New physics in rare B decays after Moriond 2021

Confronting the vector leptoquark hypothesis with new low- and high-energy data

In light of new data we present an updated phenomenological analysis of the simplified U 1 -leptoquark model addressing charged-current B-meson anomalies. The analysis shows a good compatibility of low-energy data (dominated by the lepton flavor universality ratios R D and R D ∗ ) with the high-energy constraints posed by p p → τ τ ¯ Drell-Yan data. We also show that present data are well compatible with a framework where the leptoquark couples with similar strength to both left- and right-handed third-generation fermions, a scenario that is well-motivated from a model building perspective. We find that the high-energy implications of this setup will be probed at the 95% confidence level in the high-luminosity phase of the LHC.

M W helps select Z ' models for b → s ℓ ℓ anomalies

As shown in Allanach et al. (Global fits of third family hypercharge models to neutral current B-anomalies and electroweak precision observables. arXiv:2103.12056), the Third Family Hypercharge ( Y 3 ) Model changes the Standard Model prediction for M W whilst simultaneously explaining anomalies in b → s ℓ ℓ transitions via a heavy Z ' gauge boson which is spawned by a spontaneously broken gauged U ( 1 ) Y 3 symmetry. The 2022 CDF II measurement of M W , which is far from the Standard Model prediction in the statistical sense, somewhat disfavours the Y 3 model. Here, we generalise the gauge charge assignments to the anomaly-free combination s Y 3 + t ( B 3 - L 3 ) and show that incorporating the 2022 CDF II measurement of M W selects a viable domain of integers s and t. For example, s = 1 , t = - 3 yields a p value of .08 in a two-parameter global fit to 277 electroweak and flavour changing b data, much improving a SM p value of 1 × 10 - 6 .

Tests of Lepton Universality Using B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} Decays

Tests of lepton universality in B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9  fb^{-1} . The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays is reported.

Round table on Standard Model Anomalies

This contribution to “The XVth Quark confinement and the Hadron spectrum conference" covers a description, both theoretical and experimental, of the present status of a set of very different anomalies. The discussion ranges from the long standing b → sℓℓ anomalies, (g − 2) and the new MW anomaly.