The Decay $B\to K^{\ast }\gamma$ from QCD Sum Rules

Abstract

Using the QCD sum rules approach and the complete leading--logarithmic short--distance coefficients determining the penguin--amplitude, we obtain $B(B\to K^{\ast }\gamma )=(6.8\pm 2.4)\cdot 10^{-5}$ for top--quark masses in the range (150--200) GeV and $|V_{cb}|=0.035$ for ${\tau }_B=1.5\text{ps}$. The ratio to the inclusive rate is $B(B\to K^{\ast }\gamma )/B(B\to X_s\gamma )=(20\pm 6)\%$.

8 ps, 2 uuencoded PS figures included, requires epsf.sty and revtex3, TUM-T31-43/93