Clustering structure of nuclei in deep inelastic processes

M Hirai,T Watanabe,K Saito,S Kumano

doi:10.1088/1742-6596/569/1/012021

Abstract

A clustering aspect is explained for the 9Be nucleus in charged-lepton deep inelastic scattering. Nuclear modifications of the structure function F2 are studied by the ratio REMC = FA2/FD2, where A and D are a nucleus and the deuteron, respectively. In a JLab experiment, an unexpectedly large nuclear modification slope |dREMC/dx| was found for 9 Be, which could be related to its clustering structure. We investigated a mean conventional part of a nuclear structure function FA2 by a convolution description with nucleon momentum distributions calculated by antisymmetrized (or fermionic) molecular dynamics (AMD) and also by a simple shell model. We found that clustering effects are small in the conventional part, so that the JLab result could be associated with an internal nucleon modification or a short-range nuclear correlation which is caused by high densities due to cluster formation.

Highlights

Nuclear modifications of the structure function F2 are known as the EMC effect [1], and such effects are shown by the ratio REMC(x) = F2A(x)/F2D(x), where A and D indicate a nucleus and the deuteron, respectively, and x is the Bjorken scaling variable
The momentum distribution of the antisymmetrized molecular dynamics (AMD) is shifted toward the high-momentum region in 9Be, which is caused by the fact that the dense clusters are formed within the 9Be nucleus
We consider that the nuclear structure functions consist of the mean conventional part and the remaining one depending on the maximum local density: F2A = +. (6)

Summary

Introduction

The nuclear structure functions have been measured from small x to large x for many nuclei, and the nuclear modifications have been determined by global analyses of experimental data [2]. In 2009, an anomalously large nuclear effect was reported by the JLab measurement on the beryllium-9 structure function F2 as shown in Fig. 1 [3], where the slope is shown as a functions of the scaled average nuclear density.

Results

Conclusion