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

## TL;DR

This paper explores how to measure angular and CP-violation observables in ar;B^{*+} l^-ar{
u}_{l} decays at hadron colliders, using simulation-based correction methods to improve experimental precision for potential new physics signals.

## Contribution

It introduces a novel correction method for reconstructing decay observables in hadron collider experiments, enhancing measurement precision despite reconstruction inaccuracies.

## Key findings

- The method achieves a factor of 2 precision loss for the $D^{*+}$ polarization fraction.
- A factor of 5 precision loss is observed for CP-violating observable measurements.
- Simulation studies demonstrate the feasibility of extracting phase space distributions with controlled systematic uncertainties.

## 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.