A study of w boson decay charge asymmetry using hadronic tau decays in proton - anti-proton collisions at √s = 1.8 TeV

Abstract

This dissertation presents a measurement of the tau charge asymmetry in events where the taus are produced by W decays. This charge asymmetry appears as different rapidity distributions for positive and negative taus. Two competing effects generate tau charge asymmetry. The production mechanism for the W gauge boson generates a charge asymmetry which is a function of the ratio of parton distribution functions, d(x)=u(x), measured at x ~ MW/√s. This is the dominant effect for tau charge asymmetry at small rapidity. At higher rapidity, however, the competing charge asymmetry from parity violation in W decay to taus becomes dominant. This tau asymmetry measurement is consistent with the Standard Model with a x2 per degree of freedom equal to 2.5 for 4 degrees of freedom when the asymmetry measurement is folded about y = 0, taking advantage of the CP symmetry of the underlying physics, and 8.9 for 8 degrees of freedom when it is not. This measurement introduces some methods and variables of interest to future analyses using hadronic decay modes of taus. This work was done using the CDF detector in $\bar{p}$p collisions at √s = 1.8 TeV at Fermilab's Tevatron accelerator.

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