分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We present a calculation of the strange and charm quark contributions to the nucleon spin from anomalous Ward identity (AWI). It is performed with overlap valence quarks on 2+1-flavor domain-wall fermion gauge configurations on a 243×64 lattice with the light sea mass at mπ=330 MeV. To satisfy the AWI, the overlap fermion for the pseudoscalar density and the overlap Dirac operator for the topological density, which do not have multiplicative renormalization, are used to renormalize the form factor of the local axial-vector current at finite q2. For the charm quark, we find the positive pseudoscalar term almost cancels the negative topological term for each q2, leading to a very small net contribution. For the strange quark, the pseudoscalar term is less positive than that of the charm and this results in a negative strange quark spin when combined with the topological contribution. The gA(q2) at q2=0 is obtained by a global fit of the pseudoscalar and the topological form factors, together with gA(q2) and the induced pseudoscalar form factor hA(q2) at finite q2. The chiral extrapolation to the physical pion mass gives Δs+Δs¯=−0.084(12)(21) which is consistent with that from the recent global analysis of deep inelastic scattering experiments.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We introduce a stochastic sandwich method with low-mode substitution to evaluate the connected three-point functions. The isovector matrix elements of the nucleon for the axial-vector coupling g3A, scalar couplings g3S and the quark momentum fraction ⟨x⟩u−d are calculated with overlap fermion on 2+1 flavor domain-wall configurations on a 243×64 lattice at mπ=330 MeV with lattice spacing a=0.114 fm.
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