On the decay mode $\Lambda_b \to X_s \gamma$

P. Colangelo; F. De Fazio; F. Loparco

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arXiv · 2306.02748

On the decay mode $\Lambda_b \to X_s \gamma$

P. Colangelo·F. De Fazio·F. Loparco

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Abstract

We study the inclusive $H_b \to X_s \gamma$ decay with $H_b$ a beauty baryon, in particular $\Lambda_b$, employing an expansion in the heavy quark mass at $\mathit{O}(m_b^{-3})$ at leading order in $\alpha_s$, keeping the dependence on the hadron spin. For a polarized baryon we compute the distribution $\displaystyle\frac{d^2\Gamma}{dy \, d \cos \theta_P}$, with $y=2E_\gamma/m_b$, $E_\gamma$ the photon energy and $\theta_P$ 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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P. Colangelo, F. De Fazio, F. Loparco. 2023-06-05. On the decay mode $\Lambda_b \to X_s \gamma$. https://arxiv.org/abs/2306.02748

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