Nucleon scalar and tensor charges using lattice QCD simulations at the physical value of the pion mass

作者：Alexandrou C; Constantinou M; Dimopoulos P; Frezzotti R; Hadjiyiannakou K; Jansen K; Kallidonis C; Kostrzewa B; Koutsou G; Mangin Brinet M; Aviles Casco A Vaquero; Wenger U

来源：PHYSICAL REVIEW D, 2017, 95(11): 114514.

DOI：10.1103/PhysRevD.95.114514

We present results on the light, strange and charm nucleon scalar and tensor charges from lattice QCD, using simulations with N-f = 2 flavors of twisted mass clover-improved fermions with a physical value of the pion mass. Both connected and disconnected contributions are included, enabling us to extract the isoscalar, strange and charm charges for the first time directly at the physical point. Furthermore, the renormalization is computed nonperturbatively for both isovector and isoscalar quantities. We investigate excited state effects by analyzing several sink-source time separations and by employing a set of methods to probe ground state dominance. Our final results for the scalar charges are g(S)(u) = 5.20(42)(15)(12), g(S)(d) = 4.27(26) (15)(12), g(S)(s) = 0.33(7)(1)(4), and g(S)(c) = 0.062(13)(3)(5) and for the tensor charges g(T)(u) = 0.794(16)(2)(13), g(T)(d) = - 0.210(10)(2)(13), g(T)(d) = 0.00032(24)(0), and g(T)(c) = 0.00062(85)(0) in the (MS) over bar scheme at 2 GeV. The first error is statistical, the second is the systematic error due to the renormalization and the third the systematic arising from estimating the contamination due to the excited states, when our data are precise enough to probe the first excited state.

• 出版日期2017-6-26