On the decay mode Λ_b → X_s γ

2023/06/05 by Colangelo, P., De Fazio, F., Loparco, F.
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph)

paper · doi:10.48550/arxiv.2306.02748

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) at leading order in α_s, keeping the dependence on the hadron spin. For a polarized baryon we compute the distribution (d²Γ)/(dy d cos θ_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.

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