Flavor changing neutral current processes in B and K decays in the supergravity model

Flavor changing neutral current processes such as b --> s gamma, b --> sl(+)l(-), b --> s nu<(nu)over bar>, epsilon(K), Delta m(B), K+ -->pi(+)nu<(nu)over bar>, and K-L --> pi(0)nu<(nu)over bar> are calculated in the supersymmetric standard model based on supergravity. We consider two assumptions for the soft supersymmetry breaking terms. In the minimal case soft breaking terms for all scalar fields are taken to be universal at the GUT scale, whereas those terms are different for the squark-slepton sector and the Higgs sector in the nonminimal case. In the calculation we have taken into account the next-to-leading order QCD correction to the b --> s gamma branching ratio, the results from the CERN LEP II superparticles search, and the condition of the radiative electroweak symmetry breaking. We shaw that Delta m(B) and epsilon(K) can be enhanced up to 40% compared to the standard model values in the nonminimal case. In the same parameter region the b --> s nu<(nu)over bar>, K+ --> pi(+) nu<(nu)over bar>, and K-L --> pi(0)nu<(nu)over bar> branching ratios are reduced up to 10%. The corresponding deviation in the minimal case is 20% for Delta m(B) and epsilon(K) and within 3% for b --> s nu<(nu)over bar>, K+ --> pi(+) nu<(nu)over bar>, and K-L --> pi(0) nu<(nu)over bar>. For the b --> sl(+)l(-) process a significant deviation from the standard model is realized only when the b --> s gamma amplitude has an opposite sign to the standard model prediction. The significance of these results from possible future improvements of the b --> s gamma branching ratio measurement and top squark search is discussed. [S0556-2821(98)04217-9]