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Title: Measurements of charged two-particle exclusive states in photon-photon interactions

Abstract

A description is given of an experiment performed at the PEP electron-positron storage ring, using the DELCO detector, to measure the formation of charged particle pairs from interactions of pairs of virtual photons radiated from the colliding electron beams. The final states which are measured are electron-positron pairs, charged pion pairs, charged kaon pairs, and proton pairs. Electron-positron pairs are separated from other data by use of gas Cerenkov counters. The shapes of all kinematic distributions are found to agree with predictions of quantum electrodynamics. These data also are used as an accurate normalization for subtraction of the muon-pair background and for measurement of the cross sections of the three hadronic channels. Pion pairs are measured in the mass range from 0.6 to 2.0 GeV, where production of the f (1270) resonance is observed to interfere with significant continuum production. The continuum is well described by single-pion exchange, allowing a measurement of the f two-photon partial width of 3.47 +- 0.37 keV. No a priori assumption is made about the ratio of helicity amplitudes, and the phenomenological model used in fitting the data is constrained to satisfy elastic unitarity. If unitarity is not required, then the fitted partial width ismore » a factor of 0.83 lower than the quoted value. The Q/sup 2/ dependence of the cross section is found to be consistent with predictions of the Generalized Vector Dominance Model. Kaon pairs and proton pairs are identified by time-of-flight measurements. Kaon pairs are measured in the mass range from 1.3 to 2.0 GeV, where production of the f' (1520) resonance is observed. The ratio of the f and f' two-photon partial widths is found to be consistent with SU(3) quark model predictions with a mixing angle of 28 +- 4 degrees. Twenty-three proton pairs are observed.« less

Authors:
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
OSTI Identifier:
5937587
Report Number(s):
SLAC-294
ON: DE86009667
DOE Contract Number:  
AC03-76SF00515
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PHOTON-PHOTON INTERACTIONS; EXCLUSIVE INTERACTIONS; CHERENKOV COUNTERS; CROSS SECTIONS; ELECTRON PAIRS; EXPERIMENTAL DATA; KAONS; MASS SPECTRA; PAIR PRODUCTION; PEP STORAGE RINGS; PIONS; PROTONS; QUANTUM ELECTRODYNAMICS; TIME-OF-FLIGHT METHOD; BARYONS; BASIC INTERACTIONS; BOSONS; DATA; ELECTRODYNAMICS; ELECTROMAGNETIC INTERACTIONS; ELEMENTARY PARTICLES; FERMIONS; FIELD THEORIES; HADRONS; INFORMATION; INTERACTIONS; MEASURING INSTRUMENTS; MESONS; NUCLEONS; NUMERICAL DATA; PARTICLE INTERACTIONS; PSEUDOSCALAR MESONS; QUANTUM FIELD THEORY; RADIATION DETECTORS; SPECTRA; STORAGE RINGS; STRANGE MESONS; STRANGE PARTICLES; 645101* - High Energy Physics- Particle Interactions & Properties-Experimental- Electromagnetic Interactions & Properties

Citation Formats

Johnson, R P. Measurements of charged two-particle exclusive states in photon-photon interactions. United States: N. p., 1986. Web. doi:10.2172/5937587.
Johnson, R P. Measurements of charged two-particle exclusive states in photon-photon interactions. United States. https://doi.org/10.2172/5937587
Johnson, R P. 1986. "Measurements of charged two-particle exclusive states in photon-photon interactions". United States. https://doi.org/10.2172/5937587. https://www.osti.gov/servlets/purl/5937587.
@article{osti_5937587,
title = {Measurements of charged two-particle exclusive states in photon-photon interactions},
author = {Johnson, R P},
abstractNote = {A description is given of an experiment performed at the PEP electron-positron storage ring, using the DELCO detector, to measure the formation of charged particle pairs from interactions of pairs of virtual photons radiated from the colliding electron beams. The final states which are measured are electron-positron pairs, charged pion pairs, charged kaon pairs, and proton pairs. Electron-positron pairs are separated from other data by use of gas Cerenkov counters. The shapes of all kinematic distributions are found to agree with predictions of quantum electrodynamics. These data also are used as an accurate normalization for subtraction of the muon-pair background and for measurement of the cross sections of the three hadronic channels. Pion pairs are measured in the mass range from 0.6 to 2.0 GeV, where production of the f (1270) resonance is observed to interfere with significant continuum production. The continuum is well described by single-pion exchange, allowing a measurement of the f two-photon partial width of 3.47 +- 0.37 keV. No a priori assumption is made about the ratio of helicity amplitudes, and the phenomenological model used in fitting the data is constrained to satisfy elastic unitarity. If unitarity is not required, then the fitted partial width is a factor of 0.83 lower than the quoted value. The Q/sup 2/ dependence of the cross section is found to be consistent with predictions of the Generalized Vector Dominance Model. Kaon pairs and proton pairs are identified by time-of-flight measurements. Kaon pairs are measured in the mass range from 1.3 to 2.0 GeV, where production of the f' (1520) resonance is observed. The ratio of the f and f' two-photon partial widths is found to be consistent with SU(3) quark model predictions with a mixing angle of 28 +- 4 degrees. Twenty-three proton pairs are observed.},
doi = {10.2172/5937587},
url = {https://www.osti.gov/biblio/5937587}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Mar 01 00:00:00 EST 1986},
month = {Sat Mar 01 00:00:00 EST 1986}
}