3,383 research outputs found
UHE neutrino damping in a thermal gas of relic neutrinos
We present a calculation of the damping of an ultra-energetic (UHE) cosmic
neutrino travelling through the thermal gas of relic neutrinos, using the
formalism of finite-temperature field theory. From the self-energy diagram due
to Z exchange, we obtain the annihilation cross section for an UHE neutrino
interacting with an antineutrino from the background. This method allows us to
derive the full expressions for the UHE neutrino transmission probability,
taking into account the momentum of relic neutrinos. We compare our results
with the approximations in use in the literature. We discuss the effect of
thermal motion on the shape of the absorption dips for different UHE neutrino
fluxes as well as in the context of relic neutrino clustering. We find that for
ratios of the neutrino mass to the relic background temperature or
smaller, the thermal broadening of the absorption lines could significantly
affect the determination of the neutrino mass and of the characteristics of the
population of UHE sources.Comment: 18 pages, 6 figures. Typos corrected. More accurate treatment of the
interaction with relic neutrino clusters. Accepted for publication in
Astroparticle Physic
Neutrino telescopes under the ocean: The case for ANTARES
Neutrino telescopes offer an alternative way to explore the Universe. Several
projects are in operation or under construction. A detector under the ocean is
very promising because of the very accurate angular resolution that it
provides. The ANTARES project is intended to demonstrate the feasibilty of such
a detector.Comment: Talk given at the Neutrino98 conference, Takayama, Japan, June 4-9,
199
Thermal effects on the absorption of ultra-high energy neutrinos by the cosmic neutrino background
We use the formalism of finite-temperature field theory to study the
interactions of ultra-high energy (UHE) cosmic neutrinos with the background of
relic neutrinos and to derive general expressions for the UHE neutrino
transmission probability. This approach allows us to take into account the
thermal effects introduced by the momentum distribution of the relic neutrinos.
We compare our results with the approximate expressions existing in the
literature and discuss the influence of thermal effects on the absorption dips
in the context of favoured neutrino mass schemes, as well as in the case of
clustered relic neutrinos.Comment: 3 pages, 2 figures. Prepared for the Proceedings of the 9th
International Conference on Topics in Astroparticle and Underground Physics
(TAUP 2005), Zaragoza (Spain), September 10-14, 200
The Offline Software Framework of the Pierre Auger Observatory
The Pierre Auger Observatory is designed to unveil the nature and the origins
of the highest energy cosmic rays. The large and geographically dispersed
collaboration of physicists and the wide-ranging collection of simulation and
reconstruction tasks pose some special challenges for the offline analysis
software. We have designed and implemented a general purpose framework which
allows collaborators to contribute algorithms and sequencing instructions to
build up the variety of applications they require. The framework includes
machinery to manage these user codes, to organize the abundance of
user-contributed configuration files, to facilitate multi-format file handling,
and to provide access to event and time-dependent detector information which
can reside in various data sources. A number of utilities are also provided,
including a novel geometry package which allows manipulation of abstract
geometrical objects independent of coordinate system choice. The framework is
implemented in C++, and takes advantage of object oriented design and common
open source tools, while keeping the user side simple enough for C++ novices to
learn in a reasonable time. The distribution system incorporates unit and
acceptance testing in order to support rapid development of both the core
framework and contributed user code.Comment: 4 pages, 2 figures, presented at IEEE NSS/MIC, 23-29 October 2005,
Puerto Ric
Tunability of Critical Casimir Interactions by Boundary Conditions
We experimentally demonstrate that critical Casimir forces in colloidal
systems can be continuously tuned by the choice of boundary conditions. The
interaction potential of a colloidal particle in a mixture of water and
2,6-lutidine has been measured above a substrate with a gradient in its
preferential adsorption properties for the mixture's components. We find that
the interaction potentials at constant temperature but different positions
relative to the gradient continuously change from attraction to repulsion. This
demonstrates that critical Casimir forces respond not only to minute
temperature changes but also to small changes in the surface properties.Comment: 4 figures;
http://www.iop.org/EJ/article/0295-5075/88/2/26001/epl_88_2_26001.htm
Silicon Photonics for Coherent Terahertz Generation and Detection
Silicon-plasmonic internal photoemission devices can act as photomixers for generating terahertz frequency carriers (T-waves) for transmitters (Tx), or they function as receivers (Rx) for coherently downconverting Twave signals to the baseband. In a first demonstration, we monolithically integrate a Tx and a Rx on a silicon chip and operate them in a carrier frequency range up to 1THz . With a co-integrated transmission line both components can be connected
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