Semileptonic neutral current decays of $\Xi_b$ with dileptons or dineutrinos in the final state

Abstract

We perform a detailed analysis of semileptonic $\Xi_b$ decays mediated by flavor-changing neutral currents ($b\to s$ and $b\to d$) with dilepton or dineutrino final states within the perturbative QCD framework. All independent form factors including vector, axial-vector, tensor, and pseudotensor currents are calculated and are used to analyze the decay branching fractions and angular distributions. Our numerical results for the branching fractions of $\Xi_b\to \Xi \ell^+\ell^-$ decays suggest they are within measurable reach for the LHCb experiment in the near future. Furthermore, we show that a measurement of the ratio $\mathcal{B}(\Xi_b^-\to \Sigma^- \mu^+\mu^-) / \mathcal{B}(\Xi_b^-\to \Xi^- \mu^+\mu^-)$ will allow for an independent determination of $|V_{td}/V_{ts}|$. For the case of unpolarized $\Xi_b$ baryons, we derive several angular observables, which can provide new and complementary constraints on Wilson coefficients in semileptonic FCNC transitions compared to those from mesonic decays. Finally, we present a combined analysis of dilepton and dineutrino channels, comparing various observables in detail. Our results offer further insights into the long-standing anomalies observed in $B$ meson decays.