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D. Cabrera

Publications and source records attributed to D. Cabrera.

At least 37 records · Page 2Linked to original sources
arXiv2008

Heavy Flavor in the sQGP

We attempt a unified treatment of heavy quarkonia and heavy-quark diffusion in the Quark-Gluon Plasma. Our approach is based on finite-temperature T-matrices with interaction potentials estimated from the heavy-quark internal energy computed in thermal lattice QCD (lQCD). In the charmonium sector S-wave bound states (J/ψ, η_c) survive up to temperatures of ~2 T_c, not inconsistent with constraints from euclidean correlation functions in lQCD. In the open-heavy flavor sector, the T-matrix interaction reduces heavy-quark diffusion substantially, leading to fair agreement with single-electron spectra at RHIC and suggestive for a small viscosity-to-entropy ratio close to T_c.

hep-ph↗
arXiv2006

T-Matrix Approach to Quarkonium Correlation Functions in the QGP

We study the evolution of heavy quarkonium states with temperature in a Quark Gluon Plasma (QGP) by evaluating the in-medium Q-\bar{Q} T-matrix within a reduced Bethe-Salpeter equation in both S- and P-wave channels. The underlying interaction kernel is extracted from recent finite-temperature QCD lattice calculations of the singlet free energy of a Q-\bar{Q} pair. The bound states are found to gradually move above the Q-\bar{Q} threshold after which they rapidly dissolve in the hot system. The T-matrix approach is particularly suited to investigate these mechanisms as it provides a unified treatment of bound and scattering states including threshold effects and the transition to the (perturbative) continuum. We apply the T-matrix to calculate Q-\bar{Q} spectral functions as well as pertinent Euclidean-time correlation functions which are compared to results from lattice QCD. A detailed analysis reveals large sensitivities to the interplay of bound and scattering states, to temperature dependent threshold energies and to the "reconstructed" correlator used for normalization. We furthermore investigate the impact of finite-width effects on the single-quark propagators in the QGP as estimated from recent applications of heavy-quark rescattering to RHIC data.

hep-ph↗
arXiv2006

The kaon optical potential modified by Θ^+ Pentaquark excitation

We study the kaon nuclear optical potential including the effect of the Θ^+ pentaquark in a self-consistent approach, starting from an extension of the Juelich meson-exchange potential as bare kaon-nucleon interaction. Significant differences between a fully self-consistent calculation and the low-density Tρapproximation are observed. Whereas te influence of the KN -> Θ^+ absorption process is found to be negligible, due to the small Θ^+ KN coupling, the two-nucleon mechanism (KNN -> Θ^+ N), estimated from the two-meson coupling of the pentaquark, provides the necessary additional kaon absorption to reconcile with data the systematically low theoretical K^+ nucleus reaction cross sections.

hep-ph↗
arXiv2006

Q\bar{Q} modes in the Quark-Gluon Plasma

We study the evolution of heavy quarkonium states with temperature in a Quark-Gluon Plasma by evaluating an in-medium Q\bar{Q} T-matrix within a reduced Bethe-Salpeter equation in S- and P-wave channels. The interaction kernel is extracted from finite-temperature QCD lattice calculations of the singlet free energy of a Q\bar{Q} pair. Quarkonium bound states are found to gradually move across the Q\bar{Q} threshold after which they rapidly dissolve in the hot system. We calculate Euclidean-time correlation functions and compare to results from lattice QCD. We also study finite-width effects in the heavy-quark propagators.

hep-ph↗
arXiv2006

Charm and Charmonium in the Quark-Gluon Plasma

In the first part of the talk, we briefly review the problem of parton-energy loss and thermalization at the Relativistic Heavy-Ion Collider and discuss how heavy quarks (charm and bottom) can help to resolve the existing experimental and theoretical puzzles. The second part of the talk is devoted to the properties of heavy quarkonia in the (strongly interacting) Quark-Gluon Plasma (sQGP) and their consequences for observables in heavy-ion collisions.

nucl-th↗
arXiv2005

Chiral dynamics of baryon resonances and hadrons in a nuclear medium

In these lectures I make an introduction to chiral unitary theory applied to the meson baryon interaction and show how several well known resonances are dynamically generated, and others are predicted. Two very recent experiments are analyzed, one of them showing the existence of two $Λ(1405)$ states and the other one providing support for the $Λ(1520)$ resonance as a quasibound state of $Σ(1385) π$. The use of chiral Lagrangians to account for the hadronic interaction at the elementary level introduces a new approach to deal with the modification of meson and baryon properties in a nuclear medium. Examples of it for $\bar{K}$, $η$ and $ϕ$ modification in the nuclear medium are presented.

nucl-th↗
arXiv2005

Evaluation of the $ππ$ scattering amplitude in the $σ$-channel at finite density

The $ππ$ scattering amplitude in the $σ$-channel is studied at finite baryonic density in the framework of a chiral unitary approach which successfully reproduces the meson meson phase shifts and generates the $f_0$ and $σ$ resonances in vacuum. We address here a new variety of mechanisms recently suggested to modify the $ππ$ interaction in the medium, as well as the role of the $s-$wave selfenergy, in addition to the $p-$wave, in the dressing of the pion propagators.

nucl-th↗
arXiv2005

Chiral dynamics of hadrons in nuclei

In this talk I report on selected topics of hadron modification in the nuclear medium using the chiral unitary approach to describe the dynamics of the problems. I shall mention how antikaons, $η$, and $ϕ$ are modified in the medium and will report upon different experiments done or planned to measure the $ϕ$ width in the medium.

nucl-th↗
arXiv2005

Bound states of $Θ^+$ in nuclei

We study the binding energy and the width of the $Θ^+$ in nuclei, associated to the $K N$ and $ K πN$ components. The first one leads to negligible contributions while the second one leads to a sizeable attraction, enough to bind the $Θ^+$ in nuclei. Pauli blocking and binding effects on the $K N$ decay reduce considerably the $Θ^+$ decay width in nuclei and medium effects associated to the $ K πN$ component also lead to a very small width, as a consequence of which one finds separation between the bound levels considerably larger than the width of the states.

nucl-th↗
arXiv2005

$Θ^+$ Hypernuclei

We present results for the selfenergy of the $Θ^+$ pentaquark in nuclei associated with two sources: the $KN$ decay of the $Θ^+$ and the two meson baryon decay channels of the $Θ^+$ partners in an antidecuplet of baryons. The first source is shown to produce a small potential, unable to bind the $Θ^+$ in nuclei, while the second source gives rise to a large attractive potential. At the same time we show that the width of the $Θ^+$ in nuclei is small, such that, in light and medium nuclei, many bound $Θ^+$ states would appear with a separation between levels appreciably larger than the width of the states, thus creating an ideal scenario for pentaquark spectroscopy in nuclei.

nucl-th↗
arXiv2004

$Θ^+$ pentaquark in the nuclear medium

We study the interaction of the $Θ^+$ pentaquark with nuclear matter associated to the $KN$ decay channels and to the two meson cloud. We find that the potential is attractive and could be strong enough to lead to the existence of $Θ^+$ nuclear bound states.

nucl-th↗
arXiv2004

Interaction of the $Θ^+$ with the nuclear medium

We study the selfenergy of the $Θ^+$ pentaquark in nuclei associated with two types of interaction: the KN decay of the $Θ^+$ and two meson baryon decay channels of the $Θ^+$. Whereas the potential related to the first source is quite weak, the second kind of interaction produces a large and attractive potential that could lead to the existence of $Θ^+$ nuclear bound states.

nucl-th↗
arXiv2004

Kaon-antikaon nuclear optical potentials and the kappa meson in the nuclear medium

We study the properties of the kappa meson in the nuclear medium, starting from a chiral unitary model of S-wave, I=1/2 K-pi scattering, which describes the elastic K-pi phase shifts and generates a pole in the amplitude. Medium effects are considered by including pion and kaon selfenergies. We explore the changes in the kappa pole position and in the K-pi scattering amplitude at finite density, with two different models for the kaon selfenergy.

nucl-th↗
arXiv2003

Mass dependence of inclusive nuclear $ϕ$ photoproduction

Based on a prior determination of the $ϕ$ selfenergy in a nuclear medium we perform a theoretical study of inclusive $ϕ$ photoproduction in nuclei, looking at the $A$ dependence of the cross sections for different $ϕ$ momenta. We find sizeable reductions in the nuclear cross sections with respect to the elementary one, using a $ϕ$ selfenergy which implies a width about six times the free one at normal nuclear density. The calculations are done to match the set up for an ongoing experiment at {\it SPring8/Osaka} which should provide valuable information on the renormalization of the $ϕ$ properties in nuclei.

nucl-th↗
arXiv2003

Phi meson mass and decay width in nuclear matter

The $ϕ$ meson spectrum, which in vacuum is dominated by its coupling to the $\bar{K} K$ system, is modified in nuclear matter. Following a model based on chiral SU(3) dynamics we calculate the $ϕ$ meson selfenergy in nuclear matter considering the $K$ and $\bar{K}$ in-medium properties. For the latter we use the results of previous calculations which account for $S-$ and $P-$wave kaon-nucleon interactions based on the lowest order meson-baryon chiral effective Lagrangian, and this leads to a dressing of the kaon propagators in the medium. In addition, a set of vertex corrections is evaluated to fulfill gauge invariance, which involves contact couplings of the $ϕ$ meson to $S-$wave and $P-$wave kaon-baryon vertices. Within this scheme the mass shift and decay width of the $ϕ$ meson in nuclear matter are studied.

nucl-th↗
arXiv2002

Chiral approach to the rho meson in nuclear matter

In this work, the properties of the $ρ$ meson at rest in cold symmetric nuclear matter are studied. We make use of a chiral unitary approach to pion-pion scattering in the vector-isovector channel, calculated from the lowest order Chiral Perturbation Theory ($χPT$) lagrangian including explicit resonance fields. Low energy chiral constraints are considered by matching our expressions to those of one loop $χPT$. To account for the medium corrections, the $ρ$ couples to $ππ$ pairs which are properly renormalized in the nuclear medium, accounting for both $p-h$ and $Δ-h$ excitations. The terms where the $ρ$ couples directly to the hadrons in the $p-h$ or $Δ-h$ excitations are also accounted for. In addition, the $ρ$ is also allowed to couple to $N^{*}(1520)-h$ components.

nucl-th↗
arXiv2001

The rho meson in nuclear matter - a chiral unitary approach

In this work, the properties of the $ρ$ meson at rest in cold symmetric nuclear matter are studied. We make use of a chiral unitary approach to pion-pion scattering in the vector-isovector channel, calculated from the lowest order Chiral Perturbation Theory ($χPT$) lagrangian including explicit resonance fields. Low energy chiral constraints are considered by matching our expressions to those of one loop $χPT$. To account for the medium corrections, the $ρ$ couples to $ππ$ pairs which are properly renormalized in the nuclear medium, accounting for both $p-h$ and $Δ-h$ excitations. The terms where the $ρ$ couples directly to the hadrons in the $p-h$ or $Δ-h$ excitations are also accounted for. In addition, the $ρ$ is also allowed to couple to $N^{*}(1520)-h$ components.

nucl-th↗
arXiv2001

Chiral unitary theory: application to nuclear problems

In this talk we briefly describe some basic elements of chiral perturbation theory, $χPT$, and how the implementation of unitarity and other novel elements lead to a better expansion of the $T$ matrix for meson meson and meson baryon interactions. Applications are then done to the $ ππ$ interaction in nuclear matter in the scalar and vector channels, antikaons in nuclei and $K^-$ atoms, and how the $ϕ$ meson properties are changed in a nuclear medium.

nucl-th↗