Generalized Drell-Hearn-Gerasimov sum rule at order ) in chiral perturbation theory

Abstract

We calculate the forward spin-dependent photon-nucleon Compton amplitudes S 1 and S 2 as functions of photon energy ν and mass Q 2 at the nextto-leading (O(p 4 )) order in chiral perturbation theory, from which we extract the contribution to a generalized Drell-Hearn-Gerasimov sum rule at low Q 2 . The result indicates a much rapid Q 2 variation of the sum rule than a simple dimensional analysis would yield.

Measurement of the Q2 Dependence of the Deuteron Spin Structure Function g1 and its Moments at Low Q2Adhikari1, Deur2, Fassi3 et al. 2018Phys. Rev. Lett.284320View full textAdd to dashboardCite

“…[25] would agree and the ones of Ref. [26] would not, while the opposite occurs for another observable. Furthermore, the experimental and theoretical uncertainties of the first generation of experiments and calculations limited the usefulness of these comparisons.…”

“…In the low and high Q 2 limits where Γ 1 can be related to global properties of the target, the sum rule tests our understanding of the nucleon spin structure. At intermediate Q 2 it has been used to test nonperturbative QCD calculations of Γ 1 such as the AdS/QCD approach [23], phenomenological models of the nucleon structure [24] and, at lower Q 2 , χPT calculations [25][26][27].…”

“…No data on δ p LT exist although some are anticipated soon [16]. This state of affairs triggered a refinement of the χPT calculations [25][26][27] and a very low Q 2 experimental program.…”

Photoproduction of nucleon resonances and nucleon spin structure function in the resonance region

“…[19]. The dashed-double dotted line is the χPT prediction [31]. Our result with the non-resonant part and the two-body exchange currents contributions is shown by the dashed-dotted line.…”

“…However, for the difference between the proton and the neutron, the contribution of this resonance is absent. In this case, chiral perturbation theory is useful, but it is valid only to as low as 0.2 GeV 2 [31]. In Fig.…”