Strong decays of charmed baryons in heavy hadron chiral perturbation theory

Abstract

Strong decays of charmed baryons are analyzed in the framework of heavy hadron chiral perturbation theory (HHChPT) in which heavy quark symmetry and chiral symmetry are synthesized. HHChPT works excellently for describing the strong decays of $s$-wave charmed baryons. For $L=1$ orbitally excited states, two of the unknown couplings, namely, ${h}_{2}$ and ${h}_{10}$, are determined from the resonant ${\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\pi}\ensuremath{\pi}$ mode produced in the ${\ensuremath{\Lambda}}_{c}(2593)$ decay and the width of ${\ensuremath{\Sigma}}_{c}(2800)$, respectively. Predictions for the strong decays of the $p$-wave charmed baryon states ${\ensuremath{\Lambda}}_{c}(2625)$, ${\ensuremath{\Xi}}_{c}(2790)$ and ${\ensuremath{\Xi}}_{c}(2815)$ are presented. Since the decay ${\ensuremath{\Lambda}}_{c}(2593{)}^{+}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\ensuremath{\pi}\ensuremath{\pi}$ receives nonresonant contributions, our value for ${h}_{2}$ is smaller than the previous estimates. We also discuss the first positive-parity excited charmed baryons. We conjecture that the charmed baryon ${\ensuremath{\Lambda}}_{c}(2880)$ with ${J}^{P}=\frac{5}{2}\genfrac{}{}{0}{}{+}{}$ is an admixture of ${\ensuremath{\Lambda}}_{c2}(\frac{5}{2}\genfrac{}{}{0}{}{+}{})$ with an ${\stackrel{\texttildelow{}}{\ensuremath{\Lambda}}}_{c3}^{\ensuremath{'}\ensuremath{'}}(\frac{5}{2}\genfrac{}{}{0}{}{+}{})$; both are $L=2$ orbitally excited states. The potential model suggests ${J}^{P}=\frac{5}{2}\genfrac{}{}{0}{}{\ensuremath{-}}{}$ or $\frac{3}{2}\genfrac{}{}{0}{}{+}{}$ for ${\ensuremath{\Lambda}}_{c}(2940{)}^{+}$. Measurements of the ratio of ${\ensuremath{\Sigma}}_{c}^{*}\ensuremath{\pi}/{\ensuremath{\Sigma}}_{c}\ensuremath{\pi}$ will enable us to discriminate the ${J}^{P}$ assignments for ${\ensuremath{\Lambda}}_{c}(2940)$. We advocate that the ${J}^{P}$ quantum numbers of ${\ensuremath{\Xi}}_{c}(2980)$ and ${\ensuremath{\Xi}}_{c}(3077)$ are $\frac{1}{2}\genfrac{}{}{0}{}{+}{}$ and $\frac{5}{2}\genfrac{}{}{0}{}{+}{}$, respectively. Under this ${J}^{P}$ assignment, it is easy to understand why ${\ensuremath{\Xi}}_{c}(2980)$ is broader than ${\ensuremath{\Xi}}_{c}(3077)$.