arXiv subjects

G. Toledo Sanchez

Publications and source records attributed to G. Toledo Sanchez.

29 records · Page 2Linked to original sources

arXiv2005

Radiative two-pion decay of the tau lepton

We consider the bremsstrahlung and model-dependent contributions to the radiative decay $τ^- \to π^-π^0ν_τγ$ in the context of a meson dominance model. We focus on several observables related to this decay, including the branching ratio and the photon and di-pion spectra. Particular attention is paid to the sensitivity of different observables upon the effects of model-dependent contributions and of the magnetic dipole moment of the $ρ^-(770)$ vector meson. Important numerical differences are found with respect to results obtained in the framework of chiral perturbation theory.

hep-ph↗

arXiv2004

Gauge invariance, radiative interferences and properties of vector mesons

We state the implications on the properties of vector mesons due to gauge invariance. In particular, we find that polarized vector mesons exhibit a property in the radiation distribution of order $ω^{-1}$ in the photon energy, namely it is null when the gyromagnetic ratio becomes $g=2$. Therefore, the generalization of the Burnett-Kroll theorem for polarized vector-meson states is held only if $g=2$. In addition, radiative interferences between the electric charge and any gauge invariant term is found to be parametrized by a common global factor which can be used to extract information of the involved states by a proper choice of the kinematical region, where they could be relevant.

hep-ph↗

arXiv2004

Color screening in a constituent quark model of hadronic matter

The effect of color screening on the formation of a heavy quark-antiquark ($Q\bar{Q}$) bound state--such as the $J/ψ$ meson--is studied using a constituent-quark model. The response of the nuclear medium to the addition of two color charges is simulated directly in terms of its quark constituents via a string-flip potential that allows for quark confinement within hadrons yet enables the hadrons to separate without generating unphysical long-range forces. Medium modifications to the properties of the heavy meson, such as its energy and its mean-square radius, are extracted by solving Schrödinger's equation for the $Q\bar{Q}$ pair in the presence of a (screened) density-dependent potential. The density dependence of the heavy-quark potential is in qualitative agreement with earlier studies of its temperature dependence extracted from lattice calculations at finite temperature. In the present model it is confirmed that abrupt changes in the properties of the $J/ψ$-meson in the hadronic medium ({\it plasma}), correlate strongly with the deconfining phase transition.

nucl-th↗

arXiv2002

Extracting vector mesons magnetic dipole moment from radiative decays

The possibility that the magnetic dipole moment (MDM) of light charged vector mesons could be measured from radiative processes involving the production (τ\to ρνγ) and decay(ρ\to ππγ) of vector mesons is studied in a model independent way, via the soft-photon approximation. The angular and energy distribution of photons emitted at small angles respect to the final charged particle is found be sensitive to the effects of the MDM. We also show that model dependent contributions have a general structure, by gauge invariance requirements, that allows suppress them in the same kinematical region where the MDM effect is more important in the model independent approach.

hep-ph↗

arXiv2002

Structure of radiative interferences and g=2 for vector mesons

The result by Burnett-Kroll (BK) states that for radiative decays the interference of ${\cal O}(ω^{-1})$ in the photon energy $ω$, vanishes after sum over polarizations of the involved particles. Using radiative decays of vector mesons we show that if the vector meson is polarized the ${\cal O}(ω^{-1})$ terms are null only for the canonical value of the magnetic dipole moment of the vector meson, namely ${\bf g}=2$ in Bohr's magneton units. A subtle cancellation of all ${\cal O}(ω^{-1})$ terms happens when summing over all polarizations to recover the Burnett-Kroll result. We also show the source of these terms and the corresponding cancellation for the unpolarized case and exhibit a global structure that can make them individually vanish in a particular kinematical region.

hep-ph↗

arXiv2001

Modeling the strangeness content of hadronic matter

The strangeness content of hadronic matter is studied in a string-flip model that reproduces various aspects of the QCD-inspired phenomenology, such as quark clustering at low density and color deconfinement at high density, while avoiding long range van der Waals forces. Hadronic matter is modeled in terms of its quark constituents by taking into account its internal flavor (u,d,s) and color (red, blue, green) degrees of freedom. Variational Monte-Carlo simulations in three spatial dimensions are performed for the ground-state energy of the system. The onset of the transition to strange matter is found to be influenced by weak, yet not negligible, clustering correlations. The phase diagram of the system displays an interesting structure containing both continuous and discontinuous phase transitions. Strange matter is found to be absolutely stable in the model.

nucl-th↗

arXiv2001

Beyond the soft photon approximation in radiative production and decay of charged vector mesons

We study the effects of model-dependent contributions and the electric quadrupole moment of vector mesons in the decays $V^- \to P^-P^0γ$ and $τ^- \to νV^-γ$. Their interference with the amplitude originating from the radiation due to electric charges vanishes for photons emitted collinearly to the charged particle in the final state. This brings further support to our claim in previous works, that measurements of the photon energy spectrum for nearly collinear photons in those decays are suitable for a first measurement of the magnetic dipole moment of charged vector mesons.

hep-ph↗

arXiv1999

Gauge invariance and finite width effects in radiative two-pion tau lepton decay

The contribution of the rho^{\pm} vector meson to the tau -> pi pi nu gamma decay is considered as a potential source for the determination of the magnetic dipole moment of this light vector meson. In order to keep gauge-invariance of the whole decay amplitude, a procedure similar to the fermion loop-scheme for charged gauge bosons is implemented to incorporate the finite width effects of the rho^{\pm} vector meson. The absorptive pieces of the one-loop corrections to the propagators and electromagnetic vertices of the rho^{\pm} meson and W^{\pm} gauge boson have identical forms in the limit of massless particles in the loops, suggesting this to be a universal feature of spin-one unstable particles. Model-dependent contributions to the tau -> pi pi nu gamma decay are suppressed by fixing the two-pion invariant mass distribution at the rho meson mass value. The resulting photon energy and angular distribution is relatively sensitive to the effects of the rho magnetic dipole moment.

hep-ph↗

arXiv1999

Vector-meson magnetic dipole moment effects in radiative tau decays

We study the possibility that the magnetic dipole moment of light charged vector mesons could be measured from their effects in τ^- --> V^-ν_τγdecays. We conclude that the energy spectrum and angular distribution of photons emitted at small angles with respect to vector mesons is sensitive the effects of the magnetic dipole moment. Model-dependent contributions and photon radiation off other electromagnetic multipoles are small in this region. We also compute the effects of the magnetic dipole moment on the integrated rates and photon energy spectrum of these $τ$ lepton decays.

hep-ph↗

arXiv1997

Further remarks on isospin breaking in charmless semileptonic B decays

We consider the isospin breaking corrections to charmless semileptonic decays of B mesons. Both, the recently measured branching ratios of exclusive decays by the CLEO Collaboration and the end-point reion of the inclusive lepton spectrum in form factor models, can be affected by these corrections. Isospin corrections can affect the determination of |V_ub| from exclusive semileptonic B decays at a level comparable to present statistical uncertainties.

hep-ph↗

arXiv1997

Effects of the magnetic dipole moment of charged vector mesons in their radiative decay distribution

We consider the effects of anomalous magnetic dipole moments of vector mesons in the decay distribution of photons emitted in two-pseudoscalar decays of charged vector mesons. By choosing a kinematical configuration appropriate to isolate these effects from model-dependent and dominant bremsstrahlung contributions, we show that this method can provide a valid alternative for a measurement of the unknown magnetic dipole moments of charged vector mesons.

hep-ph↗