New Physics Research In Λ_b Baryon Demileptonic Decay

In recent years,the standard model theory of particle physics has stood the test of almost all experiments.However,recently,the experimental results of R(D(*))differ from the results of the standard model theory by 3.1 σ,which implies the destruction of the lepton flavor universality and is a new physical signal that is more obvious in the process of b→cτvτ.For this reason,we perform a detailed study of the new physical effects in the process of Λb→ Λcτvτ.Under the assumption that we only have left-hand neutrinos,we calculated the helicity amplitudes of all possible operators in the process of Λb→Λcτvτ.Within the latest results of Λb→Λc form factors from lattice QCD calculations,we study these decays in a model-independent manner.The differential and total branching fractions,the longitudinal polarizations of final leptons and hadrons,the forward-backward asymmetries in the lepton side,the convexity parameters,and the ratio R(Λc)are calculated.Assuming that the new physical effect only appears in the third-generation fermion,we give the correlation of R(D)、R(D*)and R(Λc).We perform a minimum χ2 fit of the Wilson coefficient of each operator to the latest experimental data of different observables,including the ratios R(D(*))、R(J/Ψ)、PT(D*)and P((D*).It is found that the left-handed scalar operator affects the branching fraction remarkably.Using the fitted values of the Wilson coefficients of the single NP operators,we also give a prognosis for the physical observables of Λb→Λcτvτ,including the ratio R(Ac),forward-backward asymmetry,and other polarized observables as well as the differential branching fraction.Furthermore,based on the above analysis model-independent,this paper makes further research on the W’ model,the scalar leptoquark model,and the vector leptoquark model.This article has a certain guiding significance for the experimental exploration of new physics...