Search for the Electric Dipole Moment of the τ Lepton

Abstract

We have searched for a T/CP violation signature arising from an electric dipole form factor (dτ ) of the τ lepton in the e + e − → τ + τ − reaction. Using an optimal observable method for 29.5 fb −1 of data collected with the Belle detector at the KEKB collider at √ s = 10.58 GeV, we obtained the preliminary result Re(dτ ) = (1.15 ± 1.70) × 10 −17 ecm and Im(dτ ) = (−0.83 ± 0.86) × 10 −17 ecm for the real and imaginary parts of dτ , respectively, and set the 95% confidence level limits −2.2 < Re(dτ ) < 4.5 (10 −17 ecm) and −2.5 < Im(dτ ) < 0.8 (10 −17 ecm).

First Results and Prospects for 흉 Lepton Physics at Belle II

“…The most precise measurement for , to date, was published by Belle with about 30 fb −1 of data [5]. An update, using 833 fb −1 , was recently submitted for publication [6]. This improves the result to −1.85 × 10 −17 < ( ) < 0.61 × 10 −17 and −1.03 × 10 −17 < ( ) < 0.23 × 10 −17 .…”

First Results and Prospects for Tau Lepton Physics at Belle II

“…To date, Belle published the most precise measurement with about 30 fb −1 of data for the [7]. An update using 833 fb −1 , which improves approximately by a factor of five to an upper limit of −1.85 × 10 −17 < ( ) < 0.61 × 10 −17 and −1.03 × 10 −17 < ( ) < 0.23 × 10 −17 , was recently submitted for publication [8].…”

The physics of heavy flavours at SuperB

“…One can measure the τ EDM using an angular asymmetry in e + e − → τ + τ − transitions. The current limit on the |τ | EDM is ≤ 5 × 10 −17 ecm and comes from the Belle Collaboration [53], using a data sample of 29.5 fb −1 . The anticipated reach for SuperB using 75 ab −1 of data is d τ ≤ 17 − 34 × 10 −20 ecm without a polarised electron beam.…”