arXiv subjects

Raquel Molina

Publications and source records attributed to Raquel Molina.

30 records · Page 2Linked to original sources

arXiv2017

On the chiral covariant approach to $ρρ$ scattering

We examine in detail a recent work (D.~Gülmez, U.-G.~Meißner and J.~A.~Oller, Eur. Phys. J. C 77:460 (2017)), where improvements to make $ρρ$ scattering relativistically covariant are made. The paper has the remarkable conclusion that the $J=2$ state disappears with a potential which is much more attractive than for $J=0$, where a bound state is found. We trace this abnormal conclusion to the fact that an "on-shell" factorization of the potential is done in a region where this potential is singular and develops a large discontinuous and unphysical imaginary part. A method is developed, evaluating the loops with full $ρ$ propagators, and we show that they do not develop singularities and do not have an imaginary part below threshold. With this result for the loops we define an effective potential, which when used with the Bethe-Salpeter equation provides a state with $J=2$ around the energy of the $f_2(1270)$. In addition, the coupling of the state to $ρρ$ is evaluated and we find that this coupling and the $T$ matrix around the energy of the bound state are remarkably similar to those obtained with a drastic approximation used previously, in which the $q^2$ terms of the propagators of the exchanged $ρ$ mesons are dropped, once the cut-off in the $ρρ$ loop function is tuned to reproduce the bound state at the same energy.

nucl-th↗

arXiv2016

Rho resonance parameters from lattice QCD

We perform a high-precision calculation of the phase shifts for $π$-$π$ scattering in the I = 1, J = 1 channel in the elastic region using elongated lattices with two mass-degenerate quark favors ($N_f = 2$). We extract the $ρ$ resonance parameters using a Breit-Wigner fit at two different quark masses, corresponding to $m_π = 226$MeV and $m_π = 315$MeV, and perform an extrapolation to the physical point. The extrapolation is based on a unitarized chiral perturbation theory model that describes well the phase-shifts around the resonance for both quark masses. We find that the extrapolated value, $m_ρ = 720(1)(15)$MeV, is significantly lower that the physical rho mass and we argue that this shift could be due to the absence of the strange quark in our calculation.

hep-lat↗

arXiv2016

Weak decays of heavy hadrons into dynamically generated resonances

In this review we give a perspective of the theoretical work done recently on the interpretation of results from $B$, $D$, $Λ_b$, $Λ_c$ weak decays into final states that contain interacting hadrons, and how it is possible to obtain additional valuable information that is increasing our understanding of hadron interactions and the nature of many hadronic resonances. The novelty of these processes is that one begins with a clean picture at the quark level which allows one to select the basic mechanisms by means of which the process proceeds. Finally, one has a final state described in terms of quarks. To make contact with the experiments, where mesons and baryons are observed, one must hadronize, creating pairs of $q \bar q$ and writing the new states in terms of mesons and baryons. This concludes the primary hadron production in these processes. After that, the interaction of these hadrons takes place, offering a rich spectrum of resonances and special features from where it is possible to learn much about the interaction of these hadrons and the nature of many resonances in terms of the components of their wave functions.

hep-ph↗

arXiv2014

Heavy Mesons in Nuclear Matter and Nuclei

Heavy mesons in nuclear matter and nuclei are analyzed within different frameworks, paying a special attention to unitarized coupled-channel approaches. Possible experimental signatures of the properties of these mesons in matter are addressed, in particular in connection with the future FAIR facility at GSI.

nucl-th↗

arXiv2014

The width of the $ω$ meson in dense matter

We obtain the width of the $ω$ meson in dense nuclear matter by taking into account (i) the free decay of the $ω$ into three pions, which is dominated by $ρπ$ mode, (ii) the processes induced by a vector-baryon interaction dominated by vector meson exchange, and (iii) the $ω\to K \bar K$ mechanism in matter. The $ω$ meson develops an important width in matter, coming from the dominant $ω\to ρπ$ decay mode, with a value of $121 \pm 10$ MeV at normal nuclear matter density for an $ω$ at rest. At finite momentum, the width of the $ω$ meson increases moderately with values of 200 MeV at 600 MeV/c.

nucl-th↗

arXiv2013

Review of low-energy interaction of strange and charm hadrons with nucleons and nuclei

The properties of strange and charm mesons in nuclear matter and nuclei are reviewed. Different frameworks are presented and discussed paying a special attention to unitarized coupled-channel approaches. Possible experimental signatures of the in-medium properties of these mesons are also addressed, in particular in connection with the future FAIR facility at GSI.

nucl-th↗

arXiv2012

Strangeness and Charm in Nuclear Matter

The properties of strange ($K$, $\bar K$ and $\bar K^*$) and open-charm ($D$, $\bar D$ and $D^*$) mesons in dense matter are studied using a unitary approach in coupled channels for meson-baryon scattering. In the strangeness sector, the interaction with nucleons always comes through vector-meson exchange, which is evaluated by chiral and hidden gauge Lagrangians. For the interaction of charmed mesons with nucleons we extend the SU(3) Weinberg-Tomozawa Lagrangian to incorporate spin-flavor symmetry and implement a suitable flavor symmetry breaking. The in-medium solution for the scattering amplitude accounts for Pauli blocking effects and meson self-energies. On one hand, we obtain the $K$, $\bar K$ and $\bar K^*$ spectral functions in the nuclear medium and study their behaviour at finite density, temperature and momentum. We also make an estimate of the transparency ratio of the $γA \to K^+ K^{*-} A^\prime$ reaction, which we propose as a tool to detect in-medium modifications of the $\bar K^*$ meson. On the other hand, in the charm sector, several resonances with negative parity are generated dynamically by the s-wave interaction between pseudoscalar and vector meson multiplets with $1/2^+$ and $3/2^+$ baryons. The properties of these states in matter are analyzed and their influence on the open-charm meson spectral functions is studied. We finally discuss the possible formation of $D$-mesic nuclei at FAIR energies.

nucl-th↗

arXiv2010

Heavy mesons in dense matter

Charmed mesons in dense matter are studied within a unitary coupled-channel approach which takes into account Pauli-blocking effects and meson self-energies in a self-consistent manner. We obtain the open-charm meson spectral functions in this dense medium, and discuss their implications on hidden charm and charm scalar resonances and on the formation of D-mesic nuclei.

nucl-th↗

arXiv2010

Radiative decays of the Y(3940), Z(3930) and the X(4160) as dynamically generated resonances

We study the radiative decay properties of the charmonium-like X, Y and Z mesons generated dynamically from vector meson-vector meson interaction in the framework of a unitarized hidden-gauge formalism. In the present work we calculate the one- and two-photon decay widths of the hidden-charm Y(3940), Z(3930) (or X(3915)) and X(4160) mesons in the framework of the vector meson dominance formalism. We obtain good agreement with experiment in case of the two photon width of the X(3915) which we associate with the $2^+$ resonance that we find at 3922 MeV.

hep-ph↗

arXiv2010

$\bar K^*$ meson in nuclear matter

The properties of the $\bar K^*$ meson in dense matter are studied using a unitary approach in coupled channels within the framework of the local hidden gauge formalism. We obtain the $\bar K^*$ spectral function in the nuclear medium and we found that the $\bar K^*$ develops an in-medium width up to five times bigger than in free space. We also estimate the transparency ratio of the $γA \to K^+ K^{*-} A^\prime$ reaction, which we propose as a feasible experimental scenario to detect in-medium modifications of the $\bar K^*$ meson.

nucl-th↗

arXiv2009

Charm and Hidden Charm Scalar Resonances in Nuclear Matter

We study the properties of the scalar charm resonances $D_{s0}(2317)$ and $D_0(2400)$, and the theoretical hidden charm state X(3700) in nuclear matter. We find that for the $D_{s0}(2317)$ and X(3700) resonances, with negligible and small width at zero density, respectively, the width becomes about $100 {\rm MeV}$ and $200 {\rm MeV}$ at normal nuclear matter density, accordingly. For $D_0(2400)$ the change in width is relatively less important. We discuss the origin of this new width and trace it to reactions occurring in the nucleus. We also propose a possible experimental test for those modifications in nuclear matter, which will bring valuable information on the nature of those scalar resonances and the interaction of $D$ mesons with nucleons.

nucl-th↗

arXiv2008

Strangeness and charm at FAIR

We study the properties of strange and charm mesons in hot and dense matter within a self-consistent coupled-channel approach for the experimental conditions of density and temperature expected for the CBM experiment at FAIR/GSI. The in-medium solution at finite temperature accounts for Pauli blocking effects, mean-field binding on all the baryons involved, and meson self-energies. In the strange sector, the $\bar K$ spectral function spreads over a wide range of energies, reflecting the melting of the $Λ(1405)$ resonance and the contribution of $(Λ,Σ,Σ^*)N^{-1}$ components at finite temperature. In the case of charm mesons, the dynamically-generated $Λ_c(2593)$ and $Σ_c(2880)$ resonances remain close to their free-space position while acquiring a remarkable width. As a result, the $D$ meson spectral density shows a single pronounced peak for energies close to the $D$ meson free-space mass that broadens with increasing matter density with an extended tail particularly towards lower energies. We also discuss the implications for the $D_{s0}(2317)$, $D_0(2400)$ and the predicted X(3700) resonances at FAIR energies.

hep-ph↗