Diffractive dissociation of alpha particles as a test of isophobic short-range correlations inside nuclei

Jennifer Rittenhouse West,Stanley J Brodsky,Guy F De Téramond,Iván Schmidt

doi:10.1016/j.physletb.2020.135423

Abstract

The CLAS collaboration at Jefferson Laboratory has compared nuclear parton distributions for a range of nuclear targets and found that the EMC effect measured in deep inelastic lepton-nucleus scattering has a strongly “isophobic” nature. This surprising observation suggests short-range correlations between neighboring n and p nucleons in nuclear wavefunctions that are much stronger compared to p−p or n−n correlations. In this paper we propose a definitive experimental test of the nucleon-nucleon explanation of the isophobic nature of the EMC effect: the diffractive dissociation on a nuclear target A of high energy He4 nuclei to pairs of nucleons n and p with high relative transverse momentum, α+A→n+p+A′+X. The comparison of n−p events with p−p and n−n events directly tests the postulated breaking of isospin symmetry. The experiment also tests alternative QCD-level explanations for the isophobic EMC effect. In particular it will test a proposal for hidden-color degrees of freedom in nuclear wavefunctions based on isospin-zero [ud] diquarks.

Highlights

Diffractive dissociation of relativistic hadrons is an important tool for probing hadron structure
Their work was motivated by theoretical studies of diffractive excitation in quantum chromodynamics [2], where diffraction arises from nuclear transparency to the projectile wave function with small transverse separation between the projectile’s constituents [3]
The term isophobic refers to strong isospin quantum numbers, applies to both nucleon and quark doublets under SU (2)I and is defined by Σ I = Σ Iz = 0. This means that for nucleon-nucleon interactions, proton-neutron interactions are highly favored over neutron-neutron or proton-proton; protonneutron isospin quantum numbers sum to zero, the interaction is labeled “isophobic.” Isophobic short-range correlations (SRCs) could provide a solution to the long-standing problem observed in deep inelastic scattering (DIS) experiments of leptons

Summary

Introduction

Diffractive dissociation of relativistic hadrons is an important tool for probing hadron structure. We discuss how diffractive dissociation of nuclei can test a new model for the isophobic nature of the EMC effect, in which short-range quark-quark correlations in nuclei are dominated by color-singlet 12-quark configurations: the “hexa-diquark.” Formed out of nearestneighbor scalar [ud] diquarks, this multi-diquark model may form strongly bound tetra-diquark + valence quark states and may be visible in the MARATHON experiment on A = 3 nuclei at JLab [9].

Results

Conclusion