Bryon D. Anderson - US grants

This equipment will be used to carry out an approved experiment to probe the nuclear equation of state (EOS) by measuring triple-differential cross sections for neutrons from high-multiplicity collisions of equal-mass nuclei as a function of mass number and bombarding energy. Calculations indicate that this experiment can probe the EOS with good sensitivity, and measurement of collective flow of neutrons will provide information complementary to Plastic Ball and Streamer Chamber measurements of charged particles. The wide dynamic range of neutron energies from about 20 MeV to nearly three times the kinetic energy per nucleon of the projectile, is in marked contrast to the Plastic Ball measurements with energies from about 40 to 200 MeV/nucleon. The ability to detect neutrons over this wide dynamic range of energies (and in many detectors simultaneously) compensates for the reduced neutron detection efficiency.

This is a proposal by the Medium-Energy Nuclear Physics Group at Kent State University (KSU) to study Gamow-Teller strength, stretched-state excitations, analyzing powers, and polarization-transfer observables in (p,n) reactions supplemented by (n,p) reactions; to probe the nuclear equation-of-state (EOS) by measuring triple-differential cross sections for neutrons from high-multiplicity collisions of equal-mass nuclei as a function of mass number and bombarding energy, where the azimuthal angle of the reaction plane is determined by measuring the transverse velocities of charged fragments emitted in a collision; and to probe nucleon and nuclear structure via electron-induced reactions. KSU is committed to an experiment to determine the electric form factor of the neutron by using the KSU polarimeter to measure the polarization of the recoil neutron after quasielastic scattering of a longitudinally-polarized electron from an unpolarized neutron in deuterium. Also KSU has submitted letters of intent to CEBAF for experiments on the charge form factor of the neutron, the photoproduction and electroproduction of rho mesons, neutron knockout in the quasielastic (e,e'n) coincidence reaction, and two-nucleon knockout (e,e'2N) reactions. The group is continuing to develop improved instrumentation for the detection of neutrons. Current projects include improved neutron polarimeters and higher efficiency neutron detectors.

This grant provides a state-of-the-art MicroVAX 3500 computer system for use by the Kent State University Intermediate Energy Nuclear Physics faculty and students involved in NSF sponsored research. Essential features of the system include: fast processing time for large scale data replay, line-shape fitting, and analysis codes; large memory; high speed communications; and multi-user environment.

9409265 Anderson Research will be carried out in nucleon and nuclear structure via electron and proton induced reactions. Polarization transfer in neutron-proton charge exchange reactions will be used to probe the medium effects on the nucleon-nucleon potential. The charge- structure of the neutron will be probed in polarization transfer studies of electron-induced neutron knockout reactions. A high- efficiency neutron polarimeter will be assembled and calibrated for these purposes. The charge exchange reactions will be carried out at the Indiana University Cyclotron Facility, while measurements of the neutron's charge structure will be carried out at the MIT/Bates lab and at CEBAF. Other related experiments will also be carried out at these laboratories. ***

This three-year grant will support the research of three faculty members, two post-doctoral fellows, and three graduate students to perform a variety of experiments in medium-energy nuclear physics. Much of the activity of the group is focused around measurements of the neutron polarization. These experiments include studies of the complete set of spin observables in the reaction of polarized protons with a variety of targets at the neutron polarization facility at the Indiana University Cyclotron Facility. These experiments use specialized detectors developed by Kent State to measure normal and sideways polarizations of the neutron simultaneously. Measurements with 2H 3He, and 4He targets would study the nucleon-nucleon interaction part that is mediated by a single pion or rho meson. Other experiments would study the isovector response of the nuclear continuum and the isovector giant dipole resonance. The determination of the electric form factor of the neutron would be obtained from neutron polarization measurements using polarized electron beams at the MIT-Bates Laboratory and the Thomas Jefferson National Accelerator Facility (TJNAF). Other experiments include a search for three-body forces and a search for pion-field effects. This grant would also support experiments with the Crystal Ball at the Brookhaven National Laboratory AGS and the CLAS detector at Hall B at TJNAF in order to study neutral baryon resonances and nucleon resonances, respectively.

0072240
Anderson
This project is centered around the study of the structure of the
nucleon, primarily by the measurement of the electric form factor of the neutron. This group will play a pivotal role in an approved experiment at the Thomas Jefferson National Accelerator Facility (JLab) designed to measure the electric form factor of the neutron as a function of momentum transfer. Because the neutron is overall neutral, the electric form factor is very sensitive to the details of the constituents and their motions. This measurement provides one of the best experimental tests available for any model of the nucleon and is generally considered to be one of the most important measurements to be performed in intermediate-energy nuclear physics. The experiment will be performed by the scattering of longitudinally polarized electrons from a liquid deuterium target and detecting the knock-out neutron in coincidence with the scattered electron. The Kent State group has the responsibility for providing the neutron detector array for this experiment. The array consists of thirty-six separate neutron detectors arranged so as to both
detect the neutron and determine its spin. The transfer of the spin from the electron beam to the neutron is directly related to the charge form factor of the neutron. The detector array is called a neutron
polarimeter. The Kent State group has used a similar polarimeter in
experiments at other accelerator facilities and will have the
responsibility for the installation, operation, and maintenance of this
detector array for the experiment. This project will be part of the
Ph.D. dissertation research of two Kent State graduate students.
Support from this award will also enable this group to finish the
analysis of experiments performed at the Indiana University Cyclotron
Facility to study the spin dependence of the nuclear force, to search
for three-body contributions to the nuclear force, and also to analyze
measurements of baryon resonances using the Crystal Ball Spectrometer at the Brookhaven AGS accelerator. These measurements were performed with earlier support from the National Science Foundation and are part of the dissertation projects of three Kent State graduate students.

This award is to support the research activities of two professors,
their graduate students and a Senior Research Associate at Kent State
University in the area of experimental medium-energy nuclear physics.
The general objectives are the study of the structure of the nucleon
(neutron or proton) and the nature of the nuclear force. This group is
involved in experiments being performed, or to be performed at the
Jefferson National Accelerator Facility (Jlab) in Virginia and at the
Relativistic Heavy-Ion Collider (RHIC) on Long Island, New York. An
experiment is in progress at Jlab to determine the charge distribution
inside the neutron. The neutron, while neutral overall, is known to
consist of objects with both positive and negative charges. These
objects are called "quarks". The quarks are held together by the
exchange of particles called "gluons". Exactly how the quarks combine,
move, and interact inside the neutron is not known. A precise
measurement of the charge distribution, called the Electric Form Factor,
will provide one of the most sensitive tests available of various models
of the neutron structure. These measurements are only recently possible
and require the electron beam characteristics now available at Jlab and
involve the use of a large-volume neutron polarimeter developed by this
group in experiments performed during the last decade at other
accelerator facilities. The development, installation, calibration, and
operation of the polarimeter represents the unique contribution of this
group to this important experiment. This group plans also to perform
another experiment at Jlab to study short-range correlation between
nucleons inside nuclei. Such short-range correlations are known to
exist, but the exact nature and strength of such correlations are only
poorly determined. This group will bring its expertise with neutron
detectors to help study such correlations involving neutrons.

This group has recently joined an effort planned to study interactions
between colliding beams of polarized protons using the "STAR" detector
at RHIC (STAR stands for Solenoidal Tracker at RHIC). The object of
this study is to determine the exact origin of the intrinsic angular
momentum, or spin, of the proton. The spin, like the charge
distribution, arises from the existence, interactions and movements of
the constituents of the proton, generally believed to be the quarks and
gluons. To date, only the contributions from the quarks has been
determined; this project offers the possibility of determining the
contribution to the spin of the proton due to gluons. In order to
measure these contributions, it is necessary to observe hadronic jets
produced at relatively small angles in the collisions. This group,
together with a collaboration of other researchers from Indiana
University, Argonne National Laboratory, and others, will construct a
new "end-cap calorimeter" to be installed at one end of the present STAR
detector at RHIC. It will be this group's responsibility to provide
characterizations and calibrations of the multi-anode photomultiplier
tubes used for particle detection in this new calorimeter.