Phenomenological Studies Of Lepton Flavor Universality In Heavy-flavored Hadrons' Decays

The Standard Model of particle physics has successfully unified the electro-weak and strong interactions that has described the microscopic world with unprecedented power since its estab-lishment.It becomes one of the two pillars of physics that stand side by side with the general theory of relativity which describing massive macroscopic objects.So far,most of the experi-mental results can be reasonably explained with Standard Model.However,there are still some phenomena that the Standard Model cannot answer,such as neutrino mass,asymmetry between matter and antimatter,dark matter,dark energy,etc.In addition,there are also deviations that cannot be ignored even in those experimental phenomena that fit well with the Standard Model predictions.There could be some new physical laws that we have not discovered yet.Therefore,the urgent problem need to be solved for particle physics is to find direct and indirect evidences for these New Physics.In the recent years,the anomalies of Lepton Flavor Universality found in B-meson decays experimentally has attracted many theoretical and experimental attentions.This could be a signal of new physics beyond the SM.Many large experimental devices such as Large Hadron Collider have measured B-meson decays.These decay processes mainly include b?cr? and b?sl+l-semileptonic decays at the quark level.The measurement results show that there could be violation of lepton flavor universality.RD and RD*exceed the SM predictions by 1.4? and 2.5? respectively.The difference with the Standard Model prediction is about 3.08a if taking into account the correlation between them.The measurement results for RK and RK*also show deviations below from the Standard Model prediction value of 2.5a.Besides,other observables of these decay processes have different degrees of deviation.In the literature,many new physical models have been proposed to explain these phenomena.The main content of this paper is to discuss the violation of Lepton Flavor Universality under the new physics model and to find the possible reasons behind these anomalies.Moti-vated by these recent experimental progresses,we study the b?c?v decay anomalies in the Supersymmetry with R-parity violation.In this scenario,the down-type squarks can interact with quarks and leptons via the RPV couplings.Therefore,they contribute to b?c?v transition at the tree level and could explain the current RD(*).anomalies.Besides B? D(*)?v,we also study Bc?J/??v,Bc??c?v,and ?b??c?v decay.All of them are b?c?v transition at the quark level,and the latter two decays have not been measured yet.Using the latest ex-perimental data of various low-energy flavor processes,we will derive constraints on the RPV couplings.Then studies in the RPV SUSY are made for the five b?c?v decays,focusing on the branching ratios,the lepton flavor universality ratios,lepton forward-backward asymmetries,polarizations of daughter hadrons and ? lepton.We have shown that the RPV SUSY can explain the RD(*)anomalies well at 2? level,after taking into account various flavor constraints.In the allowed parameter space,the differential branching fractions and lepton flavor universality ratios are largely enhanced by the RPV SUSY effects,especially in the large dilepton invariant mass region.In addition,a lower bound B(B+?K+vv)>7.37×10-6 is obtained.We also find interesting correlations among RD,RD*,B(B+?K+vv),B(B??v),and gz?L?L/gZlLlL.With the SuperKEKB and the future High-Luminosity LHC,our results are expected to provide more information on the b?c?v transitions and could correlate with the direct search for SUSY in the future with high-energy colliders.We have studied the b?sl+l-decay in the Z' model.tcZ' and bsZ' couplings can enter into Flavor Changing Neutral Current b?s?+?-through penguin diagrams and tree diagrams,thus affect the decays of B and the Bs-Bs mixing.New physical effect can also impact the decay of top quark by producing the FCNC t?c?+?-decay.We restrict the coupling parameters with the latest experimental fitting values of RK(*)etc.Through analysis we found that the constraints from Bs-Bs mixing are generally stronger than B decay anomaly.We also calculate the branching ratio of t?c?+?-decay.