Precision determination of the electroweak mixing angle and test of neutral current universality from the tau polarization measurements at OPAL
Date
2018-08-16
Authors
Graham, Kevin
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Abstract
Measurements of the Ƭ lepton polarization and forward-backward polarization asymmetry
near the Z° resonance using the OPAL detector are described. The measurements are
based on analyses of [special characters omitted] decays
from a sample of 144, 810 [special characters omitted] candidates corresponding to an integrated
luminosity of 151 pb-1. Assuming that the Ƭ lepton decays according to V-A theory,
the average Ƭ polarization near [special characters omitted] is measured to be [special characters omitted] = (-14.10 ± 0.73 ± 0.55)% and the Ƭ polarization forward-backward asymmetry to be [special characters omitted] = (-10.55 ±
0.76 ± 0.25)%, where the first error is statistical and the second systematic. Taking into
account the small effects of the photon propagator, photon-Z° interference and photonic
radiative corrections, these results can be expressed in terms of the lepton neutral current
asymmetry parameters:
AƬ = 0.1466 ± 0.0076 ± 0.0057,
Ae = 0.1464 ± 0.0108 ± 0.0036.
These measurements are consistent with the hypothesis of lepton universality and combine
to give [special characters omitted] = 0.1455 ± 0.0073. Within the context of the standard model this
combined result corresponds to sin [special characters omitted] = 0.23172 ± 0.00092. Combining these results
with those from the other OPAL neutral current measurements yields a value of
sin [special characters omitted] = 0.23211 ± 0.00068.
Description
Keywords
Heavy particles (Nuclear physics), Kaons, Radioactive decay