SemiCharmTag: a tool for Semileptonic Charm tagging
A method for selecting and/or rejecting leptons from charm semileptonic decays based on the tagging of the secondary vertex using a hadron track is introduced. The method is developed for dimuon Drell-Yan measurements in LHCb using full simulations in proton-proton collisions at $\sqrt{s}=13.6$ TeV. We focus on the invariant mass range between 2.9 and 5 GeV/$c^2$ with single muon transverse momentum larger than 1 GeV/$c$. A novel strategy is detailed for background rejection, achieving an improvement of the signal over background of a factor $\sim 4$ at an efficiency of 81% while maintaining the Drell-Yan kinematic distributions largely unbiased except at the acceptance edges. Moreover, a second approach is presented for the construction of unbiased background-pure samples of single muons from charm decays, achieving a charm efficiency of 21.4% at a Drell-Yan efficiency of 1.1%.