Charmed baryons in nuclear matter

T F Caramés,G Krein,C E Fontoura,J Vijande,A Valcarce

doi:10.1103/physrevd.98.114019

Abstract

We study the temperature and baryon density dependence of the masses of the lightest charmed baryons $\Lambda_c$, $\Sigma_c$ and $\Sigma^*_c$. We also look at the effects of the temperature and baryon density on the binding energies of the $\Lambda_c N$ and $\Lambda_c \Lambda_c$ systems. Baryon masses and baryon-baryon interactions are evaluated within a chiral constituent quark model. Medium effects are incorporated in those parameters of the model related to the dynamical breaking of chiral symmetry, which are the masses of the constituent quarks, the $\sigma$ and $\pi$ meson masses, and quark-meson couplings. We find that while the in-medium $\Lambda_c$ mass decreases monotonically with temperature, those of $\Sigma_c$ and $\Sigma^*_c$ have a nonmonotonic dependence. These features can be understood in terms of a simple group theory analysis regarding the one-gluon exchange interaction in those hadrons. The in-medium $\Lambda_c N$ and $\Lambda_c \Lambda_c$ interactions are governed by a delicate balance involving a stronger attraction due to the decrease of the $\sigma$ meson mass, suppression of coupled-channel effects and lower thresholds, leading to shallow bound states with binding energies of a few~MeV. The $\Lambda_c$ baryon could possibly be bound to a large nucleus, in qualitative agreement with results based on relativistic mean field models or QCD sum rules. Ongoing experiments at RHIC or LHCb or the planned ones at FAIR and J-PARC may take advantage of the present results.

Highlights

The study of hadrons containing charm quarks is of broad interest nowadays in our quest to understand the fundamental theory of the strong interaction, quantum chromodynamics (QCD)
In a medium composed predominantly by light quarks, like an atomic nucleus whose properties are determined by the nonperturbative physics at the energy scale ΛQCD, the charm quark plays the role of an impurity particle because of its large mass, mc ≃ 5ΛQCD [8]
In the QCD sum rules calculations, ⟪qq⟫=hqqi at ρB=ρ0 1⁄4 1 is essentially equal to the one in our calculation, the results show that there are differences in the way chiral symmetry restoration works in the different models

Summary

INTRODUCTION

The study of hadrons containing charm quarks is of broad interest nowadays in our quest to understand the fundamental theory of the strong interaction, quantum chromodynamics (QCD). When using a density dependence based on a factorization hypothesis for the four-quark condensate, that reference predicts that the Λc mass increases with density, while the opposite behavior is obtained when using a density dependence predicted by a perturbative chiral quark model for the four-quark condensate The latter result points toward the possibility that the Λc might be bound to a nucleus, provided, it can be produced almost at rest in the nucleus. Our ability of making first-principles, analytical calculations of nonperturbative QCD phenomena is very limited and, the use of models is still a valid alternative for making progress Within such a perspective, in the present work we employ a widely used chiral constituent quark model [53,54] to evaluate the in-medium masses of charmed hadrons as well as their in-medium lowenergy interactions with nucleons and other charmed baryons.

QUARK-QUARK AND BARYON-BARYON INTERACTIONS

IN-MEDIUM CHARMED BARYON MASSES

IN-MEDIUM BINDING OF CHARMED BARYONS

SUMMARY