Test of CP invariance in e+ e- ---> Z0 ---> tau+ tau- and a limit on the weak dipole moment of the tau lepton

Using a sample of 5558 Z 0 → τ + τ − decays produced at LEP a direct test of CP -invariance in the neutral current reaction e + e − → τ + τ − is performed. Samples of events where eachy τ decays into a single particle have been isolated for the construction of CP -odd observables. Three different event classes are considered: lepton-lepton, lepton-hadron, and hadron-hadron. No evidence for a non-zero expectation value of the considered CP -observables and hence for CP -violation is observed. Quantitatively, we deduce from this null result an estimate on the weak dipole moment d ̃ τ (m 2 Z = (−4.5 ± 5.3 ± 1.4) × 10 −17 e cm for the lepton-lepton signature and d ̃ τ (m 2 Z = (1.4 ± 3.7 ± 1.3) × 10 −17 e cm for the hadron-hadron signature. Combining these results we place a limit with 95% confidence of | d ̃ τ |⩽7.0 × 10 −17 e cm.

electron positron: colliding beams
colliding beams: electron positron
electron positron: annihilation
annihilation: electron positron
Z0: electroproduction
electroproduction: Z0
Z0: leptonic decay
leptonic decay: Z0
Z0: width
tau: pair production

References(33)

Figures(0)

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