Measurements of charged two-particle exclusive states in photon-photon interactions
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.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 5937587
- Report Number(s):
- SLAC-294; ON: DE86009667
- Country of Publication:
- United States
- Language:
- English
Similar Records
Preface and Summary
Measurement of the central exclusive production of charged particle pairs in proton-proton collisions at $\sqrt{s}$ = 200 GeV with the STAR detector at RHIC
Related Subjects
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