Baryon spectrum with $N_f=2+1+1$ twisted mass fermions

TL;DR

This study computes low-lying baryon masses using twisted mass fermions with multiple lattice spacings, analyzing isospin breaking, and providing predictions consistent with experimental data and new estimates for charmed baryons.

Contribution

It presents a comprehensive lattice QCD calculation of baryon spectra with $N_f=2+1+1$ twisted mass fermions, including continuum and chiral extrapolations, and offers predictions for yet unmeasured charmed baryons.

Findings

Good agreement with experimental baryon masses after extrapolation.

Isospin breaking effects vanish in the continuum limit.

Predictions for masses of doubly and triply charmed baryons.

Abstract

The masses of the low lying baryons are evaluated using a total of ten ensembles of dynamical twisted mass fermion gauge configurations. The simulations are performed using two degenerate flavors of light quarks, and a strange and a charm quark fixed to approximately their physical values. The light sea quarks correspond to pseudo scalar masses in the range of about 210~MeV to 430~MeV. We use the Iwasaki improved gluonic action at three values of the coupling constant corresponding to lattice spacing $a=0.094$~fm, 0.082~fm and 0.065~fm determined from the nucleon mass. We check for both finite volume and cut-off effects on the baryon masses. We examine the issue of isospin symmetry breaking for the octet and decuplet baryons and its dependence on the lattice spacing. We show that in the continuum limit isospin breaking is consistent with zero, as expected. We performed a chiral extrapolation of the forty baryon masses using SU(2) $\chi$PT. After taking the continuum limit and extrapolating to the physical pion mass our results are in good agreement with experiment. We provide predictions for the mass of the doubly charmed $\Xi_{cc}^*$, as well as of the doubly and triply charmed $\Omega$s that have not yet been determined experimentally.