Precise predictions for Λ$_{b}$ → Λ$_{c}$ semileptonic decays

We calculate the Lambda(b )-> Lambda(c)l nu form factors and decay rates for all possible b -> cl (nu) over bar four-Fermi interactions beyond the Standard Model, including nonzero charged lepton masses and terms up to order alpha(s)Lambda(QCD)/m(c,b) and Lambda QCD(2) m(c)(2) in the heavy quark effective theory. At this order, we obtain model independent predictions for semileptonic Lambda(b) -> Lambda(c) decays in terms of only two unknown sub-subleading Isgur-Wise functions, which can be determined from fitting LHCb and lattice QCD data. We thus obtain model independent results for Lambda(b )-> Lambda(c)l (nu) over bar decays, including predictions for the ratio R(Lambda(c)) = beta(Lambda(b )-> Lambda(c)tau(nu) over bar)/beta(Lambda(b) -> Lambda(c)mu(nu) over bar) in the presence of new physics, that are more precise than prior results in the literature, and systematically improvable with better data on the decays with mu(or e) in the final state. We also explore tests of factorization in Lambda(b )-> Lambda(c)pi decays, and we emphasize the importance of measuring at LHCb the double differential rate d(2)Gamma(Lambda(b) -> Lambda(c)l (nu) over bar)/(dq(2)d cos theta), in addition to the q(2) spectrum.