# $b \to c\tau\bar\nu$ decays in supersymmetry with $R$-parity violation

## TL;DR

This paper investigates how R-parity violating supersymmetry can explain anomalies in B meson decays involving tau leptons, predicting observable effects in decay rates, asymmetries, and polarizations that can be tested at future colliders.

## Contribution

It demonstrates that RPV SUSY can account for the $R_{D^{(*)}}$ anomalies within current flavor constraints and predicts specific enhancements in decay observables.

## Key findings

- RPV SUSY explains $R_{D^{(*)}}$ anomalies at 2σ level.
- Enhanced differential branching fractions and LFU ratios in large dilepton mass region.
- Lower bound on $ ext{Br}(B^+ o K^+
u ar
u)$ established.

## Abstract

In the past few years, several hints of lepton flavour universality (LFU) violation have emerged in the $b \to c \tau \bar\nu$ and $b \to s \ell^+ \ell^-$ data. Quite recently, the Belle Collaboration has reported the first measurement of the $D^*$ longitudinal polarization fraction in the $B \to D^* \tau \bar\nu$ decay. Motivated by this intriguing result, together with the recent measurements of $R_{J/\psi}$ and $\tau$ polarization, we study $b \to c \tau \bar\nu$ decays in the Supersymmetry (SUSY) with $R$-parity violation (RPV). We consider $B \to D^{(*)} \tau \bar\nu$, $B_c \to \eta_c \tau \bar\nu$, $B_c \to J/\psi \tau \bar\nu$ and $\Lambda_b \to \Lambda_c \tau \bar\nu$ modes and focus on the branching ratios, the LFU ratios, the forward-backward asymmetries, polarizations of daughter hadrons and $\tau$ lepton. It is found that the RPV SUSY can explain the $R_{D^{(*)}}$ anomalies at $2\sigma$ level, after taking into account various flavour constraints. In the allowed parameter space, the differential branching fractions and LFU ratios are largely enhanced by the SUSY effects, especially in the large dilepton invariant mass region. In addition, a lower bound $\mathcal B(B^+ \to K^+ \nu \bar\nu) > 7.37 \times 10^{-6}$ is obtained. These observables could provide testable signatures at the High-Luminosity LHC and SuperKEKB, and correlate with direct searches for SUSY.