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Institute
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.
Using 448 million Ο(2S) events, the spin-singlet P-wave charmonium state hc(11P1) is studied via the Ο(2S)βΟ0hc decay followed by the hcβΞ³Ξ·c transition. The branching fractions are measured to be BInc(Ο(2S)βΟ0hc)ΓBTag(hcβΞ³Ξ·c)=(4.22+0.27β0.26Β±0.19)Γ10β4 , BInc(Ο(2S)βΟ0hc)=(7.32Β±0.34Β±0.41)Γ10β4, and BTag(hcβΞ³Ξ·c)=(57.66+3.62β3.50Β±0.58)%, where the uncertainties are statistical and systematic, respectively. The hc(11P1) mass and width are determined to be M=(3525.32Β±0.06Β±0.15) MeV/c2 and Ξ=(0.78+0.27β0.24Β±0.12) MeV. Using the center of gravity mass of the three ΟcJ(13PJ) mesons (M(c.o.g.)), the 1P hyperfine mass splitting is estimated to be Ξhyp=M(hc)βM(c.o.g.)=(0.03Β±0.06Β±0.15) MeV/c2, which is consistent with the expectation that the 1P hyperfine splitting is zero at the lowest-order.
The integrated luminosities of data samples collected in the BESIII experiment in 2016β2017 at center-of-mass energies between 4.19 and 4.28 GeV are measured with a precision better than 1% by analyzing large-angle Bhabha scattering events. The integrated luminosities of old datasets collected in 2010β2014 are updated by considering corrections related to detector performance, offsetting the effect of newly discovered readout errors in the electromagnetic calorimeter, which can haphazardly occur.
Based on a sample of (10.09Β±0.04)Γ109 J/Ο events collected with the BESIII detector operating at the BEPCII storage ring, a partial wave analysis of the decay J/ΟβΞ³Ξ·Ξ·β² is performed. An isoscalar state with exotic quantum numbers JPC=1β+, denoted as Ξ·1(1855), has been observed for the first time with statistical significance larger than 19Ο. Its mass and width are measured to be (1855Β±9+6β1)~MeV/c2 and (188Β±18+3β8)~MeV, respectively. The product branching fraction B(J/ΟβΞ³Ξ·1(1855)βΞ³Ξ·Ξ·β²) is measured to be (2.70Β±0.41+0.16β0.35)Γ10β6. The first uncertainties are statistical and the second are systematic. In addition, an upper limit on the branching ratio B(f0(1710)βΞ·Ξ·β²)/B(f0(1710)βΟΟ) is determined to be 1.61Γ10β3 at 90\% confidence level, which lends support to the hypothesis that the f0(1710) has a large glueball component.
Based on (10087Β±44)Γ106 J/Ο events collected with the BESIII detector, the process J/ΟβΞ³Ο+ΟβΞ·β² is studied using two dominant decay channels of the Ξ·β² meson, Ξ·β²βΞ³Ο+Οβ and Ξ·β²βΞ·Ο+Οβ,Ξ·βΞ³Ξ³. The X(2600) is observed with a statistical significance larger than 20Ο in the Ο+ΟβΞ·β² invariant mass spectrum, and it has a strong correlation to a structure around 1.5 GeV/{\it c}2 in the Ο+Οβ invariant mass spectrum. A simultaneous fit on the Ο+ΟβΞ·β² and Ο+Οβ invariant mass spectra with the two Ξ·β² decay modes indicates that the mass and width of the X(2600) state are 2617.8Β±2.1+18.2β1.9 MeV/{\it c}2 and 200Β±8+20β17 MeV, respectively. The corresponding branching fractions are measured to be B(J/ΟβΞ³X(2600))β
B(X(2600)βf0(1500)Ξ·β²)β
B(f0(1500)βΟ+Οβ) = (3.39Β±0.18+0.91β0.66)Γ10β5 and B(J/ΟβΞ³X(2600))β
B(X(2600)βfβ²2(1525)Ξ·β²)β
B(fβ²2(1525)βΟ+Οβ) = (2.43Β±0.13+0.31β1.11)Γ10β5, where the first uncertainties are statistical, and the second systematic.
Analyzing (448.1Β±2.9)Γ106 Ο(3686) events collected with the BESIII detector at the BEPCII collider, the Ο(3686)βΟK0SK0S decay is observed for the first time. The branching fraction for this decay is determined to be BΟ(3686)βΟK0SK0S=(7.04Β±0.39Β±0.36)Γ10β5, where the first uncertainty is statistical and the second is systematic.
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.
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 B(J/Ο β Dβe +Ξ½e + c.c.) < 7.1 Γ 10β8 is obtained at 90% confidence level. This is an improvement of more than two orders of magnitude over the previous best limit.
Using a sample of about 1010ββπ½/π events collected at a center-of-mass energy βπ =3.097ββGeV with the BESIII detector, the electromagnetic Dalitz decays π½/πβπ+β’πββ’π+β’πββ’πβ², with πβ²βπΎβ’π+β’πβ and πβ²βπ+β’πββ’π, have been studied. The decay π½/πβπ+β’πββ’πβ‘(1835) is observed with a significance of 15β’π, and also an π+β’πβ invariant-mass dependent transition form factor of π½/πβπ+β’πββ’πβ‘(1835) is presented for the first time. The intermediate states πβ‘(2120) and πβ‘(2370) are also observed in the π+β’πββ’πβ² invariant-mass spectrum with significances of 5.3β’π and 7.3β’π. The corresponding product branching fractions for π½/πβπ+β’πββ’π, πβπ+β’πββ’πβ² [π=πβ‘(1835), πβ‘(2120), and πβ‘(2370)] are reported.
Observation of the doubly Cabibbo-suppressed decays DβΊ β KβΊΟβ°Οβ° and DβΊ β KβΊΟβ°Ξ·
(2021)
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±0.6statΒ±0.1syst)Γ10β4 with statistical significances of 8.0Ο and 5.0Ο, 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 (4.7+1.9β1.6statΒ±0.2syst)Γ10β4, with a statistical significance of 3.3Ο. 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 4.5Γ10β4.