Study on the mixing of $\Xi_c$ and $\Xi'_c$ by the transition $\Xi_{b}\to\Xi^{(')}_c$

Abstract

Recently, the LHCb collaboration has observed the decays $\Xi^0_{b}\to\Xi^+_{c}D^-_s$ and $\Xi^-_{b}\to\Xi^0_{c}D^-_s$. They measured the relative branching fractions times the ratio of beauty-baryon production cross-sections $\mathcal{R}(\frac{\Xi^0_b}{\Lambda_b})\equiv\frac{\sigma(\Xi_b^0)}{\sigma(\Lambda^0_b)}\times\frac{B(\Xi^0_{b}\to\Xi^+_{c}D^-_s)}{B(\Lambda^0_{b}\to\Lambda^+_{c}D^-_s)}$ and $\mathcal{R}(\frac{\Xi^-_b}{\Lambda_b})\equiv\frac{\sigma(\Xi^-_b)}{\sigma(\Lambda^0_b)}\times\frac{B(\Xi^-_{b}\to\Xi^0_{c}D^-_s)}{B(\Lambda^0_{b}\to\Lambda^+_{c}D^-_s)}$. Once the ratio $\frac{\sigma(\Xi_b^0)}{\sigma(\Lambda^0_b)}$ or $\frac{\sigma(\Xi_b^-)}{\sigma(\Lambda^0_b)}$ is known, one can determine the relative branching fractions which can be used to exam the mixing of $\Xi_c$ and $\Xi'_c$. In previous literature, $\Xi_c$ and $\Xi'_c$ were assumed to belong to SU(3)$_F$ antitriple and sextet, respectively. However, recent experimental measurements such as the ratio $\Gamma(\Xi_{cc}\to\Xi_c\pi^+)/\Gamma(\Xi_{cc}\to\Xi'_c\pi^+)$ indicate the spin-flavor structures of $\Xi_{c}$ and $\Xi'_{c}$ are a mixture of $\Xi^{\bar 3}_{c}$ and $\Xi^{6}_{c}$. The exact value of mixing angle $\theta$ is still under debate. In theoretical models, the mixing angle was fitted to be about $16.27^\circ\pm2.30^\circ$ or $85.54^\circ\pm2.30^\circ$ based on decay channels $\Xi_{cc} \to\Xi^{(')}_{cc} $. While in lattice calculation, a small angle ($1.2^\circ\pm0.1^\circ$) is preferred. To address such discrepancy and test the mixing of $\Xi_c$ and $\Xi'_c$, here we propose the analysis of semileptonic and non-leptonic decays of $\Xi_{b}\to\Xi_{c}$ and $\Xi_{b}\to\Xi^{'}_{c}$. We calculate the decay rate of $\Xi_{b}\to\Xi_{c}$ and $\Xi_{b}\to\Xi^{'}_{c}$ based on light-front quark model and study the effect of the mixing angle on the ratios of weak decays $\Xi_{b}\to\Xi_{c}$ and $\Xi_{b}\to\Xi^{'}_{c}$.....