2,638 research outputs found
Relativistic Mean-Field Hadronic Models under Nuclear Matter Constraints
Relativistic mean-field (RMF) models have been widely used in the study of
many hadronic frameworks because of several important aspects not always
present in nonrelativistic models, such as intrinsic Lorentz covariance,
automatic inclusion of spin, appropriate saturation mechanism for nuclear
matter, causality and, therefore, no problems related to superluminal speed of
sound. With the aim of identifying the models which best satisfy well known
properties of nuclear matter, we have analyzed parameterizations of seven
different types of RMF models under three different sets of constraints related
to symmetric nuclear matter, pure neutron matter, symmetry energy, and its
derivatives. One of these (SET1) is formed of the same constraints used in a
recent work [M. Dutra et al., Phys. Rev. C 85, 035201 (2012)] in which we
analyzed Skyrme parameterizations. The results pointed to models
consistent with all constraints. By using another set of constraints, namely,
SET2a, formed by the updated versions of the previous one, we found models
approved simultaneously. Finally, in the third set, named SET2b, in which the
values of the constraints are more restrictive, we found consistent models.
Another interesting feature of our analysis is that the results change
dramatically if we do not consider the constraint regarding the volume part of
the isospin incompressibility (). In this case, we have
approved models in SET2a and in SET2b.Comment: 63 pages, 3 figures and 9 tables. Version accepted for publication in
PR
Relativistic Mean-Field Models and Nuclear Matter Constraints
This work presents a preliminary study of 147 relativistic mean-field (RMF)
hadronic models used in the literature, regarding their behavior in the nuclear
matter regime. We analyze here different kinds of such models, namely: (i)
linear models, (ii) nonlinear \sigma^3+\sigma^4 models, (iii)
\sigma^3+\sigma^4+\omega^4 models, (iv) models containing mixing terms in the
fields \sigma and \omega, (v) density dependent models, and (vi) point-coupling
ones. In the finite range models, the attractive (repulsive) interaction is
described in the Lagrangian density by the \sigma (\omega) field. The isospin
dependence of the interaction is modeled by the \rho meson field. We submit
these sets of RMF models to eleven macroscopic (experimental and empirical)
constraints, used in a recent study in which 240 Skyrme parametrizations were
analyzed. Such constraints cover a wide range of properties related to
symmetric nuclear matter (SNM), pure neutron matter (PNM), and both SNM and
PNM.Comment: 3 Pages, submitted for proceedings of XXXV Reuni\~ao de Trabalho
sobre F\'isica Nuclear no Brasil 201
Skyrme Interaction and Nuclear Matter Constraints
This paper presents a detailed assessment of the ability of the 240 Skyrme
interaction parameter sets in the literature to satisfy a series of criteria
derived from macroscopic properties of nuclear matter in the vicinity of
nuclear saturation density at zero temperature and their density dependence,
derived by the liquid drop model, experiments with giant resonances and
heavy-ion collisions. The objective is to identify those parameterizations
which best satisfy the current understanding of the physics of nuclear matter
over a wide range of applications. Out of the 240 models, only 16 are shown to
satisfy all these constraints. Additional, more microscopic, constraints on
density dependence of the neutron and proton effective mass beta-equilibrium
matter, Landau parameters of symmetric and pure neutron nuclear matter, and
observational data on high- and low-mass cold neutron stars further reduce this
number to 5, a very small group of recommended Skyrme parameterizations to be
used in future applications of the Skyrme interaction of nuclear matter related
observables. Full information on partial fulfillment of individual constraints
by all Skyrme models considered is given. The results are discussed in terms of
the physical interpretation of the Skyrme interaction and the validity of its
use in mean-field models. Future work on application of the Skyrme forces,
selected on the basis of variables of nuclear matter, in Hartree-Fock
calculation of properties of finite nuclei, is outlined.Comment: 86 pages, 14 figure
Efeito da substituição do grĂŁo de milho por grĂŁo de arroz integral sem casca na produção e composição do leiteÂč.
Consumo de matĂ©ria seca, de fibra em detergente neutro e sua relação com a produção de leite em vacas alimentadas com nĂveis crescentes de gordura na dietaÂč.
Produção de forragem de sorgo consorciado com eucalipto no sistema de integração-lavoura-pecuåria-floresta.
Charmonium suppression from purely geometrical effects
The extend to which geometrical effects contribute to the production and
suppression of the and minijet pairs in general is
investigated for high energy heavy ion collisions at SPS, RHIC and LHC
energies. For the energy range under investigation, the geometrical effects
referred to are shadowing and anti-shadowing, respectively. Due to those
effects, the parton distributions in nuclei deviate from the naive
extrapolation from the free nucleon result; . The strength
of the shadowing/anti-shadowing effect increases with the mass number. The
consequences of gluonic shadowing effects for the distribution of
's at GeV, GeV and TeV are
calculated for some relevant combinations of nuclei, as well as the
distribution of minijets at midrapidity for in the final state.Comment: corrected some typos, improved shadowing ratio
Color-Octet Fraction in J/Psi Production and Absorption
The cross section between a pair and a nucleon is small and
sensitive to the separation if the pair is in a color-singlet
state, but very large and insensitive to the separation if it is in a
color-octet state. We use this property in an absorption model involving both
color components to deduce the color structure of pairs produced in
reactions. Our analysis shows that the NA3, NA38 and E772
data are not inconsistent with the theoretical picture that color-octet and
color-singlet precursors are produced in roughly equal proportions if the
produced color-singlet precursors are pointlike and transparent. However, if
the color-singlet precursors are not transparent but have a cross section of a
few mb, these data do show a definite preference for a larger fraction of
color-singlet precursors. In either case, the color-octet fraction increases
with , approaching unity as becomes large.Comment: 9 pages, updated to include new result
NA60 results on spectra and the spectral function in In-In collisions
The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158
AGeV In-In collisions. A strong excess of pairs is observed above the yield
expected from neutral meson decays. The unprecedented sample size of close to
400K events and the good mass resolution of about 2% have made it possible to
isolate the excess by subtraction of the decay sources (keeping the ).
The shape of the resulting mass spectrum exhibits considerable broadening, but
essentially no shift in mass. The acceptance-corrected transverse-momentum
spectra have a shape atypical for radial flow and show a significant mass
dependence, pointing to different sources in different mass regions.Comment: 4 pages, 4 figures, Quark Matter 2006 conference proceeding
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