Phenomenological Study Of New Physics Effects In The Angular Distribution Of ?_b??_c(???)?(?v_??)(?)_? Decay

The Standard Model of particle physics is a theory designed to describe the three fundamen-tal interactions of nature:the strong,the weak,and the electromagnetic interaction.It has been tested by numerous experiments since its establishment,and is considered as one of the most suc-cessful theories throughout history.However,there are still some experimental phenomena that could be reasonably explained within the Standard Model.The theoretical predictions of some observations are quite different from the experimental measurements.which provides therefore some space for New Physics beyond the Standard Model.With respect to the searches for New Physics.the current particle physics experiments are mainly developed in two directions:on the one hand.the energy of the collider is increased to search for new particles directly:on the other hand,the luminosity of the collider is increased to search for New Physics signals indirectly by testing the Standard Model precisely.Up to now.there is however no direct signal of new parti-cles beyond the Standard Model at the energy frontier.and searchiing for New Physics requires some sort of indirect approaches.The angular distribution of some b-hadron decay processes can serve as a bridge between experimental measurements and theoretical predictions.Higher luminosity and higher accuracy of experimental measurements will allow us to study the angu-lar distribution of various decays in more detail,allowing us to test the Standard Model more accurately and to look for signs of New Physics.In recent years,the experimental discovery of R(D(*))anomaly by the BaBar,Belle and LHCb collaborations has attracted a lot of attention,and there have been many studies on the New Physics behind it.The ?b? ?c?v? decay process,being induced by the same quark-level b?c?v? transition,can also receive contributions from these New Physics contributions.It is more sensitive to different Lorentz structures than the mesonic counterpart,because of the spin 1/2 nature of ?b baryon.But a major difficulty in studying the angular distribution of this process is that the momentum of ? lepton is difficult to be determined experimentally.Therefore,this thesis further considers the ??v?? cascade decay to construct a measurable angular distribu-tion.First,we briefly introduce the Standard Model and effective theory,along with the helicity amplitude method used to calculate the angular distribution.Next.we calculate the angular dis-tribution of the ?b??c(? ??)?(?v??)v? process within the most general framework of the effective Hamiltonian given at the mb scale.Then,we construct various observables from the angular distribution and investigate the influence of the New Physics,constrained by the current experimental data,on these observables.We find that the tensor-type New Physics has relatively large contributions to the observable AFBA,AFB?,CF,AC(1),and AC(2).In addition,we construct the CP-violating observables(AT(1)>and(AT(2)>,which are absent in the Standard Model and therefore smoking-gun signal of New Physics.In particular,the observable<AT(2)>only receives contributions from tensor-type New Physics;as a result,if it were observed to be nonzero,we can confirm not only the existence of New Physics but also the tensor-type interaction.In conclusion,the angular distribution of ?b??c(???)?(?v??)v? process can be used to study the New Physics effects in the b? c?V? process.With further and deeper studies from both experimental and theoretical aspects,we could find or exclude the indirect evidence of New Physics beyond the Standard Model.