Electroweak penguin decays with di-leptons

Abstract

Electroweak penguin decays proceed via flavour changing neutral currents that, in the Standard Model (SM), are forbidden at the tree-level and only allowed via higher order loop diagrams. New particles beyond the SM could significantly affect these rare processes, altering their predicted branching fractions and angular distributions. Recent results from the LHCb experiment on semileptonic b → s + − processes are reviewed. While most observables show good agreement with SM predictions, an interesting local deviation is observed in an angular observable of the decay B 0 → K * 0 µ + µ − . Recently, also a test of lepton universality using the branching fraction ratio R K = B(B + → K + µ + µ − )/B(B + → K + e + e − ) has also shown an interesting tension with the SM prediction.

Correlating $B_q^0 \to μ^+μ^-$ and $K_L \to π^0ν\barν$ Decays with Four Generations

“…A third measurement of interest by LHCb is the socalled P ′ 5 anomaly. The significance (3.7σ), however, did not change from 1 fb −1 [19] to 3 fb −1 [20]. Given that this is one out of many angular variables in B 0 → K * 0 µ + µ − , it remains to be seen whether the "anomaly" is genuine.…”