Dense Hadronic Matter Research Articles

Dense hadronic and quark matter and its astrophysical applications

Dense hadronic and quark matter and its astrophysical applications

Indirect Observation of an In-Mediumη′Mass Reduction insNN=200 GeVAu+AuCollisions

PHENIX and STAR data on the intercept parameter of the two-pion Bose-Einstein correlation functions in sqrt(s_{NN}) = 200 GeV Au+Au collisions are analyzed in terms of different models of hadronic multiplicities. To describe this combined PHENIX and STAR dataset, an in-medium eta' mass reduction of at least 200 MeV is needed, at the 99.9 % confidence level in the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the 9th "prodigal" Goldstone boson.

Thermodynamics of dense hadronic matter in a parity doublet model

We study thermodynamics of nuclear matter in a two-flavored parity doublet model within the mean field approximation. Parameters of the model are chosen to reproduce correctly the properties of the nuclear ground state. The model predicts two phase transitions in nuclear matter, a liquid-gas phase transition at normal nuclear density and a chiral transition at higher density. At finite temperature the pion decay constant exhibits a considerable reduction at intermediate values of chemical potential, which is traced back to the presence of the liquid-gas transition, and approaches zero at higher chemical potential associated with the chiral symmetry restoration. A "transition" from meson-rich to baryon-rich matter is also discussed.

Charmed hadrons in nuclear medium

We study the properties of charmed hadrons in dense matter within a coupled-channel approach which accounts for Pauli blocking effects and meson self-energies in a self-consistent manner. We analyze the behaviour in this dense environment of dynamically-generated baryonic resonances as well as the open-charm meson spectral functions. We discuss the implications of the in-medium properties of open-charm mesons on the Ds0(2317) and the predicted X(3700) scalar resonances.

Dilatons for dense hadronic matter

The idea that the explicit breaking of scale invariance by the trace anomaly of QCD can be rephrased as a spontaneous breaking has been recently exploited to capture the low-energy strong interaction dynamics of dense (and also hot) matter in terms of two dilaton fields, the “soft” ( χ s ) and the “hard” ( χ h ) fields, in the frame work of the hidden local gauge symmetry. In the Freund-Nambu model, the spontaneous symmetry breaking of scale symmetry is induced by an explicitly breaking term, while the spontaneous symmetry breaking is possible in the flat potential model which is scale symmetric. We discuss the interplay of the soft and hard dilatons using the spontaneously broken scale symmetry schemes and uncover a novel structure of dense matter hitherto unexplored.

Dmesons and charmonium states in asymmetric nuclear matter at finite temperatures

We investigate the in-medium masses of $D$ and $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons in the isospin-asymmetric nuclear matter at finite temperatures arising due to the interactions with the nucleons, the scalar-isoscalar meson $\ensuremath{\sigma}$, and the scalar-isovector meson $\ensuremath{\delta}$ within a SU(4) model. However, since the chiral symmetry is explicitly broken for the SU(4) case due to the large charm quark mass, we use the SU(4) symmetry here only to obtain the interactions of the $D$ and $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons with the light hadron sector but use the observed values of the heavy hadron masses and empirical values of the decay constants. The in-medium masses of $J/\ensuremath{\psi}$ and the excited charmonium states [$\ensuremath{\psi}(3686)$ and $\ensuremath{\psi}(3770)$] are also calculated in the hot isospin-asymmetric nuclear matter in the present investigation. These mass modifications arise due to the interaction of the charmonium states with the gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD within the effective chiral model. The change in the mass of $J/\ensuremath{\psi}$ in the nuclear matter with the density is seen to be rather small, as has been shown in the literature by using various approaches, whereas the masses of the excited states of charmonium [$\ensuremath{\psi}(3686)$ and $\ensuremath{\psi}(3770)$] are seen to have considerable drop at high densities. The present study of the in-medium masses of $D$ ($\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$) mesons as well as of the charmonium states will be of relevance for the observables from the compressed baryonic matter, like the production and collective flow of the $D$ ($\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$) mesons, resulting from the asymmetric heavy-ion collision experiments planned at the future facility of the GSI Facility for Antiproton and Ion Research. The mass modifications of $D$ and $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons as well as of the charmonium states in hot nuclear medium can modify the decay of the charmonium states (${\ensuremath{\Psi}}^{\ensuremath{'}},{\ensuremath{\chi}}_{c},J/\ensuremath{\Psi}$) to $D\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ pairs in the hot dense hadronic matter. The small attractive potentials observed for the $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons may lead to formation of the $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesic nuclei.

Hot and dense hadronic matter in an effective mean-field approach

We investigate the equation of state of hadronic matter at finite values of baryon density and temperature reachable in high energy heavy ion collisions. The analysis is performed by requiring the Gibbs conditions on the global conservation of baryon number, electric charge fraction and zero net strangeness. We consider an effective relativistic mean-field model with the inclusion of Delta-isobars, hyperons and lightest pseudoscalar and vector mesons degrees of freedom. In this context, we study the influence of the Delta-isobars degrees of freedom in the hadronic equation of state and, in connection, the behavior of different particle-antiparticle ratios and strangeness production.

Kaons in dense half-Skyrmion matter

Dense hadronic matter at low temperature is expected to be in crystal and at high density make a transition to a {\em chirally restored but color-confined} state which is a novel phase hitherto unexplored. This phase transition is predicted in both skyrmion matter in 4D and instanton matter in 5D, the former in the form of half-skyrmions and the latter in the form of half-instantons or dyons. We predict that when $K^-$'s are embedded in this half-skyrmion or half-instanton (dyonic) matter which may be reached not far above the normal density, there arises an enhanced attraction from the soft dilaton field figuring for the trace anomaly of QCD and the Wess-Zumino term. This attraction may have relevance for a possible strong binding of anti-kaons in dense nuclear matter and for kaon condensation in neutron-star matter. Such kaon property in the half-skyrmion phase is highly non-perturbarive and may not be accessible by low-order chiral perturbation theory. Relevance of the half-skyrmion or dyonic matter to compact stars is discussed.

Dilatons in hidden local symmetry for hadrons in dense matter

With the explicit breaking of scale invariance by the trace anomaly of QCD rephrased in terms of spontaneous breaking, low-energy strong interaction dynamics of dense and/or hot matter can be effectively captured by – in addition to the Nambu–Goldstone bosons and the vector mesons – two dilaton fields, the “soft” field that is locked to chiral symmetry and the “hard” field which remains unaffected by chiral symmetry. The scale anomaly in which the soft component intervenes can be shown to vanish at the chiral transition, while that of the hard component remains broken throughout the QCD sector. We argue for a remarkable role of the “homogeneous Wess–Zumino term” of the form ω μ B μ on the structure of a single baryon as well as dense baryonic matter. The emerging structure of the dense hadronic matter so obtained suggests a chiral symmetry restored but (quark-)confined phase at high density and a possible remedy to the defect found in the structure of holographic dense matter described in string theory.

The high-acceptance dielectron spectrometer HADES

HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion induced collisions. Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from 18 to 85 degree, a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons is achieved combining time-of-flight and energy loss measurements over a large momentum range. This paper describes the main features and the performance of the detector system.

Dmesons in asymmetric nuclear matter

We calculate the in-medium $D$ and $\overline{D}$ meson masses in isospin-asymmetric nuclear matter in an effective chiral model. The $D$ and $\overline{D}$ mass modifications arising from their interactions with the nucleons and the scalar mesons in the effective hadronic model are seen to be appreciable at high densities and have a strong isospin dependence. These mass modifications can open the channels of the decay of the charmonium states $({\ensuremath{\Psi}}^{'},{\ensuremath{\chi}}_{c},J/\ensuremath{\Psi})$ to $D\overline{D}$ pairs in dense hadronic matter. The isospin asymmetry in the doublet $D=({D}^{0},{D}^{+})$ is seen to be particularly appreciable at high densities and should show in observables such as their production and flow in asymmetric heavy-ion collisions in the compressed baryonic matter experiments in the future facility of FAIR, GSI. The results of the present work are compared to calculations of the $D(\overline{D}$) in-medium masses in the literature using the QCD sum rule approach, quark meson coupling model, and coupled channel approach as well as to those from studies of quarkonium dissociation using heavy-quark potentials from lattice QCD at finite temperatures.

KAONIC CLUSTERS AT DAFNE: THE AMADEUS EXPERIMENT

The AMADEUS experiment will perform the first complete experimental study of the case of the so-called Deeply Bound Kaonic Nuclear States or simply Kaonic Clusters. Such a study has deep consequences in a still open sector of the strangeness hadronic/nuclear physics: how the hadron masses and hadron interactions change in the nuclear medium with consequences on the structure of cold dense hadronic matter. AMADEUS will perform exclusive - full acceptance - measurements, all particles in the formation and decay processes will be detected.

Baryons and Vector Dominance in Holographic Dual QCD

The infinite tower of vector mesons encoded in holographic dual QCD bring drastic changes to the soliton structure of the nucleon. The nucleon is given by a point-like instanton in 5D surrounded by a vector meson cloud with the vector dominance restored by the infinite tower. I discuss the possible relevance of this structure in hot and dense hadronic matter.

ISOVECTOR COMPONENTS OF LIGHT SCALAR MESON AND NUCLEAR MATTER PROPERTIES

We have predicted (contribution to this issue) an isovector component of the light scalar meson sector by using the chiral symmetry transformation formalism. On the basis of this result, we study dense hadronic matter in a generalized relativistic mean field approach with σ, ω and ρ mesons as well as nonlinear self-couplings of the I = 1 component of a light scalar meson field and compare its predictions for neutron star properties with results from different models for nuclear matter found in the literature.

Disappearance of squeezed back-to-back correlations: a new signal of hadron freeze-out from a supercooled quark gluon plasma

We briefly discuss four different possible types of transitions from quark to hadronic matter and their characteristic signatures in terms of correlations. We also highlight the effects arising from mass modification of hadrons in hot and dense hadronic matter, as well as their quantum statistical consequences: the appearance of squeezed quantum states and the associated experimental signatures, i.e., the back-to-back correlations of particle-antiparticle pairs. We briefly review the theoretical results of these squeezed quanta, generated by in-medium modified masses, starting from the first indication of the existence of surprising particle-antiparticle correlations, and ending by considering the effects of chiral dynamics on these correlation patterns. Nevertheless, a prerequisite for such a signature is the experimental verification of its observability. Therefore, the experimental observation of back-to-back correlations in high energy heavy ion reactions would be a unique signature, proving the existence of in-medium mass modification of hadronic states. On the other hand, their disappearance at some threshold centrality or collision energy would indicate that the hadron formation mechanism would have qualitatively changed: asymptotic hadrons above such a threshold are not formed from medium modified hadrons anymore, but rather by new degrees of freedom characterizing the medium. Furthermore, the disappearance of the squeezed BBC could also serve as a signature of a sudden, non-equilibrium hadronization scenario from a supercooled quark-gluon plasma phase.

Equation of state for hot and dense matter: [formula omitted] model with scaled hadron masses and couplings

The proposed earlier relativistic mean-field model with hadron masses and coupling constants depending on the σ-meson field is generalized to finite temperatures. Within this approach we simulate the in-medium behavior of the hadron masses motivated by the Brown–Rho scaling. The high-lying baryon resonances and boson excitations as well as excitations of the σ, ω and ρ fields interacting via mean fields are incorporated into this scheme. Thermodynamic properties of hot and dense hadronic matter are elaborated with the constructed equation of state. Even at zero baryon density, effective masses of σ – ω – ρ – N excitations abruptly drop down for T ≳ 170 MeV and reach zero at a critical temperature T = T c σ ∼ 210 MeV . Below T c σ (at T ∼ 190 MeV ) the specific heat gets a peak like at crossover. We demonstrate that our EoS can be matched with that computed on the lattice for high temperatures provided the baryon resonance couplings with nucleon are partially suppressed. In this case the quark liquid would masquerade as the hadron one. The model is applied to the description of heavy ion collisions in a broad collision energy range. It might be especially helpful for studying phase diagram in the region near possible phase transitions.

FROM TRAPPED ATOMS TO LIBERATED QUARKS

We discuss some aspects of cold atomic gases in the unitarity limit that are of interest in connection with the physics of dense hadronic matter. We consider, in particular, the equation of state at zero temperature, the magnitude of the pairing gap, and the phase diagram at non-zero polarization.

SIGNATURES OF ISOVECTOR COMPONENTS OF A LIGHT SCALAR MESON IN PULSARS

In a previous work, we have predicted an isovector component of the light scalar meson sector by using the chiral symmetry transformation formalism. On the basis of this result, we study dense hadronic matter in a generalized relativistic mean field approach with σ, ω and ρ mesons as well as nonlinear self-couplings of the I = 1 component of a light scalar meson field and compare its predictions for neutron star properties and with results from different models for nuclear matter found in the literature.

SEARCH FOR KAONIC NUCLEI AT DAΦNE2: THE AMADEUS PROJECT

The planned upgrade of DAΦNE at LNF with a peak luminosity in the order of L = 1033 cm -2 s -1 will be the ideal machine to search for and prove the existence of antikaon-mediated deeply bound nuclear cluster. Antikaon-mediated deeply bound nuclear clusters will allow the study of most important problems in hadron physics today, namely, how the hadron masses and hadron interactions change in the nuclear medium and what is the structure of cold dense hadronic matter. AMADEUS will use the KLOE detector with an additional dedicated target and detector system around the interaction zone to perform exclusive measurements – all particles in the formation and decay processes of deeply bound nuclear clusters will be detected. These measurements will prove beyond doubt the anticipated formation production of antikaon-mediated deeply bound nuclear clusters.

Topological Structure of Dense Hadronic Matter

I present a summary of work done on dense hadronic matter, based on the Skyrme model, which provides a unified approach to high density. In this picture, dense hadronic matter is described by the classical soliton configuration with minimum energy for the given baryon number density. By incorporating the meson fluctuations on such ground state we obtain an effective Lagrangian for meson dynamics in a dense medium.