161.
Full-folding optical potential for preequilibrium nucleon scattering at
low energies
- Avrigeanu, M.; Antonov, A. N.; Lenske, H.; Stetcu, I.
The real part of the optical potential for the nucleon-nucleus scattering at
lower energies (E_i<100MeV) has been calculated including nucleonic and mesonic
form factors by a double folding approach. Realistic density- and
energy-dependent effective NN-interactions DDM3Y, BDM3Y and HLM3Y based on the
Reid and Paris potentials are used in this respect. The effects of the nucleon
density distribution and the average relative momentum on the folded potential
have been analysed. A good agreement with the phenomenological potential of
Lagrange-Lejeune, as well as with the parametrization of
Jeukenne-Lejeune-Mahaux for both neutron and proton double-folded potentials is
obtained. The results indicate that the strongly simplified model interactions
used in preequilibrium reaction theory...
162.
Modelling the many-body dynamics of heavy ion collisions: Present status
and future perspective
- Hartnack, C.; Puri, Rajeev K.; Aichelin, J.; Konopka, J.; Bass, S. A.; Stoecker, H.; Greiner, W.
Basic problems of the semiclassical microscopic modelling of strongly
interactingsystems are discussed within the framework of Quantum Molecular
Dynamics (QMD). This model allows to study the influence of several types of
nucleonic interactions on a large variety of observables and phenomena
occurring in heavy ion collisions at relativistic energies.It is shown that the
same predictions can be obtained with several -- numerically completely
different and independently written -- programs as far as the same model
parameters are employed and the same basic approximations are made. Many
observables are robust against variations of the details of the model
assumptions used. Some of the physical results, however, depend also on rather
technical...
163.
Analysis of flow effects in relativistic heavy-ion collisions within the
CBUU approach
- Hombach, A.; Cassing, W.; Teis, S.; Mosel, U.
We study flow phenomena in relativistic heavy-ion collisions, both in
transverse and radial direction, in comparison to experimental data. The
collective dynamics of the nucleus-nucleus collision is described within a
transport model of the coupled channel BUU type (CBUU). This recently developed
version includes all nucleonic resonances up to 1.95 GeV in mass and mean-field
potentials both of the Skyrme and momentum dependent MDYI type. We find that
heavy resonances play an important role in the description of transverse flow
above 1 AGeV incident energy. For radial flow we analyse reaction times and
equilibration and extract the parameters $T$ and $\beta$ for temperature and
collective flow velocity within different...
164.
R-ratios and moments of nuclear structure functions
- Rinat, A. S.; Taragin, M. F.
We study implications of a model, which links nuclear and nucleon structure
functions. Computed Callen-Gross functions $\kappa^A(x,Q^2)=
2xF_1^A(x,Q^2)/F_2^A(x,Q^2)$ appear for finite $Q^2$ to be close to their
asymptotic value 1. Using those $\kappa$, we compure $R$ ratios for $Q^2\ge 5
GeV^2$. We review approximate methods in use for the extraction of $R$ from
inclusive scattering and ENC data. Further we calcuate ratios of the moments of
$F_k$ and find these to describe the data, in particular their $Q^2$
dependence. The above observables, as well as inclusive cross sections, are
sensitive tests for the underlying relation between nucleonic and nuclear
structure functions. In view of the overall agreement, we speculate...
165.
Nuclear Skins and Halos in the Mean-Field Theory
- Mizutori, S.; Dobaczewski, J.; Lalazissis, G. A.; Nazarewicz, W.; Reinhard, P. -G.
Nuclei with large neutron-to-proton ratios have neutron skins, which manifest
themselves in an excess of neutrons at distances greater than the radius of the
proton distribution. In addition, some drip-line nuclei develop very extended
halo structures. The neutron halo is a threshold effect; it appears when the
valence neutrons occupy weakly bound orbits. In this study, nuclear skins and
halos are analyzed within the self-consistent Skyrme-Hartree-Fock-Bogoliubov
and relativistic Hartree-Bogoliubov theories for spherical shapes. It is
demonstrated that skins, halos, and surface thickness can be analyzed in a
model-independent way in terms of nucleonic density form factors. Such an
analysis allows for defining a quantitative measure of the halo size....
166.
The Role of Meson Retardation in the NN Interaction above Pion Threshold
- Schwamb, Michael; Arenhoevel, Hartmuth
A model is developed for the hadronic interaction in the two-nucleon system
above pion threshold which is based on meson, nucleon and $\Delta$ degrees of
freedom and which includes full meson retardation in the exchange operators.
For technical reasons, the model allows maximal one meson to be present
explicitly. Thus the Hilbert space contains besides $NN$ and $N\Delta$ also
configurations consisting of two nucleons and one meson. For this reason, only
two- and three-body unitarity is obeyed, and the model is suited for reactions
in the two nucleon sector only, where one pion is produced or absorbed.
Starting from a realistic pure nucleonic retarded potential, which had to...
167.
Dispersion relations at finite temperature and density for nucleons and
pions
- Hurtado, Rafael; Morales, John; Quimbay, Carlos
We calculate the nucleonic and pionic dispersion relations at finite
temperature T and non-vanishing chemical potentials $(\mu_f)$ in the context of
an effective chiral theory that describes the strong and electromagnetic
interactions for nucleons and pions. The dispersion relations are calculated in
the broken chiral symmetry phase, where the nucleons are massive and pions are
taken as massless. The calculation is performed at lowest order in the energy
expansion, working in the framework of the real time formalism of thermal field
theory in the Feynman gauge. These one-loop dispersion relations are obtained
at leading order with respect to T and $\mu_f$. We also evaluate the effective
masses of the...
168.
Patterns of the ground states in the presence of random interactions:
nucleon systems
- Zhao, Y. M.; Arima, A.; Shimizu, N.; Ogawa, K.; Yoshinaga, N.; Scholten, O.
We present our results on properties of ground states for nucleonic systems
in the presence of random two-body interactions. In particular we present
probability distributions for parity, seniority, spectroscopic (i.e., in the
laboratory framework) quadrupole moments and $\alpha$ clustering in the ground
states. We find that the probability distribution for the parity of the ground
states obtained by a two-body random ensemble simulates that of realistic
nuclei: positive parity is dominant in the ground states of even-even nuclei
while for odd-odd nuclei and odd-mass nuclei we obtain with almost equal
probability ground states with positive and negative parity. In addition we
find that for the ground states, assuming pure...
169.
Low-momentum interactions for nuclei
- Schwenk, Achim
We show how the renormalization group is used to construct a low-momentum
nucleon-nucleon interaction V_{low k}, which unifies all potential models used
in nuclear structure calculations. V_{low k} can be directly applied to the
nuclear shell model or to nucleonic matter without a G matrix resummation. It
is argued that V_{low k} parameterizes a high-order chiral effective field
theory two-nucleon force. We use cutoff dependence as a tool to assess the
error in the truncation of nuclear forces to two-nucleon interactions and
introduce a low-momentum three-nucleon force, which regulates A=3,4 binding
energies. The adjusted three-nucleon interaction is perturbative for small
cutoffs. In contrast to other precision interactions, the error...
170.
Electromagnetic excitation rates for nuclear isomers in a hot dense
plasma
- Luu, T. C.; Friar, J. L.; Hayes, A. C.
In high neutron flux environments where isomers can be strongly populated by
nucleonic reactions, isotope abundances from reaction network chains can be
affected by the population of nuclear isomers. At high temperatures and
densities there is the additional possibility of populating these isomers
electromagnetically. Here we examine the rates for electromagnetic excitation
of the isotopes of several isomers of interest both in astrophysics and applied
physics (e.g. 235U, 193Ir, and 87Y,88Y). We consider six possible
electromagnetic processes, namely, photo-absorption, inverse internal
conversion, inelastic electron scattering, Coulomb excitation, (gamma,gamma)
and (e,e'gamma) reactions. We find that for plasma temperatures kT~ 1-10 keV
the electromagnetic reactions rates are negligible. Thus, we conclude that
reaction...
171.
Momentum-space treatment of Coulomb interaction in three-nucleon
reactions with two protons
- Deltuva, A.; Fonseca, A. C.; Sauer, P. U.
The Coulomb interaction between the two protons is included in the
calculation of proton-deuteron elastic scattering, radiative proton-deuteron
capture and two-body electromagnetic disintegration of ${}^3\mathrm{He}$. The
hadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn
potential and its realistic extension CD Bonn + $\Delta$ to a coupled-channel
two-baryon potential, allowing for single virtual $\Delta$-isobar excitation.
Calculations are done using integral equations in momentum space. The screening
and renormalization approach is employed for including the Coulomb interaction.
Convergence of the procedure is found already at moderate screening radii. The
reliability of the method is demonstrated. The Coulomb effect on observables is
seen at low energies for the whole kinematic...
172.
Benchmark calculation for proton-deuteron elastic scattering observables
including Coulomb
- Deltuva, A.; Fonseca, A. C.; Kievsky, A.; Rosati, S.; Sauer, P. U.; Viviani, M.
Two independent calculations of proton-deuteron elastic scattering
observables including Coulomb repulsion between the two protons are compared in
the proton lab energy region between 3 MeV and 65 MeV. The hadron dynamics is
based on the purely nucleonic charge-dependent AV18 potential. Calculations are
done both in coordinate space and momentum space. The coordinate-space
calculations are based on a variational solution of the three-body
Schr\"odinger equation using a correlated hyperspherical expansion for the wave
function. The momentum-space calculations proceed via the solution of the
Alt-Grassberger-Sandhas equation using the screened Coulomb potential and the
renormalization approach. Both methods agree within 1% on all observables,
showing the reliability of both numerical techniques in...
173.
Strangeness production in proton-proton and proton-nucleus collisions
- Shyam, Radhey
In these lectures we discuss the investigation of the strange meson
production in proton-proton ($pp$) and in proton-nucleus ($pA$) reactions
within an effective Lagrangian model. The kaon production proceeds mainly via
the excitations of $N^*$(1650), $N^*$(1710), and $N^*$(1720) resonant
intermediate nucleonic states, in the collision of two initial state nucleons.
Therefore, the strangeness production is expected to provide information about
the resonances lying at higher excitation energies. For beam energies very
close to the kaon production threshold the hyperon-proton final state
interaction effects are quite important. Thus, these studies provide a check on
the models of hyperon-nucleon interactions. The in-medium production of kaons
show strong sensitivity to the self energies...
174.
TeV Neutrinos from SuperNova Remnants embedded in Giant Molecular Clouds
- Cavasinni, Vincenzo; Grasso, Dario; Maccione, Luca
The recent detection of $\gamma$-rays with energy up to 10 TeV from dense
regions surrounding some Supernova Remnants (SNR) provides strong, though still
not conclusive, evidence that the nucleonic component of galactic Cosmic Rays
is accelerated in the supernova outflows. Neutrino telescopes could further
support the validity of such scenario by detecting neutrinos coming from the
same regions. We re-evaluate the TeV range neutrino-photon flux ratio to be
expected from pion decay, finding small differences respect to previous
derivations. We apply our results and the recent HESS measurements of the very
high energy $\gamma$-ray flux from the molecular cloud complex in the Galactic
Centre, to estimate the neutrino flux...
175.
Constraints to the EOS of ultradense matter with model-independent
astrophysical observations
- Lavagetto, G.; Bombaci, I.; D'Ai', A.; Vidana, I.; Robba, N. R.
The recent discovery of burst oscillations at 1122 Hz in the x-ray transient
XTE J1739-285, together with the measurement of the mass of the binary
millisecond pulsar PSR J0751+1807 (2.1 +- 0.2 solar masses) can finally allow
us to put strong, model-independent observational constraints to the equation
of state of compact stars. We show that the measurement of the moment of
inertia of PSR J0737+3039A, together with these constraints, could allow to
discriminate further the details of the inner structure of neutron stars.
Moreover, we show that if XTE J1739-285 is constituted of nucleonic matter, any
equation of state allows only a narrow range of very high masses,...
176.
Continuous phase transition and negative specific heat in finite nuclei
- De, J. N.; Samaddar, S. K.; Shlomo, S.; Natowitz, J. B.
The liquid-gas phase transition in finite nuclei is studied in a heated
liquid-drop model where the nuclear drop is assumed to be in thermodynamic
equilibrium with its own evaporated nucleonic vapor conserving the total baryon
number and isospin of the system. It is found that in the liquid-vapor
coexistence region the pressure is not a constant on an isotherm indicating
that the transition is continuous. At constant pressure, the caloric curve
shows some anomalies, namely, the systems studied exhibit negative heat
capacity in a small temperature domain. The dependence of this specific feature
on the mass and isospin of the nucleus, Coulomb interaction and the chosen
pressure is studied....
177.
Scaling of Anisotropic Flow and Momentum-Space Densities for Light
Particles in Intermediate Energy Heavy Ion Collisions
- Yan, T. Z.; Ma, Y. G.; Cai, X. Z.; Chen, J. G.; Fang, D. Q.; Guo, W.; Ma, C. W.; Ma, E. J.; Shen, W. Q.; Tian, W. D.; Wang, K.
Anisotropic flows ($v_2$ and $v_4$) of light nuclear clusters are studied by
Isospin-Dependent Quantum Molecular Dynamics model for the system of $^{86}$Kr
+ $^{124}$Sn at intermediate energy and large impact parameters.
Number-of-nucleon scaling of the elliptic flow ($v_2$) are demonstrated for the
light fragments up to $A$ = 4, and the ratio of $v_4/v_2^2$ shows a constant
value of 1/2. In addition, the momentum-space densities of different clusters
are also surveyed as functions of transverse momentum, in-plane transverse
momentum and azimuth angle relative to the reaction plane. The results can be
essentially described by momentum-space power law. All the above phenomena
indicate that there exists a number-of-nucleon scaling for...
178.
Improved short-range correlations and 0nbb nuclear matrix elements of
76Ge and 82Se
- Kortelainen, Markus; Suhonen, Jouni
We calculate the nuclear matrix elements of the neutrinoless double beta
($0\nu\beta\beta$) decays of $^{76}$Ge and $^{82}$Se for the light-neutrino
exchange mechanism. The nuclear wave functions are obtained by using realistic
two-body forces within the proton-neutron quasiparticle random-phase
approximation (pnQRPA). We include the effects that come from the finite size
of a nucleon, from the higher-order terms of nucleonic weak currents, and from
the nucleon-nucleon short-range correlations. Most importantly, we improve on
the presently available calculations by replacing the rudimentary Jastrow
short-range correlations by the more advanced unitary correlation operator
method (UCOM). The UCOM corrected matrix elements turn out to be notably larger
in magnitude than the Jastrow corrected ones....
179.
Propagation of UHE Protons over Cosmological Distances
- R. J. Protheroe,P. A. Johnson
We describe the results of a hybrid matrix--Monte Carlo calculation of
cascading of UHE cosmic rays through the cosmic background radiation
fields over cosmological distances. We calculate the fl-ray and neutrino
emission that results from the cascade, as well as the effect of cascading
on the primary spectrum. We discuss the results for various cosmic ray
injection spectra.
1 Introduction
It was first noted by Greisen [1], and Zatsepin and Kuz'min [2] that the nucleonic
component of UHE cosmic-rays above 10
20
eV will be severely attenuated
in the cosmic microwave background due primarily to photopion production
interactions with the low energy photons. The details of the propagation of the
highest energy cosmic-rays...
180.
Propagation of Ultra High Energy Protons and Gamma Rays over Cosmological Distances and Implications for Topological Defect Models
- R. J. Protheroe,P. A. Johnson
We describe the results of a hybrid matrix--Monte Carlo calculation of cascading
of UHE cosmic rays and fl-rays through the cosmic background radiation fields over
cosmological distances. We calculate the fl-ray and neutrino emission that results
from the cascade, as well as the effect of cascading on the primary spectrum. We
discuss the results for various cosmic ray injection spectra and primary species.
Certain models for the production of the highest energy cosmic rays are ruled out.
1 Introduction
It was first noted by Greisen [1], and Zatsepin and Kuz'min [2] (GZK) that the nucleonic
component of UHE cosmic rays above 100 EeV (1 EeV = 10
18
eV) will...
