136 research outputs found
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
Possible explanation of the discrepancy of the light-cone QCD sum rule calculation of g(D*Dpi) coupling with experiment
The introduction of an explicit negative radial excitation contribution in
the hadronic side of the light cone QCD sum rule (LCSR) of Belyaev, Braun,
Khodjamirian and Ruckl, can explain the large experimental value of g(D*Dpi),
recently measured by CLEO. At the same time, it considerably improves the
stability of the sum rule when varying the Borel parameter.Comment: 9 pages, 1 PostScript figure
(D* to D + gamma) and (B* to B + gamma) as derived from QCD Sum Rules
The method of QCD sum rules in the presence of the external electromagnetic
field is used to analyze radiative decays of charmed or bottomed
mesons such as and , with the
susceptibilities obtained previously from the study of baryon magnetic moments.
Our predictions on decays agree very well with the experimental
data. There are differences among the various theoretical predictions on
decays but the data are not yet available.Comment: 11 pages, Late
Rare B -> K^* l^+ l^- decay, two Higgs doublet model, and light cone QCD sum rules
The decay width, forward-backward asymmetry and lepton longitudinal and
transversal polarization for the exclusive K^* -> l^+ l^- decay in a two Higgs
doublet model are computed. It is shown that all these quantities are very
effective tools for establishing new physics.Comment: 18 pages, 7 figures, LaTeX formatte
Covariant Light-Front Approach for s-wave and p-wave Mesons: Its Application to Decay Constants and Form Factors
We study the decay constants and form factors of the ground-state s-wave and
low-lying p-wave mesons within a covariant light-front approach. Numerical
results of the form factors for transitions between a heavy pseudoscalar meson
and an s-wave or p-wave meson and their momentum dependence are presented in
detail. In particular, form factors for heavy-to-light and B to D**
transitions, where D** denotes generically a p-wave charmed meson, are compared
with other model calculations. The experimental measurements of the decays B^-
to D** pi^- and B to D D**_s are employed to test the decay constants of D**_s
and the B to D** transition form factors. The heavy quark limit behavior of the
decay constants and form factors is examined and it is found that the
requirement of heavy quark symmetry is satisfied. The universal Isgur-Wise (IW)
functions, one for s-wave to s-wave and two for s-wave to p-wave transitions,
are obtained. The values of IW functions at zero recoil and their slope
parameters can be used to test the Bjorken and Uraltsev sum rules.Comment: 59 pages, 6 figures. Version to appear in Phys. Rev. D. Changes are:
(i) D_s to phi transition form factors are discussed and compared with the
recent FOCUS measurements and (ii) zero mode effects are clarifie
Radiative Scalar Meson Decays in the Light-Front Quark Model
We construct a relativistic wavefunction for scalar mesons within the
framework of light-front quark model(LFQM). This scalar wavefunction is used to
perform relativistic calculations of absolute widths for the radiative decay
processes, and
which incorporate the effects of glueball-
mixing. The mixed physical states are assumed to be ,and
for which the flavor-glue content is taken from the mixing
calculations of other works. Since experimental data for these processes are
poor, our results are compared with those of a recent non-relativistic model
calculation. We find that while the relativistic corrections introduced by the
LFQM reduce the magnitudes of the decay widths by 50-70%, the relative
strengths between different decay processes are fairly well preserved. We also
calculate decay widths for the processes and
(0^{++})\to\gamma\gamm involving the light scalars and
to test the simple model of these mesons. Our results of
model for these processes are not quite consistent with well-established data,
further supporting the idea that and are not conventional
states.Comment: 10 pages, 4 figure
Poincare Invariant Algebra From Instant to Light-Front Quantization
We present the Poincare algebra interpolating between instant and light-front
time quantizations. The angular momentum operators satisfying SU(2) algebra are
constructed in an arbitrary interpolation angle and shown to be identical to
the ordinary angular momentum and Leutwyler-Stern angular momentum in the
instant and light-front quantization limits, respectively. The exchange of the
dynamical role between the transverse angular mometum and the boost operators
is manifest in our newly constructed algebra.Comment: 21 pages, 3 figures, 1 tabl
Vertex functions for d-wave mesons in the light-front approach
While the light-front quark model (LFQM) is employed to calculate hadronic
transition matrix elements, the vertex functions must be pre-determined. In
this work we derive the vertex functions for all d-wave states in this model.
Especially, since both of and are mesons, the Lorentz
structures of their vertex functions are the same. Thus when one needs to study
the processes where is involved, all the corresponding formulas for
states can be directly applied, only the coefficient of the vertex
function should be replaced by that for . The results would be useful
for studying the newly observed resonances which are supposed to be d-wave
mesons and furthermore the possible 2S-1D mixing in with the LFQM.Comment: 12 pages, 2 figures, some typos corrected and more discussions added.
Accepted by EPJ
Consistent treatment of spin-1 mesons in the light-front formalism
We analyze the matrix element of the electroweak current between q \qb
vector meson states in the framework of a covariant extension of the
light-front formalism. The light-front matrix element of a one-body current is
naturally associated with zero modes, which affect some of the form factors
that are necessary to represent the Lorentz structure of the light-front
integral. The angular condition contains some information on zero modes, i.e.,
only if the effect of zero modes is accounted for correctly, is it satisfied.
With plausible assumptions we derive from the angular condition several
consistency conditions which can be used quite generally to determine the zero
mode contribution of form factors. The correctness of this method is tested by
the phenomenological success of the derived form factors. We compare the
predictions of our formalism with those of the standard light-front approach
and with available data. As examples we discuss the magnetic moment of the
, the coupling constant , and the coupling constants of
the pseudoscalar density, and , which provide a phenomenological
link between constituent and current quark masses.Comment: 36 pages, figure 1 is include
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
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