EPJ

2023 Impact factor 4.2
EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 5, 525-533
DOI 10.1007/s100529800860

Impacts on searching for signatures of new physics from $K^+ \rightarrow\pi^+ \nu \overline{\nu}$ decay

Gi-Chol Cho

Theory Group, KEK, Tsukuba, Ibaraki 305, Japan

Received: 27 October 1997 / Revised version: 21 January 1998 / Published online: 10 March 1998

Abstract
We study impacts on new physics search from the rare decay $K^+ \rightarrow\pi^+ \nu \overline{\nu}$.In a certain class of new physics models, the extra contributions to FCNC processes can be parametrized by its ratio to the standard model (SM) contribution with the common CKM factors. The ratio R1 has been used in the analysis of xd and $\epsilon_K^{}$ parameters. In the above class of models, the $K^+ \rightarrow\pi^+ \nu \overline{\nu}$ decay amplitude can be parametrized by the ratio R2. Then the experimentally allowed region for new physics contributions can be given in terms of R1,R2 and the CP violating phase $\delta$ of the CKM matrix. Constraints on R1 and $\cos\delta$ are obtained by taking account of current experimental data and theoretical uncertainties on $B^0\mbox{-}\overline{B^0}$ and $K^0\mbox{-}\overline{K^0}$ mixings. We study impacts of future improved measurements by using $(R_1, R_2, \cos\delta)$ basis. We discuss contributions in the minimal supersymmetric SM and the two Higgs doublet model as examples.

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