Angular and CP-violation analyses of $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ decays at hadron collider experiments

Abstract

The $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ branching fraction ratio $R(D^{*})$ has shown intriguing discrepancies between the Standard Model prediction and measurements performed at BaBar, Belle and LHCb experiments, a possible sign of beyond the Standard Model physics. Theoretical studies prove how observables related to the $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ differential decay distribution can be used to further constrain New Physics contributions, but their experimental measurements is lacking to date. This article presents the attainable precision on the measurement of $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ angular and CP-violating observables by exploiting approximate reconstruction algorithms using information from detectable final-state particles only, a case of special interest for hadron collider experiments. The resolution on the phase space variables is studied using $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ decays simulated in a forward detector geometry like LHCb. A novel method to correct the observable values for the reconstruction inaccuracies based on detector simulation is successfully tested on simulated data and the decrease in precision with respect to a perfect reconstruction is evaluated. The $D^{*+}$ longitudinal polarization fraction and one of the CP-violating observables can be measured losing a factor 2 and 5 in precision, respectively. The extraction of phase space distributions from the template fit selecting $\bar{B}\to D^{*+} l^-\bar{\nu}_{l}$ decays and associated systematic uncertainties are also discussed.