68 research outputs found
Production of light pseudoscalars in external electromagnetic fields by the Schwinger mechanism
We generalize the Schwinger mechanism and calculate the probability of the
decay of intense electromagnetic fields to pseudoscalar particles. We also
point out that our estimate for axion emission in a previous paper was
incorrect.Comment: 25 pages including 9 figures. Version that matches published versio
Long range forces induced by neutrinos at finite temperature
We revisit and extend previous work on neutrino mediated long range forces in
a backround at finite temperature. For Dirac neutrinos, we correct existing
results. We also give new results concerning spin-dependent as well as
spin-independent long range forces associated to Majorana neutrinos. An
interesting outcome of the investigation is that, for both types of neutrinos
whether massless or not, the effect of the relic neutrino heat bath is to
convert those forces into attractive ones in the supra-millimeter scale while
they stay repulsive within the sub-millimeter scale.Comment: 8 pages, Latex, 1 figur
Casimir-Polder forces in the presence of the cosmic photon heat bath
We study the effect of a photon background at finite temperature on the
Van der Waals interactions among neutral bodies. It turns out that the
long-range Casimir-Polder force is unaffected for distances much less than
and strongly enhanced for distances much above .Comment: 8 pages, 2 figure
Higgs triplet effects in purely leptonic processes
We consider the effect of complex Higgs triplets on purely leptonic processes
and survey the experimental constraints on the mass and couplings of their
single and double charge members. Present day experiments tolerate values of
the Yukawa couplings of these scalars at the level of the standard electroweak
gauge couplings. We show that the proposed measurement of the ratio
R_{LCD}=\sigma (\nu_{\mu}e)/ [\sigma (\bb\nu_{\mu}e) + \sigma (\nu_e e )]
would allow to explore a large region of the parameter space inaccessible to
the usual ratio R=\sigma (\nu_{\mu}e)/\sigma (\bb\nu_{\mu}e).Comment: 14 pages, LaTeX, Three figures included using uufiles. A postscript
version is available at ftp://ftp.ifae.es/preprint/ft/uabft378.p
Neutrino magnetic moments and photo-disintegration of deuterium
Neutrinos with non-zero magnetic moments can dissociate deuterium nuclei by a
photon exchange, in addition to the weak neutral current process. We calculate
the neutrino-magnetic moment induced photo-dissociation cross section of
deuterium using the equivalent photon method. This process would contribute
extra events to the neutral current reaction which is observed with high
precision in the salt-phase of SNO experiment. Using the SNO data and the
recent laboratory measurements of the reaction which
give a more precise value of the solar flux we find that the neutrino
effective magnetic moment is which can be interpreted as an upper bound (at ) on the neutrino magnetic moments.Comment: 7 pages, new references and some comments adde
Neutrino oscillations in the Sun probe long-range leptonic forces
Lepton number charges might be the source of long range forces. If one
accepts that neutrinos produced in the Sun do indeed oscillate while crossing
the interior of the Sun, then the shift in the phase of the neutrino
wavefunction caused by an hypothetical potential associated to the leptonic
charge of the electrons in the Sun could affect the oscillation pattern beyond
what is actually observed. We show that a "fine structure" constant
in excess of is incompatible with present
observational data. This bound is not valid for forces whose range is shorter
than the size of the Sun.Comment: 6 pages, no figures. References adde
Majorana Neutrinos and Long Range Forces
We establish that forces mediated by the exchange of a pair of Majorana
neutrinos differ from those due to Dirac neutrino exchange.Comment: 7 pages, Latex, 1 postcript figure. False statement about neutrino
bounding in neutron stars mende
Photon Spectrum Produced by the Late Decay of a Cosmic Neutrino Background
We obtain the photon spectrum induced by a cosmic background of unstable
neutrinos. We study the spectrum in a variety of cosmological scenarios and
also we allow for the neutrinos having a momentum distribution (only a critical
matter dominated universe and neutrinos at rest have been considered until
now). Our results can be helpful when extracting bounds on neutrino electric
and magnetic moments from cosmic photon background observations.Comment: RevTex, 14 pages, 3 figures; minor changes, references added. To
appear in Phys. Rev.
Axions and their Relatives
A review of the status of axions and axion-like particles is given. Special
attention is devoted to the recent results of the PVLAS collaboration, which
are in conflict with the CAST data and with the astrophysical constraints.
Solutions to the puzzle and the implications for new physics are discussed. The
question of axion-like particles being dark matter is also addressed.Comment: Updated version of an invited talk at the Axion Training (CERN,
December 2005). To appear as a Lecture Notes in Physics (Springer-Verlag),
edited by B. Beltran, M. Kuster and G. Raffel
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