20 research outputs found
meson in dense matter
We study the properties of mesons in nuclear matter using a
unitary approach in coupled channels within the framework of the local hidden
gauge formalism and incorporating the decay channel in matter. The
in-medium interaction accounts for Pauli blocking effects and
incorporates the self-energy in a self-consistent manner. We also
obtain the (off-shell) spectral function and analyze its behaviour
at finite density and momentum. At normal nuclear matter density, the meson feels a moderately attractive potential while the width
becomes five times larger than in free space. We estimate the transparency
ratio of the reaction, which we propose as
a feasible scenario at present facilities to detect the changes of the
properties of the 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 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 is very delicate, and depends on
the approach adopted for the antikaon self-energy. Three approaches for the
self-energy are considered: non-interacting , on-shell self-energy
and single-particle spectral density. With respect to the on-shell approach,
the use of an energy dependent spectral density, including both s-
and p-wave components of the 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 -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 interaction,
described through a G-matrix, generates dynamically the (2593)
resonance. This resonance is the charm counterpart of the (1405)
resonance generated from the s-wave 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 -meson
results in an overall reduction of the in-medium -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
condensate state may occur at densities 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
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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 ( and ) 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 and open-charm meson self-energies in a self-consistent manner. In the sector, the and 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 meson spectral density shows a single pronounced peak for energies close to the meson free-space mass that broadens with increasing matter density with an extended tail particularly towards lower energies. The potential shows a moderate repulsive behavior coming from the dominant I=1 contribution of the interaction. The low-density theorem is, however, not a good approximation for the self-energy in spite of the absence of resonance-hole contributions close to threshold in this case. We speculate the possibility of -mesic nuclei as well as discuss some consequences for the 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