Particle and Astroparticle Seminar

PIONEER: a next generation pion decay experiment

Chloé Malbrunot

TRIUMF and McGill

Measurement of the charged-pion branching ratio to electrons vs. muons R_e/μ is extremely sensitive to a wide variety of new physics effects. The precision of the SM prediction for R_e/μ is ~1 part in 10⁴, 15 times more precise than the current experimental result. A next-generation experiment, PIONEER, is aiming at reducing the precision gap between theory and experiment, testing lepton flavor universality at an unprece- dented level, and probing new physics mass scales up to the PeV range. Additionally, PIONEER is aiming at a 3 to 10-fold improvement in the pion beta decay, π⁺ → π⁰e+ν(γ) measurement which determines |V_ud| in a theoretically pristine manner. This measurement would shed new lights on tensions in CKM unitarity.

PIONEER will use a combination of new detector technologies based an LGAD silicon tracking target, a deep calorimeter with high solid angle coverage, and high-speed electronics to optimize its energy and time resolution with respect to previous experiments.

I will present PIONEER's detector concept and goals in the light of previous experiments' results.