In common with a number of simple processes involving elementaryparticles, charged pion decays are profoundly shaped by applicableStandard Model (SM) symmetries and properties. Given the highly preciseSM theoretical description, pion decays are used as selective probes ofSM parameters, and of possible SM extensions. The PEN experiment at PSIis studying the \pi^+ \to e^+\nu_e(\gamma) π + → e + ν e ( γ ) ,or \pi_{e2(\gamma)} π e 2 ( γ ) decay. The primary goal is to reach the relative precision of 5 \times 10^{-4} 5 × 10 − 4 in R_{e/\mu}^\pi R e / μ π ,the branching ratio for \pi_{e2(\gamma)} π e 2 ( γ ) decay. We review the PEN research program, its present status, andprospects.
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Frequency and Time Domain Nuclear–Electronic Orbital Equation-of-Motion Coupled Cluster Methods: Combination Bands and Electronic–Protonic Double Excitations
- Award ID(s):
- 1954348
- PAR ID:
- 10195519
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry Letters
- Volume:
- 11
- Issue:
- 15
- ISSN:
- 1948-7185
- Page Range / eLocation ID:
- 6435 to 6442
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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