arXiv subjects

J. J. Cobos-Martínez

Publications and source records attributed to J. J. Cobos-Martínez.

26 records · Page 2Linked to original sources

arXiv2017

$ϕ$ meson in nuclear matter and nuclei

The mass and decay width of the $ϕ$ meson in cold nuclear matter are computed in an effective Lagrangian approach, with the medium dependence of these properties obtained by evaluating kaon-antikaon loop contributions to the $ϕ$ self-energy. At normal nuclear matter density, we find a downward shift of the $ϕ$ mass by a few percent, while the decay width is enhanced by an order of magnitude. We also present $ϕ$--nucleus bound state energies and absorption widths for some selected nuclei, using complex optical potentials obtained in the local density approximation. Our results suggest that the $ϕ$ should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.

nucl-th↗

arXiv2017

Partial restoration of chiral symmetry in cold nuclear matter: the $ϕ$-meson case

The work presented at this workshop is divided into two parts. In the first part, the mass and decay width of the $ϕ$-meson in cold nuclear matter are computed in an effective Lagrangian approach. The medium dependence of these properties are obtained by evaluating kaon-antikaon loop contributions to the $ϕ$-meson self-energy, employing medium-modified kaon masses calculated using the quark-meson coupling model. The loop integral is regularized with a dipole form factor, and the sensitivity of the results to the choice of cutoff mass in the form factor is investigated. At normal nuclear matter density, we find a downward shift of the $ϕ$ mass by a few percent, while the decay width is enhanced by an order of magnitude. Our results support the literature which suggest that one should observe a small downward mass shift and a large broadening of the decay width. In the second part, we present $ϕ$-meson--nucleus bound state energies and absorption widths for four selected nuclei, calculated by solving the Klein-Gordon equation with complex optical potentials. The attractive potential for the $ϕ$-meson in the nuclear medium originates from the in-medium enhanced KK loop in the $ϕ$-meson selfenergy. The results suggest that the $ϕ$-meson should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.

nucl-th↗

arXiv2017

Heavy quarkonia in a contact interaction and an algebraic model: mass spectrum, decay constants, charge radii and elastic and transition form factors

For the flavor-singlet heavy quark system of bottomonia, we compute the masses of the ground state mesons in four different channels, namely, pseudo-scalar ($η_{b}(1S)$), vector ($Υ(1S)$), scalar ($χ_{b_0}(1P)$) and axial vector ($χ_{b_{1}}(1P)$). We also calculate the weak decay constants of the $η_{b}(1S)$ and $Υ(1S)$ as well as the charge radius of $η_{b}(1S)$. It complements our previous study of the corresponding charmonia systems: $η_c(1S)$, $J/Ψ(1S)$, $χ_{c_0}(1P)$) and ($χ_{c_{1}}(1P)$). The unified formalism for this analysis is provided by a symmetry-preserving Schwinger-Dyson equations treatment of a vector$\times$vector contact interaction. Whenever a comparison is possible, our results are in fairly good agreement with experimental data and model calculations based upon Schwinger-Dyson and Bethe-Salpeter equations involving sophisticated interaction kernels. Within the same framework, we also report the elastic and transition form factors to two photons for the pseudo-scalar channels $η_{c}(1S)$ and $η_{b}(1S)$ in addition to the elastic form factors for the vector mesons $J/Ψ$ and $Υ$ for a wide range of photon momentum transfer squared ($Q^2$). For $η_{c}(1S)$ and $η_{b}(1S)$, we also provide predictions of an algebraic model which correlates remarkably well between the known infrared and ultraviolet limits of these form factors.

nucl-th↗

arXiv2017

$Φ$-meson--nucleus bound states

$ϕ$-meson--nucleus bound state energies and absorption widths are calculated for seven selected nuclei by solving the Klein-Gordon equation with complex optical potentials. Essential input for the calculations, namely the medium-modified $K$ and $\overline{K}$ meson masses, as well as the density distributions in nuclei, are obtained from the quark-meson coupling model. The attractive potential for the $ϕ$-meson in the nuclear medium originates from the in-medium enhanced $K\overline{K}$ loop in the $ϕ$-meson self-energy. The results suggest that the $ϕ$-meson should form bound states with all the nuclei considered. However, the identification of the signal for these predicted bound states will need careful investigation because of their sizable absorption widths.

nucl-th↗

arXiv2017

$ϕ$ meson mass and decay width in nuclear matter and nuclei

The mass and decay width of the $ϕ$ meson in cold nuclear matter are computed in an effective Lagrangian approach. The medium dependence of these properties are obtained by evaluating kaon-antikaon loop contributions to the $ϕ$ self-energy, employing the medium-modified kaon masses, calculated using the quark-meson coupling model. The loop integral is regularized with a dipole form factor, and the sensitivity of the results to the choice of cutoff mass in the form factor is investigated. At normal nuclear matter density we find a downward shift of the $ϕ$ mass by a few percent, while the decay width is enhanced by an order of magnitude. For a large variation of the cutoff mass parameter, the results for the $ϕ$ mass and the decay width turn out to vary very little. Our results support results in the literature which suggest that one should observe a small downward mass shift and a large broadening of the decay width. In order to explore the possibility of studying the binding and absorption of $ϕ$ mesons in nuclei, we also present the single-particle binding energies and half-widths of $ϕ$-nucleus bound states for some selected nuclei.

nucl-th↗

arXiv2016

$η_{c}$ Elastic and Transition Form Factors: Contact Interaction and Algebraic Model

For the flavor-singlet heavy quark system of charmonia in the pseudoscalar ($η_c(1S)$) channel, we calculate the elastic (EFF) and transition form factors (TFF) ($η_c(1S) \rightarrow γγ^*$) for a wide range of photon momentum transfer squared ($Q^2$). The framework for this analysis is provided by a symmetry-preserving Schwinger-Dyson equation (SDE) and Bethe-Salpeter equation (BSE) treatment of a vector$\times$vector contact interaction (CI). We also employ an algebraic model (AM), developed earlier to describe the light quark systems. It correctly correlates infrared and ultraviolet dynamics of quantum chromodynamics (QCD). The CI results agree with the lattice data for low $Q^2$. For $Q^2 \geqslant Q_0^2$, the results start deviating from the lattice results by more than $20 \%$. $Q_0^2 \thickapprox 2.5 {\rm GeV}^2$ for the EFF and $\thickapprox 25 {\rm GeV}^2$ for the TFF. We also present the results for the EFF, TFF as well as $η_c(1S)$ parton distribution amplitude for the AM. Wherever the comparison is possible, these results are in excellent agreement with the lattice, perturbative QCD, the results obtained through an SDE-BSE study, employing refined truncations, as well as the experimental findings of the BABAR experiment.

hep-ph↗

arXiv2016

Landau-Khalatnikov-Fradkin transformations in Reduced Quantum Electrodynamics

We derive the Landau-Khalatnikov-Frandkin transformation (LKFT) for the fermion propagator in quantum electrodynamics (QED) described within a brane-world inspired framework where photons are allowed to move in $d_γ$ space-time (bulk) dimensions, while electrons remain confined to a $d_e$-dimensional brane, with $d_e < d_γ$, referred to in the literature as reduced quantum electrodynamics, RQED$_{d_γ,d_e}$. Specializing to the case of graphene, namely, RQED$_{4,3}$ with massless fermions, we derive the nonperturbative form of the fermion propagator starting from its bare counterpart and then compare its weak coupling expansion to known one- and two-loop perturbative results. The agreement of the gauge-dependent terms of order $α$ and $α^{2}$ is reminiscent from the structure of LKFT in ordinary QED in arbitrary space-time dimensions and provides strong constraints for the multiplicative renormalizability of RQED$_{d_γ,d_e}$.

hep-ph↗

arXiv2016

Charmonia in a Contact Interaction

For the flavour-singlet heavy quark system of charmonia, we compute the masses of the ground state mesons in four different channels: pseudo-scalar ($η_c(1S)$), vector ($J/Ψ(1S)$), scalar ($χ_{c_0}(1P)$) and axial vector ($χ_{c_{1}}(1P)$), as well as the weak decay constants of the $η_c(1S)$ and $J/Ψ(1S)$ and the charge radius of $η_c(1S)$. The framework for this analysis is provided by a symmetry-preserving Schwinger-Dyson equation (SDEs) treatment of a vector$\times$vector contact interaction (CI). The results found for the meson masses and the weak decay constants, for the spin-spin combinations studied, are in fairly good agreement with experimental data and earlier model calculations based upon Schwinger-Dyson and Bethe-Salpeter equations (BSEs) involving sophisticated interaction kernels. The charge radius of $η_c(1S)$ is consistent with the results from refined SDE studies and lattice Quantum Chromodynamics (QCD).

hep-ph↗