Diffractive Dissociation of Alpha Particles as a Test of Isophobic Short-Range Correlations inside Nuclei

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 ${}^4\mathrm{He}$ nuclei to pairs of nucleons $n$ and $p$ with high relative transverse momentum, $\alpha +A\to n+p+A^{\prime }+X$. 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.

Comments: 5 pages, references added, clarifications due to helpful referee comments (latexdiff for all changes). Accepted for publication in Physics Letters B