The Phenomenological Study Of The Two-body Hadronic Decays Of B_c Meson

Over the past thirty years,there have been great successes in theoretical studies and experimental measurements in the B meson puhysics.but there still exist many problems to be resolved.Take the hadronic decays of the doubly heavy Bc meson as an example,the measurement data are not enough and the relevant theoretical frameworks are still needed to be constructed and tested.In the review part of this thesis,we present simple introductions to the nonrela.tivistic quantum chromodynamics(NRQCD)effective theory.the SU(3)flavor symmetry and the quark model of hadrons.The major works in this thesis include:(1)employing the NRQCD effective theory,we calculated the form factors of Bc meson into S-wavc and P-wave charmonium states at the leading order accuracy;(2)based on the SU(3)flavor symmetry,we studied the general relations among different channels of two-body hadronic Bc meson decays.NRQCD is an important theoretical framework to study the productions and decays of heavy quarkonium in which the relative velocity between the heavy quarks Q and Q is small.The Bc meson is composed of two different heavy quarks b and c(or c and b),which has attracted great attention in theoretical and experimental sides.Its decay rates can be expanded as the series of the long distance matrix elements of NRQCD along with the short-distance coefficient.Through precise analysis of these properties,we can get more information about the hadronic mechanism of heavy quarkonium and Bc meson,furthermore,the NRQCD effective theory itself can also be tested.The transitions of Bc to S wave charmonium include:the form factors f+LO(q2)and fnLO(q2)from the contributions of vector current in Bc??c transition;and the form factor VLO(q2)from the contribution of vector current and the ones A0,1,2LO(q2)from the contribution of axial vector current in Bc?J/? transition.The transitions of Bc to P wave charmonium include:(1)the form factors Aihc(q2)with i =(1,2,3)and Vhc(q2)for the spin-singlet hc(1Pi);(2)the form factors f0vo(q2)and f+Xco(q2)for the scalar Xc0(3-P0);(3)the form factors AiXcl(q2)with i=(1,2,3)and Vxel(q2)for the axial-vector meson Xcl(3Pi);(4)the form factors VXc2(q2)and Ai?c2(q2)with i =(1.2,3)for the tensor meson Xc2(3P2)In Chapter 5,based on the SU(3)flavor symmetry,we will study the two-body hadron-ic:B,meson decays.Since both b and c quarks in a Bc meson can decay indendently.there exist a lot of weak decay modes.Although only few Bc meson decay channels have been observed,the future LHCb experiments shall give a precise measurements of certain two-body hadronic Bc meson decays along with large data accumulation.We analyzed the weak decay amplitudes relations of the Bc meson into two hadronic states under the assumption of the SU(3)flavor symmetry.For the decays into two mesons,the relations among amplitudes of Bc into Dq + P(V),Bq + P(V)and P(V)+ P(V)decay modes were investigated systematically,where P and V denote the pseudoscalar and vector meson respectively.For the decays into two light baryons we give the decays amplitudes of Bc?T8+T8 and Bc ? T10 +T10 decay modes,where Ts and T10 are the SU(3)octet and SU(3)decuplet light baryons.In the SU(3)flavor symmetry,the dynamics mechanism is hidden and then the free parameters a3,a6,a8 and o15 can not be obtained directly,whose value can refer to the experimental data fit.We found the parameter-dependent decay amplitudes and defined the ratios R of the decay widths between the different de-cay channels.When experimental measurements for some relevant decay modes become available,one can determine those free parameters by fitting the data.The testing of the results of the two-body decays of the Bc Meson can help us to uncderstand the SU(3)flavor symmetry and the CP violat.ion.