arXiv subjects

M. Sutherland

Publications and source records attributed to M. Sutherland.

25 records · Page 2Linked to original sources

arXiv1994

Linear and higher order power corrections in semileptonic B decays

In previous work we have developed a relativistic quark model of mesons which is consistent with all QCD constraints at zeroth and first order in the heavy quark expansion. Here we obtain first order model predictions for the differential decay spectrum, the forward-backward asymmetry $A_{FB}$ and the $D^{\ast}$ polarization parameter $α$ in the decay $B\to D^{\ast}\ellν$. We compare these with the predictions of QCD sum rules at first order. The model suggests why the corrections allowed at first order are small, concurrently with substantial corrections at second order.

hep-ph↗

arXiv1994

What can a relativistic quark model tell us about charmed mesons?

A relativistic quark model is extended to incorporate chiral and gauge symmetries. We obtain the DD*pi and DD*gamma couplings and find that the ratio Gamma(D*0->D0pi0)/Gamma(D*0->D0gamma) constrains the charm-quark mass close to 1.45 GeV. Large 1/mc corrections appear in the heavy-quark contribution to the DD*gamma coupling. The model is extended further to describe seven excited D meson states. We find that semileptonic B decays into the ground and excited D meson states do not account for the total semileptonic decay width of the B0. The nonresonant contributions to the processes B0->D(*)pi+ell+nu appear to be large enough to account for the discrepancy.

hep-ph↗

arXiv1994

Anomalous Thresholds and the Isgur-Wise Function

The original de Rafael-Taron bound on the slope of the Isgur-Wise function at zero recoil is known to be violated in QCD by singularities appearing in an unphysical region. To be consistent, quark models must have corresponding singularity structures. In an existing relativistic quark-loop model, the meson-quark-antiquark vertex is such that the required singularity is an anomalous threshold. We also discuss the implications of another anomalous threshold, whose location is determined by quark masses alone.

hep-ph↗

arXiv1993

1/m_c Expansion of Omega_b -> Omega_c^(*) Semileptonic Decay Form Factors

A simple model of Omega_Q and Omega_Q^(*) baryons containing one heavy quark Q is constructed. Amplitudes are represented by loop graphs with one line for the heavy quark and another for the light degrees of freedom. The latter are modelled as a freely-propagating vector particle interacting nonlocally with the heavy baryon and a free heavy quark. It is argued that the physics of confinement plays an inessential role in determining semileptonic decay form factors. The model has a well-defined heavy-quark expansion which has a form consistent (through order 1/m_Q) with that determined by QCD through the heavy-quark effective theory. The slope of the Isgur-Wise function is consistent with the Bjorken sum rule bound. The effect of the Omega_Q^* - Omega_Q mass splitting on the first-order form factors is examined.

hep-ph↗

arXiv1993

Comparison of 1/mQ^2 Corrections in Mesons and Baryons

We extend our relativistic quark model to the study of the decay Lambda_b -> Lambda_c ell nu and verify that the model satisfies the heavy-quark symmetry constraints at order 1/mQ^2. We isolate a strong dependence on a parameter which measures the relative distortion in the light-quark wave functions of the Lambda_b and Lambda_c. This parameter and the 1/mQ^2 corrections turn out to be small. The dependence on a corresponding parameter in the meson case leads to large 1/mQ^2 corrections.

hep-ph↗

arXiv1993

Simply Modeling B -> K* gamma

A simple relativistic model of heavy-light mesons is applied to the rare decay B -> K* gamma in the standard model. We find Gamma(B -> K* gamma)/Gamma(b -> s gamma)=(17 \pm 4)% and BR(B -> K* gamma)=(4.8 \pm 1.9) \times 10^{-5}(V_cb/.04)^2. These numbers are reduced by only 20% in the heavy-quark limit.

hep-ph↗

arXiv1993

Hyperfine Effects and Large $1/{m}_{Q}^{2}$ Corrections

Effects associated with hyperfine mass splitting between pseudo\-scalar and vector mesons may induce surprisingly large $1/{m}_{Q}^{2}$ corrections in the heavy quark expansion. We demonstrate this in a relativistic quark model by calculating to all orders in $1/{m}_{Q}$, with and without hyperfine effects, and comparing to the first order results. Total corrections of 30\% or more are quite possible in the decay rates for $B\rightarrow Dlν$ and $B\rightarrow D^{\ast}lν$ near zero recoil.

hep-ph↗