A recent recap paper provides the state of the art properties of the tau lepton. The tau lepton mass, previously noted in this blog post, is consistent with Koide's rule to the extent of current experimental precision.
BelleII provides the most precise measurement of the τ lepton mass: 1777.09 ± 0.08 ± 0.11 MeV/c2, where the first uncertainty is statistical, and the second one is systematic. . . .
The τ lepton lifetime . . . [has a] Current world’s best result of [290.17 ± 0.53 ± 0.33] × 10^−15 s, where the first uncertainty is statistical, and the second one is systematic.
. . .
[The predicted electric dipole moment of the tau lepton is indistinguishable from zero in the Standard Model. The anomalous magnetic dipole moment of the tau lepton in the Standard Model is] 117721(5) × 10^−8. . . . [The tau EDM is experimentally limited to be] |ℜ,ℑ(dτ)| < (0.1–1) × 10^−18 ecm. [The bounds on the anomalous magnetic dipole moment will be measured at Belle II in the near future.]
. . .
[Lepton flavor universality between electrons and muons have been tested in tau decays are are consistent within two sigma of the predicted universality.] we provide a result of Rµ = 0.9675 ± 0.0007 ± 0.0036, where the first uncertainty is statistical, and the second one is systematic, leading to |gµ/ge| = 0.9974±0.0019. This is the most precise test in a single measurement. Here, the systematic uncertainty is larger than the statistical one, with the leading contribution coming from particle identification (0.32%) and trigger efficiency (0.10%).
. . .
No CPV is observed in the charged leptons sector (in the SM, it is predicted only in the quarks sector). . . . [the BaBar observed a] value is 2.8σ away from the SM prediction. [Belle II will be measuring this in the near future.]
[Heavy neutral leptons, i.e. fourth generation neutrinos are highly constrained by tau decays at Belle II (ignoring constraints from other sources) as shown in the figure below]
No comments:
Post a Comment