Coherent deeply virtual Compton scattering off ³He and neutron generalized parton distributions

Dipartimento di Fisica e Geologia, Università degli studi di Perugia and INFN sezione di Perugia, via A. Pascoli, 06100 Perugia, Italy

^a e-mail: matteo.rinaldi@pg.infn.it
^b e-mail: sergio.scopetta@pg.infn.it

Published online: 9 June 2014

Abstract

It has been recently proposed to study coherent deeply virtual Compton scattering (DVCS) off ³He nuclei to access neutron generalized parton distributions (GPDs). In particular, it has been shown that, in Impulse Approximation (IA) and at low momentum transfer, the sum of the quark helicity conserving GPDs of ³He, H and E, is dominated by the neutron contribution. This peculiar result makes the ³He target very promising to access the neutron information. We present here the IA calculation of the spin dependent GPD $\mathrm{See\; Formula\; in\; PDF}$ of ³He. Also for this quantity the neutron contribution is found to be the dominant one, at low momentum transfer. The known forward limit of the IA calculation of $\mathrm{See\; Formula\; in\; PDF}$, yielding the polarized parton distributions of ³He, is correctly recovered. The extraction of the neutron information could be anyway non trivial, so that a procedure, able to take into account the nuclear effects encoded in the IA analysis, is proposed. These calculations, essential for the evaluation of the coherent DVCS cross section asymmetries, which depend on the GPDs H,E and $\mathrm{See\; Formula\; in\; PDF}$, represent a crucial step for planning possible experiments at Jefferson Lab.