English

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

High Energy Physics - Phenomenology 2024-05-30 v3 High Energy Physics - Experiment

Abstract

We discuss the impact of the recent LHCb update on the two lepton-flavour universality ratios RKR_K and RKR_{K^*}, and the CMS update of B(Bsμ+μ)B({B_s \to \mu^+\mu^-}) regarding the possibility of New Physics in bs+b\to 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 bb-quark mass. We discuss three different frameworks for this analysis: i) an update limited to the experimental data 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 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 RK()R_{K^{(\ast)}} while the hypothesis of a lepton-flavour-universal contribution to the Wilson coefficient of the semileptonic O9O_{9\ell} operators (possibly with a very small lepton-flavour-universality violating component) is 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 C9μ\mathcal{C}_{9\mu} Wilson coefficient are consistent throughout the different bsμ+μb\to s\mu^+\mu^- modes and that there is no significant evidence of non-constant q2q^2 dependencies, which would indicate the presence of a long-distance charm-loop contribution beyond those already included.

Keywords

Cite

@article{arxiv.2304.07330,
  title  = {To (b)e or not to (b)e: No electrons at LHCb},
  author = {Marcel Algueró and Aritra Biswas and Bernat Capdevila and Sébastien Descotes-Genon and Joaquim Matias and Martín Novoa-Brunet},
  journal= {arXiv preprint arXiv:2304.07330},
  year   = {2024}
}

Comments

37 pages, 7 figures, we include additional predictions of $P_i$ and $Q_i$ observables in the low $q^2$ region

R2 v1 2026-06-28T10:06:28.683Z