On the decay mode Λb → Xs γ

Abstract

Abstract We study the inclusive H b → X s γ decay with H b a beauty baryon, in particular Λ b , employing an expansion in the heavy quark mass at O m b − 3 $$ \mathcal{O}\left({m}_b^{-3}\right) $$ at leading order in α s , keeping the dependence on the hadron spin. For a polarized baryon we compute the distribution d 2 Γ dy d cos θ P $$ \frac{d^2\Gamma}{dy\ d\cos {\theta}_P} $$ , with y = 2E γ /m b , E γ the photon energy and θ P the angle between the baryon spin vector and the photon momentum in the H b 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.

Keywords

• Bottom Quarks
• Nonperturbative Effects
• Rare Decays