Strange form factors of the nucleon with a nonlocal chiral effective Lagrangian

Abstract

The strange form factors of the nucleon are studied with the nonlocal chiral effective Lagrangian. One loop contributions from both octet and decuplet intermediate states are included. The relativistic regulator is obtained by the nonlocal Lagrangian where the gauge link is introduced to guarantee the local gauge symmetry. With the kaon loop, the calculated charge form factor is positive, while the magnetic form factor is negative. The strange magnetic moment is −0.041 þ0.012 −0.014 with Λ ¼ 0.9 AE 0.1 determined from the nucleon electromagnetic form factors. Our results are comparable with the recent lattice simulation.

Electromagnetic form factors of octet baryons with the nonlocal chiral effective theory

“…The nonlocal interaction generates both the regulator which makes the loop integral convergent and the Q 2 dependence of form factors at tree level. The obtained electromagnetic form factors and strange form factors of the nucleon are very close to the experimental data [25,26]. This nonlocal chiral effective theory was also applied to study the parton distribution functions and Sivers functions of the sea quarks in nucleons [27,28].…”

“…The momentum dependence of the form factors at tree level can be easily obtained with the Fourier transformation of the correlation function. As in our previous work [25,26], the correlation function is chosen such that the charge and magnetic form factors at tree level have the same momentum dependence as the baryon-meson vertex, i.e., G B;tree M ðqÞ ¼ μ B G B;tree E ðqÞ ¼ μ BF ðqÞ, whereFðqÞ is the Fourier transformation of the correlation function FðaÞ. Therefore, the corresponding functionsF 1 ðqÞ andF 2 ðqÞ of Σ þ , for example, are expressed as…”

“…The gauge invariant nonlocal Lagrangian can be obtained using the method in [25,26,39]. For instance, the local interaction between hyperons and K − meson can be written as…”

“…Recently, we proposed a nonlocal chiral effective Lagrangian which makes it possible to study the hadron properties at relatively large Q 2 [25,26]. The nonlocal interaction generates both the regulator which makes the loop integral convergent and the Q 2 dependence of form factors at tree level.…”

Sivers distribution functions of sea quarks in a proton with the chiral Lagrangian

“…Here because we include the decuplet intermediate state, the monopole regulator is not sufficient to get rid of the UV divergence in Fig.1b. From the previous calculation of electromagnetic form factors, strange form factors and asymmetry of sea quark distributions of proton, reasonable Λ π in the dipole regulator is around 1 GeV [55,56]. For ρ meson, the parameter Λ ρ was chosen to be 1.85 GeV in Ref.…”