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

Direct photon production in hadronic events from e+e- → hadrons has been studied at √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+e- → hadrons at √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 4π 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 α/sub s/ = 0.19 +- 0.07, independent of fragmentation. The asymmetry in the energy-energy correlation cross section yields different results for α/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