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Observation of the doubly Cabibbo-suppressed decays DβΊ β KβΊΟβ°Οβ° and DβΊ β KβΊΟβ°Ξ·
(2022)
By analyzing e+eβ annihilation data corresponding to an integrated luminosity of 2.93fbβ1 collected at the center-of-mass energy of 3.773\,GeV with the BESIII detector, we report the first observations of the doubly Cabibbo-suppressed decays D+βK+Ο0Ο0 and D+βK+Ο0Ξ·. The branching fractions of D+βK+Ο0Ο0 and D+βK+Ο0Ξ· are measured to be (2.1Β±0.4statΒ±0.1syst)Γ10β4 and (2.1Β±0.5statΒ±0.1syst)Γ10β4 with statistical significances of 8.8Ο and 5.5Ο, respectively. In addition, we search for the subprocesses D+βKβ(892)+Ο0 and D+βKβ(892)+Ξ· with Kβ(892)+βK+Ο0. The branching fraction of D+βKβ(892)+Ξ· is determined to be (4.4+1.8β1.5statΒ±0.2syst)Γ10β4, with a statistical significance of 3.2Ο. No significant signal for D+βKβ(892)+Ο0 is found and we set an upper limit on the branching fraction of this decay at the 90\% confidence level to be 5.4Γ10β4.
Utilizing the data set corresponding to an integrated luminosity of 3.19 fbβ1 collected by the BESIII detector at a center-of-mass energy of 4.178 GeV, we perform an amplitude analysis of the D+sβΟ+ΟβΟ+ decay. The sample contains 13,797 candidate events with a signal purity of βΌ80%. We use a quasi-model-independent approach to measure the magnitude and phase of the D+sβΟ+ΟβΟ+ decay, where the P and D waves are parameterized by a sum of three Breit-Wigner amplitudes Ο(770)0, Ο(1450)0, and f2(1270). The fit fractions of different decay channels are also reported.
Utilizing the data set corresponding to an integrated luminosity of 3.19 fbβ1 collected by the BESIII detector at a center-of-mass energy of 4.178 GeV, we perform an amplitude analysis of the D+sβΟ+ΟβΟ+ decay. The sample contains 13,797 candidates with a signal purity of βΌ80%. The amplitude and phase of the contributing ΟΟ S wave are measured based on a quasi-model-independent approach, along with the amplitudes and phases of the P and D waves parametrized by Breit-Wigner models. The fit fractions of different intermediate decay channels are also reported.
Observation of the doubly Cabibbo-suppressed decays DβΊ β KβΊΟβ°Οβ° and DβΊ β KβΊΟβ°Ξ·
(2022)
By analyzing e+eβ annihilation data corresponding to an integrated luminosity of 2.93fbβ1 collected at the center-of-mass energy of 3.773\,GeV with the BESIII detector, we report the first observations of the doubly Cabibbo-suppressed decays D+βK+Ο0Ο0 and D+βK+Ο0Ξ·. The branching fractions of D+βK+Ο0Ο0 and D+βK+Ο0Ξ· are measured to be (2.1Β±0.4statΒ±0.1syst)Γ10β4 and (2.1Β±0.5statΒ±0.1syst)Γ10β4 with statistical significances of 8.8Ο and 5.5Ο, respectively. In addition, we search for the subprocesses D+βKβ(892)+Ο0 and D+βKβ(892)+Ξ· with Kβ(892)+βK+Ο0. The branching fraction of D+βKβ(892)+Ξ· is determined to be (4.4+1.8β1.5statΒ±0.2syst)Γ10β4, with a statistical significance of 3.2Ο. No significant signal for D+βKβ(892)+Ο0 is found and we set an upper limit on the branching fraction of this decay at the 90\% confidence level to be 5.4Γ10β4.
Using a sample of (10.09Β±0.04)Γ109 J/Ο events collected with the BESIII detector, a partial wave analysis of J/ΟβΞ³Ξ·β²Ξ·β² is performed.The masses and widths of the observed resonances and their branching fractions are reported. The main contribution is from J/ΟβΞ³f0(2020) with f0(2020)βΞ·β²Ξ·β², which is found with a significance of greater than 25Ο. The product branching fraction B(J/Ο β Ξ³f0(2020))β
B(f0(2020) β Ξ·β²Ξ·β² is measured to be (2.63Β±0.06(stat.) + 0.31β0.46(syst.))Γ10β4.
Using 10.1 Γ 109 J/Ο events produced by the Beijing Electron Positron Collider (BEPCII) at a center-of-mass energy βs = 3.097 GeV and collected with the BESIII detector, we present a search for the rare semi-leptonic decay J/Ο β Dβe+Ξ½e + c.c. No excess of signal above background is observed, and an upper limit on the branching fraction β¬(J/ΟβββDβe+Ξ½eβ+βc. c.)β<β7.1βΓβ10β8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.
We report new measurements of the branching fraction β¬β‘(π·+π ββ+β’π), where β+ is either π+ or π+β‘(βπ+β’Β―ππ), based on 6.32ββfbβ1 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 π·+π βπ+β’ππ and π·+π βπ+β’ππ components yields β¬β‘(π·+π βπ+β’ππ)=(5.21Β±0.25Β±0.17)Γ10β2, β¬β‘(π·+π βπ+β’ππ)=(5.35Β±0.13Β±0.16)Γ10β3, and the ratio of decay widths π
=Ξβ‘(π·+π βπ+β’ππ)Ξβ‘(π·+π βπ+β’ππ)=9.7β’3+0.61β0.58Β±0.36, where the first uncertainties are statistical and the second systematic. No evidence of πΆβ’π asymmetry is observed in the decay rates π·Β±π βπΒ±β’ππ and π·Β±π βπΒ±β’ππ: π΄πΆβ’πβ‘(πΒ±β’π)=(β1.2Β±2.5Β±1.0)% and π΄πΆβ’πβ‘(πΒ±β’π)=(+2.9Β±4.8Β±1.0)%. Constraining our measurement to the Standard Model expectation of lepton universality (π
=9.75), we find the more precise results β¬β‘(π·+π βπ+β’ππ)=(5.22Β±0.10Β±0.14)Γ10β2 and π΄πΆβ’πβ‘(πΒ±β’ππ)=(β0.1Β±1.9Β±1.0)%. Combining our results with inputs external to our analysis, we determine the πβΒ―π quark mixing matrix element, π·+π decay constant, and ratio of the decay constants to be |ππβ’π |=0.973Β±0.009Β±0.014, ππ·+π =249.9Β±2.4Β±3.5ββMeV, and ππ·+π /ππ·+=1.232Β±0.035, respectively.
The decays D β KβΟ+Ο+Οβ and D β KβΟ+Ο 0 are studied in a sample of quantum-correlated DDΒ― pairs produced through the process e+eβ β Ο(3770) β DDΒ―, exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fbβ1 . Here D indicates a quantum superposition of a D0 and a DΒ― 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 Ξ³ of the Unitarity Triangle in Bβ β DKβ decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3Ο = 0.52+0.12β0.10 and RKΟΟ0 = 0.78 Β± 0.04, with values for the average strong-phase differences that are Ξ΄ K3Ο D = (167+31β19)β¦ and Ξ΄KΟΟ0D = (196+14β15β¦ , where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D β KβΟ+Ο+Οβ to yield results that will allow for a more sensitive measurement of Ξ³ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6β¦.
Though immensely successful, the standard model of particle physics does not offer any explanation as to why our Universe contains so much more matter than antimatter. A key to a dynamically generated matterβantimatter asymmetry is the existence of processes that violate the combined charge conjugation and parity (CP) symmetry1. As such, precision tests of CP symmetry may be used to search for physics beyond the standard model. However, hadrons decay through an interplay of strong and weak processes, quantified in terms of relative phases between the amplitudes. Although previous experiments constructed CP observables that depend on both strong and weak phases, we present an approach where sequential two-body decays of entangled multi-strange baryonβantibaryon pairs provide a separation between these phases. Our method, exploiting spin entanglement between the double-strange Ξβ baryon and its antiparticle2 ΞΒ―+
, has enabled a direct determination of the weak-phase difference, (ΞΎPβββΞΎS)β= (1.2βΒ±β3.4βΒ±β0.8)βΓβ10β2βrad. Furthermore, three independent CP observables can be constructed from our measured parameters. The precision in the estimated parameters for a given data sample size is several orders of magnitude greater than achieved with previous methods3. Finally, we provide an independent measurement of the recently debated Ξ decay parameter Ξ±Ξ (refs.β4,5). The ΞΞΒ―
asymmetry is in agreement with and compatible in precision to the most precise previous measurement.
We measure the inclusive semielectronic decay branching fraction of the D+s meson. A double-tag technique is applied to e+eβ annihilation data collected by the BESIII experiment at the BEPCII collider, operating in the center-of-mass energy range 4.178β4.230 GeV. We select positrons fromD+sβXe+Ξ½e 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(6.30Β±0.13(stat.)Β±0.09(syst.)Β±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, Ξ(D+sβXe+Ξ½e)Ξ(D0βXe+Ξ½e)=0.790Β±0.016(stat.)Β±0.011(syst.)Β±0.016(ext.). Our results are consistent with and more precise than previous measurements.
Measurement of the branching fraction of leptonic decay D+s β Ο+Ξ½Ο via Ο+ β Ο+Ο0Β―Ξ½Ο
(2021)
By analyzing 6.32 fb β 1 of e+ eβ 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 β Ο + Ξ½Ο, with Ο+ β Ο + Ο0Β―Ξ½Ο, to be B D + s β Ο + Ξ½ Ο = (5.29 Β± 0.25 stat Β± 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 Β± 5.8 stat Β± 4.8syst) MeV, using the known values of the Ο + 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 Β± 5.9 stat Β± 4.9syst) MeV and |Vcs| = 0.980 Β± 0.023 stat Β± 0.019 syst. Using the branching fraction of B D + s β ΞΌ + Ξ½ΞΌ = (5.35Β±0.21)Γ10β3, we obtain the ratio of the branching fractions B D + s β Ο + Ξ½Ο/B D +s β ΞΌ+Ξ½ΞΌ = 9.89Β±0.71, which is consistent with the standard model prediction of lepton flavor universality.
Using (1310.6Β±7.0)Γ106 π½/π events acquired with the BESIII detector at the BEPCII storage rings, the decay πβ²βπ+β’πββ’π+β’πβ is observed for the first time with a significance of 8β’π via the process π½/πβπΎβ’πβ². We measure the branching fraction of πβ²βπ+β’πββ’π+β’πβ to be β¬β‘(πβ²βπ+β’πββ’π+β’πβ)=(1.97Β±0.33β’(stat)Β±0.19β’(syst))Γ10β5, where the first and second uncertainties are statistical and systematic, respectively
Using data samples collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energies from 4.178 to 4.600 GeV, we study the process eΓΎeβ β Ο0XΓ°3872ΓΞ³ and search for ZcΓ°4020Γ0 β XΓ°3872ΓΞ³. We find no significant signal and set upper limits on ΟΓ°eΓΎeβ β Ο0XΓ°3872ΓΞ³Γ Β· BΓ°XΓ°3872Γ β ΟΓΎΟβJ=ΟΓ and ΟΓ°eΓΎeβ β Ο0ZcΓ°4020Γ0Γ Β· BΓ°ZcΓ°4020Γ0 β XΓ°3872ΓΞ³Γ Β· BΓ°XΓ°3872Γ β ΟΓΎΟβJ=ΟΓ for each energy point at 90% confidence level, which is of the order of several tenths pb.
Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider, we search for the process π+β’πββππβ’πβ’π+β’πβ. The search is performed using five large datasets recorded at center-of-mass energies of 4.23, 4.26, 4.36, 4.42, and 4.60 GeV. The ππ meson is reconstructed in 16 exclusive decay modes. No signal is observed in the ππ mass region at any center-of-mass energy. The upper limits on the reaction cross sections are determined to be 6.2, 10.8, 27.6, 22.6 and 23.7 pb at the 90% confidence level at the center-of-mass energies listed above.
Using a sample of 1.31Γ109ββπ½/π events collected with the BESIII detector, we perform a study of π½/πβπΎβ’πβ’πβ’πβ² to search for the πβ‘(2370) and ππ in the πβ’πβ’πβ² invariant mass distribution. No significant signal for the πβ‘(2370) is observed, and we set an upper limit for the product branching fraction of β¬(π½/πβπΎβ’πβ‘(2370)Β·β¬β‘(πβ‘(2370)βπβ’πβ’πβ²)<9.2Γ10β6 at the 90% confidence level. A clear ππ signal is observed for the first time, yielding a product branching fraction of β¬β‘(π½/πβπΎβ’ππ)Β·β¬β‘(ππβπβ’πβ’πβ²)=(4.86Β±0.62β’(stat)Β±0.45β’(sys))Γ10β5.
We measure the Born cross sections of the process π+β’πββπΎ+β’πΎββ’πΎ+β’πΎβ at center-of-mass (c.m.) energies, βπ , between 2.100 and 3.080 GeV. The data were collected using the BESIII detector at the BEPCII collider. An enhancement at βπ =2.232ββGeV is observed, very close to the π+β’πββΞβ’Β―Ξ production threshold. A similar enhancement at the same c.m. energy is observed in the π+β’πββπβ’πΎ+β’πΎβ cross section. The energy dependence of the πΎ+β’πΎββ’πΎ+β’πΎβ and πβ’πΎ+β’πΎβ cross sections differs significantly from that of π+β’πββπβ’π+β’πβ.
A partial-wave analysis of the decay π½/πβπΎ+β’πΎββ’π0 has been made using (223.7Β±1.4)Γ106ββπ½/π events collected with the BESIII detector in 2009. The analysis, which is performed within the isobar-model approach, reveals contributions from πΎ*2β’(1430)Β±, πΎ*2β’(1980)Β± and πΎ*4β’(2045)Β± decaying to πΎΒ±β’π0. The two latter states are observed in π½/π decays for the first time. Two resonance signals decaying to πΎ+β’πΎβ are also observed. These contributions cannot be reliably identified and their possible interpretations are discussed. The measured branching fraction π΅β‘(π½/πβπΎ+β’πΎββ’π0) of (2.88Β±0.01Β±0.12)Γ10β3 is more precise than previous results. Branching fractions for the reported contributions are presented as well. The results of the partial-wave analysis differ significantly from those previously obtained by BESII and BABAR.
Using π+β’πββΞ+πβ’Β―Ξβπ production from a 567ββpbβ1 data sample collected by BESIII at 4.6 GeV, a full angular analysis is carried out simultaneously on the four decay modes of Ξ+πβπβ’πΎ0π, Ξβ’π+, Ξ£+β’π0, and Ξ£0β’π+. For the first time, the Ξ+π transverse polarization is studied in unpolarized π+β’πβ collisions, where a nonzero effect is observed with a statistical significance of 2.1β’π. The decay asymmetry parameters of the Ξ+π weak hadronic decays into πβ’πΎ0π, Ξβ’π+, Ξ£+β’π0 and Ξ£0β’π+ are measured to be 0.18Β±0.43β’(stat)Β±0.14β’(syst), β0.80Β±0.11β’(stat)Β±0.02β’(syst), β0.57Β±0.10β’(stat)Β±0.07β’(syst), and β0.73Β±0.17β’(stat)Β±0.07β’(syst), respectively. In comparison with previous results, the measurements for the Ξβ’π+ and Ξ£+β’π0 modes are consistent but with improved precision, while the parameters for the πβ’πΎ0π and Ξ£0β’π+ modes are measured for the first time.
We present the first experimental search for the rare charm decay D0βΟ0Ξ½Β―Ξ½. It is based on an e+eβ collision sample consisting of 10.6Γ10^6 pairs of D0Β―D0 mesons collected by the BESIII detector at βs=3.773 GeV, corresponding to an integrated luminosity of 2.93 fb^β1. A data-driven method is used to ensure the reliability of the background modeling. No significant D0βΟ0Ξ½Β―Ξ½ signal is observed in data and an upper limit of the branching fraction is set to be 2.1Γ10^-4 at the 90% confidence level. This is the first experimental constraint on charmed-hadron decays into dineutrino final states.
There has recently been a dramatic renewal of interest in hadron spectroscopy and charm physics. This renaissance has been driven in part by the discovery of a plethora of charmonium-like XYZ states at BESIII and B factories, and the observation of an intriguing proton-antiproton threshold enhancement and the possibly related X(1835) meson state at BESIII, as well as the threshold measurements of charm mesons and charm baryons.
We present a detailed survey of the important topics in tau-charm physics and hadron physics that can be further explored at BESIII during the remaining operation period of BEPCII. This survey will help in the optimization of the data-taking plan over the coming years, and provides physics motivation for the possible upgrade of BEPCII to higher luminosity.
The Born cross sections for the process e+eββΞ·β²Ο+Οβ 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 6.3Ο and a mass and width of M=(2108Β±46Β±25)~MeV/c2 and Ξ=(138Β±36Β±30)~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in e+eββΞ·β²Ο+Οβ and BESIII in e+eββΟΟ0 within two standard deviations.
The Born cross sections for the process e+eββΞ·β²Ο+Οβ 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 6.3Ο and a mass and width of M=(2108Β±46Β±25)~MeV/c2 and Ξ=(138Β±36Β±30)~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in e+eββΞ·β²Ο+Οβ and BESIII in e+eββΟΟ0 within two standard deviations.
The Born cross sections for the process e+eββΞ·β²Ο+Οβ 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 6.3Ο and a mass and width of M=(2111Β±43Β±25)~MeV/c2 and Ξ=(135Β±34Β±30)~MeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in e+eββΞ·β²Ο+Οβ and BESIII in e+eββΟΟ0 within two standard deviations.
We study the electromagnetic Dalitz decay π½/πβπ+β’πββ’π and search for dielectron decays of a dark gauge boson (πΎβ²) in π½/πβπΎβ²β’π with the two π decay modes πβπΎβ’πΎ and πβπ+β’πββ’π0 using (1310.6Β±7.0)Γ106ββπ½/π events collected with the BESIII detector. The branching fraction of π½/πβπ+β’πββ’π is measured to be (1.43Β±0.04β’(stat)Β±0.06β’(syst))Γ10β5, 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 Ξ=2.84Β±0.11β’(stat)Β±0.08β’(syst)ββGeV/π2. We find no evidence of πΎβ² production and set 90% confidence level upper limits on the product branching fraction β¬β‘(π½/πβπΎβ²β’π)Γβ¬β‘(πΎβ²βπ+β’πβ) as well as the kinetic mixing strength between the standard model photon and πΎβ² in the mass range of 0.01β€ππΎβ²β€2.4ββGeV/π2.
We report new measurements of the cross sections for the production of Dbar D final states at the Ο(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fbβ1 of e+eβ 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+Dβ 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 Ο(e+eβ β D0bar D0) nb and Ο(e+eβ β D+Dβ) = (2.830 Β± 0.011 Β± 0.026) nb, where the uncertainties are statistical and systematic, respectively.
Measurement of the absolute branching fraction of the inclusive decay ΞcβΊβββΞβ
+β
X
(2018)
Based on an π+β’πβ collision data sample corresponding to an integrated luminosity of 567ββpbβ1 taken at the center-of-mass energy of βπ =4.6ββGeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay Ξ+πβΞ+π to be β¬β‘(Ξ+πβΞ+π)=(38.β’2+2.8β2.2Β±0.9)% using the double-tag method, where π refers to any possible final state particles. In addition, we search for direct πΆβ’π violation in the charge asymmetry of this inclusive decay for the first time, and obtain ππΆβ’πβ‘[β¬β‘(Ξ+πβΞ+π)ββ¬β‘(Β―Ξβπ β Β―Ξ+π)]/[β¬β‘(Ξ+πβΞ+π)+β¬β‘(Β―Ξβπ β Β―Ξ+π)]=(2.β’1+7.0β6.6Β±1.6)%, a statistically limited result with no evidence of πΆβ’π violation.
Using a 3.19ββfbβ1 data sample collected at an π+β’πβ center-of-mass energy of πΈcm=4.178ββGeV with the BESIII detector, we measure the branching fraction of the leptonic decay π·+π βπ+β’ππ to be β¬π·+π βπ+β’ππ=(5.49Β±0.1β’6statΒ±0.1β’5syst)Γ10β3. Combining our branching fraction with the masses of the π·+π and π+ and the lifetime of the π·+π , we determine ππ·+π β’|ππβ’π |=246.2Β±3.β’6statΒ±3.β’5systββMeV. Using the πβπ quark mixing matrix element |ππβ’π | determined from a global standard model fit, we evaluate the π·+π decay constant ππ·+π =252.9Β±3.β’7statΒ±3.β’6systββMeV. Alternatively, using the value of ππ·+π calculated by lattice quantum chromodynamics, we find |ππβ’π |=0.985Β±0.01β’4statΒ±0.01β’4syst. These values of β¬π·+π βπ+β’ππ, ππ·+π β’|ππβ’π |, ππ·+π and |ππβ’π | are each the most precise results to date.
An amplitude analysis of the πΎπβ’πΎπ system produced in radiative π½/π decays is performed using the (1310.6Β±7.0)Γ106ββπ½/π decays collected by the BESIII detector. Two approaches are presented. A mass-dependent analysis is performed by parametrizing the πΎπβ’πΎπ 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 πΎπβ’πΎπ 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 π0β‘(1710), π0β‘(2200), and πβ²2β‘(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 π½/π decays to πΎπβ’πΎπ is measured to be (8.1Β±0.4)Γ10β4, where the uncertainty is systematic and the statistical uncertainty is negligible.
The Born cross sections are measured for the first time for the processes e+eββDβ+sDβs0(2317)β+c.c. and e+eββDβ+sDs1(2460)β+c.c. at the center-of-mass energy sβ= 4.600~GeV, 4.612~GeV, 4.626~GeV, 4.640~GeV, 4.660~GeV, 4.68~GeV, and 4.700~GeV, and for e+eββDβ+sDs1(2536)β+c.c. at sβ= 4.660~GeV, 4.680~GeV, and 4.700~GeV, using data samples collected with the BESIII detector at the BEPCII collider. No structures are observed in cross-section distributions for any of the processes.
By analyzing an e+eβ annihilation data sample corresponding to an integrated luminosity of 2.93 fbβ1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fraction of the D0βΟβΞΌ+Ξ½ΞΌ decay for the first time. We obtain BD0βΟβΞΌ+Ξ½ΞΌ=(1.35Β±0.09statΒ±0.09syst)Γ10β3. Using the world average of BD0βΟβe+Ξ½e, we find a branching fraction ratio of BD0βΟβΞΌ+Ξ½ΞΌ/BD0βΟβe+Ξ½e=0.90Β±0.11, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. Combining the world average of BD+βΟ0ΞΌ+Ξ½ΞΌ and the lifetimes of D0(+), we obtain a partial decay width ratio of ΞD0βΟβΞΌ+Ξ½ΞΌ/(2ΞD+βΟ0ΞΌ+Ξ½ΞΌ)=0.71Β±0.14, which is consistent with the isospin symmetry expectation of one within 2.1Ο. For the reported values of BD0βΟβΞΌ+Ξ½ΞΌ/BD0βΟβe+Ξ½e and ΞD0βΟβΞΌ+Ξ½ΞΌ/2ΞD+βΟ0ΞΌ+Ξ½ΞΌ, the uncertainty is the quadratic sum of the statistical and systematic uncertainties.
Amplitude analysis and branching-fraction measurement of DββΊβββKββ°Kβ»ΟβΊΟβΊ
(2021)
Using 6.32ββfbβ1 of π+β’πβ collision data collected by the BESIII detector at the center-of-mass energies between 4.178 and 4.226 GeV, an amplitude analysis of the π·+π βπΎ0πβ’πΎββ’π+β’π+ decays is performed for the first time to determine the intermediate-resonant contributions. The dominant component is the π·+π βπΎ*β’(892)+β’Β―πΎ*β’(892)0 decay with a fraction of (40.6Β±2.β’9statΒ±4.β’9sys)%. Our results of the amplitude analysis are used to obtain a more precise measurement of the branching fraction of the π·+π βπΎ0πβ’πΎββ’π+β’π+ decay, which is determined to be (1.46Β±0.0β’5statΒ±0.0β’5sys)%.
By analyzing an e+eβ annihilation data sample corresponding to an integrated luminosity of 2.93 fbβ1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fraction of the D0βΟβΞΌ+Ξ½ΞΌ decay for the first time. We obtain BD0βΟβΞΌ+Ξ½ΞΌ=(1.35Β±0.09statΒ±0.09syst)Γ10β3. Using the world average of BD0βΟβe+Ξ½e, we find a branching fraction ratio of BD0βΟβΞΌ+Ξ½ΞΌ/BD0βΟβe+Ξ½e=0.90Β±0.11, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. Combining the world average of BD+βΟ0ΞΌ+Ξ½ΞΌ and the lifetimes of D0(+), we obtain a partial decay width ratio of ΞD0βΟβΞΌ+Ξ½ΞΌ/(2ΞD+βΟ0ΞΌ+Ξ½ΞΌ)=0.71Β±0.14, which is consistent with the isospin symmetry expectation of one within 2.1Ο. For the reported values of BD0βΟβΞΌ+Ξ½ΞΌ/BD0βΟβe+Ξ½e and ΞD0βΟβΞΌ+Ξ½ΞΌ/2ΞD+βΟ0ΞΌ+Ξ½ΞΌ, the uncertainty is the quadratic sum of the statistical and systematic uncertainties.
By analyzing an e+eβ annihilation data sample corresponding to an integrated luminosity of 2.93 fbβ1 collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we measure the branching fraction of the D0βΟβΞΌ+Ξ½ΞΌ decay for the first time. We obtain BD0βΟβΞΌ+Ξ½ΞΌ=(1.35Β±0.09statΒ±0.09syst)Γ10β3. Combining with theoretical predictions, we extract the CKM matrix element |Vcd|=0.204Β±0.007statΒ±0.007systΒ±0.014theory. Using the world average of BD0βΟβe+Ξ½e, we find a branching fraction ratio of BD0βΟβΞΌ+Ξ½ΞΌ/BD0βΟβe+Ξ½e=0.90Β±0.11, which agrees with the theoretical expectation of lepton flavor universality within the uncertainty. Combining the world average of BD+βΟ0ΞΌ+Ξ½ΞΌ and the lifetimes of D0(+), we obtain a partial decay width ratio of ΞD0βΟβΞΌ+Ξ½ΞΌ/(2ΞD+βΟ0ΞΌ+Ξ½ΞΌ)=0.71Β±0.14, which is consistent with the isospin symmetry expectation of one within 2.1Ο. For the reported values of BD0βΟβΞΌ+Ξ½ΞΌ/BD0βΟβe+Ξ½e and ΞD0βΟβΞΌ+Ξ½ΞΌ/2ΞD+βΟ0ΞΌ+Ξ½ΞΌ, the uncertainty is the quadratic sum of the statistical and systematic uncertainties.
Using a data sample of 4.481Γ108ββπβ‘(3686) events collected with the BESIII detector, we report the first observation of the four-lepton-decays π½/πβπ+β’πββ’π+β’πβ and π½/πβπ+β’πββ’π+β’πβ utilizing the process πβ‘(3686)βπ+β’πββ’π½/π. The branching fractions are determined to be [5.48Β±0.31β’(stat)Β±0.45β’(syst)]Γ10β5 and [3.53Β±0.22β’(stat)Β±0.13β’(syst)]Γ10β5, respectively. The results are consistent with theoretical predictions. No significant signal is observed for π½/πβπ+β’πββ’π+β’πβ, and an upper limit on the branching fraction is set at 1.6Γ10β6 at the 90% confidence level. A πΆβ’π asymmetry observable is constructed for the first two channels, which is measured to be (β0.012Β±0.054Β±0.010) and (0.062Β±0.059Β±0.006), respectively. No evidence for πΆβ’π violation is observed in this process.
The rare decay πβ²βπ+β’πββ’π+β’πβ is studied using a sample of 1.3Γ109ββπ½/π events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be (2.42Β±0.0β’5statΒ±0.0β’8syst)Γ10β3. Due to the inclusion of new data, this result supersedes the last BESIII result on this branching fraction. In addition, the πΆβ’π-violating asymmetry in the angle between the decay planes of the π+β’πβ-pair and the π+β’πβ-pair is investigated. A measurable value would indicate physics beyond the standard model; the result is ππΆβ’π=(2.9Β±3.β’7statΒ±1.β’1syst)%, which is consistent with the standard model expectation of no πΆβ’π-violation. The precision is comparable to the asymmetry measurement in the πΎ0πΏβπ+β’πββ’π+β’πβ decay where the observed (14Β±2)% effect is driven by a standard model mechanism.
We report a study of the processes of π+β’πββπΎ+β’π·βπ β’π·*0 and πΎ+β’π·*βπ β’π·0 based on π+β’πβ 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 3.7ββfbβ1. An excess of events over the known contributions of the conventional charmed mesons is observed near the π·βπ β’π·*0 and π·*βπ β’π·0 mass thresholds in the πΎ+ recoil-mass spectrum for events collected at βπ =4.681ββGeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5+1.8
β2.6Β±2.1)ββMeV/π2 and (12.8+5.3β4.4Β±3.0)ββMeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3ββπ over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into π·βπ β’π·*0 and π·*βπ β’π·0. However, the properties of the excess need further exploration with more statistics.
Ten hadronic final states of the βπ decays are investigated via the process πβ‘(3686)βπ0β’βπ, using a data sample of (448.1Β±2.9)Γ106ββπβ‘(3686) events collected with the BESIII detector. The decay channel βπβπΎ+β’πΎββ’π+β’πββ’π0 is observed for the first time and has a measured significance of 6.0β’π. The corresponding branching fraction is determined to be β¬β‘(βπβπΎ+β’πΎββ’π+β’πββ’π0)=(3.3Β±0.6Β±0.6)Γ10β3 (where the uncertainties are statistical and systematic, respectively). Evidence for the decays βπβπ+β’πββ’π0β’π and βπβπΎ0πβ’πΎΒ±β’πββ’π+β’πβ is found with a significance of 3.6β’π and 3.8β’π, respectively. The corresponding branching fractions (and upper limits) are obtained to be β¬β‘(βπβπ+β’πββ’π0β’π)=(7.2Β±1.8Β±1.3)Γ10β3 (<1.8Γ10β2) and β¬β‘(βπβπΎ0πβ’πΎΒ±β’πββ’π+β’πβ)=(2.8Β±0.9Β±0.5)Γ10β3 (<4.7Γ10β3). Upper limits on the branching fractions for the final states βπβπΎ+β’πΎββ’π0, πΎ+β’πΎββ’π, πΎ+β’πΎββ’π+β’πββ’π, 2β’(πΎ+β’πΎβ)β’π0, πΎ+β’πΎββ’π0β’π, πΎ0πβ’πΎΒ±β’πβ, and πβ’Β―πβ’π0β’π0 are determined at a confidence level of 90%.
We report a study of the processes of e+eββK+(DβsDβ0+DββsD0) based on e+eβ 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 3.7 fbβ1. An excess over the known contributions of the conventional charmed mesons is observed near the DβsDβ0 and DββsD0 mass thresholds in the K+ recoil-mass spectrum for events collected at sβ=4.681 GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5+1.8β2.6Β±2.1) MeV/c2 and (12.8+5.3β4.4Β±3.0) MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 Ο over the pure contributions from the conventional charmed mesons. This is the first candidate of the charged hidden-charm tetraquark with strangeness, decaying into DβsDβ0 and DββsD0. However, the genuine properties of the excess need further exploration with more statistics.
We report a study of the processes of e+eββK+(DβsDβ0+DββsD0) based on e+eβ 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 3.7 fbβ1. An excess over the known contributions of the conventional charmed mesons is observed near the DβsDβ0 and DββsD0 mass thresholds in the K+ recoil-mass spectrum for events collected at sβ=4.681 GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5+1.8β2.6Β±2.1) MeV/c2 and (12.8+5.3β4.4Β±3.0) MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 Ο over the contributions only from the conventional charmed mesons. This is the first candidate of the charged hidden-charm tetraquark with strangeness, decaying into DβsDβ0 and DββsD0. However, the properties of the excess need further exploration with more statistics.
Using a dedicated data sample taken in 2018 on the J/Ο peak, we perform a detailed study of the trigger efficiencies of the BESIII detector. The efficiencies are determined from three representative physics processes, namely Bhabha scattering, dimuon production and generic hadronic events with charged particles. The combined efficiency of all active triggers approaches 100% in most cases, with uncertainties small enough not to affect most physics analyses.
Using 2.93ββfbβ1 of π+β’πβ 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 π·0β’(+) decays to exclusive final states with an π, e.g., π·0βπΎββ’π+β’π, πΎ0πβ’π0β’π, πΎ+β’πΎββ’π, πΎ0πβ’πΎ0πβ’π, πΎββ’π+β’π0β’π, πΎ0πβ’π+β’πββ’π, πΎ0πβ’π0β’π0β’π, and π+β’πββ’π0β’π; π·+βπΎ0πβ’π+β’π, πΎ0πβ’πΎ+β’π, πΎββ’π+β’π+β’π, πΎ0πβ’π+β’π0β’π, π+β’π+β’πββ’π, and π+β’π0β’π0β’π. Among these decays, the π·0βπΎββ’π+β’π and π·+βπΎ0 πβ’π+β’π decays have the largest branching fractions, which are β¬β‘(π·0βπΎββ’π+β’π) = (1.853Β±0.02β’5statΒ±0.03β’1syst)% and β¬β‘(π·+βπΎ0πβ’π+β’π) = (1.309Β±0.03β’7statΒ±0.03β’1syst)%, respectively. The charge-parity asymmetries for the six decays with highest event yields are determined, and no statistically significant charge-parity violation is found.
Using 2.93ββfbβ1 of π+β’πβ annihilation data collected at a center-of-mass energy βπ =3.773ββGeV with the BESIII detector operating at the BEPCII collider, we search for the semileptonic π·0β’(+) decays into a π1β’(1235)β(0) axial-vector meson for the first time. No significant signal is observed for either charge combination. The upper limits on the product branching fractions are β¬π·0βπ1β’(1235)ββ’π+β’ππΒ·β¬π1β’(1235) ββ πβ’πβ<1.12Γ10β4 and β¬π·+βπ1β’(1235)0β’π+β’ππΒ·β¬π1β’(1235)0βπβ’π0<1.75Γ10β4 at the 90% confidence level.
Using 2.93ββfbβ1 of π+β’πβ 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 π·+βπΎ+β’π+β’πββ’π0 is reported. After removing decays that contain narrow intermediate resonances, including π·+βπΎ+β’π, π·+βπΎ+β’π, and π·+βπΎ+β’π, the branching fraction of the decay π·+βπΎ+β’π+β’πββ’π0 is measured to be (1.13Β±0.0β’8statΒ±0.0β’3syst)Γ10β3. The ratio of branching fractions of π·+βπΎ+β’π+β’πββ’π0 over π·+βπΎββ’π+β’π+β’π0 is found to be (1.81Β±0.15)%, which corresponds to (6.28Β±0.52)β’tan4β‘ππΆ, where ππΆ 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 π·Β±βπΎΒ±β’πΒ±β’πββ’π0 is also determined, and no evidence for πΆβ’π violation is found. In addition, the first evidence for the π·+βπΎ+β’π decay, with a statistical significance of 3.3β’π, is presented and the branching fraction is measured to be β¬β‘(π·+βπΎ+β’π) = (5.β’7+2.5β2.1statΒ±0.β’2syst)Γ10β5.
By analyzing a data sample corresponding to an integrated luminosity of 2.93ββfbβ1 collected at a center-of-mass energy of 3.773 GeV with By analyzing a data sample corresponding to an integrated luminosity of 2.93ββfbβ1 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 π·+βπβ’π+β’ππ decay to be β¬π·+βπβ’π+β’ππ=(10.4Β±1.β’0statΒ±0.β’5syst)Γ10β4. Using the world averaged value of β¬π·+βπβ’π+β’ππ, the ratio of the two branching fractions is determined to be β¬π·+βπβ’π+β’ππ/β¬π·+βπβ’π+β’ππ=0.91Β±0.13(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 ππ+β‘(0) and the πβπ Cabibbo-Kobayashi-Maskawa matrix element |ππβ’π| to be ππ+β‘(0)β’|ππβ’π|=0.087Β±0.00β’8statΒ±0.00β’2syst. Taking the input of |ππβ’π| from the global fit in the standard model, we determine ππ+β‘(0)=0.39Β±0.0β’4statΒ±0.0β’1syst. On the other hand, using the value of ππ+β‘(0) calculated in theory, we find |ππβ’π| = 0.242Β±0.02β’2statΒ±0.00β’6systΒ±0.03β’3theory.
he Born cross sections for the process π+β’πββπβ²β’π+β’πβ 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 6.3β’π and a mass and width of π=(2111Β±43Β±25)ββMeV/π2 and Ξ=(135Β±34Β±30)ββMeV, where the uncertainties are statistical and systematic, respectively. These measured resonance parameters agree with the measurements of BABAR in π+β’πββπβ²β’π+β’πβ and BESIII in π+β’πββπβ’π0 within two standard deviations.
We report an amplitude analysis and branching fraction measurement of π·+
π βπΎ+β’πΎββ’π+ decay using a data sample of 3.19ββfbβ1 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 πΎ+β’πΎβ mass region to determine the πΎ+β’πΎβ 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 β¬β‘(π·+π βπΎ+β’πΎββ’π+)=(5.47Β±0.0β’8statΒ±0.1β’3sys)%.
The processes π+β’πββπ·+ π β’π·π β’1β’(2460)β+c.c. and π+β’πββπ·*+ π β’π·π β’1β’(2460)β+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 π+β’πββπ·+ π β’π·π β’1β’(2460)β+c.c. at nine center-of-mass energies between 4.467 GeV and 4.600 GeV and those of π+β’πββπ·*+ π β’π·π β’1β’(2460)β+c.c. at βπ =4.590ββGeV and 4.600 GeV are measured. No obvious charmonium or charmoniumlike structure is seen in the measured cross sections.
Study of the process eβΊeβ»βββΟβ°Οβ°J/Ο and neutral charmoniumlike state Zc(3900)β°
(2020)
Cross sections of the process π+β’πββπ0β’π0β’π½/π at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4ββfbβ1 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 πβ‘(4220). The mass and width of the πβ‘(4220) are determined to be (4220.4Β±2.4Β±2.3) MeV/π2 and (46.2Β±4.7Β±2.1)ββMeV, respectively, where the first uncertainties are statistical and the second systematic. The mass and width are consistent with those measured in the process π+β’πββπ+β’πββ’π½/π. The neutral charmonium-like state ππβ’(3900)0 is observed prominently in the π0β’π½/π invariant-mass spectrum, and, for the first time, an amplitude analysis is performed to study its properties. The spin-parity of ππβ’(3900)0 is determined to be π½π=1+, and the pole position is (3893.1Β±2.2Β±3.0)βπβ’(22.2Β±2.6Β±7.0)ββMeV/π2, which is consistent with previous studies of electrically charged ππβ’(3900)Β±. In addition, cross sections of π+β’πβ β π0β’ππβ’(3900)0 β π0β’π0β’π½/π are extracted, and the corresponding line shape is found to agree with that of the πβ‘(4220).