Numerical study of Regge cuts due to absorption in neutral pion photoproduction
Miller, Robert Alan
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https://hdl.handle.net/2142/25851
Description
Title
Numerical study of Regge cuts due to absorption in neutral pion photoproduction
Author(s)
Miller, Robert Alan
Issue Date
1970
Doctoral Committee Chair(s)
Wyld, H.W.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
numerical study
Regge cuts
absorption
neutral pion photoproduction
absorptive Regge models
Language
en
Abstract
We examine in some detail the numerical features of some absorptive
Regge models of neutral pion photoproduction. We start be reviewing the
formalism in a consistent notation. The formalism contains derivations
of the two expressions commonly used to calculate absorbed scattering
amplitudes and their relation to Regge cut parametrizations. The physical
picture behind the derivations is that absorbed Regge scattering is the
result of secondary scattering of the products of the pure Regge exchange
so that particles are scattered into inelastic channels. The scattering
of the particles which remain in the channel of interest is taken to be
elastic scattering as measured experimentally. The oldest of the two
absorptive expressions is the Gottfried-Jackson partial wave form; the
newer expression involves an integral over the intermediate scattering
angle. The integral absorption expression is used for most of the calculations
in this work. Unitarity and factorization are discussed briefly
regarding their relation to the calculations presented.
Numerical results are obtained by choosing a specific parametrization
for the Regge exchange and performing the required numerical integrations.
We present graphs of the discontinuities across the Regge cut which is
generated, the contribution to the s- and t-channel scattering amplitudes
due to the cut, and the fit to the data which is obtained. The s dependence
of the absorptive corrections is discussed.
We find that the straightforward absorptive Regge model does not fit
the data well. For this reason we examine the effects produced by the
modifications of the straightforward model which have been used in several
published fits. We find that the omission of the nonsense wrong-signature
zero has a beneficial effect. We argue that, independent of the presence
or absence of a nonsense wrong-signature zero, the effects of the cut calculated
in the manner presented are too small, and that an arbitrary
multiplication of the cut amplitude bya factor of about 2 is necessary
in the types of absorptive Regge fits which have been tried.
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