Penguin-box expansion: Flavour-changing neutral-current processes and a heavy top quark

  • Buchalla G
  • Buras A
  • Harlander M
  • 4

    Readers

    Mendeley users who have this article in their library.
  • 83

    Citations

    Citations of this article.

Abstract

We propose a Penguin-Box Expansion (PBE) for flavour-changing neutral-current (FCNC) processes. The basic elements of this expansion are universal mt-dependent functions resulting from various box and penguin diagrams common to many FCNC processes. The mt-independent coefficients of these functions can be calculated by using renormalization group techniques. Of particular interest is a manifestly gauge independent formulation of PBE. We illustrate these ideas by discussing the semi-leptonic decays K → πνν, KL→ μμ, KL→ π0e+e-and the ratio ε{lunate}′ ε{lunate}. We find simple analytic formulae for all these decays which exhibit the dependence on mtand other parameters of the standard model. We point out that due to the decrease of sin δ with increasing mt, the branching ratios for CP-violating semi-leptonic decays exhibit, in contrast to CP-conserving decays, a much weaker dependence on mtthan expected on the basis of the box and penguin diagram functions alone. New insight suppression of ε{lunate}′ ε{lunate} for large mtis obtained. Analyzing the relevant hadronic matrix elements beyond the 1 N approach, we find that for 100 GeV {slanted equal to or less-than}mt{slanted equal to or less-than} 300 GeV, the values -25 × 10-3{slanted equal to or less-than} ε{lunate}′ ε{lunate} {slanted equal to or less-than}3.2 × 10-3are possible. The structure of PBE beyond the leading logarithmic approximation is presented. © 1991.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Authors

  • Gerhard Buchalla

  • Andrzej J. Buras

  • Michaela K. Harlander

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free