Analysis of the Lambdab -> Lambdac + l nul decay within a light-front constituent quark model
Abstract
We present an investigation of the Isgur-Wise form factor relevant for the semileptonic decay Lambdab -> c + l nul performed within a light-front constituent quark model. Adopting different baryon wave functions it is found that the Isgur-Wise form factor depends sensitively on the baryon structure. It is shown however that the shape of the Isgur-Wise function in the full recoil range relevant for the Lambdab -> c + l nul decay can be effectively constrained using recent lattice QCD results at low recoil. Then, the Lambdab -> c + l nul decay is investigated including both radiative effects and first-order power corrections in the inverse heavy-quark mass. Our final predictions for the exclusive semileptonic branching ratio, the longitudinal and transverse asymmetries, and the longitudinal to transverse decay ratio are: Br(Lambdab -> c + l nul) = (6.3 +/- 1.6) % |Vbc / 0.040|**2 ~ tau(Lambdab) / (1.24 ps), aL = -0.945 +/- 0.014, aT = -0.62 +/- 0.09 and RL/T = 1.57 +/- 0.15, respectively. Moreover, both the longitudinal asymmetry and the (partially integrated) longitudinal to transverse decay ratio are found to be only marginally affected by the model dependence of the Isgur-Wise form factor as well as by first-order power corrections; therefore, their experimental determination might be a very interesting tool for testing the SM and for investigating possible New Physics.
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