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J. M. Verde-Velasco

Publications and source records attributed to J. M. Verde-Velasco.

13 recordsLinked to original sources
arXiv2008

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

We evaluate static properties and semileptonic decays for the ground state of doubly heavy $Ξ, Ξ', Ξ^*$ and $Ω, Ω', Ω^*$ baryons. Working in the framework of a nonrelativistic quark model, we solve the three--body problem by means of a variational ansazt made possible by heavy quark spin symmetry constraints. To check the dependence of our results on the inter-quark interaction we use five different quark-quark potentials that include a confining term plus Coulomb and hyperfine terms coming from one--gluon exchange. Our results for static properties (masses, charge and mass radii, magnetic moments...) are, with a few exceptions for the magnetic moments, in good agreement with a previous Faddeev calculation. Our much simpler wave functions are used to evaluate semileptonic decays of doubly heavy $Ξ,Ξ'(J=1/2)$ and $Ω, Ω'(J=1/2)$ baryons. Our results for the decay widths are in good agreement with calculations done within a relativistic quark model in the quark--diquark approximation.

hep-ph↗
arXiv2008

Test of the heavy quark-light diquark approximation for baryons with a heavy quark

We check a commonly used approximation in which a baryon with a heavy quark is described as a heavy quark-light diquark system. The heavy quark influences the diquark internal motion reducing the average distance between the two light quarks. Besides, we show how the average distance between the heavy quark and any of the light quarks, and that between the heavy quark and the center of mass of the light diquark, are smaller than the distance between the two light quarks, which seems to contradict the heavy quark-light diquark picture. This latter result is in agreement with expectations from QCD sum rules and lattice QCD calculations. Our results also show that the diquark approximations produces larger masses than the ones obtained in a full calculation.

hep-ph↗
arXiv2007

Static and dynamic properties of hadronic systems with heavy quarks b and c

This thesis has been devoted to the study of different properties of hadrons with one and two heavy quarks $c$ and/or $b$. All calculations have been done in the framework of a nonrelativistic constituent quark model. In order to check the sensitivity of our results to the inter--quark interaction we have used five different quark--quark potentials. The spread in results gives an estimation of theoretical uncertainties and so has been quoted. Most observables studied change only at the level of a few per cent when changing the interaction potential. Another source of theoretical uncertainty is the use of nonrelativistic kinematics in the evaluation of the orbital wave functions and the construction of our nonrelativistic states, although we think that a good part of these relativistic effects are contained in an effective way in the parameters of the quark-quark potentials, which were adjusted in the original works to reproduce the experimental spectra of mesons. Mesons wave functions have been evaluated using a Numerov algorithm, while for baryons the three body problem has been solved using a variational approach with ansatz wave functions that include simplifications that arise from HQS and HQSS. To compute hadron decays we have relied on the impulse approximation, which induces small axial and vector current conservation violations due to binding effects. These binding effects, though they affect some of the weak form factors analyzed, have little influence on the decay widths.

hep-ph↗
arXiv2007

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 $Ξ$ and $Ω$ 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 $Ξ, Ξ'(J=1/2)$ and $Ω, Ω'(J=1/2)$ 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.

nucl-th↗
arXiv2006

Study of exclusive semileptonic and nonleptonic decays of $B_c^-$ in a nonrelativistic quark model

We present results for different observables measured in semileptonic and non-leptonic decays of the $B_c^-$ meson. The calculations have been done within the framework of a nonrelativistic constituent quark model. In order to check the sensitivity of all our results against the inter-quark interaction we use five different quark--quark potentials. We obtain form factors, decay widths and asymmetry parameters for semileptonic $B_c^-\to c\bar c$ and $B_c^-\to \bar B$ decays. In the limit of infinite heavy quark mass our model reproduces the constraints of heavy quark spin symmetry. For the actual heavy quark masses we find nonetheless large corrections to that limiting situation for some form factors. We also analyze exclusive non-leptonic two--meson decay channels within the factorization approximation.

hep-ph↗
arXiv2006

Doubly heavy quark baryon spectroscopy and semileptonic decay

Working in the framework of a nonrelativistic quark model we evaluate the spectra and semileptonic decay widths for the ground state of doubly heavy $Ξ$ and $Ω$ baryons. We solve the three-body problem using a variational ansatz made possible by the constraints imposed by heavy quark spin symmetry. In order to check the dependence of our resultson the inter-quark interaction we have used five different quarkquark potentials which include Coulomb and hyperfine terms coming fromone-gluon exchange, plus a confining term. Our results for the spectra are in good agreement with a previous calculation done using a Faddeev approach. For the semileptonic decay our results for the total decay widths are in a good agreement with the ones obtained within a relativistic quark model in the quark-diquark approximation.

hep-ph↗
arXiv2006

Study of semileptonic and nonleptonic decays of the $B_c^-$ 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.

hep-ph↗
arXiv2006

Study of the semileptonic decays B->pi, D->pi and D->K

The semileptonic decay B->pi is studied starting from a simple quark model that takes into account the effect of the B* resonance. A novel, multiply subtracted, Omnes dispersion relation has been implemented to extend the predictions of the quark model to all q^2 values accesible in the physical decay. By comparison to the experimental data, we extract |V_ub|=0.0034 +/- 0.0003(exp.) +/- 0.0007(theory). As a further test of the model, we have also studied D->pi and D->K decays for which we get good agreement with experiment.

hep-ph↗
arXiv2006

Strong one-pion decay of $Σ_c$, $Σ_c^*$ and $Ξ_c^*$

Working in the framework of a nonrelativistic quark model we evaluate the widths for the strong one-pion decays $Σ_c\toΛ_c π$, $Σ_c^*\toΛ_c π$ and $Ξ_c^{*}\toΞ_c π$. 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.

hep-ph↗
arXiv2005

Strong one-pion decay of ground state charmed baryons

We evaluate the widths for the strong decays $Σ_c\toΛ_c π$, $Σ_c^*\toΛ_c π$ and $Ξ_c^{*}\toΞ_c π$. The calculations have been done within 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 weak axial current matrix elements. Our results are in good agreement with experimental data.

hep-ph↗
arXiv2005

Study of the strong $Σ_c\to Λ_c π$, $Σ_c^{*}\to Λ_c π$ and $Ξ_c^{*}\to Ξ_c π$ decays in a nonrelativistic quark model

We present results for the strong widths corresponding to the $Σ_c\to Λ_c π$, $Σ_c^{*}\to Λ_c π$ and $Ξ_c^{*}\to Ξ_c π$ 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 \hbox{$Γ(Σ_c^{++}\to Λ_c^+ π^+)=2.41 \pm0.07\pm0.02 \mathrm{MeV}$}, {$Γ(Σ_c^{+}\to Λ_c^+ π^0)=2.79 \pm0.08\pm0.02 \mathrm{MeV}$}, {$Γ(Σ_c^{0}\to Λ_c^+ π^-)=2.37 \pm0.07\pm0.02 \mathrm{MeV}$}, {$Γ(Σ_c^{* ++}\to Λ_c^+ π^+)=17.52\pm0.74\pm0.12 \mathrm{MeV}$}, {$Γ(Σ_c^{* +}\to Λ_c^+ π^0)=17.31\pm0.73\pm0.12 \mathrm{MeV}$}, {$Γ(Σ_c^{* 0}\to Λ_c^+ π^-)=16.90\pm0.71\pm0.12 \mathrm{MeV}$}, {$Γ(Ξ_c^{* +}\to Ξ_c^0 π^++Ξ_c^+π^0)=3.18\pm0.10\pm0.01 \mathrm{MeV}$} and {$Γ(Ξ_c^{* 0}\to Ξ_c^+ π^-+Ξ_c^0π^0)=3.03\pm0.10\pm0.01 \mathrm{MeV}$} are in good agreement with experimental determinations.

hep-ph↗
arXiv2005

Study of the leptonic decays of pseudoscalar $B, D$ and vector $B^*, D^*$ mesons and of the semileptonic $B\to D$ and $B\to D^*$ 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 $Λ_b\to Λ_c$ 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 $g_{B^*Bπ}(0)=60.5\pm 1.1$ and $g_{D^*Dπ}(0)=22.1\pm0.4$. The ratio $R=(g_{B^*Bπ}(0) f_{B^*}\sqrt{M_D})/ (g_{D^*Dπ}(0) f_{D^*}\sqrt{M_B})=1.105\pm0.005$ agrees with the heavy quark symmetry prediction of 1.

hep-ph↗