16 research outputs found
Deformation effects in the Si+C and Si+Si reaction Search
The possible occurence of highly deformed configurations is investigated in
the Ca and Ni di-nuclear systems as formed in the
Si+C,Si reactions by using the properties of emitted light
charged particles. Inclusive as well as exclusive data of the heavy fragments
and their associated light charged particles have been collected by using the
{\sc ICARE} charged particle multidetector array. The data are analysed by
Monte Carlo CASCADE statistical-model calculations using a consistent set of
parameters with spin-dependent level densities. Significant deformation effects
at high spin are observed as well as an unexpected large Be cluster
emission of a binary nature.Comment: 3 pages latex, 2 eps figures, paper presented in "wokshop on physics
with multidetector array (pmda2000)Calcutta, India (to be published at
PRAMANA, journal of Physics, India
Vanishing spin alignment : experimental indication of triaxial nuclear molecule
Fragment-fragment- coincidences have been measured for at an energy corresponding to the population of a conjectured
resonance in Ni. Fragment angular distributions as well as -ray
angular correlations indicate that the spin orientations of the outgoing
fragments are perpendicular to the orbital angular momentum. This differs from
the and the resonances, and
suggests two oblate nuclei interacting in an equator-to-equator
molecular configuration.Comment: 14 pages standard REVTeX file, 3 ps Figures -- Accepted for
publication in Physical Review C (Rapid Communication
Chaotic Scattering in Heavy--Ion Reactions
We discuss the relevance of chaotic scattering in heavy--ion reactions at
energies around the Coulomb barrier. A model in two and three dimensions which
takes into account rotational degrees of freedom is discussed both classically
and quantum-mechanically. The typical chaotic features found in this
description of heavy-ion collisions are connected with the anomalous behaviour
of several experimental data.Comment: 35 pages in RevTex (version 3.0) plus 27 PostScript figures
obtainable by anonymous ftp from VAXFCT.CT.INFN.IT in directory kaos. Fig. 1
upon request to the authors. To be published in the October Focus issue on
chaotic scattering of CHAO
Measurement of the Neutron Spin Structure Function with a Polarized ^3He Target
Results are reported from the HERMES experiment at HERA on a measurement of
the neutron spin structure function in deep inelastic scattering
using 27.5 GeV longitudinally polarized positrons incident on a polarized
He internal gas target. The data cover the kinematic range
and . The integral evaluated at a fixed of is . Assuming Regge behavior at low , the first
moment is .Comment: 4 pages TEX, text available at
http://www.krl.caltech.edu/preprints/OAP.htm
Flavor Decomposition of the Polarized Quark Distributions in the Nucleon from Inclusive and Semi-inclusive Deep-inelastic Scattering
Spin asymmetries of semi-inclusive cross sections for the production of
positively and negatively charged hadrons have been measured in deep-inelastic
scattering of polarized positrons on polarized hydrogen and 3He targets, in the
kinematic range 0.023<x<0.6 and 1 GeV^2<Q^2<10 GeV^2. Polarized quark
distributions are extracted as a function of x for up $(u+u_bar) and down
(d+d_bar) flavors. The up quark polarization is positive and the down quark
polarization is negative in the measured range. The polarization of the sea is
compatible with zero. The first moments of the polarized quark distributions
are presented. The isospin non-singlet combination Delta_q_3 is consistent with
the prediction based on the Bjorken sum rule. The moments of the polarized
quark distributions are compared to predictions based on SU(3)_f flavor
symmetry and to a prediction from lattice QCD.Comment: 14 pages, 6 figures (eps format), 10 tables in Latex New version
contains tables of asymmetries and correlation matri
Observation of a coherence length effect in exclusive ρ(0) electroproduction
Exclusive incoherent electroproduction of the ρ0(770) meson from 1H, 2H, 3He, and 14N targets has been studied by the HERMES experiment at squared four-momentum transfer Q^2>0.4 GeV^2 and positron energy loss ν from 9 to 20 GeV. The ratio of the 14N to 1H cross sections per nucleon, known as the nuclear transparency, was found to decrease with increasing coherence length of quark-antiquark fluctuations of the virtual photon. The data provide clear evidence of the interaction of the quark-antiquark fluctuations with the nuclear medium