Gravitational form factors of the nucleon and their mechanical structure: Twist-2 case

초록

We present a series of recent works on the gravitational form factors (GFFs) of the nucleon within a pion mean-field approach, which is also called the chiral quark-soliton model. We investigate the flavor structure of the mass, angular momentum, and D-term form factors of the nucleon. The main findings of the present work are given as follows: the contribution of the strange quark is rather small for the mass and angular momentum form factors, it plays an essential role in the D-term form factors. It indicates that the D-term form factor is sensitive to the outer part of the nucleon. The flavor blindness, i.e, Du−d ≃ 0, is valid only if the strange quark is considered. We also discuss the effects of twist-4 operators. Though the gluonic contributions are suppressed by the packing fraction of the instanton vacuum in the twist-2 case, contributions from twist-4 operators are significant. © Copyright owned by the author(s).