$b \to c$ semileptonic sum rule: SU(3)$_{\rm{F}}$ symmetry violation

Fuente: arXiv
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Autor principal: Iguro, Syuhei
Formato: Preprint
Publicado: 2026
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author Iguro, Syuhei
author_facet Iguro, Syuhei
contents To clarify possible deviations in $b\to cτ\overlineν$ processes, the $b\to c$ semileptonic sum rule provides a valuable tool. This relation, derived based on heavy quark symmetry (HQS), offers a powerful consistency check among experimental results. In this work, we extend the previously proposed sum rule for $\{B\to D^{(*)} l\overlineν,\,Λ_b\to Λ_c l\overlineν\}$ to include $\{B_s\to D_s^{(*)} l\overlineν,\,Ξ_b\to Ξ_c l\overlineν\}$, thereby enabling more useful cross-checks. Although the relation is supported by HQS and SU(3) flavor symmetry, both symmetries are broken in reality, and the size of the violation needs to be quantified to assess the validity of the sum rule. While the violation is expected to be moderate based on chiral perturbation theory, we perform a numerical evaluation and compare it with future experimental sensitivities. We find that the violation remains smaller than the expected experimental uncertainty. Therefore another new physics agnostic and predictive sum rules are constructed to check the consistency.
format Preprint
id arxiv_https___arxiv_org_abs_2604_05186
institution arXiv
publishDate 2026
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spellingShingle $b \to c$ semileptonic sum rule: SU(3)$_{\rm{F}}$ symmetry violation
Iguro, Syuhei
High Energy Physics - Phenomenology
High Energy Physics - Experiment
To clarify possible deviations in $b\to cτ\overlineν$ processes, the $b\to c$ semileptonic sum rule provides a valuable tool. This relation, derived based on heavy quark symmetry (HQS), offers a powerful consistency check among experimental results. In this work, we extend the previously proposed sum rule for $\{B\to D^{(*)} l\overlineν,\,Λ_b\to Λ_c l\overlineν\}$ to include $\{B_s\to D_s^{(*)} l\overlineν,\,Ξ_b\to Ξ_c l\overlineν\}$, thereby enabling more useful cross-checks. Although the relation is supported by HQS and SU(3) flavor symmetry, both symmetries are broken in reality, and the size of the violation needs to be quantified to assess the validity of the sum rule. While the violation is expected to be moderate based on chiral perturbation theory, we perform a numerical evaluation and compare it with future experimental sensitivities. We find that the violation remains smaller than the expected experimental uncertainty. Therefore another new physics agnostic and predictive sum rules are constructed to check the consistency.
title $b \to c$ semileptonic sum rule: SU(3)$_{\rm{F}}$ symmetry violation
topic High Energy Physics - Phenomenology
High Energy Physics - Experiment
url https://arxiv.org/abs/2604.05186