[en] The use of heavy quark symmetry to study bottom and charmed baryons leads to important simplifications of the non-relativistic three body problem, which turns out to be easily solved by a simple variational ansatz. Our simple scheme reproduces previous results (baryon masses, charge and mass radii, ...) obtained by solving the Faddeev equations with simple non-relativistic quark-quark potentials, adjusted to the light and heavy-light meson spectra. Wave functions, parameterized in a simple manner, are also given and thus they can be easily used to compute further observables. Our method has been also used to find the predictions for strangeness-less baryons of the SU(2) chirally inspired quark-quark interactions. We find that the one pion exchange term of the chirally inspired interactions leads to relative changes of the Λ_b and Λ_c binding energies as large as 90%

[en] Data on ΛΛ hypernuclei provide a unique method to learn details about the strangeness S=-2 sector of the baryon-baryon interaction. From the free space Bonn-Juelich potentials, determined from data on baryon-baryon scattering in the S=0, -1 channels, we construct an interaction in the S=-2 sector to describe the experimentally known ΛΛ hypernuclei. After including short-range (Jastrow) and RPA correlations, we find masses for these ΛΛ hypernuclei in a reasonable agreement with data, taking into account theoretical and experimental uncertainties. Thus, we provide a natural extension, at low energies, of the Bonn-Juelich one-boson exchange potentials to the S=-2 channel

[en] We evaluate pionic decay widths of Λ hypernuclei using a shell model for both the nuclear bound and continuum nucleon wave functions in the final state and distorted waves for the outgoing pion. An excellent agreement with the recent KEK measurement of π^-decay widths of _Λ¹²C and _Λ²⁸Si is found. In addition, results for _Λ⁵⁶Fe are consistent with the existing upper bound

[en] In this work we investigate the possible condensation of tetraneutron resonant states in the lower density neutron rich gas regions inside Neutron Stars (NSs). Using a relativistic density functional approach we characterize the system containing different hadronic species including, besides tetraneutrons, nucleons and a set of light clusters (${}^3$He, $\mathrm{\alpha <!--\; ??\; -->}$ particles, deuterium and tritium). $\mathrm{\sigma <!--\; ??\; -->}$, $\mathrm{\omega <!--\; ??\; -->}$ and $\mathrm{\rho <!--\; ??\; -->}$ mesonic fields provide the interaction in the nuclear system. We study how the tetraneutron presence could significantly impact the nucleon pairing fractions and the distribution of baryonic charge among species. For this we assume that they can be thermodynamically produced in an equilibrated medium and scan a range of coupling strengths to the mesonic fields from prescriptions based on isospin symmetry arguments. We find that tetraneutrons may appear over a range of densities belonging to the outer NS crust carrying a sizable amount of baryonic charge thus depleting the nucleon pairing fractions.

[en] We evaluate masses of bottom and charmed baryons using several non-relativistic quark potentials which parameters have been adjusted to the meson spectra. Heavy Quark Symmetry leads to important simplifications of the three body problem, which turns out to be easily solved by a simple variational ansatz. The wave functions obtained can be readily used to compute further observables as mass densities or form factors. The quark-quark potentials explored so far, show an overall good agreement with the experimental masses

[en] The BABAR Collaboration has recently reported products of branching fractions that include B meson semileptonic decays into final states with charged and neutral D₁(2420) and D₂*(2460), two narrow orbitally excited charmed mesons. We evaluate these branching fractions, together with those concerning D₀*(2400) and D₁^'(2430) mesons, within the framework of a constituent quark model. The calculation is performed in two steps, one of which involves a semileptonic decay and the other is mediated by a strong process. Our results are in agreement with the experimental data. We also extend the study to semileptonic decays of B_s into orbitally excited charmed-strange mesons, providing predictions to the possible measurements to be carried out at LHC.

[en] We investigate the semileptonic and nonleptonic decays of B_s mesons. We work within the context of nonrelativistic constituent quark models. We calculate the different form factors that parameterize the hadron matrix elements. (author)

[en] We present the results of a nonrelativistic constituent quark model study of the semileptonic decays Λ_b⁰→Λ_c⁺l^-ν_l and Ξ_b⁰→Ξ_c⁺l^-ν_l (l=e,μ). We work on coordinate space, with baryon wave functions recently obtained from a variational approach based on heavy quark symmetry. We develop a novel expansion of the electroweak current operator, which supplemented with heavy quark effective theory constraints, allows us to predict the baryon form factors and the decay distributions for all q² (or equivalently w) values accessible in the physical decays. Our results for the partially integrated longitudinal and transverse decay widths, in the vicinity of the w=1 point, are in excellent agreement with lattice calculations. Comparison of our integrated Λ_b-decay width to experiment allows us to extract the V_cb Cabbibo-Kobayashi-Maskawa matrix element for which we obtain a value of |V_cb|=0.040±0.005(stat)_-0.002^+0.001(theory) also in excellent agreement with a recent determination by the DELPHI Collaboration from the exclusive B_d⁰→D*⁺l^-ν_l decay. Besides for the Λ_b(Ξ_b)-decay, the longitudinal and transverse asymmetries and the longitudinal to transverse decay ratio are < a_L>=-0.954±0.001(-0.945±0.002), < a_T>=-0.665±0.002(-0.628±0.004), and R_L/T=1.63±0.02(1.53±0.04), respectively

[en] We present results for the strong widths corresponding to the Σ_c→Λ_cπ, Σ_c*→Λ_cπ and Ξ_c*→Ξ_cπ decays. The calculations have been done in a nonrelativistic constituent quark model with wave functions that take advantage of the constraints imposed by heavy quark symmetry. Partial conservation of axial current hypothesis allows us to determine the strong vertices from an analysis of the axial current matrix elements. Our results Γ(Σ_c⁺⁺→Λ_c⁺π⁺)=2.41±0.07±0.02 MeV, Γ(Σ_c⁺→Λ_c⁺π⁰)=2.79±0.08±0.02 MeV, Γ(Σ_c⁰→Λ_c⁺π^-)=2.37±0.07±0.02 MeV, Γ(Σ_c*⁺⁺→Λ_c⁺π⁺)=17.52±0.74±0.12 MeV, Γ(Σ_c*⁺→Λ_c⁺π⁰)=17.31±0.73±0.12 MeV, Γ(Σ_c*⁰→Λ_c⁺π^-)=16.90±0.71±0.12 MeV, Γ(Ξ_c*⁺→Ξ_c⁰π⁺+Ξ_c⁺π⁰)=3.18±0.10±0.01 MeV, and Γ(Ξ_c*⁰→Ξ_c⁺π^-+Ξ_c⁰π⁰)=3.03±0.10±0.01 MeV are in good agreement with experimental determinations

[en] 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 percent satisfy f_VM_V/f_PM_P=1, a result expected in heavy quark symmetry when the heavy quark masses tend to infinity. We also analyze the semileptonic B→D and B→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| Cabibbo-Kobayashi-Maskawa matrix element. From the B→D semileptonic decay we get |V_cb|=0.040±0.006, in perfect agreement with our previous determination based on the study of the semileptonic Λ_b→Λ_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*Bπ(0)=60.5±1.1 and g_D*Dπ(0)=22.1±0.4. The ratio R=(g_B*Bπ(0)f_B*√(M_D))/(g_D*Dπ(0)f_D*√(M_B))=1.105±0.005 agrees with the heavy quark symmetry prediction of 1