To (b)e or not to (b)e: no electrons at LHCb

Marcel Algueró; Aritra Biswas; Bernat Capdevila; Sébastien Descotes-Genon; Joaquim Matias; Martin Novoa-Brunet

doi:10.1140/epjc/s10052-023-11824-0

2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2023) 83: 648
https://doi.org/10.1140/epjc/s10052-023-11824-0

Regular Article - Theoretical Physics

To (b)e or not to (b)e: no electrons at LHCb

Marcel Algueró¹^,2, Aritra Biswas¹^,2^b, Bernat Capdevila¹^,2^,3, Sébastien Descotes-Genon⁴, Joaquim Matias¹^,2 and Martin Novoa-Brunet⁵

¹ Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain
² Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, Campus UAB, 08193, Bellaterra, (Barcelona), Spain
³ DAMTP, University of Cambridge, Wilberforce Road, CB3 0WA, Cambridge, UK
⁴ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405, Orsay, France
⁵ Istituto Nazionale di Fisica Nucleare, Sezione di Bari, Via Orabona 4, 70126, Bari, Italy

^b abiswas@ifae.es

Received: 28 April 2023
Accepted: 9 July 2023
Published online: 21 July 2023

Abstract

We discuss the impact of the recent LHCb update on the two lepton-flavour universality ratios $R_{K}$ $$R_K$$ and $R_{K^{*}}$ $R_{K^*}$ , and the CMS update of $B (B_{s} \to μ^{+} μ^{-})$ $B({B_s \rightarrow \mu ^+\mu ^-})$ regarding the possibility of New Physics in $b \to s ℓ^{+} ℓ^{-}$ $b\rightarrow s\ell ^+\ell ^-$ decays. We perform global fits of the New Physics Wilson coefficients defined in the model-independent approach of the Weak Effective Theory at the b-quark mass. We discuss three different frameworks for this analysis: (i) an update limited to the experimental data but using the same theoretical framework as in earlier works, (ii) a full update concerning both the experimental inputs and the theoretical framework, (iii) an analysis without the LHCb results on electron modes. The comparison between these various sets of results allows us to identify the differences stemming from the various components of the analysis: new experimental results, new inputs for the hadronic form factors, the role played by LHCb data on electron modes. As expected, the significance of all New Physics hypotheses gets reduced after the LHCb announcements on $R_{K^{(*)}}$ $R_{K^{(*)}}$ while the hypothesis of a lepton-flavour-universal contribution to the Wilson coefficient of the semileptonic $O_{9 ℓ}$ $O_{9\ell }$ operators (possibly with a very small lepton-flavour-universality violating component) is clearly reinforced. We also discuss the possibility of a long-distance charm-loop contribution through a mode-by-mode analysis and we find that the preferred values for the $C_{9 μ}$ ${\mathcal C}_{9\mu }$ Wilson coefficient are consistent throughout the different $b \to s μ^{+} μ^{-}$ $b\rightarrow s\mu ^+\mu ^-$ modes and that there is no significant evidence of non-constant $q^{2}$ $$q^2$$ dependencies, which would indicate the presence of a long-distance charm-loop contribution beyond those already included.

© The Author(s) 2023

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