626 research outputs found
Cross sections for the production of fragments with Z greater than or equal to 8 by fragmentation of Z greater than or equal to 9 and less than or equal to 26 nuclei
Charge changing nuclear collisions in plastic nuclear track detectors were studied using a new experimental technique of automatic track measurement for etched tracks in plastic detectors. Partial cross sections for the production of fragments of charge Z approximately 8 were measured for projectile nuclei of charge 9 approximately Z approximately 26 in the detector material CR39 and in silver. for this purpose three independent experiments were performed using Bevalac beams. The first one was an exposure of a stack of CR39 plastic plates to 1.8 GeV/nucl. Ar-40 nuclei. The second one was an exposure of another CR39 stack of 1.7 GeV/nucl. Fe-56 projectiles. In the third experiment a mixed stack of CR39 plates and silver foils was irradiated with 1.7 GeV/nucl. Fe-56 nuclei. Thus the measurement of nuclear cross sections in a light target (CR39 = C12H18O7) and as well in a heavy target (silver) was possible
Results from the Analysis of Crystal Ball Meson Production Measurements at BNL
The Crystal Ball spectrometer, with its nearly complete angular coverage, is
an efficient detector of photon and neutron final states. While installed in
the C6 beamline of the Alternating Gradient Synchrotron (AGS) of Brookhaven
National Laboratory (BNL), this feature was used in a series of precise
measurements of reactions with all-neutral final states. Here we concentrate on
the analysis of data from the pion-induced reactions: pi- p --> gamma n, pi- p
--> pi0 n, pi- p --> eta n, and pi- p --> pi0 pi0 n.Comment: Conference contribution to MESON 2006 - Krakow, Pola
Nucleon Polarisabilities from Compton Scattering off the One- and Few-Nucleon System
These proceedings sketch how combining recent theoretical advances with data
from the new generation of high-precision Compton scattering experiments on
both the proton and few-nucleon systems offers fresh, detailed insight into the
Physics of the nucleon polarisabilities. A multipole-analysis is presented to
simplify their interpretation. Predictions from Chiral Effective Field Theory
with special emphasis on the spin-polarisabilities can serve as guideline for
doubly-polarised experiments below 300 MeV. The strong energy-dependence of the
scalar magnetic dipole-polarisability turns out to be crucial to
understand the proton and deuteron data. Finally, a high-accuracy determination
of the proton and neutron polarisabilities shows that they are identical within
error-bars. For details and a better list of references, consult the given
references.Comment: 10 pages LaTeX2e with 7 figures in 8 .eps files, using graphicx.
Invited seminar given at the 26th Course of the International School of
Nuclear Physics: Lepton Scattering and the Structure of Hadrons and Nuclei,
Erice (Italy), 16th - 24th September 2004. To be published in Prog. Nucl.
Part. Phys. 54, No. 2 as part of the proceeding
The polarizability of the pion: no conflict between dispersion theory and chiral perturbation theory
Recent attempts to determine the pion polarizability by dispersion relations
yield values that disagree with the predictions of chiral perturbation theory.
These dispersion relations are based on specific forms for the absorptive part
of the Compton amplitudes. The analytic properties of these forms are examined,
and the strong enhancement of intermediate-meson contributions is shown to be
connected with spurious singularities. If the basic requirements of dispersion
relations are taken into account, the results of dispersion theory and
effective field theory are not inconsistent.Comment: 30 pages, 8 figures, 6 table
Momentum dependence of the N to Delta transition form factors
We present a new method to determine the momentum dependence of the N to
Delta transition form factors and demonstrate its effectiveness in the quenched
theory at on a lattice. We address a number of
technical issues such as the optimal combination of matrix elements and the
simultaneous overconstrained analysis of all lattice vector momenta
contributing to a given momentum transfer squared, .Comment: Talk presented at Lattice 2004 (spectrum), Fermilab, 21-26 Jun. 2004.
3 pages, 3 figures. One typo in phenomenological Ansatz correcte
A method to polarise antiprotons in storage rings and create polarised antineutrons
An intense circularely polarised photon beam interacts with a cooled
antiproton beam in a storage ring. Due to spin dependent absorption cross
sections for the reaction gamma+antiproton > pi- + antineutron a built-up of
polarisation of the stored antiprotons takes place. Figures-of-merit around 0.1
can be reached in principle over a wide range of antiproton energies. In this
process antineutrons with Polarisation > 70% emerge. The method is presented
for the case of 300 MeV/c cooled antiproton beam
Low-energy and low-momentum representation of the virtual Compton scattering amplitude
We perform an expansion of the virtual Compton scattering amplitude for low
energies and low momenta and show that this expansion covers the transition
from the regime to be investigated in the scheduled photon electroproduction
experiments to the real Compton scattering regime.
We discuss the relation of the generalized polarizabilities of virtual
Compton scattering to the polarizabilities of real Compton scattering.Comment: 13 pages, LaTeX2e/RevTeX, no figure
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