Search for D^{*}(2007)^{0} rightarrow mu ^{+} mu ^{-} in B^{-}rightarrow pi ^{-} mu ^{+} mu ^{-} decays

Abstract

The very rare {{D} ^*} (2007)^0!rightarrow {mu ^+mu ^-} decay is searched for by analysing {{{B} ^-}} !rightarrow {{pi } ^-} {mu ^+mu ^-} decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9text {,fb} ^{-1}. The signal signature corresponds to simultaneous peaks in the {mu ^+mu ^-} and {{pi } ^-} {mu ^+mu ^-} invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at mathcal{B}({{D} ^*} (2007)^0!rightarrow {mu ^+mu ^-} ) < 2.6times 10^{-8} at 90% confidence level. This is the first limit on the branching fraction of {{D} ^*} (2007)^0!rightarrow {mu ^+mu ^-} decays and the most stringent limit on {{D} ^*} (2007)^0 decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays.