374 research outputs found
Study of the winter 2005 Antarctica polar vortex
During winter and springtime, the flow above Antarctica at high altitude
(upper troposphere and stratosphere) is dominated by the presence of a vortex
centered above the continent. It lasts typically from August to November. This
vortex is characterized by a strong cyclonic jet centered above the polar high.
In a recent study of our group (Hagelin et al., 2008) of four different sites
in the Antarctic internal plateau (South Pole, Dome C, Dome A and Dome F), it
was made the hypothesis that the wind speed strength in the upper atmosphere
should be related to the distance of the site to the center of the Antarctic
polar vortex. This high altitude wind is very important from an astronomical
point of view since it might trigger the onset of the optical turbulence and
strongly affect other optical turbulence parameters. What we are interested in
here is to localize the position of the minimum value of the wind speed at high
altitude in order to confirm the hypothesis of Hagelin et al. (2008).Comment: 3rd ARENA conference, 11-15 May 2009 EAS Publication Serie
A different glance to the site testing above Dome C
Due to the recent interest shown by astronomers towards the Antarctic Plateau
as a potential site for large astronomical facilities, we assisted in the last
years to a strengthening of site testing activities in this region,
particularly at Dome C. Most of the results collected so far concern
meteorologic parameters and optical turbulence measurements based on different
principles using different instruments. At present we have several elements
indicating that, above the first 20-30 meters, the quality of the optical
turbulence above Dome C is better than above whatever other site in the world.
The challenging question, crucial to know which kind of facilities to build on,
is to establish how much better the Dome C is than a mid-latitude site. In this
contribution we will provide some complementary elements and strategies of
analysis aiming to answer to this question. We will try to concentrate the
attention on critical points, i.e. open questions that still require
explanation/attention.Comment: 3 figures, EAS Publications Series, Volume 25, 2007, pp.5
Mt. Graham: Optical turbulence vertical distribution at standard and high vertical resolution
A characterization of the optical turbulence vertical distribution and all
the main integrated astroclimatic parameters derived from the CN2 and the wind
speed profiles above Mt. Graham is presented. The statistic includes
measurements related to 43 nights done with a Generalized Scidar (GS) used in
standard configuration with a vertical resolution of ~1 km on the whole 20-22
km and with the new technique (HVR-GS) in the first kilometer. The latter
achieves a resolution of ~ 20-30 m in this region of the atmosphere.
Measurements done in different periods of the year permit us to provide a
seasonal variation analysis of the CN2. A discretized distribution of the
typical CN2 profiles useful for the Ground Layer Adaptive Optics (GLAO)
simulations is provided and a specific analysis for the LBT Laser Guide Star
system ARGOS case is done including the calculation of the 'gray zones' for J,
H and K bands. Mt. Graham confirms to be an excellent site with median values
of the seeing without dome contribution equal to 0.72", the isoplanatic angle
equal to 2.5" and the wavefront coherence time equal to 4.8 msec. We provide a
cumulative distribution of the percentage of turbulence developed below H*
where H* is included in the (0,1 km) range. We find that 50% of the whole
turbulence develops in the first 80 m from the ground. The turbulence
decreasing rate is very similar to what has been observed above Mauna Kea.Comment: 12 pages, 6 figures, Proc. SPIE Conference "Ground-based and Airborne
Telescopes III", 27 June 2010, San Diego, California, US
Grand Unification of Quark and Lepton FCNCs
In the context of Supersymmetric Grand Unified theories with soft breaking
terms arising at the Planck scale, it is generally possible to link flavor
changing neutral current and CP violating processes occurring in the leptonic
and hadronic sectors. We study the correlation between flavor changing squark
and slepton mass insertions in models \`a la SU(5). We show that the
constraints coming from lepton flavor violation exhibit a strong impact on
CP-violating B decays.Comment: 4 pages, 1 figur
One-particle inclusive CP asymmetries
One-particle inclusive CP asymmetries in the decays of the type B -> D(*) X
are considered in the framework of a QCD based method to calculate the rates
for one-particle inclusive decays.Comment: Latex, 13 pages, 6 figures (eps). Analytical and numerical results
unchanged, extended discussion of model assumptions and systematic
uncertainties. Version to be published in Phys. Rev. D 62, 0960xx. Additional
transparencies are available via the WWW at
http://www-ttp.physik.uni-karlsruhe.de/Slides
Supersymmetry, local horizontal unification, and a solution to the flavor puzzle
Supersymmetric gauge models with local horizontal symmetries are known to
generate large flavor changing neutral current effects induced by supersymmetry
breaking D-terms. We show how the presence of a U(1) gauge symmetry solves this
problem. We then construct a realistic gauge model with SU(2)_H x U(1)_H as the
local horizontal symmetry and suggest that the U(1)_H factor may be identified
with the anomalous U(1) induced by string compactification. This model explains
the observed hierarchies among the quark masses and mixing angles, accommodates
naturally the solar and atmospheric neutrino data, and provides simultaneously
a solution to the supersymmetric flavor problem. The model can be excluded if
the rare decay \mu --> e \gamma is not observed in the current round of
experiments.Comment: 10 pages in RevTe
Probing Lepton Flavor Violation at Future Colliders
Supersymmetric theories with significant lepton flavor violation have
and nearly degenerate. In this case, pair production
of and at LEPII and at
the Next Linear Collider leads to the phenomenon of slepton oscillations, which
is analogous to neutrino oscillations. The reach in and gives a probe of lepton flavor violation which is significantly more
powerful than the current bounds from rare processes, such as . Polarizable beams and the mode at the NLC are found to
be promising options.Comment: 10 pages, 3 figures, RevTeX, minor corrections, published versio
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