Decay chain information on the newly discovered double charm baryon state $\Xi_{cc}^{++}$

TL;DR

This paper interprets a new double charm baryon state as a decay chain involving $ ightarrow ext{Sigma}_c^{++} + ar{K}^{*0}$, calculates decay rates and polarizations, and estimates branching ratios around 10.5% and 2.5%.

Contribution

It provides a detailed theoretical analysis of the decay mechanisms and polarization effects of the $ ext{Xi}_{cc}^{++}$ baryon using a covariant confined quark model, offering new predictions for decay rates.

Findings

Decay rate for $ ext{Xi}_{cc}^{++} o ext{Sigma}_c^{++} ar{K}^{*0}$ is approximately 10.5%.

Decay rate for $ ext{Xi}_{cc}^{++} o ext{Sigma}_c^{++} ar{K}^0$ is approximately 2.5%.

Polarization and helicity amplitude calculations support the decay mechanism analysis.

Abstract

We interprete the new double charm baryon state found by the LHCb Collaboration in the invariant mass distribution of the set of final state particles $(\Lambda_c^+\,K^-\,\pi^+\,\pi^+)$ as being at the origin of the decay chain $\Xi_{cc}^{++} \to \Sigma_c^{++} (\to \Lambda_c^+ \pi^+) +\bar K^{*0} (\to K^- \pi^+)$. The nonleptonic decay $\Xi_{cc}^{++} \to \Sigma_c^{++} + \bar K^{*0}$ belongs to a class of decays where the quark flavor composition is such that the decay proceeds solely via the factorizing contribution precluding a contamination from internal $W$-exchange. We use the covariant confined quark model previously developed by us to calculate the four helicity amplitudes that describe the dynamics of the transition $\Xi_{cc}^{++} \to \Sigma_c^{++}$ induced by the effective $(c \to u)$ current. We then proceed to calculate the rate of the decay as well as the polarization of the $\Sigma_c^{++}$ and $\Lambda_c^+$ baryons and the longitudinal/transverse composition of the $\bar K^{*0}$. We estimate the decay $\Xi_{cc}^{++} \to \Sigma_c^{++} \bar K^{*0}$ to have a branching rate of $B(\Xi_{cc}^{++} \to \Sigma_c^{++} \bar K^{*0}) \sim 10.5 \%$. As a byproduct of our investigation we have also analyzed the decay $\Xi_{cc}^{++} \to \Sigma_c^{++} \bar K^{0}$ for which we find a branching ratio of $B(\Xi_{cc}^{++} \to \Sigma_c^{++} \bar K^0) \sim 2.5 \%$.