A measurement of the inclusive [tau] topological and exclusive [tau] [yields] [mu][nu] [bar [nu]] branching ratios with OPAL at LEP

Thesis/Dissertation · Tue Dec 31 23:00:00 EST 1991

OSTI ID:7197471

O'Neill, B P

This dissertation describes an analysis of the inclusive [tau] topological and exclusive [tau] [yields] [mu][nu][bar [nu]] decay branching fractions completed on a copious sample of [tau] leptons. The data were produced by the Large Electron Positron (LEP) accelerator running at the Z[sup 0] peak and were recorded by the OPAL detector. The final [tau] decay sample consisted of 3304 [tau] pair events limited to the barrel region of the detector with a Monte Carlo determined background of only 1.9% attributed mainly to e[sup +]e[sup [minus]] [yields] [mu][sup +][mu][sup [minus]] and e[sup +]e[sup [minus]] [yields] q[bar q] events. A total of 899 [tau] [yields] [mu][nu][bar [nu]] decays were identified with an estimated purity of 94%. Correcting for background, identification efficiency, and events pre-selection bias, a value of B[sub [mu]](%) = 16.6 [+-] 0.5 [+-] 0.4 was obtained. The [tau] topological branching ratios measured with applied corrections for photon converting tracks are given by B[sub 1](%) = 85.4 [+-] 0.4 [+-] 0.4, B[sub 3](%) = 14.2 [+-] 0.4 [+-] 0.5, and B[sub 5](%) = 0.11 [+-] 0.05 [+-] 0.11. The current discrepancy related to the fundamental assumption of lepton universality with regard to the [tau] sector is examined. A second discrepancy involving the difference between the inclusive and sum of exclusive one-prong [tau] decay branching fractions is also addressed. Using pre-1990 results, the difference between B[sup inc][sub 1] and [Sigma]B[sup exc][sub 1] stands at 5.8% [+-] 1.4% with the inclusion of theoretical constraints for poorly measured [tau] decay modes. The new measurements of B[sub [mu]] and B[sub 1] resulted in [Delta]B[sub 1](%) = 6.4 [+-] 1.6.

• Research Organization: California Univ., Riverside, CA (United States)
• OSTI ID: 7197471
• Country of Publication: United States
• Language: English

Related Subjects

662370* -- Decays of Leptons-- (1992-)
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BASIC INTERACTIONS
BRANCHING RATIO
DECAY
ELEMENTARY PARTICLES
EXCLUSIVE INTERACTIONS
FERMIONS
HEAVY LEPTONS
INCLUSIVE INTERACTIONS
INTERACTIONS
LEPTONIC DECAY
LEPTONS
MUONS
PARTICLE DECAY
PARTICLE INTERACTIONS
POSTULATED PARTICLES
TAU PARTICLES
WEAK INTERACTIONS
WEAK PARTICLE DECAY