Diquark Induced Short-Range Nucleon-Nucleon Correlations \& the EMC Effect

TL;DR

This paper proposes that diquark formation in short-range nucleon pairs explains the QCD physics behind short-range correlations and the EMC effect, linking nucleon structure to observed quark distribution distortions in nuclei.

Contribution

It introduces a diquark-based model for SRCs as the fundamental QCD mechanism behind the EMC effect, emphasizing the role of scalar isospin-singlet diquarks in nucleon pairs.

Findings

Diquark formation explains short-range correlations in nuclei.

The model predicts specific quark distribution distortions in nuclear targets.

Implications for lepton scattering experiments on light nuclei.

Abstract

Diquark formation across a short-range nucleon-nucleon pair is proposed as the underlying QCD physics of short-range correlations (SRC) in nuclei. SRC pairs have been proposed as the cause of distorted quark behavior in nuclei; experimentally observed quark momentum distribution distortions termed the EMC effect. The strong spatial overlap of SRC pairs brings nucleon constituents within range of inter-nucleon QCD potentials and any bonds formed - such as the diquark bond - affects their distributions. In this SRC model, diquarks form in the $\rm 3_C \otimes 3_C \rightarrow \bar{3}_C$ channel of $\rm SU(3)_C$ acting on valence quarks from highly overlapping nucleon wavefunctions. The most energetically favorable diquark is a valence $u$ quark from one nucleon with a valence $d$ quark from the other in a spin-0 state bound together via continual single gluon exchange and an attractive quantum chromodynamics short-range potential. Formation of a new scalar isospin-singlet $[ud]$ diquark across a NN pair is proposed as the primary QCD-level theoretical foundation for SRC models of distorted structure functions in $\rm A\geq 3$ nuclei. Contributions from the higher mass spin-1 isospin triplet states $(ud)$, $(uu)$ and $(dd)$ are possible, with the spin-1 $(ud)$ diquark proposed as a higher mass but viable structure function distortion mechanism for the spin-1 ground state deuteron. Predictions are made for lepton scattering experiments on $\rm ^3H$ and $\rm ^3He$ nuclear targets, with implications for the coefficients of the 3-valence quark Fock states in the nucleon wavefunction.