A-2 meson production in pi-minus proton interactions at five BeV
Schafer, Elton Duane
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https://hdl.handle.net/2142/25777
Description
Title
A-2 meson production in pi-minus proton interactions at five BeV
Author(s)
Schafer, Elton Duane
Issue Date
1969
Doctoral Committee Chair(s)
Ascoli, Giulio
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
A2 mesons
hydrogen bubble chamber
incident pions
Language
en
Abstract
"A study of the A2 meson has been made on data obtained from
pi p interactions at 5 BeV/c in the 72""Alvarez liquid hydrogen bubble
chamber. The p pi decay mode in the 4-constraint, p pi+ pi- pi- final state is
treated in detail.
Fit.s to the 3TI invariant mass spectrum yield a central mass
value and width of 1.296±.008 and .l05±.035 BeV. respectively, for the
A2 when the events are treated as constituting a single resosant particle.
Limited statistics render inconclusive an investigation of a possible mass
splitting at the center of the A2 peak. A production crosS section of
l20±46 ub. for the quasi-two-body reaction. pi- p -> A-2 p, is also obtained
from X2 fits to the 3TI mass spectrum. This result is in good agreement
with cross. section measurements reported at other incident pion momenta.
The spin-parity analysis of the Ppi decay mode yields results
p +
which are consistent with a J = 2 assignment for both halves of the A2""
The angular distribution of the decay plane indicates a J = 2 spin state
with alkl = 1 component along the normal to the decay plane. A projection
of the P helicity state population is consistent with a completely
transver.se polarization (i.e. t helicity, I A I = 1) for the intermediate
p!s from the A2 decay.
A calculation of the spin-density matrix elements, assuming a
JF= 2+ assignment for the A2, yields results consistent with resonance
production via p meson exchange. The values for the density matrix elements
are also in.general agreement with those computed from the npi decay
mode."
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