Study of semileptonic and nonleptonic decays of the Bc−B_c^- meson

We evaluate semileptonic and two--meson nonleptonic decays of the $B_c^-$ meson in the framework of a nonrelativistic quark model. The former are done in spectator approximation using one--body current operators at the quark level. Our model reproduces the constraints of heavy quark spin symmetry obtained in the limit of infinite heavy quark mass. For the two--meson nonleptonic decays we work in factorization approximation. We compare our results to the ones obtained in different relativistic approaches.Comment: Talk given at the IVth International Conference on Quarks an Nuclear Physics, Madrid, June 5th-10th 200

Masses and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model

We evaluate masses and semileptonic decay widths for the ground state of doubly heavy $\Xi$ and $\Omega$ baryons in the framework of a nonrelativistic quark model. We solve the three-body problem by means of a variational ansatz made possible by heavy-quark spin symmetry constraints. Our masses are comparable to the ones obtained in relativistic calculations and we get one of the best agreements with lattice data. Our simple wave functions are used to evaluate semileptonic decays of doubly heavy $\Xi, \Xi'(J=1/2)$ and $\Omega, \Omega'(J=1/2)$ baryons. Our results for the decay widths are in reasonable agreement with calculations done in a relativistic calculation in the quark-diquark approximation. We also check that our wave functions comply with what it is expected in the infinite heavy quark mass limit.Comment: 3 latex pages, two tables. To appear in the INPC07 proceeding

Masses and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model

We evaluate masses and semileptonic decay widths for the ground state of doubly heavy $\Xi$ and $\Omega$ baryons in the framework of a nonrelativistic quark model. We solve the three-body problem by means of a variational ansatz made possible by heavy-quark spin symmetry constraints. Our masses are comparable to the ones obtained in relativistic calculations and we get one of the best agreements with lattice data. Our simple wave functions are used to evaluate semileptonic decays of doubly heavy $\Xi, \Xi'(J=1/2)$ and $\Omega, \Omega'(J=1/2)$ baryons. Our results for the decay widths are in reasonable agreement with calculations done in a relativistic calculation in the quark-diquark approximation. We also check that our wave functions comply with what it is expected in the infinite heavy quark mass limit.Comment: 3 latex pages, two tables. To appear in the INPC07 proceeding

Strong one-pion decay of Σc\Sigma_c, Σc∗\Sigma_c^* and Ξc∗\Xi_c^*

Working in the framework of a nonrelativistic quark model we evaluate the widths for the strong one-pion decays $\Sigma_c\to\Lambda_c \pi$, $\Sigma_c^*\to\Lambda_c \pi$ and $\Xi_c^{*}\to\Xi_c \pi$. We take advantage of the constraints imposed by heavy quark symmetry to solve the three-body problem by means of a simple variational ansatz. We use partial conservation of the axial current hypothesis to get the strong vertices from weak axial current matrix elements. Our results are in good agreement with experimental data.Comment: 3 latex pages. Contribution to the Proceedings of the Quark Confinement and the Hadron Spectrum VII Conference (QCHS7) Ponta Delgada (PT) Sept 2-7, 200

Quark model study of the semileptonic B -> pi decay

The semileptonic decay B->pi is studied starting from a simple quark model and taking into account the effect of the B* resonance. A novel, multiply subtracted, Omn\`es dispersion relation has been implemented to extend the predictions of the quark model to all physical q^2 values. We find |V_{ub}|=0.0034 +/- 0.0003(exp.)+/- 0.0007(theory), in good agreement with experiment.Comment: Three pages, two figures. To appear in the proceedings of Quark Confinament and Hadron Spectrum VII. Azores, September 200

Study of the leptonic decays of pseudoscalar B,DB, D and vector B∗,D∗B^*, D^* mesons and of the semileptonic B→DB\to D and B→D∗B\to D^* decays

We present results for different observables in weak decays of pseudoscalar and vector mesons with a heavy $c$ or $b$ quark. The calculations are done in a nonrelativistic constituent quark model improved at some instances by heavy quark effective theory constraints. We determine pseudoscalar and vector meson decay constants that within a few per cent satisfy $f_V M_V/f_P M_P=1$, a result expected in heavy quark symmetry when the heavy quark masses tend to infinity. We also analyze the semileptonic $B\to D$ and $B\to D^*$ decays for which we evaluate the different form factors. Here we impose heavy quark effective theory constraints among form factors that are not satisfied by a direct quark model calculation. The value of the form factors at zero recoil allows us to determine, by comparison with experimental data, the value of the $|V_{cb}|$ Cabbibo-Kobayashi-Maskawa matrix element. From the $B\to D$ semileptonic decay we get $|V_{cb}|=0.040\pm0.006$ in perfect agreement with our previous determination based on the study of the semileptonic $\Lambda_b\to \Lambda_c$ decay and also in excellent agreement with a recent experimental determination by the DELPHI Collaboration. We further make use of the partial conservation of axial current hypothesis to determine the strong coupling constants $g_{B^*B\pi}(0)=60.5\pm 1.1$ and $g_{D^*D\pi}(0)=22.1\pm0.4$. The ratio $R=(g_{B^*B\pi}(0) f_{B^*}\sqrt{M_D})/ (g_{D^*D\pi}(0) f_{D^*}\sqrt{M_B})=1.105\pm0.005$ agrees with the heavy quark symmetry prediction of 1.Comment: 19 Latex pages,6 figures, references added, corrected typos, content enlarge