Radiative decays of the $Σ_c$, $Ξ'_c$ and $Ω_c$ charmed baryons

TL;DR

The paper calculates electromagnetic decay widths of charmed baryons in the flavor ${\bf 6}_{\rm F}$ sextet using a nonrelativistic three-quark model with two harmonic-oscillator shells. Electromagnetic transitions are evaluated from ground and $P$-wave states to ground states, and from second-shell states to ground and $P$-wave final states, including the first calculations for $D_\rho$-wave, $\rho$-mode mixed, and $\rho$-mode radial excitations. By combining mass spectra from the model with a nonrelativistic EM transition operator, the study provides radiative widths and explores how these widths can distinguish competing assignments for ambiguous resonances such as $\Omega_c(3327)$ and $\Xi'_c(2923)^{+/0}$. Uncertainties from experimental mass inputs and model parameters are propagated via a Monte Carlo approach to yield robust error estimates. The results demonstrate that radiative decays, though smaller than strong widths, offer critical branching-ratio information to identify and assign singly charmed baryon resonances, and they present a framework for future investigations of ${\bf \bar{3}}_{\rm F}$ and higher excitations.

Abstract

In this work, we study the radiative decays of the $Σ_c$, $Ξ'_c$ and $Ω_c$ charmed baryons, which belong to the flavor sextet ($\bf {6}_{\rm F}$), within the constituent quark model formalism. The electromagnetic transitions are calculated from the ground and $P$-wave states to ground states, as well as from the second shell states to both the ground and $P$-wave final states. These decays play a crucial role in confirming the existence of certain resonances when strong decays are not allowed. Moreover, electromagnetic decay widths are particularly useful for identifying resonances when states have the same mass and total decay width. A relevant case is the $Ω_c (3327)$ state, whose branching ratios between the strong decay channels are comparable; thus, the radiative decay widths may help assign this state. We also make the assignment of the recently discovered $Ξ'_c(2923)^{+}$ baryon, which is consistent with being the isospin partner of the $Ξ'_c(2923)^{0}$. This study presents, for the first time, the calculation of electromagnetic decays for $D_ρ$-wave states, $ρ-λ$ mixed states, and $ρ$-mode radially excited states in the charm sector. Throughout our calculations, we account for uncertainties arising from both experimental and model-dependent errors.

Figures (2)

• Figure 1: The $SU_f(3)$ flavor sextet of the ground-state singly charmed baryons: the states with ${\bf J}^P = {\bf \frac{1}{2}}^+$ are at the left side, and those with ${\bf J}^P = {\bf \frac{3}{2}}^+$ at the right side.
• Figure 2: Comparison between the predicted masses of singly charmed baryon belonging to the ${\bf 6}_{\rm F}$-plet, as from Ref. Garcia-Tecocoatzi:2022zrf, with the experimental data from the PDG ParticleDataGroup:2024cfk. The predicted masses are displayed in teal, while the experimental masses are reported in black ParticleDataGroup:2024cfk.