P. Abreu et al., FIRST STUDY OF THE INTERFERENCE BETWEEN INITIAL AND FINAL-STATE RADIATION AT THE Z-RESONANCE, Zeitschrift fur Physik. C, Particles and fields, 72(1), 1996, pp. 31-38
The interference between initial and final state radiation in the proc
ess e(+)e(-) --> mu(+)mu(-) at root s approximate to M(Z) has been stu
died by measuring the forward-backward asymmetry as a function of the
acoplanarity angle between the final state muons. The interference is
expected to be sensitive to the space-time separation of the initial a
nd final state radiation. The measured asymmetry distribution has been
compared to theoretical predictions using the KORALZ generator, with
and without O(alpha) interference, The magnitude of the interference b
etween initial and final state radiation was found to be of the order
predicted and to follow the expected distribution. Using the theoretic
al predictions, a value of Gamma(Z) = 2.50 +/- 0.21 (stat.) +/- 0.06 (
syst.) GeV. has been extracted, The interpretation of this result is d
iscussed. There is an additional uncertainty in the estimate of Gamma(
Z) from as yet uncalculated higher order interference terms. By assumi
ng a value of Gamma(Z) consistent with the world average, the data wer
e used to estimate the size of these uncalculated corrections.