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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.
The process ๐+โข๐โโ๐โข๐โฒ 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 ๐ฝ๐โข๐ถ=1โโ is observed with mass ๐=(2177.5ยฑ4.8โข(stat)ยฑ19.5โข(syst))โขMeV/๐2 and width ฮ=(149.0ยฑ15.6โข(stat)ยฑ8.9โข(syst))โโMeV with a statistical significance larger than 10โข๐, including systematic uncertainties. If the observed structure is identified with the ๐โก(2170), then the ratio of partial width between the ๐โข๐โฒ by BESIII and ๐โข๐ by BABAR is (โฌ๐
๐โข๐โขฮ๐
๐โข๐)/(โฌ๐
๐โข๐โฒโขฮ๐
๐โข๐)=0.23ยฑ0.10โข(stat)ยฑ0.18โข(syst), which is smaller than the prediction of the ๐ โขยฏ๐ โข๐ hybrid models by several orders of magnitude.
Using 2.93โโfbโ1 of ๐+โข๐โ annihilation data collected at a center-of-mass energy โ๐ =3.773โโGeV with the BESIII detector operating at the BEPCII collider, we search for the semileptonic ๐ท0โข(+) decays into a ๐1โข(1235)โ(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 โฌ๐ท0โ๐1โข(1235)โโข๐+โข๐๐ยทโฌ๐1โข(1235) โโ ๐โข๐โ<1.12ร10โ4 and โฌ๐ท+โ๐1โข(1235)0โข๐+โข๐๐ยทโฌ๐1โข(1235)0โ๐โข๐0<1.75ร10โ4 at the 90% confidence level.
Using 2.93โโfbโ1 of ๐+โข๐โ 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 ๐ท0โข(+) decays to exclusive final states with an ๐, e.g., ๐ท0โ๐พโโข๐+โข๐, ๐พ0๐โข๐0โข๐, ๐พ+โข๐พโโข๐, ๐พ0๐โข๐พ0๐โข๐, ๐พโโข๐+โข๐0โข๐, ๐พ0๐โข๐+โข๐โโข๐, ๐พ0๐โข๐0โข๐0โข๐, and ๐+โข๐โโข๐0โข๐; ๐ท+โ๐พ0๐โข๐+โข๐, ๐พ0๐โข๐พ+โข๐, ๐พโโข๐+โข๐+โข๐, ๐พ0๐โข๐+โข๐0โข๐, ๐+โข๐+โข๐โโข๐, and ๐+โข๐0โข๐0โข๐. Among these decays, the ๐ท0โ๐พโโข๐+โข๐ and ๐ท+โ๐พ0 ๐โข๐+โข๐ decays have the largest branching fractions, which are โฌโก(๐ท0โ๐พโโข๐+โข๐) = (1.853ยฑ0.02โข5statยฑ0.03โข1syst)% and โฌโก(๐ท+โ๐พ0๐โข๐+โข๐) = (1.309ยฑ0.03โข7statยฑ0.03โข1syst)%, 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 6.32 fbโ1 of electron-positron collision data recorded by the BESIII detector at center-of-mass energies between 4.178 and 4.226~GeV, we present the first search for the decay D+sโa0(980)0e+ฮฝe, a0(980)0โฯ0ฮท, which could proceed via a0(980)-f0(980) mixing. No significant signal is observed. An upper limit of 1.2ร10โ4 at the 90% confidence level is set on the product of the branching fractions of D+sโa0(980)0e+ฮฝe and a0(980)0โฯ0ฮท decays.
The decays D โ Kโฯ+ฯ+ฯโ and D โ Kโฯ+ฯ 0 are studied in a sample of quantum-correlated DDยฏ pairs produced through the process e+eโ โ ฯ(3770) โ DDยฏ, exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fbโ1 . Here D indicates a quantum superposition of a D0 and a Dยฏ 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 ฮณ of the Unitarity Triangle in Bโ โ DKโ decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3ฯ = 0.52+0.12โ0.10 and RKฯฯ0 = 0.78 ยฑ 0.04, with values for the average strong-phase differences that are ฮด K3ฯ D = (167+31โ19)โฆ and ฮดKฯฯ0D = (196+14โ15โฆ , where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D โ Kโฯ+ฯ+ฯโ to yield results that will allow for a more sensitive measurement of ฮณ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6โฆ.
We report new measurements of the branching fraction โฌโก(๐ท+๐ โโ+โข๐), where โ+ is either ๐+ or ๐+โก(โ๐+โขยฏ๐๐), based on 6.32โโfbโ1 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 ๐ท+๐ โ๐+โข๐๐ and ๐ท+๐ โ๐+โข๐๐ components yields โฌโก(๐ท+๐ โ๐+โข๐๐)=(5.21ยฑ0.25ยฑ0.17)ร10โ2, โฌโก(๐ท+๐ โ๐+โข๐๐)=(5.35ยฑ0.13ยฑ0.16)ร10โ3, and the ratio of decay widths ๐
=ฮโก(๐ท+๐ โ๐+โข๐๐)ฮโก(๐ท+๐ โ๐+โข๐๐)=9.7โข3+0.61โ0.58ยฑ0.36, where the first uncertainties are statistical and the second systematic. No evidence of ๐ถโข๐ asymmetry is observed in the decay rates ๐ทยฑ๐ โ๐ยฑโข๐๐ and ๐ทยฑ๐ โ๐ยฑโข๐๐: ๐ด๐ถโข๐โก(๐ยฑโข๐)=(โ1.2ยฑ2.5ยฑ1.0)% and ๐ด๐ถโข๐โก(๐ยฑโข๐)=(+2.9ยฑ4.8ยฑ1.0)%. Constraining our measurement to the Standard Model expectation of lepton universality (๐
=9.75), we find the more precise results โฌโก(๐ท+๐ โ๐+โข๐๐)=(5.22ยฑ0.10ยฑ0.14)ร10โ2 and ๐ด๐ถโข๐โก(๐ยฑโข๐๐)=(โ0.1ยฑ1.9ยฑ1.0)%. Combining our results with inputs external to our analysis, we determine the ๐โยฏ๐ quark mixing matrix element, ๐ท+๐ decay constant, and ratio of the decay constants to be |๐๐โข๐ |=0.973ยฑ0.009ยฑ0.014, ๐๐ท+๐ =249.9ยฑ2.4ยฑ3.5โโMeV, and ๐๐ท+๐ /๐๐ท+=1.232ยฑ0.035, respectively.
Using 2.93 fbโ1 of e+eโ collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D0โK1(1270)โe+ฮฝe semileptonic decay is presented. The statistical significance of the decay D0โK1(1270)โe+ฮฝe is greater than 10ฯ. The branching fraction of D0โK1(1270)โe+ฮฝe is measured to be (1.09ยฑ0.13+0.09โ0.13ยฑ0.12)ร10โ3. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K1(1270)โโKโฯ+ฯโ.
Using 2.93 fbโ1 of e+eโ collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D0โK1(1270)โe+ฮฝe semileptonic decay is presented. The statistical significance of the decay D0โK1(1270)โe+ฮฝe is greater than 10ฯ. The branching fraction of D0โK1(1270)โe+ฮฝe is measured to be (1.09ยฑ0.13+0.09โ0.16ยฑ0.12)ร10โ3. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K1(1270)โโKโฯ+ฯโ. The fraction of longitudinal polarization in D0โK1(1270)โe+ฮฝe is determined for the first time to be 0.50ยฑ0.19statยฑ0.08syst.
Amplitude analysis and branching-fraction measurement of DโโบโโโKโโฐKโปฯโบฯโบ
(2021)
Using 6.32โโfbโ1 of ๐+โข๐โ 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 ๐ท+๐ โ๐พ0๐โข๐พโโข๐+โข๐+ decays is performed for the first time to determine the intermediate-resonant contributions. The dominant component is the ๐ท+๐ โ๐พ*โข(892)+โขยฏ๐พ*โข(892)0 decay with a fraction of (40.6ยฑ2.โข9statยฑ4.โข9sys)%. Our results of the amplitude analysis are used to obtain a more precise measurement of the branching fraction of the ๐ท+๐ โ๐พ0๐โข๐พโโข๐+โข๐+ decay, which is determined to be (1.46ยฑ0.0โข5statยฑ0.0โข5sys)%.
The observed cross sections for ๐+โข๐โโ๐+โข๐โ 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 ๐โก(4040), ๐โก(4160), and ๐โก(4415) decaying to ๐+โข๐โ, 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 4.220โโGeV/๐2, which we denote as ๐โก(4220). Analyzing a coherent sum of amplitudes yields eight solutions, one of which gives a mass of ๐๐โก(4220) = 4216.7ยฑ8.9ยฑ4.1โโMeV/๐2, a total width of ฮtot Sโก(4220) = 47.2ยฑ22.8ยฑ10.5โโMeV, and a muonic width of ฮ๐โข๐ ๐โก(4220) = 1.53ยฑ1.26ยฑ0.54โโkeV, 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 4219.4โโMeV/๐2, from 36.4 to 49.6 MeV, and from 1.09 to 1.53 keV. The statistical significance of the ๐โก(4220) signal is 3.9โข๐. Correcting the total dimuon cross section for radiative effects yields a statistical significance for this structure of 8.1โข๐.
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.
Using a sample of 1.31ร109โโ๐ฝ/๐ events collected with the BESIII detector, we perform a study of ๐ฝ/๐โ๐พโข๐โข๐โข๐โฒ to search for the ๐โก(2370) and ๐๐ in the ๐โข๐โข๐โฒ invariant mass distribution. No significant signal for the ๐โก(2370) is observed, and we set an upper limit for the product branching fraction of โฌ(๐ฝ/๐โ๐พโข๐โก(2370)ยทโฌโก(๐โก(2370)โ๐โข๐โข๐โฒ)<9.2ร10โ6 at the 90% confidence level. A clear ๐๐ signal is observed for the first time, yielding a product branching fraction of โฌโก(๐ฝ/๐โ๐พโข๐๐)ยทโฌโก(๐๐โ๐โข๐โข๐โฒ)=(4.86ยฑ0.62โข(stat)ยฑ0.45โข(sys))ร10โ5.
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.
We report a measurement of the observed cross sections of e+ eโ โ J/ฯX based on 3.21 fb โ 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(ฯ(3686) โ J/ฯX) = (64.4 ยฑ 0.6 ยฑ 1.6)% and B(ฯ(3770) โ J/ฯX) = (0.5 ยฑ 0.2 ยฑ 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 ฯ (3686) โ J/ฯX and ฯ(3770) โ J/ฯX. Instead, it can be better described with one more BW amplitude of the decay R(3760)โ J/ฯX. Under this assumption, we extracted the R (3760) mass M R (3760 ) = 3766.2 ยฑ 3.8 ยฑ 0.4 MeV/c2, total width ฮ tot R ( 3760 ) = 22.2 ยฑ 5.9 ยฑ 1.4 MeV, and product of leptonic width and decay branching fraction
ฮeeR(3760) B[R(3760) โ J/ฯX] = (79.4 ยฑ 85.5 ยฑ 11.7) eV. The significance of the R(3760) is 5.3ฯ. The first uncertainties of these measured quantities are from fits to the cross sections and second systematic.
Using (1310.6ยฑ7.0)ร106 ๐ฝ/๐ events acquired with the BESIII detector at the BEPCII storage rings, the decay ๐โฒโ๐+โข๐โโข๐+โข๐โ is observed for the first time with a significance of 8โข๐ via the process ๐ฝ/๐โ๐พโข๐โฒ. We measure the branching fraction of ๐โฒโ๐+โข๐โโข๐+โข๐โ to be โฌโก(๐โฒโ๐+โข๐โโข๐+โข๐โ)=(1.97ยฑ0.33โข(stat)ยฑ0.19โข(syst))ร10โ5, where the first and second uncertainties are statistical and systematic, respectively
The rare decay ๐โฒโ๐+โข๐โโข๐+โข๐โ is studied using a sample of 1.3ร109โโ๐ฝ/๐ events collected with the BESIII detector at BEPCII in 2009 and 2012. The branching fraction is measured with improved precision to be (2.42ยฑ0.0โข5statยฑ0.0โข8syst)ร10โ3. Due to the inclusion of new data, this result supersedes the last BESIII result on this branching fraction. In addition, the ๐ถโข๐-violating asymmetry in the angle between the decay planes of the ๐+โข๐โ-pair and the ๐+โข๐โ-pair is investigated. A measurable value would indicate physics beyond the standard model; the result is ๐๐ถโข๐=(2.9ยฑ3.โข7statยฑ1.โข1syst)%, which is consistent with the standard model expectation of no ๐ถโข๐-violation. The precision is comparable to the asymmetry measurement in the ๐พ0๐ฟโ๐+โข๐โโข๐+โข๐โ decay where the observed (14ยฑ2)% effect is driven by a standard model mechanism.
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 a sample of 106 million ๐โก(3686) decays, ๐โก(3686)โ๐พโข๐๐โข๐ฝโก(๐ฝ=0,1,2) and ๐โก(3686)โ๐พโข๐๐โข๐ฝ,๐๐โข๐ฝโ๐พโข๐ฝ/๐โก(๐ฝ=1,2) events are utilized to study inclusive ๐๐โข๐ฝโanything, ๐๐โข๐ฝโhadrons, and ๐ฝ/๐โanything distributions, including distributions of the number of charged tracks, electromagnetic calorimeter showers, and ๐0โขs, 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 โproducedโ 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.