Improved limits on the lepton-flavor violating decays tau{-}-->l{-}l{+}l{-}

Area of Science:

• Particle Physics
• Lepton Flavor Violation

Background:

• The Standard Model of particle physics allows lepton flavor conservation.
• Extensions to the Standard Model may permit lepton flavor violating (LFV) processes.
• Searches for LFV decays provide stringent tests of new physics.

Purpose of the Study:

• To search for neutrinoless, lepton-flavor violating tau lepton decays.
• To probe new physics beyond the Standard Model by constraining LFV processes.

Main Methods:

• Analysis of 376 fb^{-1} of e^{+}e^{-} collision data collected by the BABAR detector.
• Targeted search for tau lepton decays into three charged leptons across six specific decay modes.
• Comparison of observed event yields with expected background estimations.

Main Results:

• Observed event yields in all six decay modes were consistent with background predictions.
• No significant excess of events attributable to LFV tau decays was detected.
• Upper limits on branching fractions for these LFV tau decays were established.

Conclusions:

• The results place constraints on the parameters of theories beyond the Standard Model.
• The absence of observed LFV tau decays disfavors certain new physics scenarios.
• This search contributes to the ongoing effort to understand lepton flavor physics.