4,382 research outputs found
Mixing of Pseudoscalar Mesons
Eta-eta' mixing is discussed in the quark-flavor basis with the hypothesis
that the decay constants follow the pattern of particle state mixing. On
exploiting the divergences of the axial vector currents - which embody the
axial vector anomaly - all mixing parameters are fixed to first order of flavor
symmetry breaking. An alternative set of parameters is obtained from a
phenomenological analysis. We also discuss mixing in the octet-singlet basis
and show how the relevant mixing parameters are related to those in the
quark-flavor basis. The dependence of the mixing parameters on the strength of
the anomaly and the amount of flavor symmetry breaking is investigated.
Finally, we present a few applications of the quark-flavor mixing scheme, such
as radiative decays of vector mesons, the photon-pseudoscalar meson transition
form factors, the coupling constants of eta and eta' to nucleons, and the
isospin-singlet admixtures to the pi^0 meson.Comment: 21 pages, 6 figures, Proc. WORKSHOP ON ETA PHYSICS, Uppsala, October
22-27, 200
Mixing and Decay Constants of Pseudoscalar Mesons: The Sequel
We present further tests and applications of the new eta-eta' mixing scheme
recently proposed by us. The particle states are decomposed into orthonormal
basis vectors in a light-cone Fock representation. Because of flavor symmetry
breaking the mixing of the decay constants can be identical to the mixing of
particle states at most for a specific choice of this basis. Theoretical and
phenomenological considerations show that the quark flavor basis has this
property and allows, therefore, for a reduction of the number of mixing
parameters. A detailed comparison with other mixing schemes is also presented.Comment: 9 page
decays in the standard model and in scenarios with universal extra dimensions
We study the radiative decays, which are
important to investigate CP violation, and are also relevant to assess the role
of the exclusive modes induced by the transition to saturate
the inclusive decay rate. Moreover, these channels do not
display the same hierarchy as modes, for which the
decay into is enhanced with respect to one into . The
three-body radiative decays reverse the role: we find that this experimentally
observed behavior (although affected by a large uncertainty in the case of the
) is reproduced in the theoretical analysis. We compute a form factor, needed for this study, using light cone QCD sum rules, and
discuss a relation expected to hold in the large energy limit for the light
meson. Finally, we examine in two extensions of the
standard model with universal extra dimensions, to investigate the sensitivity
of this rare mode to such a kind of new physics effects.Comment: RevTeX, 17 pages, 7 figures. High resolution figures available upon
request. Matches the published versio
The Overlap Representation of Skewed Quark and Gluon Distributions
Within the framework of light-cone quantisation we derive the complete and
exact overlap representation of skewed parton distributions for unpolarised and
polarised quarks and gluons. Symmetry properties and phenomenological
applications are discussed.Comment: LaTex, 36 pages. v2: incorrect paper attached originally. v3: erratum
adde
Black hole physics, confining solutions of SU(3)-Yang-Mills equations and relativistic models of mesons
The black hole physics techniques and results are applied to find the set of
the exact solutions of the SU(3)-Yang-Mills equations in Minkowski spacetime in
the Lorentz gauge. All the solutions contain only the Coulomb-like or linear in
components of SU(3)-connection. This allows one to obtain some possible
exact and approximate solutions of the corresponding Dirac equation that can
describe the relativistic bound states. Possible application to the
relativistic models of mesons is also outlined.Comment: 13 pages, LaTeX with using the mpla1.sty file from the package of
World Scientific Publishing C
Soft-collinear effective theory and heavy-to-light currents beyond leading power
An important unresolved question in strong interaction physics concerns the
parameterization of power-suppressed long-distance effects to hard processes
that do not admit an operator product expansion (OPE). Recently Bauer et al.\
have developed an effective field theory framework that allows one to formulate
the problem of soft-collinear factorization in terms of fields and operators.
We extend the formulation of soft-collinear effective theory, previously worked
out to leading order, to second order in a power series in the inverse of the
hard scale. We give the effective Lagrangian and the expansion of ``currents''
that produce collinear particles in heavy quark decay. This is the first step
towards a theory of power corrections to hard processes where the OPE cannot be
used. We apply this framework to heavy-to-light meson transition form factors
at large recoil energy.Comment: 46 pages, LaTeX; v2: two references added, eq. (52) correcte
Proton mass effects in wide-angle Compton scattering
We investigate proton mass effects in the handbag approach to wide-angle
Compton scattering. We find that theoretical uncertainties due to the proton
mass are significant for photon energies presently studied at Jefferson Lab.
With the proposed energy upgrade such uncertainties will be clearly reduced.Comment: 4 pages, uses revtex, 3 figure
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