Constraints on New Physics from $B$ mesons

Abstract

These proceedings review the status of New Physics contributions to flavour violating B decays. The anomalies in charged and neutral current B decays related to lepton flavour universality violation have received a substantial amount of attention over the past years, and we discuss the current status in light of the new data presented earlier this year. We also recall a tension in the neutral B meson mixing observables ∆M d and ∆M s and in particular their ratio, when compared with their SM predictions obtained using tree-level determinations of the CKM matrix and the recent lattice QCD results for the relevant hadronic matrix elements. Last but not least, we advocate kaon physics as a unique probe of very high energy scales and briefly discuss the current status of ε /ε and K → πν ν.

Toward accurate form factors for $B$-to-light meson decay from lattice QCD

“…ZV is calculated as in Equation ( 14) and Z disc is defined in [31]. discretisation effects beginning at order (am h ) 4 . For the determination of Z disc see [31,32].…”

“…Decays of b quarks are an area of particular interest because they allow determination of some of the least well-known elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix [1,2] and tests of the unitarity of that matrix, a foundation of the weak sector of the SM. Increasingly small experimental uncertainties in CKM-dependent decay rates must be met with precise determinations of form factors from the theoretical side to pin down the CKM matrix elements (see, for example [3,4]). The shape of the differential decay rate in q 2 , the squared momentum-transfer between the initial and final states, parameterised by the form factors, provides added detail when testing the SM.…”