MAC Detector Research Articles

Direct photon production in e+e- annihilation.

Direct photon production in hadronic events from e+e− annihilation has been studied at s=29 GeV with use of the MAC detector at the PEP storage ring. A charge asymmetry A=(−12.3±3.5)% is observed in the final-state jets. The cross section and the charge asymmetry are in good agreement with the predictions of the fractionally charged quark-parton model. Both the charge asymmetry and total yield have been used to determine values of quark charges. Limits have been established for anomalous sources of direct photons.Received 24 September 1984DOI:https://doi.org/10.1103/PhysRevLett.54.95©1985 American Physical Society

Search for Singly Produced Supersymmetric Electrons ine+e−Interactions

A search for supersymmetric electron production via the reaction e+e−→e±γ̃ẽ∓ followed by the decay ẽ∓→e∓γ̃ has been performed with the MAC detector at the electron-positron storage ring PEP. No candidates were found in a sample corresponding to an integrated luminosity of 36.4 pb−1. For a massless γ̃ this corresponds to a lower limit on the ẽ mass of 22.4 GeV/c2 at the 95% confidence level.Received 11 October 1983DOI:https://doi.org/10.1103/PhysRevLett.52.22©1984 American Physical Society

Study of acollinear muon pair production ine+e−interactions atEc.m.=29GeV

We have studied the production of acollinear muon pairs in e+e− interactions using the MAC detector at PEP. The results are totally accounted for by the QED processes e+e−→e+e−μ+μ− and e+e−→μ+μ−γ in which only the muon pairs are detected. We have also searched for the production of the supersymmetric partners of the muon. The existence of a spin-0 supersymmetric partner of the muon with a mass <13.8 GeV/c2 is excluded at the 95% confidence level.Received 28 June 1983DOI:https://doi.org/10.1103/PhysRevD.28.2721©1983 American Physical Society

Experimental Test of Higher-Order QED and a Search for Excited Muon States

The reactions e+e−→μ+μ−γγ and e+e−→μ+μ−γ have been studied at s=29 GeV with the MAC detector at the SLAC storage ring PEP. The measured cross sections, charge asymmetry, and invariant-mass distributions are in good agreement with the predictions of QED theory. Limits are derived for the production of excited muon states.Received 6 December 1982DOI:https://doi.org/10.1103/PhysRevLett.51.257©1983 American Physical Society

Fragmentation of Heavy Quarks Produced ine+e−Annihilation

Identification of muons in hadronic events from e+e− annihilation observed in the MAC detector at the storage ring PEP provides flavor tagging of heavy primary quarks. A sample enriched in events from bb¯ production is obtained and the b-quark fragmentation function is inferred from the momentum spectrum of the muons. The b quark is found to fragment predominantly with high values of z, with 〈zb〉=0.8±0.1, and to have an over-all semimuonic branching fraction of (15.5−2.9+5.4)%.Received 19 April 1983DOI:https://doi.org/10.1103/PhysRevLett.50.2054©1983 American Physical Society

Electroweak Effects ine+e−→μ+μ−at 29 GeV

A measurement of the cross section for production of collinear muon pairs based upon a sample of about 3000 events observed in the MAC detector at the storage ring PEP is presented. From the angular asymmetry A/sub mumu/ = -0.076 +- 0.018 the axial vector weak neutral coupling is found to be given by g/sub A//sup e/g/sub A//sup ..mu../ = 0.31 +- 0.08. .AE

Lifetime of the Tau Lepton

From three-prong decays of τ leptons produced in the MAC detector at PEP, the life-time of the τ is determined to be (4.9±2.0)×10−13 sec.Received 17 May 1982DOI:https://doi.org/10.1103/PhysRevLett.49.106©1982 American Physical Society

Tests of Proportional Wire Shower Counter and Hadron Calorimeter Modules

We present results from test beam measurements at SLAC with prototype modules for the MAC detector at PEP. The modules consist of planes of proportional wires interleaved with lead sheets (shower counter) or iron plates (hadron calorimeter).