169 research outputs found
Experimental Indications for the Response of the Spectators to the Participant Blast
Precise momentum distributions of identified projectile fragments, formed in
the reactions 238U + Pb and 238U + Ti at 1 A GeV, are measured with a
high-resolution magnetic spectrometer. With increasing mass loss, the
velocities first decrease as expected from previously established systematics,
then level off, and finally increase again. Light fragments are on the average
even faster than the projectiles. This finding is interpreted as the response
of the spectators to the participant blast. The re-acceleration of projectile
spectators is sensitive to the nuclear mean field and provides a new tool for
investigating the equation of state of nuclear matter.Comment: 7 pages, 3 figures, background information on
http://www-wnt.gsi.de/kschmidt
Nuclear expansion and symmetry energy of hot nuclei
The decrease in the symmetry energy of hot nuclei populated in Ni +
Ni, Fe + Ni and Fe + Fe reactions at beam
energies of 30, 40, and 47 MeV/nucleon, as a function of excitation energy is
studied. It is observed that this decrease is mainly a consequence of
increasing expansion or decreasing density rather than the increasing
temperature. The results are in good agreement with the recently reported
microscopic calculation based on the Thomas-Fermi approach. An empirical
relation to study the symmetry energy of finite nuclei in various mass region
is proposed.Comment: 10 pages, 2 figure
Symmetry energy of fragments produced in multifragmentation
Isospin properties of fragments measured in multifragmentation of 136Xe and
124Xe projectiles in mid-peripheral collisions with a lead target at 1 A GeV
were studied within the statistical approach describing the liquid-gas nuclear
phase transition. By analyzing the isoscaling phenomenon and the mean N-over-Z
ratio of the fragments with Z=10-13 we have concluded that the symmetry energy
of hot fragments produced in multifragment environment at subnuclear densities
at high temperatures decreases in comparison with cold nuclei.Comment: 10 pages, 4 figures, background information on
http://www-w2k.gsi.de/charms
Production of medium-mass neutron-rich nuclei in reactions induced by 136Xe projectiles at 1 A GeV on a beryllium target
Production cross sections of medium-mass neutron-rich nuclei obtained in the
fragmentation of 136Xe projectiles at 1 A GeV have been measured with the
FRagment Separator (FRS) at GSI. 125Pd was identified for the first time. The
measured cross sections are compared to 238U fission yields and model
calculations in order to determine the optimum reaction mechanism to extend the
limits of the chart of the nuclides around the r-process waiting point at N=82.Comment: 9 pages, 6 figure
Measurement of the complete nuclide production and kinetic energies of the system 136Xe + hydrogen at 1 GeV per nucleon
We present an extensive overview of production cross sections and kinetic
energies for the complete set of nuclides formed in the spallation of 136Xe by
protons at the incident energy of 1 GeV per nucleon. The measurement was
performed in inverse kinematics at the FRagment Separator (GSI, Darmstadt).
Slightly below the Businaro-Gallone point, 136Xe is the stable nuclide with the
largest neutron excess. The kinematic data and cross sections collected in this
work for the full nuclide production are a general benchmark for modelling the
spallation process in a neutron-rich nuclear system, where fission is
characterised by predominantly mass-asymmetric splits.Comment: 18 pages, 14 figure
Angular Dependence in Proton-Proton Correlation Functions in Central and Reactions
The angular dependence of proton-proton correlation functions is studied in
central and nuclear reactions at E=80
MeV/A. Measurements were performed with the HiRA detector complemented by the
4 Array at NSCL. A striking angular dependence in the laboratory frame is
found within p-p correlation functions for both systems that greatly exceeds
the measured and expected isospin dependent difference between the neutron-rich
and neutron-deficient systems. Sources measured at backward angles reflect the
participant zone of the reaction, while much larger sources observed at forward
angles reflect the expanding, fragmenting and evaporating projectile remnants.
The decrease of the size of the source with increasing momentum is observed at
backward angles while a weaker trend in the opposite direction is observed at
forward angles. The results are compared to the theoretical calculations using
the BUU transport model.Comment: 8 pages, 3 figures, submitted to PR
Extrapolation of neutron-rich isotope cross-sections from projectile fragmentation
Using the measured fragmentation cross sections produced from the 48Ca and
64Ni beams at 140 MeV per nucleon on 9Be and 181Ta targets, we find that the
cross sections of unmeasured neutron rich nuclei can be extrapolated using a
systematic trend involving the average binding energy. The extrapolated
cross-sections will be very useful in planning experiments with neutron rich
isotopes produced from projectile fragmentation. The proposed method is general
and could be applied to other fragmentation systems including those used in
other radioactive ion beam facilities.Comment: accepted for publication in Europhysics Letter
Mass Spectra of Supersymmetric Yang-Mills Theories in 1+1 Dimensions
Physical mass spectra of supersymmetric Yang-Mills theories in 1+1 dimensions
are evaluated in the light-cone gauge with a compact spatial dimension. The
supercharges are constructed and the infrared regularization is unambiguously
prescribed for supercharges, instead of the light-cone Hamiltonian. This
provides a manifestly supersymmetric infrared regularization for the
discretized light-cone approach. By an exact diagonalization of the supercharge
matrix between up to several hundred color singlet bound states, we find a
rapidly increasing density of states as mass increases.Comment: LaTeX file, 32 page, 7 eps figure
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