The Determination of Pseudoscalar Meson Photoproduction Amplitudes from Complete Experiments

Journal Article · Fri Oct 21 04:00:00 EDT 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3647357· OSTI ID:21612005

Sandorfi, A M; Kamano, H ^[1]; Hoblit, S ^[2]; Lee, T-S H ^[1]

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1. Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (United States)
2. Department of Physics, University of Virginia, Charlottesville, VA 22901 (United States)

A new generation of complete experiments is currently underway with the goal of performing a high precision extraction of pseudoscalar meson photo-production amplitudes. Here we review the most general analytic form of the cross section, dependent upon the three polarization vectors of the beam, target and recoil baryon, including all single, double and triple-polarization terms involving 16 spin-dependent observables. Analytic expressions that determine the recoil baryon polarization are also presented. Different conventions are in use in the literature and we have used a numerical calculation of cross sections from Chew-Goldberger-Low-Nambu amplitudes with arbitrary spin projections to clarify apparent sign differences. As an illustration of the use of this machinery, we carry out a multipole analysis of the {gamma}p {yields} K{sup +}{Lambda} reaction and examine the impact of recently published polarization measurements. In fitting multipoles, we use a combined Monte Carlo sampling of the amplitude space, with gradient minimization, and find a shallow {chi}{sup 2} valley pitted with a very large number of local minima, despite the inclusion of recent data on 8 different observables. We conclude that, while a mathematical solution to the problem of determining an amplitude free of ambiguities may require 8 observables, as has been pointed out in the literature, experiments with realistically achievable uncertainties will require a significantly larger number.

• OSTI ID: 21612005
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1388; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
ANGULAR MOMENTUM
BARYONS
BASIC INTERACTIONS
BOSONS
CALCULATION METHODS
CHIRAL SYMMETRY
CROSS SECTIONS
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
FERMIONS
HADRONS
INTERACTIONS
KAONS
KAONS PLUS
MATHEMATICAL SOLUTIONS
MESONS
MONTE CARLO METHOD
MULTIPOLES
NUCLEONS
PARTICLE INTERACTIONS
PARTICLE PRODUCTION
PARTICLE PROPERTIES
PHOTON-BARYON INTERACTIONS
PHOTON-HADRON INTERACTIONS
PHOTON-NUCLEON INTERACTIONS
PHOTON-PROTON INTERACTIONS
PHOTOPRODUCTION
POLARIZATION
PSEUDOSCALAR MESONS
RECOILS
SPIN
STRANGE MESONS
STRANGE PARTICLES
SYMMETRY
SYMMETRY BREAKING
TENSORS
VECTORS