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

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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 ... continued below

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Pages: 138

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Johnson, R.P. March 1, 1986.

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Description

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.

Physical Description

Pages: 138

Notes

NTIS, PC A07/MF A01.

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  • Other: DE86009667
  • Report No.: SLAC-294
  • Grant Number: AC03-76SF00515
  • DOI: 10.2172/5937587 | External Link
  • Office of Scientific & Technical Information Report Number: 5937587
  • Archival Resource Key: ark:/67531/metadc1098892

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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Creation Date

  • March 1, 1986

Added to The UNT Digital Library

  • Feb. 18, 2018, 3:59 p.m.

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  • March 20, 2018, 5:50 p.m.

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Johnson, R.P. Measurements of charged two-particle exclusive states in photon-photon interactions, report, March 1, 1986; United States. (digital.library.unt.edu/ark:/67531/metadc1098892/: accessed April 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.