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By using 6.32 fbβ1 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 +β0 and determine the relative fractions and phase differences of different intermediate processes, which include K0S (770)+, K0S (1450)+, Kβ(892)0β+, Kβ(892)+β0, and Kβ(1410)0β+. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be B(D+s ! K0S +β0) = (5.43 Β± 0.30stat Β± 0.15syst) Γ 10β3.
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.
The process π+β’πββπβ’πβ² has been studied for the first time in detail using data sample collected with the BESIII detector at the BEPCII collider at center of mass energies from 2.05 to 3.08 GeV. A resonance with quantum numbers π½πβ’πΆ=1ββ is observed with mass π=(2177.5Β±4.8β’(stat)Β±19.5β’(syst))β’MeV/π2 and width Ξ=(149.0Β±15.6β’(stat)Β±8.9β’(syst))ββMeV with a statistical significance larger than 10β’π, including systematic uncertainties. If the observed structure is identified with the πβ‘(2170), then the ratio of partial width between the πβ’πβ² by BESIII and πβ’π by BABAR is (β¬π
πβ’πβ’Ξπ
πβ’π)/(β¬π
πβ’πβ²β’Ξπ
πβ’π)=0.23Β±0.10β’(stat)Β±0.18β’(syst), which is smaller than the prediction of the π β’Β―π β’π hybrid models by several orders of magnitude.
We report a measurement of the observed cross sections of e+ eβ β J/ΟX based on 3.21 fb β 1 of data accumulated at energies from 3.645 to 3.891 GeV with the BESIII detector operated at the BEPCII collider. In analysis of the cross sections, we measured the decay branching fractions of B(Ο(3686) β J/ΟX) = (64.4 Β± 0.6 Β± 1.6)% and B(Ο(3770) β J/ΟX) = (0.5 Β± 0.2 Β± 0.1)% for the first time. The energy-dependent line shape of these cross sections cannot be well described by two Breit-Wigner (BW) amplitudes of the expected decays Ο (3686) β J/ΟX and Ο(3770) β J/ΟX. Instead, it can be better described with one more BW amplitude of the decay R(3760)β J/ΟX. Under this assumption, we extracted the R (3760) mass M R (3760 ) = 3766.2 Β± 3.8 Β± 0.4 MeV/c2, total width Ξ tot R ( 3760 ) = 22.2 Β± 5.9 Β± 1.4 MeV, and product of leptonic width and decay branching fraction
ΞeeR(3760) B[R(3760) β J/ΟX] = (79.4 Β± 85.5 Β± 11.7) eV. The significance of the R(3760) is 5.3Ο. The first uncertainties of these measured quantities are from fits to the cross sections and second systematic.
Based on an e+eβ collision data sample corresponding to an integrated luminosity of 2.93 fbβ1 collected with the BESIII detector at βs=3.773 GeV, the first amplitude analysis of the singly Cabibbo-suppressed decay D+βK+K0SΟ0 is performed. From the amplitude analysis, the Kβ(892)+K0S component is found to be dominant with a fraction of (57.1Β±2.6Β±4.2)%, where the first uncertainty is statistical and the second systematic. In combination with the absolute branching fraction B(D+βK+K0SΟ0) measured by BESIII, we obtain B(D+βKβ(892)+K0S)=(8.69Β±0.40Β±0.64Β±0.51)Γ10β3, where the third uncertainty is due to the branching fraction B(D+βK+K0SΟ0). The precision of this result is significantly improved compared to the previous measurement. This result also differs from most of theoretical predictions by about 4Ο, which may help to improve the understanding of the dynamics behind.
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.
A search for the charged lepton flavor violating decay π½/πβπΒ±β’πβ with πββπββ’π0β’ππ is performed with about 10Γ109ββπ½/π events collected with the BESIII detector at the BEPCII. No significant signal is observed, and an upper limit is set on the branching fraction β¬β‘(π½/πβπΒ±β’πβ)<7.5Γ10β8 at the 90% confidence level. This improves the previously published limit by two orders of magnitude.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5 fb -1 of e+eβ 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+eβ (Ξ³ISR/FSR)Β΅ -> +Β΅-, 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.
Amplitude analysis and branching fraction measurement of the decay DββΊ β ΟβΊΟβ°Οβ°
(2022)
Using a data set corresponding to an integrated luminosity of 6.32 fbβ1 recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, an amplitude analysis of the decay D+s β Ο+Ο0Ο0 is performed, and the relative fractions and phases of different intermediate processes are determined. The absolute branching fraction of the decay D+s β Ο+Ο0Ο0 is measured to be (0.50 Β± 0.04stat Β± 0.02syst)%. Theabsolute branching fraction of the intermediate process D+s β f0(980)Ο+, f0(980) β Ο0Ο0 is determined to be (0.28 Β± 0.04stat Β± 0.04syst)%.
During the 2016-17 and 2018-19 running periods, the BESIII experiment collected 7.5~fbβ1 of e+eβ 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+eββ(Ξ³ISR/FSR)ΞΌ+ΞΌβ, 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~fbβ1 of e+eβ 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+eββ(Ξ³ISR/FSR)ΞΌ+ΞΌβ, 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~fbβ1 of e+eβ 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+eββ(Ξ³ISR/FSR)ΞΌ+ΞΌβ, 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~fbβ1 of e+eβ 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+eββ(Ξ³ISR/FSR)ΞΌ+ΞΌβ, 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~fbβ1 of e+eβ 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+eββ(Ξ³ISR/FSR)ΞΌ+ΞΌβ, 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.
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.
The observed cross sections for π+β’πββπ+β’πβ at energies from 3.8 to 4.6 GeV are measured using data samples taken with the BESIII detector operated at the BEPCII collider. We measure the muonic widths and determine the branching fractions of the charmonium states πβ‘(4040), πβ‘(4160), and πβ‘(4415) decaying to π+β’πβ, as well as making a first determination of the phase of the amplitudes. In addition, we observe evidence for a structure in the dimuon cross section near 4.220ββGeV/π2, which we denote as πβ‘(4220). Analyzing a coherent sum of amplitudes yields eight solutions, one of which gives a mass of ππβ‘(4220) = 4216.7Β±8.9Β±4.1ββMeV/π2, a total width of Ξtot Sβ‘(4220) = 47.2Β±22.8Β±10.5ββMeV, and a muonic width of Ξπβ’π πβ‘(4220) = 1.53Β±1.26Β±0.54ββkeV, where the first uncertainties are statistical and the second systematic. The eight solutions give the central values of the mass, total width, muonic width to be, respectively, in the range from 4212.8 to 4219.4ββMeV/π2, from 36.4 to 49.6 MeV, and from 1.09 to 1.53 keV. The statistical significance of the πβ‘(4220) signal is 3.9β’π. Correcting the total dimuon cross section for radiative effects yields a statistical significance for this structure of 8.1β’π.
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.
Using a sample of 106 million πβ‘(3686) decays, πβ‘(3686)βπΎβ’ππβ’π½β‘(π½=0,1,2) and πβ‘(3686)βπΎβ’ππβ’π½,ππβ’π½βπΎβ’π½/πβ‘(π½=1,2) events are utilized to study inclusive ππβ’π½βanything, ππβ’π½βhadrons, and π½/πβanything distributions, including distributions of the number of charged tracks, electromagnetic calorimeter showers, and π0β’s, and to compare them with distributions obtained from the BESIII Monte Carlo simulation. Information from each Monte Carlo simulated decay event is used to construct matrices connecting the detected distributions to the input predetection βproducedβ distributions. Assuming these matrices also apply to data, they are used to predict the analogous produced distributions of the decay events. Using these, the charged particle multiplicities are compared with results from MARK I. Further, comparison of the distributions of the number of photons in data with those in Monte Carlo simulation indicates that G-parity conservation should be taken into consideration in the simulation.
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.