We study s-wave pion-pion scattering length in lattice QCD for pion masses ranging from 330 MeV to 466 MeV.In the "Asqtad" improved staggered fermion formulation,we measure full ππ four-point correlators f...We study s-wave pion-pion scattering length in lattice QCD for pion masses ranging from 330 MeV to 466 MeV.In the "Asqtad" improved staggered fermion formulation,we measure full ππ four-point correlators for isospin I = 0 and 2 channels,and use chiral perturbation theory at next-to-leading order to extrapolate our simulation results.Extrapolating to the physical pion mass yields scattering lengths as mπaI=2 0 = 0.041 6(2) and m π a I =0 0 = 0.186(2) for isospin I = 2 and 0 channels,respectively.Our lattice simulation for ππ scattering length in I = 0 channel is an exploratory study,where we include the disconnected contribution,and our preliminary result is near to its experimental value.These simulations are carried out with MILC 2 + 1 flavor gauge configurations at lattice spacing a ≈ 0.15 fm.展开更多
Thc K+ scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiralperturbation theory with the density-dependent pion decay constant and mass. The contribution of nuclear pions to ...Thc K+ scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiralperturbation theory with the density-dependent pion decay constant and mass. The contribution of nuclear pions to thctotal K+-nucleus cross section is found to be about 5% and 12% when the excess pion numbers per nucleon nπ＝ 0.057and 0.13 are used. The inclusion of the off-mass-shell behavior of the K+π amplitude produced a significant improvementin the K+-nucleus cross section.展开更多
We analyze ππ-KK and πη-Kk couple channel [1,1] matrix Padé amplitudes of SU(3) × SU(3) chiral perturbation theory.By fitting phase shift and inelasticity data,we determine pole positions in different ch...We analyze ππ-KK and πη-Kk couple channel [1,1] matrix Padé amplitudes of SU(3) × SU(3) chiral perturbation theory.By fitting phase shift and inelasticity data,we determine pole positions in different channels (f 0 (980),a 0 (980),f 0 (600),K*0 (800),K*(892),ρ(770)) and trace their N c trajectories.We stress that a couple channel Breit-Wigner resonance should exhibit two poles on different Riemann sheets and meet each other on the real axis when N c=∞.Poles are hence classified using this criteria and we conclude that K*(892) and ρ(770) are unambiguous Breit-Wigner resonances.For scalars the situation is much less clear.We find that f 0 (980) is a molecular state rather than a Breit-Wigner resonance,while a 0 (980),though behave oddly when varying N c,do maintain a twin pole structure.展开更多
基金supported in part by the National Natural Science Foundation of China (11735003, 11975041, and11961141004)support from the National Natural Science Foundation of China (12147145)+2 种基金support from the National Natural Science Foundation of China (12105006)Project funded by China Postdoctoral Science Foundation (2021M700343)China Postdoctoral Science Foundation (2021M690008)
基金Supported by Fundamental Research Funds for the Central Universities under Grant No. 2010SCU23002the Startup Grant fromthe Institute of Nuclear Science and Technology of Sichuan University
文摘We study s-wave pion-pion scattering length in lattice QCD for pion masses ranging from 330 MeV to 466 MeV.In the "Asqtad" improved staggered fermion formulation,we measure full ππ four-point correlators for isospin I = 0 and 2 channels,and use chiral perturbation theory at next-to-leading order to extrapolate our simulation results.Extrapolating to the physical pion mass yields scattering lengths as mπaI=2 0 = 0.041 6(2) and m π a I =0 0 = 0.186(2) for isospin I = 2 and 0 channels,respectively.Our lattice simulation for ππ scattering length in I = 0 channel is an exploratory study,where we include the disconnected contribution,and our preliminary result is near to its experimental value.These simulations are carried out with MILC 2 + 1 flavor gauge configurations at lattice spacing a ≈ 0.15 fm.
文摘Thc K+ scattering cross section with the in-medium virtual pion is evaluated in the lowest-order chiralperturbation theory with the density-dependent pion decay constant and mass. The contribution of nuclear pions to thctotal K+-nucleus cross section is found to be about 5% and 12% when the excess pion numbers per nucleon nπ＝ 0.057and 0.13 are used. The inclusion of the off-mass-shell behavior of the K+π amplitude produced a significant improvementin the K+-nucleus cross section.
基金Supported by National Natural Science Foundation of China under Grant Nos.10925522,10875001,and 11021092
文摘We analyze ππ-KK and πη-Kk couple channel [1,1] matrix Padé amplitudes of SU(3) × SU(3) chiral perturbation theory.By fitting phase shift and inelasticity data,we determine pole positions in different channels (f 0 (980),a 0 (980),f 0 (600),K*0 (800),K*(892),ρ(770)) and trace their N c trajectories.We stress that a couple channel Breit-Wigner resonance should exhibit two poles on different Riemann sheets and meet each other on the real axis when N c=∞.Poles are hence classified using this criteria and we conclude that K*(892) and ρ(770) are unambiguous Breit-Wigner resonances.For scalars the situation is much less clear.We find that f 0 (980) is a molecular state rather than a Breit-Wigner resonance,while a 0 (980),though behave oddly when varying N c,do maintain a twin pole structure.
