Recent developments in theories of pion production in nucleon-nucleon collisions. Page: 1 of 14
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RECENT DEVELOPMENTS IN THEORIES OF PION
PRODUCTION IN NUCLEON-NUCLEON COLLISIONS
T.-S. H. Lee
Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
Recent developments in theories of pion production in nucleon-nucleon collisions
An important and unsolved problem in intermediate energy physics is the
mechanisms of pion absorption and production on nuclei. This difficulty was
dramatized around 1991 when the data of pp -+ ppiro reaction near threshold
from Indiana University Cyclotron Facility (IUCF) were found1,2 to be a factor
of about 5 larger than the predictions based on the widely accepted rescattering
model of Koltun and Reitan? Many theoretical works have since been done and
more extensive data have been obtained at IUCF and Uppsala. The purpose
of this contribution is to highlight and assess some of these recent theoretical
works which were extensively discussed and debated at an Institute for Nuclear
Theory (INT)/Argonne workshop held August 12-14, 1998 at Argonne.
It is necessary to first briefly review the theoretical works before discussing
the publication of the IUCF data. The pion absorption and production on
two-nucleon systems were already investigated to some extent in the 1950's, as
described in an article by Gell-Mann and Watson4 The next major step was
taken by Koltun and Reitan? They introduced the pion rescattering mechanism
to investigate pion productions on two-nucleon systems at low energies. These
earlier theoretical models can describe qualitatively the data with rather large
errors before 1970. However, they have two theoretical problems. First, the
pion-nucleon off-shell dynamics is neglected in the pion rescattering mechanism
despite that the exchanged pion has a rather large momentum q ~ 350 MeV/c.
Second, all of these earlier theories do not satisfy the irNN unitarity condition.
These two considerations motivated a lot of works5 during the period of
1975-1990 to develop the unitary -NN models for giving an unified description
of the following processes:
irN -> 7rN,
NN -> NN
Ord -> 7rd
The submitted manuscript has been authored
by a contraCtOr of the U. S. Government
under contract No. W.-31-109ENG-38.
Accordingly, the U. S. Government retains a
nonexclusive, royalty-free license to publish
or reproduce the published form of this
contribution, or allow others to do so, for
U. S. Government purposes.
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Lee, T.-S. H. Recent developments in theories of pion production in nucleon-nucleon collisions., article, November 18, 1998; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc618585/m1/1/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.