121.
Hybrid stars that masquerade as neutron stars
- Alford, Mark; Braby, Matt; Paris, Mark; Reddy, Sanjay
We show that a hybrid (nuclear + quark matter) star can have a mass-radius
relationship very similar to that predicted for a star made of purely nucleonic
matter. We show this for a generic parameterization of the quark matter
equation of state, and also for an MIT bag model, each including a
phenomenological correction based on gluonic corrections to the equation of
state. We obtain hybrid stars as heavy as 2 M_solar for reasonable values of
the bag model parameters. For nuclear matter, we use the equation of state
calculated by Akmal, Pandharipande, and Ravenhall using many-body techniques.
Both mixed and homogeneous phases of nuclear and quark matter...
122.
Production of complex particles in low energy spallation and in
fragmentation reactions by in-medium random clusterization
- Lacroix, D.; Durand, D.
Rules for in-medium complex particle production in nuclear reactions are
proposed. These rules have been implemented in two models to simulate
nucleon-nucleus and nucleus-nucleus reactions around the Fermi energy. Our work
emphasizes the effect of randomness in cluster formation, the importance of the
nucleonic Fermi motion as well as the role of conservation laws. The concepts
of total available phase-space and explored phase-space under constraint
imposed by the reaction are clarified. The compatibility of experimental
observations with a random clusterization is illustrated in a schematic
scenario of a proton-nucleus collision. The role of randomness under constraint
is also illustrated in the nucleus-nucleus case.
123.
Phase-space methods in nuclear reactions around the Fermi energy
- Lacroix, Denis; Durand, Dominique; Lehaut, Gregory; Lopez, Olivier; Vient, Emmanuel
Some prescriptions for in-medium complex particle production in nuclear
reactions are proposed. They have been implemented in two models to simulate
nucleon-nucleus (nIPSE) and nucleus-nucleus (HIPSE) reactions around the Fermi
energy \cite{Lac04,Lac05}. Our work emphasizes the effect of randomness in
cluster formation, the importance of the nucleonic Fermi motion as well as the
role of conservation laws. The key role of the phase-space exploration before
and after secondary decay is underlined. This is illustrated in the case of two
debated issues: the memory loss of the entrance channel in central collisions
and the $(N,Z)$ partitions after the pre-equilibrium stage.
124.
Interplay between QCD and nuclear responses
- Chanfray, G.; Ericson, M.
We establish the interrelation between the QCD scalar response of the nuclear
medium and its response to a scalar probe coupled to nucleons, such as the
scalar meson responsible for the nuclear binding. The relation that we derive
applies at the nucleonic as well as at the nuclear levels. Non trivial
consequences follow. One concerns the scalar QCD susceptibility of the nucleon.
The other opens the possibility of relating medium effects in the scalar meson
exchange of nuclear physics to QCD lattice studies of the nucleon mass.
125.
The High-Density Symmetry Energy and Direct Urca
- Steiner, Andrew W.
The symmetry energy of nucleonic matter is usually assumed to be quadratic in
the isospin density. While this may be justified at sub-saturation densities,
there is no need to enforce this restriction at super-saturation densities. The
presence of a quartic term can strongly modify the critical density for the
direct Urca process which leads to faster cooling of neutron stars. Neutron
star cooling predictions which lie below the observational data can, for some
equations of state, be repaired with a quartic term which effectively turns off
the direct Urca process.
126.
Scaling of Anisotropic Flows in Intermediate Energy and
Ultra-relativistic Heavy Ion Collisions
- Ma, Y. G.
Anisotropic flows ($v_2$ and $v_4$) of hadrons and light nuclear clusters are
studied by a partonic transport model and nucleonic transport model,
respectively, in ultra-relativistic and intermediate energy heavy ion
collisions. Both number-of-constituent-quark scaling of hadrons, especially for
$\phi$ meson which is composed of strange quarks, and number-of-nucleon scaling
of light nuclear clusters are discussed and explored for the elliptic flow
($v_2$). The ratios of $v_4/v_2^2$ of hadrons and nuclear clusters are,
respectively, calculated and they show different constant values which are
independent of transverse momentum. The above phenomena can be understood,
respectively, by the coalescence mechanism in quark-level or nucleon-level.
127.
Correlations in hypernuclear matter
- Konrad, P.; Lenske, H.
We investigate short range correlations in nuclear and hypernuclear matter.
Self-energies due to short range correlations and their influence on the
nucleon and $\Lambda$-hyperon spectral functions are described in an approach
accounting for a realistic treatment of mean-field dynamics and a
self-consistently derived quasi-particle interaction. Landau-Migdal theory is
used to derived the short range interaction from a phenomenological Skyrme
energy density functional, subtracting the long range pionic contributions to
the nucleonic spectral functions. We discuss our results for different
hyperon-baryon ratios to show the influence of strangeness on the correlations
in hypernuclear matter.
128.
Isospin Fractionation in Nuclear Fragmentation
- H. S. Xu,T. X. Liu,X. D. Liu,W. G. Lynch,W. P. Tan,M. B. Tsang,A. Vandermolen,A. Wagner,H. F. Xi,C. K. Gelbke,L. Beaulieu,B. Davin,T. Lefort,R. Yanez,V. Viola,R. J. Charity,Sn And
this article for systems of different overall N/Z
ratio. Using appropriate isotope ratios, the ratio of the free neutron and proton densities
at breakup can be extracted with little sensitivity to distortions from secondary decays
of particle unstable nuclei. Within the context of the equilibrium assumption, the nucleonic
gas is found to be neutron-enriched and the fragments more symmetric at breakup,
in qualitative agreement with recent calculations of mixed phase equilibrium within two
component lattice gas and mean field approaches [4--6].
2. Experimental details
129.
Energetic particles in solar flares
- Ramaty, R.
The principal properties of energetic particles accelerated in solar flares are reviewed. Particular emphasis is placed on the high-energy flare component whose acceleration is often referred to as second-phase acceleration. Stochastic Fermi acceleration is treated analytically, and the results of the computation are compared with particle and gamma-ray data to deduce information on the timing of the acceleration, the spectrum of the particles, and the energy content of the nucleonic component. A discussion of He-3 and heavy element abundances is also presented.
130.
Cosmic ray intensity gradients in the solar system
- Mckibben, R. B.
Recent progress in the determination of cosmic-ray intensity gradients is reviewed. Direct satellite measurements of the integral gradient are described together with various types of indirect measurements, including measurements of the Ar-37/Ar-39 ratio in samples from the Lost City meteorite, studies of anisotropies in neutron-monitor counting rates, and analysis of the sidereal diurnal anisotropy observed at a single point on earth. Nucleonic radial gradients and electron gradients measured by satellites in differential energy windows are discussed, and theoretical studies of the physical processes involved in these gradients are summarized. Observations of intensity gradients in heliographic latitude are reported.
131.
Nuclear processes in solar flares
- Ramaty, R.
Interaction models for the production of gamma rays in energetic particle reactions are reviewed, and new calculations of the production rates are presented. Neutron and 2.223 MeV photon production is considered along with positron and 0.511 MeV photon production, and prompt de-excitation line production. The implications of gamma-ray observations are explored, taking into account the interaction model, energetic particle spectrum and energy content, time dependences, the photospheric He-3 abundance, and the beaming of the energetic particles. It is pointed out that the solar gamma-ray line observations can provide information on the timing of the nucleonic component in flares, and on...
132.
Preliminary estimates of galactic cosmic ray exposures for manned interplanetary missions
- Wilson, John W.; Townsend, Lawrence W.; Atwell, William
Preliminary estimates of radiation exposures resulting from galactic cosmic rays are presented for interplanetary missions. The calculations use the Naval Research Laboratory cosmic ray transport code. The heavy ion portion of the transport code can be used with any number of layers of target material, consisting of up to five different constituents per layer. The nucleonic portion of the transport code can be used with any number of layers of target material of arbitrary composition except hydrogen. Calculated galactic cosmic ray particle fluxes, doses, and dose equivalents behind various thicknesses of aluminum shielding are presented for solar maximum and solar...
133.
Atmospheric electric field effects of cosmic rays detected in Mexico City.
- González, L. X.; Valdés Galicia, J. F.
Estudiamos los posibles efectos de los campos eléctricos atmosféricos, generados en las tormentas eléctricas, sobre la
intensidad de los rayos cósmicos detectados en la superficie terrestre, analizando las variaciones de las razones de conteo de la componente nucleónica de los rayos cósmicos, obtenidas por el monitor de neutrones instalado en la ciudad de México, durante tormentas eléctricas ocurridas entre 1996 y 1997, años del mínimo solar. Comparamos nuestros resultados experimentales con la teoría general de los efectos meteorológicos en los rayos cósmicos, desarrollada por Dorman (1995).
Se observó una variación en la intensidad de alrededor de 0.2%. De acuerdo con Dorman (1995),...
134.
Propagation of cosmic rays in the galaxy
- Daniel, R. R.; Stephens, S. A.
The characteristics of a model for analyzing the propagation of cosmic rays are discussed. The requirements for analyzing the relevant observational data on cosmic rays are defines as: (1) the chemical and isotopic composition of cosmic rays as a function of energy, (2) the flux and energy spectrum of the individual nucleonic components, (3) the flux and energy spectrum of the electronic component, (4) the cosmic ray prehistory, and (5) the degree of isotropy in their arrival directions as a function of energy. It is stated that the model which has been able to bring to pass the greatest measure...
135.
Group Theoretical Analysis of Light-Cone Dominated Hadronic Processes
and Twist Decomposition of Nonlocal Operators in Quantum Chromodynamics
- Lazar, Markus
In the framework of nonlocal light-cone expansion of two current operators we
construct bilocal as well as trilocal QCD light-cone operators with definite
geometric twist. We are able to decompose uniquely the appearing QCD light-cone
operators into all their twist parts on the light-cone.
The quark distribution functions and the vector meson distribution amplitudes
which are defined as forward and skewed nucleonic matrix elements of nonlocal
light-cone operators are classified with respect to geometric twist. Hereby we
found well-kown and new Wandzura-Wilczek type relations between the quark
distribution functions with dynamical twist and, additionally, between the
vector meson distribution amplitudes with dynamical twist.
Using group theoretical methods we...
136.
Cosmic Ray Acceleration by Stellar Associations? The Case of Cygnus OB2
- Butt, Yousaf; Benaglia, Paula; Combi, Jorge; Corcoran, Michael; Dame, Thomas; Drake, Jeremy; Bernado, Marina Kaufman; Milne, Peter; Miniati, Francesco; Pohl, Martin; Reimer, Olaf; Romero, Gustavo; Rupen, Michael
The origins of all extra-solar cosmic rays -- both the ultra high-energy and
lower energy Galactic variety -- remain unclear. It has been argued that the
large scale shocks and turbulence induced by the multiple interacting
supersonic winds from the many hot stars in young stellar associations may play
a role in accelerating Galactic cosmic rays -- with or without the associated
multiple supernova remnants (eg. Cesarsky & Montmerle, 1983; Bykov 2001). In
this context, the report by the HEGRA Cherenkov telescope group of a steady and
extended unidentified TeV gamma-ray source lying at the outskirts of Cygnus OB2
is particularly significant. This is the most massive stellar...
137.
The properties of the three-nucleon system with the dressed-bag model
for nn interaction. I: New scalar three-body force
- Kukulin, V. I.; Pomerantsev, V. N.; Kaskulov, M.; Faessler, Amand
A multi-component formalism is developed to describe three-body systems with
nonstatic pairwise interactions and non-nucleonic degrees of freedom. The
dressed-bag model for $NN$ interaction based on the formation of an
intermediate six-quark bag dressed by a $\sigma$-field is applied to the $3N$
system, where it results in a new three-body force between the six-quark bag
and a third nucleon. Concise variational calculations of $3N$ bound states are
carried out in the dressed-bag model including the new three-body force. It is
shown that this three-body force gives at least half the $3N$ total binding
energy, while the weight of non-nucleonic components in the $^3$H and $^3$He
wavefunctions can exceed 10%....
138.
Isospin Asymmetry in Nuclei and Neutron Stars
- Steiner, Andrew W.; Prakash, Madappa; Lattimer, James M.; Ellis, Paul J.
The roles of isospin asymmetry in nuclei and neutron stars are investigated
using a range of potential and field-theoretical models of nucleonic matter.
The parameters of these models are fixed by fitting the properties of
homogeneous bulk matter and closed-shell nuclei. We discuss and unravel the
causes of correlations among the neutron skin thickness in heavy nuclei, the
pressure of beta-equilibrated matter at a density of 0.1 fm$^{-3}$, the
derivative of the nuclear symmetry energy at the same density and the radii of
moderate mass neutron stars. Constraints on the symmetry properties of nuclear
matter from the binding energies of nuclei are examined. The extent to which
forthcoming neutron...
139.
Dibaryon model for nuclear force and the properties of the $3N$ system
- Pomerantsev, V. N.; Kukulin, V. I.; Voronchev, V. T.; Faessler, Amand
The dibaryon model for $NN$ interaction, which implies the formation of an
intermediate six-quark bag dressed by a $\sigma$-field, is applied to the $3N$
system, where it results in a new three-body force of scalar nature between the
six-quark bag and a third nucleon. A new multicomponent formalism is developed
to describe three-body systems with nonstatic pairwise interactions and
non-nucleonic degrees of freedom. Precise variational calculations of $3N$
bound states are carried out in the dressed-bag model including the new scalar
three-body force. The unified coupling constants and form factors for $2N$ and
$3N$ force operators are used in the present approach, in a sharp contrast to
conventional meson-exchange...
140.
Analysis of pC-interactions at Momentum of 4.2 GeV/c Within Framework of
FRITIOF and Cascade Models
- Galoyan, A.; Kladnitskaya, E. N.; Rogachevskii, O. V.; Togoo, R.; Uzhinskii, V. V.
Experimental data on multiplicities and kinematical characteristics of
$\pi^-$, $\pi^+$ mesons and protons in the interactions of protons with carbon
nucleus at momentum 4.2 GeV/c in a dependence of collision centrality are
analyzed. Parameter Q which is a difference between multiplicities of positive
and negative charged particles without multiplicity of slow protons with
momentum less than 0.3 GeV/c in an event, is taken as a criteria of collision
centrality. The experimental data on events with different centrality are
compared with predictions of the cascade-evaporation model and the modified
FRITIOF model. For the first time, non-nucleonic degrees of freedom in nuclei
($\Delta ^+, \Delta ^0 $ isobars) are taken into...
