J. G. Körner

Exclusive semi-leptonic decays of bottom mesons in the spectator quark model

AbstractWe calculate the exclusive semileptonic bottom meson decays

Helicity fractions of W bosons from top quark decays at NNLO in QCD

B \to D(D*) + l^ - + \bar v_l

B_c

in the spectator quark model. The helicity structure of the mesonic current transitionsB→D(D*) is matched to the helicity structure of the free quark current transitionsb→c at minimum momentum transferq2=0. The results are continued toq2≠=0 by pole-dominated form factors. Our results are compared to recent calculations that use quark model dynamics at maximum momentum transferqmax2 = (M1 −M2)2. We find agreement atqmax2. Atq2=0 there are significant differences between the predictions of the two approaches leading to marked differences in the predictions for the shape of the lepton energy spectrum, the shape of theq2-distribution, and the helicity composition of the transition measurable in the angular distributions of the decaysD*→Dπ and

The heavy mass limit in field theory and the heavy quark effective theory

W_{virtual}^ - \to l^ - + \bar v_l

NNLO

.

O(\alpha_s^{4})

We discuss the exclusive semi-leptonic (s.l.) bottom meson decaysB→D(D*)+l+v where we include non-zero lepton mass effects in the kinematics and dynamics. We develop the general formalism for the non-zero lepton mass case. We then look at how rates, spectra and angular correlations are affected by non-zero lepton masses in the context of a specific spectator quark model. Numerical results are presented for s.l. decays involving thee-, μ- and τ-leptons. We also discuss the s.l. decaysB→π(ρ),D→K(K*) and the free quark decay model.