Michael Luke

Reparameterisation invariance constraints on heavy particle effective field theories

Abstract Since fields in the heavy quark effective theory are described by both a velocity and a residual momentum, there is redundancy in the theory: small shifts in velocity may be absorbed into a redefinition of the residual momentum. We demonstrate that this trivial reparameterisation invariance has non-trivial consequences: it relates coefficients of terms of different orders in the 1 m expansion and requires linear combinations of these operators to be multiplicatively renormalised. For example, the operator − 2 2m in the effective lagrangian has zero anomalous dimension, coefficient one, and does not receive any non-perturbative contributions from matching conditions. We also demonstrate that this invariance severely restricts the forms of operators which may appear in chiral lagrangians for heavy particles.

Strong decays of excited heavy mesons in chiral perturbation theory

Abstract We construct an effective lagrangian describing the interaction of soft pions and kaons with mesons containing a heavy quark and light degrees of freedom in an orbital p wave. The formalism is easily extended to heavy mesons and baryons in arbitrary excited states. We calculate the leading contributions to the strong decays D 2 ∗ →Dπ, D 2 ∗ →D ∗ π and D 1 →D ∗ π . We confirm the relations between the rates previously obtained by Isgur and Wise using heavy quark symmetry, and find that the absolute widths are consistent with naive power counting. We also estimate the branching ratios for the two pion decays D 2 ∗ →D ∗ ππ, D 1 →D ∗ ππ and D 1 →Dππ , which are dominated by pole graphs. Our predictions depend on the masses and widths of the as yet unseen scalarpseudovector p-wave doublet. Heavy quark spin symmetry predicts Γ(D 2 ∗ →D ∗ ππ):Γ(D 1 →D ∗ ππ):Γ(D 1 →Dππ)=3:1:2 , but this relation is badly violated in practice because 1/M effects arising purely from kinematics are large.

Radiative D* decay using heavy quark and chiral symmetry

Abstract The implications of chiral SU(3) L ×SU(3) R symmetry and heavy quark symmetry for the radiative decays D ∗0 →D 0 γ , D ∗+ →D + γ , and D s ∗ →D s γ are discussed. Particular attention is paid to SU(3) violating contributions of order m q 1 2 . Experimental data on these radiative decays provide constraints on the D ∗ Dπ coupling.

Chiral perturbation theory analysis of the baryon magnetic moments

Abstract Nonanalytic m q 1 2 and mq ln mq chiral corrections to the baryon magnetic moments are computed. The calculation includes contributions from both intermediate octet and decuplet baryon states. Unlike the one-loop contributions to the baryon axial currents and masses, the contribution from decuplet intermediate states does not partially cancel that from octet intermediate states. The fit to the observed magnetic moments including m q 1 2 corrections is found to be much worse than the tree level SU(3) fit if values for the baryon-pion axial coupling constants obtained from a tree level extraction are used. Using the axial coupling constant values extracted at one loop results in a better fit to the magnetic moments than the tree level SU(3) fit. There are three linear relations amongst the magnetic moments when m q 1 2 corrections are included, and one relation including m q 1 2 , mqln mq and mq corrections. These relations are independent of the axial coupling constant of the baryons and agree well with experiment.

A QCD calculation of the interaction of quarkonium with nuclei

Abstract The interaction of quarkonium with nuclei is studied in the m Q →∞ limit of QCD, where the binding energy is found to be exactly computable. The dominant contribution to the interaction is from two-gluon operators. The forward matrix elements of these two-gluon operators can be determined from the QCD scale anomaly, and from deep inelastic scattering. We apply our results to the υ and J ψ treating the Q Q interaction as purely coulombic. We find the υ binds in nuclear matter with a binding energy of a few MeV, while for the J ψ binding is of order 10 MeV. For the J ψ in particular we expect confinement effects to produce large corrections to this result.

Flavour Changing Neutral Currents, Weak-Scale Scalars and Rare Top Decays

Abstract We examine the decays t → cγ and cZ 0 in the Standard Model with an extra scalar doublet and no discrete symmetry preventing tree-level flavour changing neutral currents. The Yukawa couplings of the new scalars are assumed to be proportional to fermion masses, evading bounds on FCNCs from the light quark sector. These rare top decays may be visible at the SSC.

Semileptonic Bc decay and heavy quark spin symmetry

Semileptonic decay of the Bc meson is studied in the heavy quark limit. The six possible form factors for Bc → Bs(B0), Bs∗(B∗0) semileptonic decay are determined by two invariant functions. Only one of these functions contributes at zero recoil, where it is calculable to lowest order in an operator product expansion in terms of the meson decay constant ƒB and the Bc wave function. A similar result is found for Bc → D0, D∗0 and for Bc → ηc, J/ψ semileptonic decay for a restricted kinematic region. Semileptonic Bc decay provides a means for determining the KM mixing angle |ub|.

B decay shape variables and the precision determination of |V(cb)| and m(b)

We present expressions for shape variables of B decay distributions in several different mass schemes, to order

The residual mass term in the heavy quark effective theory

\alpha_s^2\beta_0

Properties of baryons containing a heavy quark in the Skyrme model

and (Lambda_{QCD}/mb)^3. Such observables are sensitive to the b quark mass and matrix elements in the heavy quark effective theory, and recent measurements allow precision determinations of some of these parameters. We perform a combined fit to recent experimental results from CLEO, BABAR, and DELPHI, and discuss the theoretical uncertainties due to nonperturbative and perturbative effects. We discuss the possible discrepancy between the OPE prediction, recent BABAR results and the measured branching fraction to D and D* states. We find |Vcb| = (40.8 +- 0.9) x 10^{-3} and mb^{1S} = 4.74 +- 0.10 GeV, where the errors are dominated by experimental uncertainties.