Results on hadronic events from the MAC detector at PEP. I. Direct photon production. II. Precision R measurement and energy-energy correlations

Conference · Sun Jul 01 00:00:00 EDT 1984

OSTI ID:6587044

Heltsley, B K

Direct photon production in hadronic events from e/sup +/e/sup -/ ..-->.. hadrons has been studied at ..sqrt..s=29 GeV using the MAC detector at PEP. Both the charge asymmetry in the final state jets and total yield have been used to determine values of quark charges, which are in good agreement with the predictions of the fractionally charged quark-parton model. Limits have been established for anomalous sources of direct photons. Measurements of the total cross section and energy-energy correlations for e/sup +/e/sup -/ ..-->.. hadrons at ..sqrt..s=29 GeV with the MAC detector are presented. Two complementary event selections for the precision R measurement are described, one accepting events over nearly the entire 4..pi.. solid angle (minimizing extrapolation to unseen phase space), and the other restricted to wide angles (reducing two-photon backgrounds). The two methods agree, yield R = 3.93 +- 0.10 (which includes the effects of higher order radiative corrections), and given ..cap alpha../sub s/ = 0.19 +- 0.07, independent of fragmentation. The asymmetry in the energy-energy correlation cross section yields different results for ..cap alpha../sub s/ in different models, 0.185 in the string model and from 0.105 to 0.140 for incoherent jet formation, depending on the gluon fragmentation and momentum conservation algorithms. The string fragmentation model provides a satisfactory description of the measured correlation cross section, whereas incoherent jet fragmentation does not. 35 references.

• Research Organization: Wisconsin Univ., Madison (USA)
• DOE Contract Number: AC02-81ER40025; AC03-76SF00515
• OSTI ID: 6587044
• Report Number(s): SLAC-PUB-3393; CONF-8406183-1; ON: DE84015880
• Resource Relation: Conference: 15. international symposium on multiparticle dynamics, Lund, Sweden, 11 Jun 1984
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ELECTRON-POSITRON INTERACTIONS
ANNIHILATION
HADRONS
PARTICLE PRODUCTION
CROSS SECTIONS
GLUONS
JET MODEL
PHOTONS
QUARKS
BASIC INTERACTIONS
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
INTERACTIONS
LEPTON-LEPTON INTERACTIONS
MASSLESS PARTICLES
MATHEMATICAL MODELS
PARTICLE INTERACTIONS
PARTICLE MODELS
POSTULATED PARTICLES
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