格点量子色动力学在中国

1.格点量子色动力学概述经过多年努力,人们已经成功地将自然界四种基本相互作用(强、弱、电磁、引力)中的前三种统一在量子场论的框架之中,即粒子物理的标准模型(Standard Model,SM)。     

First lattice QCD calculation of semileptonic decays of charmed-strange baryonsΞc

While the standard model is the most successful theory to describe all the interactions and constituents of elementary particle physics,it has been constantly scrutinized for over four decades.Weak decays of charm quarks can be used to measure the coupling strength between quarks in different families and serve as an ideal probe for CP violation.As the lowest charm-strange baryons with three different flavors,Ξ;baryons(composed of csu or csd)have been extensively studied in experiments.In this study,we use state-of-the-art lattice QCD techniques to generate 2+1 clover fermion ensembles with two lattice spacings,a=(0.108,0.080 fm).Then,we present the first ab-initio lattice QCD calculation of the Ξ;→Ξ form factors.Our theoretical results for the Ξc→Ξl;v;decay widths are consistent with and approximately two times more precise than the latest measurements by the ALICE and Belle collaborations.Based on the latest experimental measurements,we independently obtain the quark-mixing matrix element |V;|,which is in good agreement with results from other theoretical approaches.     

Search for Majorana Neutrino Signal in B_c Meson Rare Decay

We study the B c meson rare decay in order to search for the Majorana neutrino signal. It is found that the corresponding decay rate is sensitive to the Majorana neutrino mass and mixing angles. The signal of B±c→ l±1l±2 M induced by the Majorana neutrino within the mass region mπmnmB may be observed at LHCb.     

Anatomy of the ρ resonance from lattice QCD at the physical point

We propose a strategy to access the qq component of the p resonance in lattice QCD. Through a mixed action formalism(overlap valence on domain wall sea), the energy of the qq component is derived at different valence quark masses, and shows a linear dependence on m_π~2. The slope is determined to be c_1 =0.505(3)GeV~(-1), from which the valence πρ sigma term is extracted to be σ_(πρ)~(val)= 9.82(6) MeV using the Feynman-Hellman theorem. At the physical pion mass, the mass of the qq component is interpolated to be m_ρ = 775.9±6.0±1.8 MeV, which is close to the p resonance mass. We also obtain the leptonic decay constant of the qq component to be f_ρ-=208.5±5.5±0.9 MeV, which can be compared with the experimental value f_ρ~(exp)≈221 MeV through the relation f_ρ~(exp)=(1/2)Zf_ρ±, with Z_ρ≈1.13 being the on-shell wavefunction renormalization of p owing to the ρ-π interaction. We emphasize that m_ρand f_ρ of the qq component, which are obtained for the first time from QCD, can be taken as the input parameters of p in effective field theory studies where p acts as a fundamental degree of freedom.