Dec 14 – 15, 2023
Centre for Particle Theory
Europe/London timezone

Plan B: New Z′ models for B-anomalies

Dec 14, 2023, 4:00 PM
Ph30 (Centre for Particle Theory)


Centre for Particle Theory

Long Talk (20 mins) Beyond the Standard Model: EFTs


Anna Mullin (University of Cambridge)


Observations of lepton flavour universality violating effects may hint at new physics, prompting analysis of the phenomenology for models with new heavy mediators of these effects, such as a $Z’$. A new physics field coupling to di-muon pairs may explain the anomalous B-meson decay measurements, including measurements of $b\rightarrow s\mu ^+ \mu ^-$ with the 2022 LHCb reanalysis of lepton flavour universality observables $R_K$ and $R_{K*}$. However, the reanalysis also poses the possibility of similar strength new physics couplings to di-electron pairs. These new interactions are naturally described on a TeV scale in the language of a dimension-6 SMEFT, with operators constrained to their most likely strengths by fits to data. We compare the statistical likelihood of couplings to di-muon and di-electron pairs, revealing new bounds for fits of a class of anomaly-free models which span scenarios encompassing dominant couplings for electrons to compare with muons. Pertinent measurements lead us to a close-to-optimal fit for a $3B_3-L_e-2L_{\mu}$ model, allowing us to draw conclusions about the likelihood of lepton flavour universality effects in this class of models.

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Other category: Flavour phenomenology
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Primary author

Anna Mullin (University of Cambridge)

Presentation materials