Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA unique discrimination between new physics scenarios in $brightarrow smu^+mu^-$ anomalies
78
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A number of observables related to the $b to s l^+ l^-$ transition show deviations from their standard model predictions. A global fit to the current $brightarrow sl^+l^-$ data suggests several new physics solutions. Considering only one operator at a time and new physics only in the muon sector, it has been shown that the new physics scenarios (I) $C_9^{rm NP}<0$, (II) $C_{9}^{rm NP} = -C_{10}^{rm NP}$, (III) $C_9^{rm NP} = -C_9^{prime rm NP}$ can account for all data. In this paper, we develop a procedure to discriminate between these scenarios through a study of the branching ratio of $B_s to mu^+mu^-$ and the distribution of $Bto K^*mu^+mu^-$ decay in the azimuthal angle. The scenario II predicts a significantly lower value of $mathcal{B}(B_sto mu^+mu^-)$ and can be distinguished from the other two scenarios if the experimental uncertainty comes down by a factor of three. On the other hand, a precise measurement of the CP averaged angular observables $S_3$ and $S_9$ in high $q^2$ bin of $Bto K^*mu^+mu^-$ decay can uniquely discriminate between the other two scenarios. We define two azimuthal angle asymmetries, proportional to $S_3$ and to $S_9$ respectively, which can be measured with small statistical uncertainty.
rate research
Read More
We develop a rigorous, semi-analytical method for maximizing any $bto ctau u$ observable in the full 20-real-dimensional parameter space of the dimension 6 effective Hamiltonian, given some fixed values of $R_{D^{(*)}}$. We apply our method to find the maximum allowed values of $F^L_{D^*}$ and $R_{J/psi}$, two observables which have both come out higher than their SM predictions in recent measurements by the Belle and LHCb collaborations. While the measurements still have large error bars, they add to the existing $R_{D^{(*)}}$ anomaly, and it is worthwhile to consider NP explanations. It has been shown that none of the existing, minimal models in the literature can explain the observed values of $F^L_{D^*}$ and $R_{J/psi}$. Using our method, we will generalize beyond the minimal models and show that there is no combination of dimension 6 Wilson operators that can come within $1sigma$ of the observed $R_{J/psi}$ value. By contrast, we will show that the observed value of $F^L_{D^*}$ can be achieved, but only with sizable contributions from tensor and mixed-chirality vector Wilson coefficients.
At Moriond 2019, Belle collaboration has announced new measurements on the flavour ratios $R_D - R_{D^*}$ which are consistent with their Standard Model predictions within $1.2sigma$. After inclusion of these measurements, the global tension in $R_D - R_{D^*}$ has reduced from $4.1sigma$ to $3.1sigma$ which is still significant. The measurements of these ratios indicate towards the violation of lepton flavor universality in $brightarrow c,l,bar{ u}$ decay. Assuming new physics in $brightarrow c,tau,bar{ u}$ transition, we have done a global fit to all available data in this sector to identify the allowed new physics solutions. We find that there are seven allowed new physics solutions which can account for all measurements in $brightarrow c,tau,bar{ u}$ transition. We show that a simultaneous measurement of the $tau$ polarization fraction and forward-backward asymmetry in $Brightarrow D,tau,bar{ u}$, the zero crossing point of forward backward asymmetry in $Brightarrow D^*taubar{ u}$ and the branching ratio of $B_crightarrow tau,bar{ u}$ decay can distinguish these seven new physics solutions if they can be measured with a required precision.
At present, there are several measurements of $B$ decays that exhibit discrepancies with the predictions of the SM, and suggest the presence of new physics (NP) in $b to s mu^+ mu^-$ transitions. Many NP models have been proposed as explanations. These involve the tree-level exchange of a leptoquark (LQ) or a flavor-changing $Z$ boson. In this paper we examine whether it is possible to distinguish the various models via CP-violating effects in $B to K^{(*)} mu^+ mu^-$. Using fits to the data, we find the following results. Of all possible LQ models, only three can explain the data, and these are all equivalent as far as $b to s mu^+ mu^-$ processes are concerned. In this single LQ model, the weak phase of the coupling can be large, leading to some sizeable CP asymmetries in $B to K^{(*)} mu^+ mu^-$. There is a spectrum of $Z$ models; the key parameter is $g_L^{mumu}$, which describes the strength of the $Z$ coupling to $mu^+mu^-$. If $g_L^{mumu}$ is small (large), the constraints from $B^0_s$-${bar B}^0_s$ mixing are stringent (weak), leading to a small (large) value of the NP weak phase, and corresponding small (large) CP asymmetries. We therefore find that the measurement of CP-violating asymmetries in $B to K^{(*)} mu^+ mu^-$ can indeed distinguish among NP $b to s mu^+ mu^-$ models
The recent measurement of $R_{K^*}$ is yet another hint of new physics (NP), and supports the idea that it is present in $bto smu^+mu^-$ decays. We perform a combined model-independent and model-dependent analysis in order to deduce properties of this NP. Like others, we find that the NP must obey one of two scenarios: (I) $C_9^{mumu}({rm NP}) < 0$ or (II) $C_9^{mumu}({rm NP}) = - C_{10}^{mumu}({rm NP}) < 0$. A third scenario, (III) $C_9^{mumu}({rm NP}) = - C_{9}^{prime mumu}({rm NP})$, is rejected largely because it predicts $R_K = 1$, in disagreement with experiment. The simplest NP models involve the tree-level exchange of a leptoquark (LQ) or a $Z$ boson. We show that scenario (II) can arise in LQ or $Z$ models, but scenario (I) is only possible with a $Z$. Fits to $Z$ models must take into account the additional constraints from $B^0_s$-${bar B}^0_s$ mixing and neutrino trident production. Although the LQs must be heavy, O(TeV), we find that the $Z$ can be light, e.g., $M_{Z} = 10$ GeV or 200 MeV.
Following updated and extended measurements of the full angular distribution of the decay $Lambda_bto Lambda(to p,pi^-)mu^+mu^-$ by the LHCb collaborations, as well as a new measurement of the $Lambda to p pi^-$ decay asymmetry parameter by the BESIII collaboration, we study the impact of these results on searches for non-standard effects in exclusive $bto smu^+mu^-$ decays. To this end, we constrain the Wilson coefficients $mathcal{C}_{9}$ and $mathcal{C}_{10}$ of the numerically leading dimension-six operators in the weak effective Hamiltonian, in addition to the relevant nuisance parameters. In stark contrast to previous analyses of this decay mode, the changes in the updated experimental results lead us to find very good compatibility with both the Standard Model and with the $bto smu^+mu^-$ anomalies observed in rare $B$-meson decays. We provide a detailed analysis of the impact of the partial angular distribution, the full angular distribution, and the $Lambda_bto Lambdamu^+mu^-$ branching fraction on the Wilson coefficients. In this process, we are also able to constrain the size of the production polarization of the $Lambda_b$ baryon at LHCb.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
