On the significance of new physics in $b\to s{\ell }^{+}{\ell }^{-}$ decays

Abstract

Motivated by deviations with respect to Standard Model predictions in $b\to s{\ell }^{+}{\ell }^{-}$ decays, we evaluate the global significance of the new physics hypothesis in this system by including the {\it look-elsewhere effect} for the first time. We estimate the trial-factor with pseudo-experiments and find that it can be as large as seven. We calculate the global significance for the new physics hypothesis by considering the most general description of a non-standard $b\to s{\ell }^{+}{\ell }^{-}$ amplitude of short-distance origin. Theoretical uncertainties are treated in a highly conservative way by absorbing the corresponding effects into a redefinition of the Standard Model amplitude. Using the most recent measurements of LHCb, ATLAS and CMS, we obtain the global significance to be $4.3$ standard deviations.

Comments: Published paper version, including discussion on the effect of C7(prime) and fixed minor numerical issue. 6 pages, 4 figures - updated to match journal submission