B → D** -- puzzle 1/2 vs 3/2

الأصل · EN

Understanding the composition of final states in B → Xc l ν could help to get a feedback on the persisting disagreement between exclusive and inclusive determinations of Vcb. In particular the series of orbital excitations D** and radial excitations (D', D*') has received a lot of attention; a misinterpretation as a scalar state of the (D' → D π) spectrum tail could have induced an experimental overestimate of the broad states contribution to the total B → Xc l ν width with respect to theoretical expectations, all of them made however in the infinite mass limit: it is the so-called 1/2 vs 3/2 puzzle. We describe first attempts to measure on the lattice form factors of B → D** l ν at realistic quark masses. Cleaner processes, like hadronic decays B → D** π and semileptonic decays Bₛ → Dₛ** l ν in the strange sector have recently been examined by phenomenologists, putting new interesting ideas on those issues with, again, the need of lattice inputs.