Rare Decays as Window to New Physics

2004/08/16 by L.M. Sehgal, L. M. Sehgal, Sehgal, L. M.
Physics and Astronomy · #Atomic and Subatomic Physics Research #Cold Atom Physics and Bose-Einstein Condensates #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #hep-ph

paper · pdf · doi:10.48550/arxiv.hep-ph/0408175

8 pages, Invited talk on DAFNE04 conference

arxiv created 2004/08/16 · openalex publication_date 2004/08/16 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

Rare decays of K mesons are reviewed from the perspective of testing the ``ones'' and ``zeros'' of the standard model. Decays K⁺ -> pi⁺ nu anti-nu and K_L -> pi⁰ nu anti-nu probe the one-loop effective Hamiltonian for s -> d nu anti-nu, and can constrain the rho, eta coordinates of the unitarity triangle. Decays such as K_L -> pi⁰ l⁺ l^-, K_L -> mu⁺ mu^-, K⁺ -> pi⁺ l⁺ l^- and K_L -> pi⁺ pi^- e⁺ e^- involve short-distance effects, as well as long-distance photon-induced contributions. Some comments are added on curious features of electroweak amplitudes in the ``gaugeless'' limit, and in the chiral electron limit m_e -> 0.

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