Refine
Language
- English (150)
Has Fulltext
- yes (150)
Is part of the Bibliography
- no (150)
Keywords
- BESIII (9)
- e +-e β Experiments (9)
- Branching fraction (8)
- Lepton colliders (4)
- Particle and Resonance Production (4)
- Quarkonium (4)
- Charm Physics (3)
- Charmed mesons (3)
- Electroweak interaction (3)
- Exotics (3)
Institute
- Physik (150)
By analyzing π+β’πβ annihilation data with an integrated luminosity of 2.93ββfbβ1 collected at the center-of-mass energy βπ =3.773βGeV with the BESIII detector, we present the first absolute measurements of the branching fractions of twenty Cabibbo-suppressed hadronic π·0β’(+) decays involving multiple pions. The highest four branching fractions obtained are β¬β‘(π·0βπ+β’πββ’π0) = (1.343Β±0.01β’3statΒ±0.01β’6syst)%, β¬β‘(π·0βπ+β’πββ’2β’π0) = (1.002Β±0.01β’9statΒ±0.02β’4syst)%, β¬β‘(π·+β2β’π+β’πββ’π0) = (1.165Β±0.02β’1statΒ±0.02β’1syst)%, and β¬β‘(π·+β2β’π+β’πββ’2β’π0) = (1.074Β±0.04β’0statΒ±0.03β’0syst)%. The πΆβ’π asymmetries for the six decays with highest signal yields are also determined and found to be compatible with zero.
By analyzing e+eβ annihilation data with an integrated luminosity of 2.93 fbβ1 collected at the center-of-mass energy sβ= 3.773 GeV with the BESIII detector, we present the first absolute measurements of the branching fractions of twenty Cabibbo-suppressed hadronic D0(+) decays involving multiple pions. The largest four branching fractions obtained are B(D0βΟ+ΟβΟ0) = >(1.343Β±0.013statΒ±0.016syst)%, B(D0βΟ+Οβ2Ο0) = (0.998Β±0.019statΒ±0.024syst)%, B(D+β2Ο+ΟβΟ0)
(1.174Β±0.021statΒ±0.021syst)%, and B(D+β2Ο+Οβ2Ο0) = (1.074Β±0.040statΒ±0.030syst)%. The CP asymmetries for the six decays with highest event yields are also determined.
Using a sample of (448.1Β±2.9)Γ106βπβ‘(3686) decays collected with the BESIII detector at BEPCII, we report an observation of Ξβ transverse polarization with a significance of 7.3β’π in the decay πβ‘(3686)βΞββ’ Β―Ξ+ (ΞββΞβ’πβ, Β―Ξ+βΒ―Ξβ’π+, Ξβπβ’πβ, Β―ΞβΒ―πβ’π+). The relative phase of the electric and magnetic form factors is determined to be Ξβ’Ξ¦=(0.667Β±0.111Β±0.058)ββrad. This is the first measurement of the relative phase for a πβ‘(3686) decay into a pair of Ξββ’Β―Ξ+ hyperons. The Ξβ decay parameters (πΌΞβ, πΞβ) and their conjugates (πΌΒ―Ξ+, πΒ―Ξ+), the angular-distribution parameter πΌπ, and the strong-phase difference πΏπβπΏπ for Ξβ’πβ scattering are measured to be consistent with previous BESIII results.
We report a measurement of the cross section for the process e+eββΟ+ΟβJ/Ο around the X(3872) mass in search for the direct formation of e+eββX(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)βΟ+ΟβJ/Ο is determined to be ΞeeΓB(X(3872)βΟ+ΟβJ/Ο)<7.5Γ10β3eV at 90% confidence level under an assumption of total width of 1.19Β±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)βΟ+ΟβJ/Ο), an upper limit on the electronic width Ξee of X(3872) is obtained to be <0.32eV at the 90% confidence level.
A measurement of the πΆβ’π-even fraction of the decay π·0βπ+β’πββ’π+β’πβ is performed with a quantum-correlated πβ‘(3770)βπ·β’Β―π· data sample collected by the BESIII experiment, corresponding to an integrated luminosity of 2.93ββfbβ1. Using a combination of πΆβ’π eigenstates, π·βπ+β’πββ’π0 and π·βπΎ0π,πΏβ’π+β’πβ as tagging modes, the πΆβ’π-even fraction is measured to be πΉ4β’π+=0.735Β±0.015Β±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 πΎ of the Cabibbo-Kobayashi-Maskawa matrix with π΅Β±βπ·β’πΎΒ± decays, and for time-dependent studies of πΆβ’π violation and mixing in the π·0βΒ―π·0 system.
A measurement of the CP-even fraction of the decay D0βΟ+ΟβΟ+Οβ is performed with a quantum-correlated Ο(3770)βDDΒ― data sample collected by the BESIII experiment, corresponding to an integrated luminosity of 2.93 fbβ1. Using a combination of CP eigenstates, DβΟ+ΟβΟ0 and DβK0S,LΟ+Οβ as tagging modes, the CP-even fraction is measured to be F4Ο+=0.735Β±0.015Β±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 Ξ³ with BΒ±βDKΒ± decays, and for time-dependent studies of CP violation and mixing in the D0-DΒ―0 system.
From December 2019 to June 2021, the BESIII experiment collected about 5.85 fbβ1 of data at center-of-mass energies between 4.61 GeV and 4.95 GeV. This is the highest collision energy BEPCII has reached so far. The accumulated e+eβ annihilation data samples are useful for studying charmonium(-like) states and charmed-hadron decays. By adopting a novel method of analyzing the production of Ξ+cΞΒ―βc pairs in e+eβ annihilation, the center-of-mass energies are measured with a precision of βΌ0.6 MeV. Integrated luminosities are measured with a precision of better than 1\% by analyzing the events of large-angle Bhabha scattering. These measurements provide important inputs to the analyses based on these data samples.
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.
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.
Measurements of absolute branching fractions of Dβ°βKβ°LΟ, Kβ°LΞ·, Kβ°LΟ, and Kβ°LΞ·β²
(2022)
We report the first measurements of the absolute branching fractions of D0 β K0 LΟ, D0 β K0LΞ·, D0 β K0LΟ, and D0 β K0LΞ·0, by analyzing 2.93 fbβ1 of eΓΎeβ 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 β K0SΟ, D0 β K0SΞ·, D0 β K0SΟ, and D0 β K0SΞ·0, the K0S β K0L asymmetries RΓ°D0; XΓ in these decay modes are obtained. The CP asymmetries in these decays are also determined. No significant CP violation is observed
Using a data sample corresponding to an integrated luminosity of 11.3ββfbβ1 collected at center-of-mass energies from 4.23 to 4.70 GeV with the BESIII detector, we measure the product of the π+β’πββπ+β’πββ’π2β‘(3823) cross section and the branching fraction β¬β‘[π2β‘(3823)βπΎβ’ππβ’1]. For the first time, resonance structure is observed in the cross section line shape of π+β’πββπ+β’πββ’π2β‘(3823) with significances exceeding 5β’π. A fit to data with two coherent Breit-Wigner resonances modeling the βπ -dependent cross section yields πβ‘(π
1)=4406.9Β±17.2Β±4.5ββMeV/π2, Ξβ‘(π
1)=128.1Β±37.2Β±2.3ββMeV, and πβ‘(π
2)=4647.9Β±8.6Β±0.8ββMeV/π2, Ξβ‘(π
2)=33.1Β±18.6Β±4.1ββMeV. Though weakly disfavored by the data, a single resonance with πβ‘(π
)=4417.5Β±26.2Β±3.5ββMeV/π2, Ξβ‘(π
)=245Β±48Β±13ββMeV is also possible to interpret data. This observation deepens our understanding of the nature of the vector charmoniumlike states. The mass of the π2β‘(3823) state is measured as (3823.12Β±0.43Β±0.13)ββMeV/π2, which is the most precise measurement to date.
Using (10.087Β±0.044)Γ109ββπ½/π 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 ΞββΞ0β’πββ’Β―ππ. No significant signal is observed and the upper limit on the branching fraction β¬β‘(ΞββΞ0β’πββ’Β―ππ) is set to be 2.59Γ10β4 at 90% confidence level. This result is one order of magnitude more strict than the previous best limit.
Using inclusive decays of the J/Ο, a precise determination of the number of J/Ο events collected with the BESIII detector is performed. For the two data sets taken in 2009 and 2012, the numbers of J/Ο events are recalculated to be (224.0Β±1.3)Γ106 and (1088.5Β±4.4)Γ106 respectively, which are in good agreement with the previous measurements. For the J/Ο sample taken in 2017--2019, the number of events is determined to be (8774.0Β±39.4)Γ106. The total number of J/Ο events collected with the BESIII detector is determined to be (10087Β±44)Γ106, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
Using inclusive decays of the J/Ο, a precise determination of the number of J/Ο events collected with the BESIII detector is performed. For the two data sets taken in 2009 and 2012, the numbers of J/Ο events are recalculated to be (224.0Β±1.3)Γ106 and (1088.5Β±4.4)Γ106 respectively, which are in good agreement with the previous measurements. For the J/Ο sample taken in 2017--2019, the number of events is determined to be (8774.0Β±39.4)Γ106. The total number of J/Ο events collected with the BESIII detector is determined to be (10087Β±44)Γ106, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
By analyzing an electron-positron collision data sample corresponding to an integrated luminosity of 2.93ββfbβ1 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 π·0 and π·+ hadronic decay modes and search for the hadronic decay π·0βπΎ0πβ’πΎ0πβ’π0 with much improved sensitivity. The results are β¬β‘(π·0βπΎ0πβ’π0β’π0β’π0)=(7.64Β±0.30Β±0.29)Γ10β3, β‘(π·0βπΎββ’π+β’π0β’π0β’π0)=9.54Β±0.30Β±0.31)Γ10β3, β¬β‘(π·0βπΎ0πβ’π+β’πββ’π0β’π0)=(12.66Β±0.45Β±0.43)Γ10β3, β¬β‘(π·+βπΎ0πβ’π+β’π0β’π0)=(29.04Β±0.62Β±0.87)Γ10β3, β¬β‘(π·+βπΎ0πβ’π+β’π+β’πββ’π0)=(15.28Β±0.57Β±0.60)Γ10β3, β¬β‘(π·+βπΎ0πβ’π+β’π0β’π0β’π0)=(5.54Β±0.44Β±0.32)Γ10β3, β¬β‘(π·+βπΎββ’π+β’π+β’π0β’π0)=(4.95Β±0.26Β±0.19)Γ10β3, and β¬β‘(π·0βπΎ0πβ’πΎ0πβ’π0)<1.45Γ10β4 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 π·βΒ―πΎβ’πβ’πβ’π and π·βΒ―πΎβ’πβ’πβ’πβ’π hadronic decays and open a bridge to access more two-body hadronic π· decays containing scalar, vector, axial, and tensor mesons in the charm sector.
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¦.
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.
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)%.
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%.
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.