7,531 research outputs found
Effects of the magnetic dipole moment of charged vector mesons in their radiative decay distribution
We consider the effects of anomalous magnetic dipole moments of vector mesons
in the decay distribution of photons emitted in two-pseudoscalar decays of
charged vector mesons. By choosing a kinematical configuration appropriate to
isolate these effects from model-dependent and dominant bremsstrahlung
contributions, we show that this method can provide a valid alternative for a
measurement of the unknown magnetic dipole moments of charged vector mesons.Comment: Latex, 11 pages incl. 3 .ps figures, to appear in Phys. Rev.
Hadron production in electron-positron annihilation computed from the gauge gravity correspondence
We provide a non-perturbative expression for the hadron production in
electron-positron annihilation at zero temperature in a strongly coupled,
large-Nc SU(Nc) field theory with Nf << Nc quark flavors. The resulting
expressions are valid to leading order in the electromagnetic coupling constant
but non-perturbatively in the SU(Nc) interactions and the mass of the quark. We
obtain this quantity by computing the imaginary part of the hadronic vacuum
polarization function Pi_q using holographic techniques, providing an
alternative to the known method that uses the spectrum of infinitely stable
mesons determined by the normalizable modes of the appropriated fields in the
bulk. Our result exhibits a structure of poles localized at specific real
values of q^2, which coincide with the ones found using the normalizable modes,
and extends it offering the unique analytic continuation of this distribution
to a function defined for values of q^2 over the complex plane. This analytic
continuation permits to include a finite decay width for the mesons. By
comparison with experimental data we find qualitatively good agreement on the
shape of the first pole, when using the rho meson parameters and choosing a
proper normalization factor. We then estimate the contribution to the anomalous
magnetic moment of the muon finding an agreement within 25%, for this choice of
parameters.Comment: 7 pages, 1 figure. Extended version with minor changes in emphasis
and references adde
Gauge invariance, radiative interferences and properties of vector mesons
We state the implications on the properties of vector mesons due to gauge
invariance. In particular, we find that polarized vector mesons exhibit a
property in the radiation distribution of order in the photon
energy, namely it is null when the gyromagnetic ratio becomes . Therefore,
the generalization of the Burnett-Kroll theorem for polarized vector-meson
states is held only if . In addition, radiative interferences between the
electric charge and any gauge invariant term is found to be parametrized by a
common global factor which can be used to extract information of the involved
states by a proper choice of the kinematical region, where they could be
relevant.Comment: 5 pages, 1 figure. To appear in the Proceedings of the IX Mexican
Workshop on Particles and Fields, Colima Mexico. Uses RevTex
Finite width induced modification to the electromagnetic form factors of spin-1 particles
The inclusion of the unstable features of a spin-1 particle, without breaking
the electromagnetic gauge invariance, can be properly accomplished by including
higher order contributions as done in the so-called fermion loop scheme (for
the W gauge boson), and the boson loop scheme (for vector mesons). This induces
a non trivial modification to the electromagnetic vertex of the particle, which
must be considered in addition to any other contribution computed as stable
particles. Considering the modified electromagnetic vertex, we obtain general
expressions for the corresponding corrections to the multipoles as a function
of the mass of the particles in the loop. For the W gauge boson no substantial
deviations from the stable case is observed. For the rho and K* mesons the mass
of the particles in the loop makes a significant effect, and can be comparable
with corrections of different nature .Comment: 11 pages, 1 figure. Extended discussion, main equations rewritten to
exhibit limiting behavior. Results for K* meson added. Accepted for
publication in PR
Comment on "Topological stability of the half-vortices in spinor exciton-polariton condensates"
We show that recent paper by Flayac et al. [Phys. Rev. B 81, 045318 (2010)
and arXiv:0911.1650] is misleading. We demonstrate the existence of static
half-quantum vortices in exciton-polariton condensates and calculate the
warping of their polarization texture produced by TE-TM splitting of polariton
band.Comment: 4 pages, 1 figure. More material was added (in particular, on the
current flow)
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