We report a feasibility study for violation inτ^(-)→Ksπ^(-)ντdecays at a Super Tau Charm Facility(STCF).With an expected luminosity of 1 ab-1 collected by STCF per year at a center-of-mass energy of 4.26 GeV,the ...We report a feasibility study for violation inτ^(-)→Ksπ^(-)ντdecays at a Super Tau Charm Facility(STCF).With an expected luminosity of 1 ab-1 collected by STCF per year at a center-of-mass energy of 4.26 GeV,the statistical sensitivity for CP violation is determined to be of order 9.7×10^(-4)by measuring the decay-rate differ-ence betweenτ^(+)→Ksπ^(+)ντandτ^(-)→Ksπ^(-)ντ.The analysis is performed using a reliable fast simulation software package,which can describe the detector responses properly and vary the responses flexibly for further optimization.Moreover,the energy-dependent efficiencies for reconstructingτ^(-)→Ksπ^(-)ντare presented.The expected CP sens-itivity is proportional to 1/T in the energy region from 4.0 to 5.0 GeV.The sensitivity of CP violation is of order 3.1×10^(-4)with 10 ab^(-1)integrated luminosity,which is equivalent to ten years'data taking in this energy region at STCF.展开更多
We study the rare decaysΛb→Λl+l−(l=e,μ,τ)in the Bethe-Salpeter equation approach.We find that the branching ratio is Br(Λb→Λμ^+μ^−)×10^6=1.051∼1.098 in our model.This result agrees with the experimenta...We study the rare decaysΛb→Λl+l−(l=e,μ,τ)in the Bethe-Salpeter equation approach.We find that the branching ratio is Br(Λb→Λμ^+μ^−)×10^6=1.051∼1.098 in our model.This result agrees with the experimental data well.In the same parametric region,we find that the branching ratio is Br(Λb→Λe^+e^−(τ^+τ^−))×10^6=0.252∼0.392(0.286∼0.489).展开更多
In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed. This approach is applied to elastic ππ scattering. The amplitudes keep single-channel unitarity and describe the e...In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed. This approach is applied to elastic ππ scattering. The amplitudes keep single-channel unitarity and describe the experimental data well, and the low-energy amplitudes are consistent with that of chiral perturbation theory. The pole locations of the σ, f0(980), ρ(770) and f2(1270) and their couplings to ππ are obtained. A virtual state appearing in the isospin-two S-wave is confirmed. The correlations between the left(and right) hand cut and the poles are discussed. Our results show that the poles are more sensitive to the right hand cut rather than the left hand cut. The proposed method could be used to study other two-body scattering processes.展开更多
基金the Double First-Class university project foundation of USTC,USTC Research Funds of the Double First-Class Initiative YD2030002005the National Natural Science Foundation of China(11625523)+1 种基金the National Natural Science Foundation of China(11805012)the Fundamental Research Funds for the Central Universities。
文摘We report a feasibility study for violation inτ^(-)→Ksπ^(-)ντdecays at a Super Tau Charm Facility(STCF).With an expected luminosity of 1 ab-1 collected by STCF per year at a center-of-mass energy of 4.26 GeV,the statistical sensitivity for CP violation is determined to be of order 9.7×10^(-4)by measuring the decay-rate differ-ence betweenτ^(+)→Ksπ^(+)ντandτ^(-)→Ksπ^(-)ντ.The analysis is performed using a reliable fast simulation software package,which can describe the detector responses properly and vary the responses flexibly for further optimization.Moreover,the energy-dependent efficiencies for reconstructingτ^(-)→Ksπ^(-)ντare presented.The expected CP sens-itivity is proportional to 1/T in the energy region from 4.0 to 5.0 GeV.The sensitivity of CP violation is of order 3.1×10^(-4)with 10 ab^(-1)integrated luminosity,which is equivalent to ten years'data taking in this energy region at STCF.
基金Supported by National Natural Science Foundation of China(11775024,11575023,11905117,11847052,11805012,11947001)。
文摘We study the rare decaysΛb→Λl+l−(l=e,μ,τ)in the Bethe-Salpeter equation approach.We find that the branching ratio is Br(Λb→Λμ^+μ^−)×10^6=1.051∼1.098 in our model.This result agrees with the experimental data well.In the same parametric region,we find that the branching ratio is Br(Λb→Λe^+e^−(τ^+τ^−))×10^6=0.252∼0.392(0.286∼0.489).
基金Supported by National Natural Science Foundation of China uder Grant Nos.11805059,11805012,11805037Fundamental Research Funds for the Central Universities+6 种基金the Joint Large Scale Scientific Facility Funds of the NSFCChinese Academy of Sciences(CAS)under Grant No.U1832121Shanghai Pujiang Program under Grant No.18PJ1401000Open Research Program of Large Research Infrastructures(2017)CAS,the DFG(SFB/TR 110,“Symmetries and the Emergence of Structure in QCD”)the Chinese Academy of Sciences(CAS) President’s International Fellowship Initiative(PIFI)under Grant No.2018DM0034Volkswagen Stiftung under Grant No.93562
文摘In this paper we propose a dispersive method to describe two-body scattering with unitarity imposed. This approach is applied to elastic ππ scattering. The amplitudes keep single-channel unitarity and describe the experimental data well, and the low-energy amplitudes are consistent with that of chiral perturbation theory. The pole locations of the σ, f0(980), ρ(770) and f2(1270) and their couplings to ππ are obtained. A virtual state appearing in the isospin-two S-wave is confirmed. The correlations between the left(and right) hand cut and the poles are discussed. Our results show that the poles are more sensitive to the right hand cut rather than the left hand cut. The proposed method could be used to study other two-body scattering processes.
基金supported by Joint Large Scale Scientific Facility Funds of the National Natural Science Foundation of China(NSFC)and Chinese Academy of Sciences(CAS)(U1932110,NSFC(11805059,11805012,11675051,12322502),and 12335002)Fundamental Research Funds for the central Universities+3 种基金supported by Deutsche Forschungsgemeinschaft(DFG)(TRR110)NSFC through funds provided to the Sino-German CRC 110“Symmetries and the Emergence of Structure in QCD”(11621131001)supported in part by VolkswagenStiftung(93562)by the CAS President’s International Fellowship Initiative(PIFI)(2018DM0034)。
