Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0...Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0.99)×10-3, excluding the decays to intermediate states, namely J/ψ→Ξ-Ξ+, J/ψ→Σ(1385)-Σ(1385)+, and J/ψ→Σ(1385)+Σ(1385)-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ-Ξ+)=(0.90±0.03±0.18)×10-3, Br(J/ψ→Σ(1385)-Σ(1385)+)=(1.23±0.07±0.30)×10-3,and Br(J/ψ→Σ(1385)+Σ(1385)-)=(1.50±0.08±0.38)×10-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos2θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ-Ξ+, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)-Σ(1385)+, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)+Σ(1385)-.展开更多
We study the hadronic decays of ∧c^+ to the final states ∑^+η and ∑^+η, using an e^+e^- annihilation data sample of 567 pb^-1 taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII col...We study the hadronic decays of ∧c^+ to the final states ∑^+η and ∑^+η, using an e^+e^- annihilation data sample of 567 pb^-1 taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays ∧^+→∑^+η and ∑^+η' and with statistical significance of and , respectively. Normalizing to the reference decays ∧^+→∑^+π^0 and ∑^+ω, we obtain the ratios of the branching fractions B(∧C^+→∑^+η)/V(∧^→∑^+π^0)and B(∧C^+→∑^+η)/B(∧C^+→∑^+ω)to be and , respectively. The upper limits at the 90% confidence level are set to be B(∧C^→∑^+η)/V(∧^+→∑^+π^0)<0.58 and B(∧C^+→∑^+η)/B(∧C^+→∑^+ω)<1.2. Using BESIII measurements of the branching fractions of the reference decays, we determine B(∧C^+→∑^+η)=(0.41±019±0.05)%(<0.68%) and B(∧C^+→∑^+η)=(1.34+0.53+0.19)%(<1.9%). Here, the first uncertainties are statistical and the second systematic. The obtained branching fraction of ∧C^+→∑^+η is consistent with the previous measurement, and the branching fraction of ∧C^+→∑^+η is measured for the first time.展开更多
The existence of doubly heavy flavor baryons has not been well established experimentally so far. In this Letter we systematically investigate the weak decays of the doubly charmed baryons, Ξ;and Ξ;, which should be...The existence of doubly heavy flavor baryons has not been well established experimentally so far. In this Letter we systematically investigate the weak decays of the doubly charmed baryons, Ξ;and Ξ;, which should be helpful for experimental searches for these particles. The long-distance contributions are first studied in the doubly heavy baryon decays, and found to be significantly enhanced. Comparing all the processes, Ξ;→Λ;K;π;π;andΞ;π;are the most favorable decay modes for experiments to search for doubly heavy baryons.展开更多
基金Supported by National Natural Science Foundation of China(10491300,10225524,10225525,10425523,10625524,10521003,10821063,10825524)Chinese Academy of Sciences(KJ95T-03)+3 种基金100Talents Program of CAS(U-11,U-24,U-25)Knowledge Innovation Project of CAS(U-602,U-34)(IHEP)National Natural Science Foundation of China(10775077,10225522)(Tsinghua University)Department of Energy(DE-FG02-04ER41291)(U.Hawaii)
文摘Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π+π- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π+π-)=(4.30±0.13±0.99)×10-3, excluding the decays to intermediate states, namely J/ψ→Ξ-Ξ+, J/ψ→Σ(1385)-Σ(1385)+, and J/ψ→Σ(1385)+Σ(1385)-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ-Ξ+)=(0.90±0.03±0.18)×10-3, Br(J/ψ→Σ(1385)-Σ(1385)+)=(1.23±0.07±0.30)×10-3,and Br(J/ψ→Σ(1385)+Σ(1385)-)=(1.50±0.08±0.38)×10-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos2θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ-Ξ+, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)-Σ(1385)+, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)+Σ(1385)-.
基金Supported in part by National Key Basic Research Program of China(2015CB856700)National Natural Science Foundation of China(NSFC)(11235011,11275266,11335008,11425524,11625523,11635010)+16 种基金the Chinese Academy of Sciences(CAS) Large-Scale Scientific Facility Programthe CAS Center for Excellence in Particle Physics(CCEPP)Joint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1332201,U1532257,U1532258)CAS(KJCX2-YW-N29,KJCX2-YW-N45,QYZDJ-SSW-SLH003)100 Talents Program of CASNational 1000 Talents Program of ChinaINPAC and Shanghai Key Laboratory for Particle Physics and CosmologyGerman Research Foundation DFG(Collaborative Research Center CRC 1044,FOR 2359)Istituto Nazionale di Fisica Nucleare,ItalyKoninklijke Nederlandse Akademie van Wetenschappen(KNAW)(530-4CDP03)Ministry of Development of Turkey(DPT2006K-120470)National Science and Technology fundThe Swedish Research CouncilU.S. Department of Energy under(DE-FG02-05ER41374,DE-SC-0010118,DE-SC-0010504,DE-SC-0012069)University of Groningen(RuG)the Helmholtzzentrum fuer Schwerionenforschung GmbH(GSI),DarmstadtWCU Program of National Research Foundation of Korea(R32-2008-000-10155-0)
文摘We study the hadronic decays of ∧c^+ to the final states ∑^+η and ∑^+η, using an e^+e^- annihilation data sample of 567 pb^-1 taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays ∧^+→∑^+η and ∑^+η' and with statistical significance of and , respectively. Normalizing to the reference decays ∧^+→∑^+π^0 and ∑^+ω, we obtain the ratios of the branching fractions B(∧C^+→∑^+η)/V(∧^→∑^+π^0)and B(∧C^+→∑^+η)/B(∧C^+→∑^+ω)to be and , respectively. The upper limits at the 90% confidence level are set to be B(∧C^→∑^+η)/V(∧^+→∑^+π^0)<0.58 and B(∧C^+→∑^+η)/B(∧C^+→∑^+ω)<1.2. Using BESIII measurements of the branching fractions of the reference decays, we determine B(∧C^+→∑^+η)=(0.41±019±0.05)%(<0.68%) and B(∧C^+→∑^+η)=(1.34+0.53+0.19)%(<1.9%). Here, the first uncertainties are statistical and the second systematic. The obtained branching fraction of ∧C^+→∑^+η is consistent with the previous measurement, and the branching fraction of ∧C^+→∑^+η is measured for the first time.
基金Supported by National Natural Science Foundation of China(11505083,11505098,11647310,11575110,11375208,11521505,11621131001,11235005,11447032,U1732101)Natural Science Foundation of Shanghai(15DZ2272100)
文摘The existence of doubly heavy flavor baryons has not been well established experimentally so far. In this Letter we systematically investigate the weak decays of the doubly charmed baryons, Ξ;and Ξ;, which should be helpful for experimental searches for these particles. The long-distance contributions are first studied in the doubly heavy baryon decays, and found to be significantly enhanced. Comparing all the processes, Ξ;→Λ;K;π;π;andΞ;π;are the most favorable decay modes for experiments to search for doubly heavy baryons.