Probing the helicity structure of $b\to s\gamma$ in ${\Lambda }_b\to \Lambda \gamma$

Abstract

We investigate the rare decay ${\Lambda }_b\to \Lambda \gamma$ which receives both short and long distance contributions. We estimate the long distance contributions and find them very small. The form factors are obtained from ${\Lambda }_c\to \Lambda \ell {\bar{\nu }}_{\ell }$ using heavy quark symmetry and a pole model. The short distance piece opens a window to new physics and we discuss the sensitivity of ${\Lambda }_b\to \Lambda \gamma$ to such effects.

Comments: Latex, 6 pages, 1 postscript figure included, uses epsf. Presented at XXIst School of Theoretical Physics, Ustron (Poland), September '97. The complete paper, including figures, is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/, or via www at http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/