On the decay mode Λb → Xsγ

Abstract

Abstract We study the inclusive Hb→ Xsγ decay with Hb a beauty baryon, in particular Λb, employing an expansion in the heavy quark mass at $$ \mathcal{O}\left({m}_b^{-3}\right) $$ O m b − 3 at leading order in αs, keeping the dependence on the hadron spin. For a polarized baryon we compute the distribution $$ \frac{d^2\Gamma}{dy\ d\cos {\theta}_P} $$ d 2 Γ dy d cos θ P , with y = 2Eγ/mb, Eγ the photon energy and θP the angle between the baryon spin vector and the photon momentum in the Hb rest-frame. We discuss the correlation between the baryon and photon polarization, and show that effects of physics beyond the Standard Model can modify the photon polarization asymmetry. We also discuss a method to treat the singular terms in the photon energy spectrum obtained by the OPE.