Study of final state photons in hadronic Z ~ and limits on new phenomena
semanticscholar(2017)
摘要
The differential cross section for final state radiation from primary quarks is obtained from a study of isolated energetic photons produced in the reaction e + e ~ Z ~ ~ h a d r o n s + 7 , as measured in the D E L P H I detector at the CERN LEP collider. When combined with the measurement of the total hadronic width of the Z ~ the observed rate determines the electroweak coupling constants of up and down type quarks, i.e., vZ/3+a~/3=l.13+_0.29 and vZ/3+a2/3=l.65+_0.43. No evidence is seen for additional photon production from anomalous decays of the Z ~ or from decays of new particles. This measurement leads to upper limits on the production cross section times branching fraction of (a) the Higgs boson in the reaction e + e ~ Z ~ + 7, H ~ hadrons, (b) an excited quark, q * ~ q + 7, and (c) the contribution of an anomalous decay of the Z ~ into a photon and hadrons. These limits, all at the 95% confidence level, vary from 3 to 10pb as the mass of the intermediate state (H,q* or Z*) varies from 10 GeV/c 2 to 80 GeV/c 2.
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