New Physics in B decays

CERN Theory Division, CH–1211 Geneva 23, Switzerland

^a e-mail: andreas.crivellin@cern.ch

Published online: 26 April 2016

Abstract

While the LHC did not observe direct evidence for physics beyond the standard model, indirect hints for new physics were uncovered in the flavour sector in the decays B → K*µ⁺ µ⁻, B → Kµ⁺ µ⁻/B → Ke⁺e⁻, B_s → øµ⁺µ⁻, B → D^(*) τv and h → τ^±µ^∓. Each observable deviates from the SM predictions at the 2 − 3σ level only, but combining all b → sµ⁺µ⁻ data via a global fit, one finds 4 − 5 σ difference for NP compared to the SM and combining B → D* τv with B → Dτv one obtains 3:9 σ.

While B → D^(*) τv and h → τv can be naturally explained by an extended Higgs sector, the b → sµ⁺µ⁻ anomalies point at a Z′ gauge boson. However, it is also possible to explain B → D^(*) τv and b → sµ⁺ µ⁻ simultaneously with leptoquarks while their effect in h → τ^±µ^∓ is far too small to account for current data. Combining a 2HDM with a gauged L_µ − L_τ symmetry allows for explaining the b → sµ⁺ µ⁻ anomalies in combination with h → τ^±µ^∓, predicting interesting correlations with τ → 3µ. In the light of these deviations from the SM we also discuss the possibilities of observing lepton flavour violating B decays (e.g. B → K^(*) τ^±µ^∓ and B_s → τ^±µ^∓).