%0 Generic
%A Kolpin, Michael
%D 2018
%F heidok:23940
%R 10.11588/heidok.00023940
%T Measurement of the differential branching fraction and angular analysis of the decay $B_s^0\to\phi\mu^+\mu^-$ and determination of the track reconstruction efficiencies at the LHCb experiment
%U https://archiv.ub.uni-heidelberg.de/volltextserver/23940/
%X The measurement of the differential branching fraction and an angular  analysis of the decay B s 0 → φμ + μ − is performed, using a dataset collected by the LHCb  experiment in proton-proton collisions in 2011 and 2012, corresponding to an integrated  luminosity of 3 fb −1 . The results are presented as function of q 2 , the square of the dimuon  invariant mass. A full set of angular observables is extracted for the first time for this  decay mode, where all measured angular coefficients are consistent with Standard Model  expectations. For the range of 1 < q 2 < 6 GeV 2 /c 4 the branching fraction is found to be  more than 3 standard deviations below the Standard Model prediction, which is derived  using a combination of light-cone sum rules and lattice QCD calculations. This tension  is compatible with observations made by other measurements of electroweak penguin  decays mediated by b → s + − transitions in this q 2 region. Possible explanations are  theoretical models which predict new heavy degrees of freedom at the TeV scale, as well  as underestimated contributions from cc-loop corrections in the SM calculations.  An important aspect of the measurements of branching fractions is the determination of  the track reconstruction efficiency. It is determined from J/ψ → μ + μ − decays, where the  data-driven tag-and-probe technique is used. During LHC Run II this measurement is  performed in a “quasi-online” approach, directly after the data has been recorded. For  the 2015 data-taking period of the LHCb experiment, the track reconstruction efficiency is  found to be (96.14 ± 0.03)%, where the uncertainty is statistical only.