49 research outputs found
Dynamical aspects of isotopic scaling
Investigation of the effect of the dynamical stage of heavy-ion collisions
indicates that the increasing width of the initial isospin distributions is
reflected by a significant modification of the isoscaling slope for the final
isotopic distributions after de-excitation. For narrow initial distributions,
the isoscaling slope assumes the limiting value of the two individual initial
nuclei while for wide initial isotopic distributions the slope for hot
fragments approaches the initial value. The isoscaling slopes for final cold
fragments increase due to secondary emissions. The experimentally observed
evolution of the isoscaling parameter in multifragmentation of hot
quasiprojectiles at E=50 AMeV, fragmentation of Kr projectiles
at E=25 AMeV and multifragmentation of target spectators at
relativistic energies was reproduced by a simulation with the dynamical stage
described using the appropriate model (deep inelastic transfer and incomplete
fusion at the Fermi energy domain and spectator-participant model at
relativistic energies) and the de-excitation stage described with the
statistical multifragmentation model. In all cases the isoscaling behavior was
reproduced by a proper description of the dynamical stage and no unambiguous
signals of the decrease of the symmetry energy coefficient were observed.Comment: LaTeX, 18 pages, 9 figures, to appear in Phys. Rev.
Effect of nuclear periphery on nucleon transfer in peripheral collisions
A comparison of experimental heavy residue cross sections from the reactions
86Kr+64Ni,112,124Sn with the model of deep-inelastic transfer (DIT) is carried
out. A modified expression for nucleon transfer probabilities is used at
non-overlapping projectile-target configurations, introducing a dependence on
isospin asymmetry at the nuclear periphery. The experimental yields of
neutron-rich nuclei close to the projectile are reproduced better and the trend
deviating from the bulk isospin equilibration is explained. For the
neutron-rich products further from the projectile, originating from hot
quasiprojectiles, the statistical multifragmentation model reproduces the mass
distributions better than the model of sequential binary decay. In the reaction
with proton-rich target 112Sn the nucleon exchange appears to depend on isospin
asymmetry of nuclear periphery only when surface separation is larger than 0.8
fm due to the stronger Coulomb interaction at more compact di-nuclear
configuration.Comment: LaTeX, 13 pages, 7 figures, to appear in Nuclear Physics
Neutron star structure with nuclear force mediated by hypothetical X17 boson
A reported MeV boson, which has been proposed as an explanation to the
Be and He anomaly, is investigated in the context of its possible
influence to neutron stars structure. Implementing a =17 MeV to the
nuclear equation of state using different incompressibility values K=245
MeV and K=260 MeV and solving Tolman-Oppenheimer-Volkoff equations, we
estimate an upper limit of for a non rotating
neutron star with span in radius between km to km. Moving
away from pure - NN with admixture of 10\% protons and simulating possible
softening of equation of state due to hyperons, we see that our estimated
limits fit quite well inside the newest reported studies, coming from neutron
stars merger event, GW190814Comment: 5 pages, 4 figures, To appear in the EPJ Web of Conference
Isotopic Scaling of Heavy Projectile Residues from the collisions of 25 MeV/nucleon 86Kr with 124Sn, 112Sn and 64Ni, 58Ni
The scaling of the yields of heavy projectile residues from the reactions of
25 MeV/nucleon 86Kr projectiles with 124Sn,112Sn and 64Ni, 58Nitargets is
studied. Isotopically resolved yield distributions of projectile fragments in
the range Z=10-36 from these reaction pairs were measured with the MARS recoil
separator in the angular range 2.7-5.3 degrees. The velocities of the residues,
monotonically decreasing with Z down to Z~26-28, are employed to characterize
the excitation energy. The yield ratios R21(N,Z) for each pair of systems are
found to exhibit isotopic scaling (isoscaling), namely, an exponential
dependence on the fragment atomic number Z and neutron number N. The isoscaling
is found to occur in the residue Z range corresponding to the maximum observed
excitation energies. The corresponding isoscaling parameters are alpha=0.43 and
beta=-0.50 for the Kr+Sn system and alpha=0.27 and beta=-0.34 for the Kr+Ni
system. For the Kr+Sn system, for which the experimental angular acceptance
range lies inside the grazing angle, isoscaling was found to occur for Z<26 and
N<34. For heavier fragments from Kr+Sn, the parameters vary monotonically,
alpha decreasing with Z and beta increasing with N. This variation is found to
be related to the evolution towards isospin equilibration and, as such, it can
serve as a tracer of the N/Z equilibration process. The present heavy-residue
data extend the observation of isotopic scaling from the intermediate mass
fragment region to the heavy-residue region. Such high-resolution mass
spectrometric data can provide important information on the role of isospin in
peripheral and mid-peripheral collisions, complementary to that accessible from
modern large-acceptance multidetector devices.Comment: 8 pages, 6 figures, submitted to Phys. Rev.