• lepton flavor
• lepton flavor violation

A test of the Lepton flavor Universality Violation is performed through the measurement
of R(J/ψ) = B(B+c → J/ψτ+ντ)/B(B+c → J/ψμ+νμ). A sample of pp collision data
corresponding to an integrated luminosity of 59.6 fb−1 has been analyzed. It has been
recorded by CMS at LHC at the center of mass energy of 13 TeV. Monte Carlo samples
are re-scaled to the data integrated luminosity with the fit of B+c → J/ψπ+ and B+ →
J/ψK+, used as control channels. These fits are performed through the sum of different
probability density functions of discriminating variables with RooFit. Candidate events
are selected by offline cuts optimized by a genetic algorithm. Some discriminant variables
are presented and evaluated with efficiencies and ROC curves. A binned maximum-
likelihood fit for these discriminating variables is performed using templates of shapes
from Monte Carlo samples. A closure test of the fit procedure is done by splitting the
Monte Carlo sample in half: one is used to extract shapes and the other one to perform
the fit. Finally, this fit procedure is used in the analysis for a preliminary evaluation of
R(J/ψ) and its errors.