P-wave meson emitting decays of heavy flavor hadrons

Abstract

At present, there exist rich amount of experimental data for the weak decays of heavy flavor hadrons. Weak leptonic and semileptonic decays are reasonably well understood in the Standard Model of fundamental interactions, however, weak hadronic decays have posed serious problems for the model as these decays experience strong interaction interference due to the gluons exchange among the quarks involved. In this thesis, two-body weak hadronic decays of heavy flavor mesons have investigated in the framework of the Standard Model. It has been found experimentally that two-body decays dominate the decay spectrum. Theoretical focus has, so far, been on the s-wave meson (i.e. pseudoscalar (P) and vector mesons (V)) emitting weak decays. However, charm and bottom mesons, being heavy, can also emit p-wave mesons, i.e. axial-vector (A), tensor (T) and scalar (S) mesons. Naively, the p-wave mesons emitting decays of the hadrons are expected to be suppressed kinematically due to the large mass of these meson resonances. However, now reasonable amount of experimental data has become available for branching ratios of the p-wave emitting decays of heavy flavor mesons which are found to be quite large, and require theoretical understanding. In this thesis, such weak decays of bottom mesons ( −B , 0 B and s B ), which are the bound state of bottom quark and a light anti- quark, and of a unique bottom-charm ( c B ) meson made up of heavy quarks only, have been investigated using the improved ISGW –II (Isgur, Scora, Grinstein and Wise) quark model. It has been the first model to calculate the form factors for s-wave meson to p-wave meson transitions using the constituent quark picture. Firstly, form factors for s-wave meson to p-wave meson transitions have been determined in this thesis using this model. Finally, branching ratios of weak hadronic decays involving b c and b u transitions are predicted that are found to be in good agreement with the available experimental data for bottom mesons ( −B , 0 B and s B ). Since c B meson is recently observed, and measurements for its weak decays are expected in future experiments, it is hoped that the predictions made in this thesis would help the experimentalists to identify the p-wave meson emitting decays of the heaviest bottom meson.