Positive and negative parity hyperons in nuclear medium

TL;DR

This study uses QCD sum rules to analyze how nuclear medium affects the properties of positive and negative parity hyperons, revealing significant shifts in residues and masses, with notable differences between parities.

Contribution

It provides a detailed comparison of hyperon properties in nuclear medium versus vacuum, including shifts in residues, masses, and self-energies, using a generalized interpolating current approach.

Findings

Residues shift positively in nuclear matter except for positive parity Sigma hyperon

Masses of hyperons decrease in nuclear medium

Negative parity hyperons experience larger shifts than positive parity ones

Abstract

The effects of nuclear medium on the residue, mass and self energy of the positive and negative parity $\Sigma$, $\Lambda$ and $\Xi$ hyperons are investigated using the QCD sum rule method. In the calculations, the general interpolating currents of hyperons with an arbitrary mixing parameter are used. We compare the results obtained in medium with those of the vacuum and calculate the shifts in the corresponding parameters. It is found that the shifts on the residues in nuclear matter are over all positive for both the positive and negative parity hyperons, except for the positive parity $\Sigma$ hyperon that the shift is negative. The shifts on the masses of these baryons are obtained to be negative. The shifts on the residues and masses of negative parity states are large compared to those of positive parities. The maximum shift belongs to the residue of the negative parity $\Lambda$ hyperon. The vector self-energies gained by the positive parity baryons are large compared to the negative parities' vector self-energies. The maximum value of the vector self-energy belongs to the positive parity $\Sigma$ hyperon. The numerical values are compared with the existing predictions in the literature.