A measurement of. Delta. sigma. sub L (np), the difference between neutron-proton total cross sections in pure longitudinal spin states

Technical Report · Mon Oct 01 04:00:00 EDT 1990

DOI:https://doi.org/10.2172/6784251· OSTI ID:6784251

Beddo, M E

A measurement off {Delta}{sigma}{sub L}(np), the difference between neutron-proton total cross sections in pure longitudinal spin states, is described. The results will help determine the isospin-zero (I = 0) scattering amplitudes, which are not well known above laboratory energies of 500 MeV, whereas the isospin-one (I = 1) amplitudes are fairly well-determined to 1 GeV. Data points were taken at the Los Alamos Meson Physics Facility (LAMPF) at Los Alamos, New Mexico, for five neutron beam energies: 484, 568, 634,720 and 788 MeV; they are the first in this energy range. Polarized neutrons were produced by charge-exchange of polarized protons on a liquid deuterium target (LD{sub 2}). Large-volume neutron counters detected the neutrons that passed through a polarized proton target. The counters subtended a range of solid angles large enough to allow extrapolation of the scattered neutrons to 0{degree}. Two modifications to the LAMPF accelerator system which were made for this work are described. They included a beam buncher,'' which modified the normal rf-time structure of the proton beam and allowed for the selection of peak-energy neutrons by time-of-flight means, and a computerized beam steering program, which reduced systematic effects due to beam motion at the LD{sub 2} target. The experimental values of {Delta}{sigma}{sub L}(np) are found to be consistent with other np data, including preliminary data from SIN and Saclay, but not with some results from Argonne which used a polarized proton beam and a polarized deuteron target. The I = 0 component was extracted from {Delta}{sigma}{sub L}(np) using existing pp data (I = 1), with the unexpected result that {Delta}{sigma}{sub L}(I = 0) was found to be essentially identical in shape to {Delta}{sigma}{sub L}(I = 1). The significance of this is not yet understood.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: W-7405-ENG-36; FG04-88ER40403
• OSTI ID: 6784251
• Report Number(s): LA-11905-T; ON: DE91000885
• Country of Publication: United States
• Language: English

Related Subjects

645103* -- High Energy Physics-- Particle Interactions & Properties-Experimental-- Strong Interactions & Baryon & Meson Properties
651000 -- Nuclear Physics
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACCELERATORS
AMPLITUDES
ANGULAR MOMENTUM
BARYON REACTIONS
BARYON-BARYON INTERACTIONS
BEAM BUNCHING
BEAM DYNAMICS
BEAMS
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DATA
DATA ACQUISITION SYSTEMS
DATA ANALYSIS
DEUTERIUM TARGET
EXPERIMENTAL DATA
HADRON REACTIONS
HADRON-HADRON INTERACTIONS
INFORMATION
INTERACTIONS
ISOSPIN
LINEAR ACCELERATORS
MEASURING INSTRUMENTS
MEASURING METHODS
NEUTRON DETECTORS
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
NUCLEON-NUCLEON INTERACTIONS
NUMERICAL DATA
PARTIAL WAVES
PARTICLE INTERACTIONS
PARTICLE PROPERTIES
POLARIZED BEAMS
PROTON REACTIONS
RADIATION DETECTORS
SCATTERING AMPLITUDES
SPIN
TARGETS
TOTAL CROSS SECTIONS