148 research outputs found
Polarization and `Model Independent' Extraction of from and
We briefly discuss the predictions of the heavy quark effective theory for
the semileptonic decays of a heavy pseudoscalar to a light one, or to a light
vector meson. We point out that measurement of combinations of differential
helicity decay rates at Cleo-c and the factories can provide a model
independent means of extracting the ratio
. We briefly discuss the corrections to this prediction.Comment: 8 pages, LaTeX, 1 figur
Final-state interaction and s-quark helicity conservation in B -> J/psi K*
The Section of charm quark spin conservation is deleted since it involves
more dynamical assumptions than previously stated. A few comments are added in
view of new experimental results.Comment: To replace the earlier version of hep-ph/0106354. Minor additions and
one deletion with no change in the main argument nor the conclusio
Heavy-Duty Diesel Vehicle Fuel Consumption Modeling Based on Road Load and Power Train Parameters
The EPA is developing a new generation emissions inventory model, MOVES (Motor Vehicle Emissions Simulator). The first version of the model outputs fuel consumption based on available modal data. However, due to the limited heavy-duty vehicle data, MOVES rates need to be supplemented with rates determined with the Physical Emission Rate Estimator (PERE). PERE combines vehicle tractive power together with vehicle powertrain parameters specific to the class of vehicle; the vehicle weight, shape, engine type, and transmission. Analysis of in-use data for heavy-duty diesel tractortrailer vehicles, city transit diesel buses, and dynamometer non-road diesel engines has enabled a determination of diesel engine efficiency and friction and transmission shift schedules for these engines and vehicles. These model parameters and a comparison of the model results to measured fuel consumption and CO2 emissions are presented
Flux Tube Zero-Point Motion, Hadronic Charge Radii, and Hybrid Meson Production Cross Sections
Flux tube zero-point motion produces quark displacements transverse to the
flux tube which make significant contributions to hadronic charge radii. In
heavy quark systems, these contributions can be related by Bjorken's sum rule
to the rates for semileptonic decay to hybrid mesons. This connection can be
generalized to other leptoproduction processes, where transverse contributions
to elastic form factor slopes are related to the cross sections for the
production of the associated hybrid states. I identify the flux tube overlap
integral responsible for these effects as the strong QCD analogue of the
Sudakov form factor of perturbative QCD.Comment: 16 pages, revised to clarify some points and to improve and correct
the notation for the flux tube wave function
Factorization and Nonfactorization in B Decays
Using NLL values for Wilson coefficients and including the contributions from
the penguin diagrams, we estimate the amount of nonfactorization in two-body
hadronic B decays. Also, we investigate the model dependence of the
nonfactorization parameters by performing the calculation using different
models for the form factors. The results support the universality of
nonfactorizable contributions in both Cabibbo-favored and Cabibbo-suppressed B
decays.Comment: 17 pages, 5 figures, revte
Hadronic Charmed Meson Decays Involving Axial Vector Mesons
Cabibbo-allowed charmed meson decays into a pseudoscalar meson and an
axial-vector meson are studied. The charm to axial-vector meson transition form
factors are evaluated in the Isgur-Scora-Grinstein-Wise quark model. The dipole
momentum dependence of the transition form factor and the presence of
a sizable long-distance -exchange are the two key ingredients for
understanding the data of . The mixing angle of
the strange axial-vector mesons is found to be or
from decays. The study of decays excludes the positive mixing-angle
solutions. It is pointed out that an observation of the decay at the level of will rule out
and favor the solution .
Though the decays are color suppressed, they are
comparable to and even larger than the color-allowed counterparts: and . The finite width effect of the axial-vector resonance is
examined. It becomes important for in particular when its width is
near 600 MeV.Comment: 19 page
Bounds on Heavy-to-Heavy Mesonic Form Factors
We provide upper and lower bounds on the form factors for B -> D, D^* by
utilizing inclusive heavy quark effective theory sum rules. These bounds are
calculated to leading order in Lambda_QCD/m_Q and alpha_s. The O(alpha_s^2
beta_0) corrections to the bounds at zero recoil are also presented. We compare
our bounds with some of the form factor models used in the literature. All the
models we investigated failed to fall within the bounds for the combination of
form factors (omega^2 - 1)/(4 omega)|omega h_{A2}+h_{A3}|^2.Comment: 27 pages, 10 figure
Transition Form Factors between Pseudoscalar and Vector Mesons in Light-Front Dynamics
We study the transition form factors between pseudoscalar and vector mesons
using a covariant fermion field theory model in dimensions. Performing
the light-front calculation in the frame in parallel with the
manifestly covariant calculation, we note that the suspected nonvanishing
zero-mode contribution to the light-front current does not exist in our
analysis of transition form factors. We also perform the light-front
calculation in a purely longitudinal frame and confirm that the form
factors obtained directly from the timelike region are identical to the ones
obtained by the analytic continuation from the spacelike region. Our results
for the decay process satisfy the constraints on the
heavy-to-heavy semileptonic decays imposed by the flavor independence in the
heavy quark limit.Comment: 20 pages, 14 figure
Decay constants, semi-leptonic and non-leptonic decays in a Bethe-Salpeter Model
We evaluate the decay constants for the B and mesons and the form factors
for the semileptonic decays of the B meson to and mesons in a
Bethe-Salpeter model. From data we extract from and from decays. The form factors are then used to obtain non-leptonic
decay partial widths for and in the
factorization approximation.Comment: 15 Pages, 3 Postscript figures (available also from [email protected]
Semileptonic B decays to excited charmed mesons
Exclusive semileptonic B decays into excited charmed mesons are investigated
at order in the heavy quark effective theory. Differential
decay rates for each helicity state of the four lightest excited mesons
(, , , and ) are examined. At zero recoil,
corrections to the matrix elements of the weak currents can
be written in terms of the leading Isgur-Wise functions for the corresponding
transition and meson mass splittings. A model independent prediction is found
for the slope parameter of the decay rate into helicity zero at zero
recoil. The differential decay rates are predicted, including
corrections with some model dependence away from zero
recoil and including order corrections. Ratios of various exclusive
branching ratios are computed. Matrix elements of the weak currents between
mesons and other excited charmed mesons are discussed at zero recoil to order
. These amplitudes vanish at leading order, and can be
written at order in terms of local matrix elements.
Applications to decay sum rules and factorization are presented.Comment: 39 pages revtex including 10 figures, uses epsf. Substantial
improvements throughout the pape
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