On the decay mode Λb → Xsγ

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 Omb−3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O}\\left({m}_b^{-3}\\right) $$\\end{document} at leading order in αs, keeping the dependence on the hadron spin. For a polarized baryon we compute the distribution d2ΓdydcosθP\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\frac{d^2\\Gamma}{dy\\ d\\cos {\ heta}_P} $$\\end{document}, 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.