Kˉ∗\bar K^* meson in dense matter

We study the properties of $\bar K^*$ mesons in nuclear matter using a unitary approach in coupled channels within the framework of the local hidden gauge formalism and incorporating the $\bar K \pi$ decay channel in matter. The in-medium $\bar K^* N$ interaction accounts for Pauli blocking effects and incorporates the $\bar K^*$ self-energy in a self-consistent manner. We also obtain the $\bar K^*$ (off-shell) spectral function and analyze its behaviour at finite density and momentum. At normal nuclear matter density, the $\bar K^*$ meson feels a moderately attractive potential while the $\bar K^*$ width becomes five times larger than in free space. We estimate the transparency ratio of the $\gamma A \to K^+ K^{* -} A^\prime$ reaction, which we propose as a feasible scenario at present facilities to detect the changes of the properties of the $\bar K^*$ meson in the nuclear medium.Comment: 26 pages, 9 figures, one new section added, version published in Phys. ReV. C, http://link.aps.org/doi/10.1103/PhysRevC.82.04521

K^-/K^+ ratio at GSI in hot and dense matter

The $K^-/K^+$ ratio in heavy-ion collisions at GSI energies is studied including the properties of the participating hadrons in hot and dense matter. The determination of the temperature and chemical potential at freeze-out conditions compatible with the ratio $K^-/K^+$ is very delicate, and depends on the approach adopted for the antikaon self-energy. Three approaches for the $K^-$ self-energy are considered: non-interacting $K^-$, on-shell self-energy and single-particle spectral density. With respect to the on-shell approach, the use of an energy dependent $\bar{K}$ spectral density, including both s- and p-wave components of the $\bar{K}N$ interaction, lowers considerably the freeze-out temperature and gives rise to the "broad-band equilibration" advocated by Brown, Rho and Song.Comment: 8 pages, 5 figures, talk given at the Strange Quark Matter Conference, Atlantic Beach, North Carolina, March 12-17, 200

Energy weighted sum rules for mesons in hot and dense matter

We study energy weighted sum rules of the pion and kaon propagator in nuclear matter at finite temperature. The sum rules are obtained from matching the Dyson form of the meson propagator with its spectral Lehmann representation at low and high energies. We calculate the sum rules for specific models of the kaon and pion self-energy. The in-medium spectral densities of the K and anti-K mesons are obtained from a chiral unitary approach in coupled channels which incorporates the S- and P-waves of the kaon-nucleon interaction. The pion self-energy is determined from the P-wave coupling to particle-hole and Delta-hole excitations, modified by short range correlations. The sum rules for the lower energy weights are fulfilled satisfactorily and reflect the contributions from the different quasi-particle and collective modes of the meson spectral function. We discuss the sensitivity of the sum rules to the distribution of spectral strength and their usefulness as quality tests of model calculations.Comment: 19 pages, 6 figures; one figure added, enhanced discussion, version to appear in PR

Properties of D-mesons in nuclear matter within a self-consistent coupled-channel approach

The spectral density of the $D$-meson in the nuclear environment is studied within a self-consistent coupled-channel approach assuming a separable potential for the bare meson-baryon interaction. The $DN$ interaction, described through a G-matrix, generates dynamically the $\Lambda_c$ (2593) resonance. This resonance is the charm counterpart of the $\Lambda$ (1405) resonance generated from the s-wave $\bar{K}N$ interaction in the I=0 channel. The medium modification of the D-meson spectral density due to the Pauli blocking of intermediate states as well as due to the dressing of the D-mesons, nucleons and pions is investigated. We observe that the inclusion of coupled-channel effects and the self-consistent dressing of the $D$-meson results in an overall reduction of the in-medium $D$-meson changes compared to previous work which neglect those effects.Comment: 23 pages, 10 figures, submitted for publicatio

The antikaon nuclear potential in hot and dense matter

The antikaon optical potential in hot and dense nuclear matter is studied within the framework of a coupled-channel self-consistent calculation taking, as bare meson-baryon interaction, the meson-exchange potential of the J\"ulich group. Typical conditions found in heavy-ion collisions at GSI are explored. As in the case of zero temperature, the angular momentum components larger than L=0 contribute significantly to the finite temperature antikaon optical potential at finite momentum. It is found that the particular treatment of the medium effects has a strong influence on the behavior of the antikaon potential with temperature. Our self-consistent model, in which antikaons and pions are dressed in the medium, gives a moderately temperature dependent antikaon potential which remains attractive at GSI temperatures, contrary to what one finds if only nuclear Pauli blocking effects are included.Comment: 30 pages, 8 figures, references added. Accepted for publication in PR

Negative Kaons in Dense Baryonic Matter

Kaon polarization operator in dense baryonic matter of arbitrary isotopic composition is calculated including s- and p-wave kaon-baryon interactions. The regular part of the polarization operator is extracted from the realistic kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly into account in the pole and regular terms with inclusion of mean-field potentials. The baryon-baryon correlations are incorporated and fluctuation contributions are estimated. Results are applied for K- in neutron star matter. Within our model a second-order phase transition to the s-wave K- condensate state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are included. We show that the second-order phase transition to the p-wave $K^-$ condensate state may occur at densities $\rho_c \sim 3\div 5 \rho_0$ in dependence on the parameter choice. We demonstrate that a first-order phase transition to a proton-enriched (approximately isospin-symmetric) nucleon matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2 \rho_0. The transition is accompanied by the suppression of hyperon concentrations.Comment: 41 pages, 24 figures, revtex4 styl

Protective intraoperative ventilation with higher versus lower levels of positive end-expiratory pressure in obese patients (PROBESE): study protocol for a randomized controlled trial

Background: Postoperative pulmonary complications (PPCs) increase the morbidity and mortality of surgery in obese patients. High levels of positive end-expiratory pressure (PEEP) with lung recruitment maneuvers may improve intraoperative respiratory function, but they can also compromise hemodynamics, and the effects on PPCs are uncertain. We hypothesized that intraoperative mechanical ventilation using high PEEP with periodic recruitment maneuvers, as compared with low PEEP without recruitment maneuvers, prevents PPCs in obese patients. Methods/design The PRotective Ventilation with Higher versus Lower PEEP during General Anesthesia for Surgery in OBESE Patients (PROBESE) study is a multicenter, two-arm, international randomized controlled trial. In total, 2013 obese patients with body mass index ≥35 kg/m2 scheduled for at least 2 h of surgery under general anesthesia and at intermediate to high risk for PPCs will be included. Patients are ventilated intraoperatively with a low tidal volume of 7 ml/kg (predicted body weight) and randomly assigned to PEEP of 12 cmH2O with lung recruitment maneuvers (high PEEP) or PEEP of 4 cmH2O without recruitment maneuvers (low PEEP). The occurrence of PPCs will be recorded as collapsed composite of single adverse pulmonary events and represents the primary endpoint. Discussion To our knowledge, the PROBESE trial is the first multicenter, international randomized controlled trial to compare the effects of two different levels of intraoperative PEEP during protective low tidal volume ventilation on PPCs in obese patients. The results of the PROBESE trial will support anesthesiologists in their decision to choose a certain PEEP level during general anesthesia for surgery in obese patients in an attempt to prevent PPCs. Trial registration ClinicalTrials.gov identifier: NCT02148692. Registered on 23 May 2014; last updated 7 June 2016. Electronic supplementary material The online version of this article (doi:10.1186/s13063-017-1929-0) contains supplementary material, which is available to authorized users

Open charm in nuclear matter at finite temperature

We study the properties of open-charm mesons ($D$ and $\bar {D}$) in nuclear matter at finite temperature within a self-consistent coupled-channel approach. The meson-baryon interactions are adopted from a type of broken SU(4) s-wave Tomozawa-Weinberg terms supplemented by an attractive scalar-isoscalar attraction. The in-medium solution at finite temperature incorporates Pauli blocking effects, mean-field binding on all the baryons involved, and $\pi$ and open-charm meson self-energies in a self-consistent manner. In the $DN$ sector, the $\Lambda_c$ and $\Sigma_c$ resonances, generated dynamically at 2593 MeV and 2770 MeV in free space, remain close to their free-space position while acquiring a remarkable width due to the thermal smearing of Pauli blocking as well as from the nuclear matter density effects. 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. The $\bar D$ potential shows a moderate repulsive behavior coming from the dominant I=1 contribution of the $\bar D N$ interaction. The low-density theorem is, however, not a good approximation for the $\bar D$ self-energy in spite of the absence of resonance-hole contributions close to threshold in this case. We speculate the possibility of $D$-mesic nuclei as well as discuss some consequences for the $J/\Psi$ suppression in heavy-ion collisions, in particular for the future CBM experiment at FAIR

Strange mesons in nuclear matter at finite temperature

We study the properties of K and K mesons in nuclear matter at finite temperature from a chiral unitary approach in coupled channels that incorporates the s and p waves of the kaon-nucleon interaction. The in-medium solution accounts for Pauli blocking effects, mean-field binding on all the baryons involved, and {pi} and kaon self-energies. We calculate K and K (off-shell) spectral functions and single-particle properties. The K effective mass gets lowered by about -50 MeV in cold nuclear matter at saturation density and by half this reduction at T=100 MeV. The p-wave contribution to the K optical potential, due to {lambda},{sigma}, and {sigma}* excitations, becomes significant for momenta larger than 200 MeV/c and reduces the attraction felt by the K in the nuclear medium. The K spectral function spreads over a wide range of energies, reflecting the melting of the {lambda}(1405) resonance and the contribution of YN{sup -1} components at finite temperature. In the KN sector, we find that the low-density theorem is a good approximation for the K self-energy close to saturation density due to the absence of resonance-hole excitations. The K potential shows a moderate repulsive behavior, whereas the quasiparticle peak is considerably broadened with increasing density andmore » temperature. We discuss the implications for the decay of the {phi} meson at GSI Schwerionen Synchrotron energies as well as in the future Facility for Antiproton and Ion Research project.« les

The width of the omega meson in the nuclear medium

We evaluate the width of the ω meson in nuclear matter. We consider the free decay mode of the ω into three pions, which is dominated by ρπ decay, and replace the ρ and π propagators by their medium-modified ones. We also take into account the quasielastic and inelastic processes induced by a vector-baryon interaction dominated by vector meson exchange, as well as the contributions coming from the ω→KK¯ mechanism with medium-modified K , K¯ propagators. We obtain a substantial increase of the ω width in the medium, reaching a value of 121 ± 10 MeV at normal nuclear matter density for an ω at rest, which comes mainly from ωN → ππN, ωNN → πNN processes associated to the dominant ω → ρπ decay mode. The value of the width increases moderately with momentum, reaching values of around 200MeV at 600MeV/c