Charmed-Baryon Spectroscopy from Lattice QCD with N_f=2+1+1 Flavors

TL;DR

This study uses lattice QCD with 2+1+1 flavors to calculate the spectrum of positive-parity ground-state charmed baryons, providing results consistent with experiments and predictions for undiscovered states.

Contribution

It presents the first lattice QCD calculation of the charmed-baryon spectrum with 2+1+1 flavors, including continuum extrapolation and chiral perturbation theory analysis.

Findings

Results agree with experimental values for well-measured baryons.

Predicted masses for unobserved doubly and triply charmed baryons.

The Xi_{cc} mass shows a 1.7 sigma deviation from experimental data.

Abstract

We present the results of a calculation of the positive-parity ground-state charmed-baryon spectrum using 2+1+1 flavors of dynamical quarks. The calculation uses a relativistic heavy-quark action for the valence charm quark, clover-Wilson fermions for the valence light and strange quarks, and HISQ sea quarks. The spectrum is calculated with a lightest pion mass around 220 MeV, and three lattice spacings (a \approx 0.12 fm, 0.09 fm, and 0.06 fm) are used to extrapolate to the continuum. The light-quark mass extrapolation is performed using heavy-hadron chiral perturbation theory up to O(m_pi^3) and at next-to-leading order in the heavy-quark mass. For the well-measured charmed baryons, our results show consistency with the experimental values. For the controversial J=1/2 Xi_{cc}, we obtain the isospin-averaged value M_{Xi_{cc}}=3595(39)(20)(6) MeV (the three uncertainties are statistics, fitting-window systematic, and systematics from other lattice artifacts, such as lattice scale setting and pion-mass determination), which shows a 1.7 sigma deviation from the experimental value. We predict the yet-to-be-discovered doubly and triply charmed baryons Xi_{cc}^*, Omega_{cc}, Omega_{cc}^* and Omega_{ccc} to have masses 3648(42)(18)(7) MeV, 3679(40)(17)(5) MeV, 3765(43)(17)(5) MeV and 4761(52)(21)(6) MeV, respectively.