Measurement of Z⁰ lepton coupling asymmetries

Thesis/Dissertation · Tue Jul 01 00:00:00 EDT 1997

DOI:https://doi.org/10.2172/531088· OSTI ID:531088

Smy, Michael Burghard ^[1]

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1. Stanford Univ., CA (United States)

Polarized Z⁰`s from e⁺e^- collisions at the SLAC Linear Collider (SLC) have been used to determine the asymmetry parameters A_e, A_μ and A_τ from the leptonic decay channels. This is the first direct measurement of A_μ. The data have been gathered by the SLC Large Detector (SLD) with the electron polarization averaging 63% during the 1993 data taking period and 77% in 1994-95. A maximum likelihood procedure as well as cross section asymmetries was used to measure the asymmetry parameters from the differential cross sections for equal luminosities of left- and right-handed electron beams. The polarization-dependent muon-pair distributions give A_μ = 0.102 ±0.034 and the tau-pairs give A_τ = 0.195 ±0.034. The initial state electronic couplings in all three leptonic channels as well as the final state angular distribution in the e⁺e^- final state measure A_e to be A_e = 0.152±0.012. Assuming lepton universality and defining a global leptonic asymmetry parameter A_e-μ-τ = 0.151±0.011. This global leptonic asymmetry value translates directly into sin²θ_W^eff=0.2310v0.0014 at the Z⁰ pole.

• Research Organization: SLAC National Accelerator Lab., Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 531088
• Report Number(s): SLAC-R-515; ON: DE97008279; TRN: 97:019317
• Resource Relation: Other Information: TH: Thesis (Ph.D.); PBD: Jul 1997
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Z NEUTRAL BOSONS
ASYMMETRY COEFFICIENTS
LEPTONIC DECAY
COUPLING CONSTANTS