Right-handed currents inBdecay reexamined

Abstract

We critically re-examine the case for and against a sizeable right-handed component in the $\stackrel{\ensuremath{\rightarrow}}{b}c$ charged current coupling with a strength \ensuremath{\xi} relative to the conventional left-handed current. Using data from CLEO on the decay $\stackrel{\ensuremath{\rightarrow}}{B}{D}^{*}\mathcal{l}\ensuremath{\nu},$ as well as our knowledge of ${V}_{\mathrm{cb}}$ extracted from both inclusive and exclusive processes, we are able to determine the presently allowed parameter space for \ensuremath{\xi} via HQET. We then identify several observables which could be measured at $B$ factories to either strengthen these constraints or otherwise observe right-handed currents. This parameter space region is found to be consistent with the low degree of ${\ensuremath{\Lambda}}_{b}$ polarization as determined by ALEPH as well as the measurements of the charged lepton and neutrino energy spectra from $b$ decay made by L3. We discuss how future measurements of semileptonic decay distributions may distinguish between exotic ${\ensuremath{\Lambda}}_{b}$ depolarization mechanisms and the existence of right-handed currents. Within the parameter space allowed by CLEO, using the left-right symmetric model as a guide, we perform a detailed search for specific sub-regions which can lead to a reduction in both the $B$ semileptonic branching fraction as well as the the average yield of charmed quarks in $B$ decay. The results provide a concrete realization of an earlier suggestion by Voloshin, but may lead to potential difficulties with certain penguin mediated decay processes.