E. Hilger

A study of Energy-Energy correlations between 12 and 46.8 GeV C.M. Energies

AbstractWe present data on energy-energy correlations (EEC) and their related asymmetry (AEEC) ine+e− annihilation in the centre of mass energy range 12<W≦46.8 GeV. The energy and angular dependence of the EEC in the central region is well described byOαs2 QCD plus a fragmentation term proportional ton

Measurements of the Reaction e+ e- --> e+ e- at Center-Of-Mass Energies of 7.0-GeV and 7.4-GeV

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Search for MonenergeticγRays fromψ(3684)Decay

n. BareO(α)s2 QCD reproduces our data for the large angle region of the AEEC. Nonperturbative effects for the latter are estimated with the help of fragmentation models. From various analyses using different approximations, we find that values forn

Measurement of the Reactione+e−→γγin the Region of theψ(3684)

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Measurement of the τ lifetime

n in the range 0.1–0.3 GeV give a good description of the data. We also compare analytical calculations in QCD for the EEC in the back-to-back region to our data. The theoretical predictions describe well both the angular and energy dependence of the data in the back-to-back region.

Measurement of the reaction e

We report here independent evidence for the decay of the recently discovered ψ(3105) particle1–3 into electron-positron pairs and new evidence for the decay of this particle into muon pairs. We also report the results of a measurement of the reaction e+e− → γγ at center of mass energies in the vicinity of 3105 MeV. These measurements were begun immediately following the discovery of the ψ(3105) at SPEAR1. At that time an apparatus primarily designed for the study of quantum electrodynamics (QED) was operating in the second interaction region at SPEAR and was applied immediately thereafter to the study of the ψ(3105). This apparatus is very similar to that described recently by Beron, et al.,4 and is capable of identifying the reactions e+e− → e+e− →, e+e− → μ+μ− and e+e− → γγ. The detection apertures and procedures used to recognize each of these reactions are identical to those described by Beron et al.,4 except that the detection aperture for the reaction e+e− → μ+μ− is larger by a factor of 2.6. All of the measurements reported in this letter were made with the detection apparatus set to accept particles produced at angles 6 close to 90° with respect to the colliding beams.