Speaker
Description
Rare decays of $B$ mesons and $b$ hadrons provide sensitive indirect probes
of effects beyond the Standard Model (SM). In the SM, these decays are
forbidden at tree level and are therefore suppressed. In particular, the
$b \to s\ell\ell$ processes give access to many observables where effects of New
Physics can be observed. The LHCb experiment is designed for these
searches due to its large acceptance and trigger efficiency, as well as
its excellent invariant mass resolution and particle identification
capabilities. Recent results on these searches will be presented,
including the new measurement of the $B_{s} \to \mu\mu$ branching fraction.
In the Standard Model the different lepton families couple universally
to gauge bosons. Therefore, the ratio of branching fractions of decays
with different lepton flavours is predicted with a very good accuracy.
The universality of lepton couplings has been tested using the LHCb Run
1 dataset, resulting in some tensions with respect to the predicted
values. Lepton non-universality would be a major departure from the
Standard Model and may also be accompanied by lepton flavour violation.
Recent tests of lepton flavour universality and searches for lepton
flavour violation decays at LHCb will be presented.
