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Register a new userConsequences of R-Parity violating interactions for anomalies in $bar Bto D^{(*)} tau bar u$ and $bto s mu^+mu^-$
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We investigate the possibility of explaining the enhancement in semileptonic decays of $bar B to D^{(*)} tau bar u$, the anomalies induced by $bto smu^+mu^-$ in $bar Bto (K, K^*, phi)mu^+mu^-$ and violation of lepton universality in $R_K = Br(bar Bto K mu^+mu^-)/Br(bar Bto K e^+e^-)$ within the framework of R-parity violating (RPV) MSSM. Exchange of down type right-handed squark coupled to quarks and leptons yield interactions which are similar to leptoquark induced interactions that have been proposed to explain the $bar B to D^{(*)} tau bar u$ by tree level interactions and $bto s mu^+mu^-$ anomalies by loop induced interactions, simultaneously. However, the Yukawa couplings in such theories have severe constraints from other rare processes in $B$ and $D$ decays. Although this interaction can provide a viable solution to $R(D^{(*)})$ anomaly, we show that with the severe constraint from $bar B to K u bar u$, it is impossible to solve the anomalies in $bto s mu^+mu^-$ process simultaneously.
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We evaluate long-distance electromagnetic (QED) contributions to $bar{B}{}^0 to D^+ tau^{-} bar{ u}_{tau}$ and $B^- to D^0 tau^{-} bar{ u}_{tau}$ relative to $bar{B}{}^0 to D^+ mu^{-} bar{ u}_{mu}$ and $B^- to D^0 mu^{-} bar{ u}_{mu}$, respectively, in the standard model. We point out that the QED corrections to the ratios $R(D^{+})$ and $R(D^{0})$ are not negligible, contrary to the expectation that radiative corrections are almost canceled out in the ratio of the two branching fractions. The reason is that long-distance QED corrections depend on the masses and relative velocities of the daughter particles. We find that theoretical predictions for $R(D^{+})^{tau/mu}$ and $R(D^{0})^{tau/mu}$ can be amplified by $sim4%$ and $sim3%$, respectively, for the soft-photon energy cut in range $20$-$40$ MeV.
The meson decays $Bto Dtau u$ and $Bto D^* tau u$ are sensitive probes of the $bto ctau u$ transition. In this work we present a complete framework to obtain the maximum information on the physics of $Bto D^{(*)}tau u$ with polarized $tau$ leptons and unpolarized $D^{(*)}$ mesons. Focusing on the hadronic decays $tauto pi u$ and $tautorho u$, we show how to extract seven $tau$ asymmetries from a fully differential analysis of the final-state kinematics. At Belle II with $50~text{ab}^{-1}$ of data, these asymmetries could potentially be measured with percent level statistical uncertainty. This would open a new window into possible new physics contributions in $bto ctau u$ and would allow us to decipher its Lorentz and gauge structure.
In a couple of recent publications ( arXiv:1706.08437 and arXiv:1712.01593 ), the authors attempted to achieve simultaneous explanation of the persistent flavor anomalies in $bto s$ and $bto c$ semileptonic decays with a minimal scheme by using only three unknown new parameters. The analysis was obtained with a handful of precise observables. Motivated by their proposal, in this paper we reanalyze the models proposed in the aforementioned papers with a total of 170 observables from those channels including newly available measurements, correlated theoretical results, and constraints. We validate our results by searching for the most influential points and outliers. By analyzing the parameter spaces and their relationship with the constraints, we gain new insight and statistical significance in those models. We also provide a new and precise calculation of $R(J/Psi)$, obtained during the analysis.
We study R-parity violating contributions to the mixing parameter $y$ for $D^0 -bar D^0$ and $B^0_{d,s} - bar B^0_{d,s}$ systems. We first obtain general expressions for new physics contributions to $y$ from effective four fermion operators. We then use them to study R-parity contributions. We find that R-parity violating contributions to $D^0 - bar D^0$ mixing, and $B_{d}^0 - bar B_{d}^0$ to be small. There may be sizable contribution to $B_s^0 -bar B_s^0$ mixing. We also obtain some interesting bounds on R-parity violating parameters using known Standard Model predictions and experimental data.
In order to explain the observed anomalies in the measurements of $R_{D^{(*)}}$ and $R_{J/psi}$, a variety of new-physics (NP) models that contribute to $bto ctau^-{bar u}$ have been proposed. In this paper, we show how CP-violating observables can be used to distinguish these NP models. Because ${vec p}_tau$ cannot be measured (the decay products of the $tau$ include the undetected $ u_tau$), obtaining the angular distribution of ${bar B}^0to D^{*+}tau^{-}{bar u}_tau$ is problematic. Instead, we focus here on ${bar B}^0to D^{*+}(to D^0 pi^+)mu^- {bar u}_mu$. This process may also receive contributions from the same NP, and LHCb intends to measure the CP-violating angular asymmetries in this decay. There are two classes of NP models that contribute to $bto cmu^-{bar u}_mu$. These involve (i) a $W$ (two types) or (ii) a leptoquark (LQ) (six types). The most popular NP models predict no CP-violating effects, so the measurement of nonzero CP-violating symmetries would rule them out. Furthermore these measurements allow one to distinguish the $W$ and LQ models, and to differentiate among several LQ models.
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