ are extracted, and the corresponding line shape is found to agree with that of the ๐โก(4220).
Using (10.087ยฑ0.044)ร109โโ๐ฝ/๐ events collected by the Beijing Spectrum III (BESIII) detector at the Beijing Electron Positron Collider II (BEPCII) collider, we search for the hyperon semileptonic decay ฮโโฮ0โข๐โโขยฏ๐๐. No significant signal is observed and the upper limit on the branching fraction โฌโก(ฮโโฮ0โข๐โโขยฏ๐๐) is set to be 2.59ร10โ4 at 90% confidence level. This result is one order of magnitude more strict than the previous best limit.
We report a study of the processes of ๐+โข๐โโ๐พ+โข๐ทโ๐ โข๐ท*0 and ๐พ+โข๐ท*โ๐ โข๐ท0 based on ๐+โข๐โ annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7โโfbโ1. An excess of events over the known contributions of the conventional charmed mesons is observed near the ๐ทโ๐ โข๐ท*0 and ๐ท*โ๐ โข๐ท0 mass thresholds in the ๐พ+ recoil-mass spectrum for events collected at โ๐ =4.681โโGeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5+1.8
โ2.6ยฑ2.1)โโMeV/๐2 and (12.8+5.3โ4.4ยฑ3.0)โโMeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3โโ๐ over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into ๐ทโ๐ โข๐ท*0 and ๐ท*โ๐ โข๐ท0. However, the properties of the excess need further exploration with more statistics.
he Born cross sections for the process ๐+โข๐โโ๐โฒโข๐+โข๐โ 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 6.3โข๐ and a mass and width of ๐=(2111ยฑ43ยฑ25)โโMeV/๐2 and ฮ=(135ยฑ34ยฑ30)โโMeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in ๐+โข๐โโ๐โฒโข๐+โข๐โ and BESIII in ๐+โข๐โโ๐โข๐0 within two standard deviations.