Hadronic τ Decays as New Physics Probes in the LHC Era

Area of Science:

• Particle Physics
• High Energy Physics
• Quantum Field Theory

Background:

• The Standard Model (SM) of particle physics successfully describes fundamental particles and forces, but it does not explain phenomena like dark matter or neutrino masses.
• Effective field theories (EFTs) provide a model-independent framework to search for physics beyond the SM (BSM) by parameterizing potential new interactions.
• Hadronic tau decays offer a rich playground for probing new physics due to their sensitivity to various interactions.

Purpose of the Study:

• To analyze the sensitivity of hadronic tau decays to nonstandard interactions within the SM EFT framework.
• To identify theoretically clean channels for disentangling all effective couplings contributing to tau decays.
• To set stringent bounds on new physics parameters using experimental data.

Main Methods:

• Utilizing a model-independent approach within the Standard Model Effective Field Theory (SMEFT).
• Analyzing both exclusive and inclusive hadronic tau decays.
• Incorporating the latest lattice QCD data and QCD dispersion relations for theoretical calculations.

Main Results:

• The tau→ππν_{τ} decay channel is identified as a particularly powerful probe for new physics.
• Sufficient theoretically clean channels exist to disentangle all relevant effective couplings.
• Ratios of nonstandard couplings to the Fermi constant are constrained at the subpercent level.

Conclusions:

• Hadronic tau decays, especially τ→ππν_{τ}, provide powerful, complementary probes of new physics beyond the Standard Model.
• Combined analysis of tau decay data and LHC measurements (pp→τν_{τ}) yields tighter constraints on lepton universality violation in gauge boson-lepton vertex corrections.