Search for semileptonic decays of non-strange B mesons into a Ds or a Lc

Present situation

Semileptonic decay branching fractions of B mesons into D0 l nu X, D+ l nu X and D*+ l nu X final states have been measured. It exists only a limit from CLEO on:

BR(B --> Ds- l+ nul K+ X)< 6 * 10-3 at 90% CL

which is not very stringent because naively one may expect that such decays can be of the order of fs * BR(B --> D** l nu X) = 5 * 10**-3. Using theoretical arguments and taking into account the masses of the particles in the final state one expects a much lower rate; of the order of 10**-3.

Decays involving a Lc have been also considered by CLEO and they obtain: BR(B --> Lc- l+ nul p X)< 1.5 * 10-3 at 90% CL.

What remains to be done

Samples of exclusively reconstructed Ds mesons and Lc baryons accompanied by an identified lepton have been isolated. It remains to count how may of them are associated with, respectively, a charged kaon or a proton emitted from the B decay vertex and not from the beam interaction point. A feasibility study has to be done to evaluate if the sensitivity of these analyses can be better than the published CLEO results.

Tools and contact-persons

The analysis can be done using events selected in the Ds-lepton (Fabrizio Parodi) and Lc-lepton (Claire Bourdarios) channels. Tools developed to measure the D** production rate in B semileptonic decays can be used also (Daniel Bloch, P. Roudeau).

Contact persons: