Soft Pion Emission in Semileptonic BB-Meson Decays

An analysis of semileptonic decays of $B$ mesons with the emission of a single soft pion is presented in the framework of the heavy-quark limit using an effective Lagrangian which implements chiral and heavy-quark symmetries. The analysis is performed at leading order of the chiral and inverse heavy mass expansions. In addition to the ground state heavy mesons some of their resonances are included. The estimates of the various effective coupling constants and form factors needed in the analysis are obtained using a chiral quark model. As the main result, a clear indication is found that the $0^{+}$ and $1^{+}$ resonances substantially affect the decay mode with a $D^{\ast}$ in the final state, and a less dramatic effect is also noticed in the $D$ mode. An analysis of the decay spectrum in the $D^{(\ast)}-\pi$ squared invariant mass is carried out, showing the main effects of including the resonances. The obtained rates show promising prospects for studies of soft pion emission in semileptonic $B$-meson decays in a $B$-meson factory where, modulo experimental cuts, about $10^5$ such decays in the $D$ meson mode and $10^4$ in the $D^{\ast}$ mode could be observed per year.Comment: 41 pages, uses revtex, epsf. 16 uuencoded postscript figures appended after `\end{document

Decays of Non-Strange Positive Parity Excited Baryons in the 1/Nc Expansion

The decays of non-strange positive parity excited baryons via emission of a pseudo-scalar meson are studied in the framework of the 1/Nc expansion to order 1/Nc. In particular, the pionic decays of the l=0 Roper baryons and of the l=2 baryons in the mass interval 1680-1950 MeV are analyzed using the available partial decay widths. Decay widths by emission of an eta meson are shown to be suppressed by a factor 1/Nc^2 with respect to the pionic ones.Comment: 16 pages, 8 table

Excited [70,ℓ+][{\bf 70},\ell^+] baryon resonances in large NcN_c QCD

We summarize results obtained in the $1/N_c$ expansion method for the masses of baryon resonances belonging to the $[{\bf 70},\ell^+]$ multiplet. They represent an extension of our previous studies from two to three flavors. A better approach to mixed symmetric states of any angular momentum and parity is also outlined.Comment: 4 pages, 1 figure, uses espcrc2.sty (included), based on a talk given by N. Matagne at the 13th International QCD Conference, QCD06, Montpellier, France, 3-7th July 200

Baryon Chiral Perturbation Theory combined with the 1/Nc{\mathbf{1/N_c}} Expansion in SU(3) I: Framework

Baryon Chiral Perturbation Theory combined with the $1/N_c$ expansion is implemented for three flavors. Baryon masses, vector charges and axial vector couplings are studied to one-loop and organized according to the $\xi$-expansion, in which the $1/N_c$ and the low energy power countings are linked according to $1/N_c={\cal{O}}(\xi)={\cal{O}}(p)$. The renormalization to ${\cal{O}}(\xi^3)$ necessary for the mentioned observables is provided, along with applications to the baryon masses and axial couplings as obtained in lattice QCD calculations.Comment: 47 pages, 7 figures. arXiv admin note: text overlap with arXiv:1210.236