Thomas Mannel

Forward-backward asymmetry of dilepton angular distribution in the decay b→ sℓ+ ℓ−

Abstract The angular distribution of l + l - in the decay of b → s l + l − is studied. We point out that a large forward-backward asymmetry in the angular distribution of the dileptons is expected from the short-distance contribution inn the standard model for a heavy top quark mass. The asymmetry is a measure of the contribution of the Z and W + W - exchange diagrams, as well as the top quark mass.

A Derivation of the heavy quark effective Lagrangian from QCD

We show how to derive the heavy quark effective theory from QCD by carrying out the usual steps for the construction of an effective theory. Using functional methods we first integrate out heavy degrees of freedom and then give the expansion of the resulting nonlocal action functional in powers of 1/mQ, mQ being the mass of the heavy quark.

Radiative rare B decays into higher K-resonances

Abstract We estimate the contributions of higher K-resonances to the radiative rare decays b→sγ. We use the spin symmetry for heavy quarks to reduce the number of independent form factors to four Isgur-Wise functions, which are estimated from the wave function model of Isgur, Scora, Grinstein, and Wise. Our results suggest a substantially larger branching fraction for the decay B→K 2 ∗ (1430)γ than previous investigations.

Semileptonic decays of bottom baryons at LEP

Abstract We study semileptonic Λb decays where the Λb originates from Z0 decays into b quarks. The differential decay distributions are calculated using the heavy quark effective theory. We investigate the energy distribution of the decay leptons. In Λb decays the lepton energy distribution is sensitive to the standard model parameters via the nontrivial Λb polarization. We also discuss a possibility to study b quark fragmentation into baryons using the semileptonic decays.

UNIBAB, version 2.0: Monte Carlo event generation for large angle Bhabha scattering at LEP

Abstract This paper describes version 2.0 of the Monte Carlo event generator UNIBAB for Bhabha scattering at LEP/SLC. UNIBAB includes higher order electromagnetic radiative corrections and the effects of soft photon exponentiation explicitly. Weak corrections are included through the use of an electroweak library.

Polarization effects in heavy Λ decays

Abstract Within the framework of the heavy quark effective theory, we study the process Λ c + →Λl + ν, with emphasis on the polarization structure in the decay. Assuming factorization of the amplitude, we perform a similar analysis for the decay Λ c + →Λπ + . The asymmetry parameter, α, is predicted to be −1 for this decay. We point out that in a certain limit, the results we obtain are also valid for the corresponding Λ b →Λ c decays.

Testing the heavy quark effective theory in B0 → D∗+ e−ν☆

Abstract We use the techniques of the heavy quark effective theory, together with recent CLEO analyses, to predict the spectra of the D∗ and D mesons in the semileptonic decays B 0 → D ∗+ e − ν and B 0 D + e − ν

Effective hamiltonian for nonleptonic B̄ or Λb decays to final states with two charmed hadrons

Abstract In nonleptonic B or Λb decays to final states containing two charmed hadrons (e.g. B → DDs, Λb → ΛcDs, etc.), the momentum transfers associated with the light degrees of freedom are small compared with the heavy bottom and charm quark masses. The effective hamiltonian for these decays is derived by scaling four-quark operators in the weak hamiltonian below the bottom and charm quark masses using the heavy quark effective theory (where the masses of the heavy quarks are taken to infinity with their four-velocities fixed). The consequences of heavy quark spin symmetry for the decays Λb → ΛcDs and Λ b → Λ c D s ∗ are discussed.

Spin symmetry in nonleptonic B decays

Abstract We apply the spin symmetry of the heavy quark effective theory to obtain relations for exclusive nonleptonic B decays with two charmed measons in the final state.

Factorization hypothesis and the non-leptonic decays of heavy hadrons

Abstract We apply the formalism of the heavy quark effective theory, in conjunction with the factorization assumption, to the non-leptonic decays of B mesons. While we are more confident that the factorization assumption is valid when one of the decay products is light, we nevertheless apply it to decays containing two heavy mesons in the final state.