Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb-1,collected by the BESⅢdetector in the energy region between 4599.53 MeV and 4698.82 MeV,we report the first obser...Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb-1,collected by the BESⅢdetector in the energy region between 4599.53 MeV and 4698.82 MeV,we report the first observations of the Cabibbo-suppressed decaysΛ_(c)^(+)→nπ^(+)π^(0),Λ_(c)^(+)→nπ^(+)π^(-)π^(+),and the Cabibbo-favored decayΛ_(c)^(+)→nK^(-)π^(+)π^(+)with statistical significances of 7.9σ,7.8σ,and>10σ,respectively.The branching fractions of these decays are measured to be B(Λ_(c)^(+)→nπ^(+)π^(0))=(0.64±0.09±0.02)%,B(Λ_(c)^(+)→nπ^(+)π^(-)π^(+))=(0.45±0.07±0.03)%,and B(Λ_(c)^(+)→nK^(-)π^(+)π^(+))=(1.90±0.08±0.09)%,where the first uncertainties are statistical and the second are systematic.We find that the branching fraction of the decayΛ_(c)^(+)→nπ^(+)π^(0)is about one order of magnitude higher than that ofΛ_(c)^(+)→nπ^(+).展开更多
In this study,by combining the equal spacing rule with recent observations of Ω_(C)(X)and Ξ_(C)(X)baryons,we predict the spectrum of the low-lying λ-mode 1P-wave excited ∑_(c) states.Furthermore,their strong decay...In this study,by combining the equal spacing rule with recent observations of Ω_(C)(X)and Ξ_(C)(X)baryons,we predict the spectrum of the low-lying λ-mode 1P-wave excited ∑_(c) states.Furthermore,their strong decay properties are predicted using the chiral quark model and the nature of∑_(c)(2800)is investigated by analyzing the invariant mass spectrum.The ∑_(c)(2800)structure observed in the Λ_(c)πmass spectrum was found to potentially arise from two overlapping P-wave resonances,∑_(c)(2813)3/2^(-)and ∑_(c)(2840)5/2^(-).These resonances have similar decay widths of Г〜40 MeV and predominantly decay into the Λ_(c)π channel.The ∑_(c)(2755)1/2^(-)state is likely to be a very narrow state with a width of Г〜15 MeV,with its decays almost saturated by the Λ_(c)π channel.Additionally,evidence of the Lc(2755)1/2^(-)resonance as a very narrow peak may be seen in the Λ_(c)π invariant mass spectrum.The other two P-wave states,∑_(c)(2746)1/2^(-)and ∑_(c)(2796)3/2^(-),are relatively narrow states with similar widths of「〜30 MeV and predominantly decay into ∑_(c)π and ∑^(*)_(c)π,respectively.This study can provide useful references for discovering these low-lying P-wave states in forthcoming experiments.展开更多
基金Supported in part by National Key R&D Program of China(2020YFA0406400,2020YFA0406300)National Natural Science Foundation of China(NSFC)(11635010,11735014,11805086,11835012,11935015,11935016,11935018,11975011,11961141012,12022510,12025502,12035009,12035013,12192260,12192261,12192262,12192263,12192264,12192265)+20 种基金the Chinese Academy of Sciences(CAS)Large-Scale Scientific Facility ProgramJoint Large-Scale Scientific Facility Funds of the NSFC and CAS(U1832207)the CAS Center for Excellence in Particle Physics(CCEPP)100 Talents Program of CASFundamental Research Funds for the Central Universities,Lanzhou University,University of Chinese Academy of SciencesThe Institute of Nuclear and Particle Physics(INPAC)Shanghai Key Laboratory for Particle Physics and CosmologyERC(758462)German Research Foundation DFG(443159800)Collaborative Research Center CRC 1044,GRK 2149Istituto Nazionale di Fisica Nucleare,ItalyMinistry of Development of Turkey(DPT2006K-120470)National Science and Technology fundNational Science Research and Innovation Fund(NSRF)via the Program Management Unit for Human Resources&Institutional Development,Research and Innovation(B16F640076STFC)(United Kingdom)Suranaree University of Technology(SUT)Thailand Science Research and Innovation(TSRI)National Science Research and Innovation Fund(NSRF)(160355)The Royal Society,UK(DH140054,DH160214)The Swedish Research CouncilU.S.Department of Energy(DEFG02-05ER41374)。
文摘Using electron-positron annihilation data samples corresponding to an integrated luminosity of 4.5 fb-1,collected by the BESⅢdetector in the energy region between 4599.53 MeV and 4698.82 MeV,we report the first observations of the Cabibbo-suppressed decaysΛ_(c)^(+)→nπ^(+)π^(0),Λ_(c)^(+)→nπ^(+)π^(-)π^(+),and the Cabibbo-favored decayΛ_(c)^(+)→nK^(-)π^(+)π^(+)with statistical significances of 7.9σ,7.8σ,and>10σ,respectively.The branching fractions of these decays are measured to be B(Λ_(c)^(+)→nπ^(+)π^(0))=(0.64±0.09±0.02)%,B(Λ_(c)^(+)→nπ^(+)π^(-)π^(+))=(0.45±0.07±0.03)%,and B(Λ_(c)^(+)→nK^(-)π^(+)π^(+))=(1.90±0.08±0.09)%,where the first uncertainties are statistical and the second are systematic.We find that the branching fraction of the decayΛ_(c)^(+)→nπ^(+)π^(0)is about one order of magnitude higher than that ofΛ_(c)^(+)→nπ^(+).
基金Supported by the National Natural Science Foundation of China(U1832173,11775078)Scientific and Technological Innovation Programs of Higher Education Institutions of Shanxi Province,China(2020L0617)。
文摘In this study,by combining the equal spacing rule with recent observations of Ω_(C)(X)and Ξ_(C)(X)baryons,we predict the spectrum of the low-lying λ-mode 1P-wave excited ∑_(c) states.Furthermore,their strong decay properties are predicted using the chiral quark model and the nature of∑_(c)(2800)is investigated by analyzing the invariant mass spectrum.The ∑_(c)(2800)structure observed in the Λ_(c)πmass spectrum was found to potentially arise from two overlapping P-wave resonances,∑_(c)(2813)3/2^(-)and ∑_(c)(2840)5/2^(-).These resonances have similar decay widths of Г〜40 MeV and predominantly decay into the Λ_(c)π channel.The ∑_(c)(2755)1/2^(-)state is likely to be a very narrow state with a width of Г〜15 MeV,with its decays almost saturated by the Λ_(c)π channel.Additionally,evidence of the Lc(2755)1/2^(-)resonance as a very narrow peak may be seen in the Λ_(c)π invariant mass spectrum.The other two P-wave states,∑_(c)(2746)1/2^(-)and ∑_(c)(2796)3/2^(-),are relatively narrow states with similar widths of「〜30 MeV and predominantly decay into ∑_(c)π and ∑^(*)_(c)π,respectively.This study can provide useful references for discovering these low-lying P-wave states in forthcoming experiments.
