Polarization in Λ→ pμ^-ν̅_μ as a probe of CP-violating new physics

@misc{salam2026polarization,
  title = {{Polarization in $Λ\to pμ^-\barν_μ$ as a probe of CP-violating new physics}},
  author = {Qazi Maaz Us Salam and Ishtiaq Ahmed},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.03375},
  eprint = {2611.03375},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.03375},
}

TY  - UNPB
TI  - Polarization in Λ→ pμ^-ν̅_μ as a probe of CP-violating new physics
AU  - Qazi Maaz Us Salam
AU  - Ishtiaq Ahmed
PY  - 2026
DA  - 2026/11/02
PB  - arXiv
DO  - 10.48550/arxiv.2611.03375
UR  - https://arxiv.org/abs/2611.03375
AB  - We investigate the normal μ polarization in the hyperon decay Λ→ pμ^-ν̅_μ as a probe of new physics that violates CP, since this polarization vanishes at tree level in the Standard Model. Using an effective Lagrangian and lattice QCD form factors, we compute its sensitivity to the imaginary parts of the couplings. With the present bounds from kaon decays and the Large Hadron Collider, one coupling at a time, this sensitivity gives an effect below the Standard Model contribution from the electromagnetic final-state interaction. Only a pseudoscalar coupling with a particular phase can exceed this contribution, by several times. The final-state interaction gives the same polarization in Λ and Λ̅ decays, so the difference between the two decays isolates the new physics effect.
ER  -