1,593 research outputs found
Measuring the 13-mixing angle and the CP phase with neutrino telescopes
The observed excess of high-energy cosmic rays from the Galactic plane in the
energy range \sim 10^18 eV may be naturally explained by neutron primaries
generated in the photo-dissociation of heavy nuclei. In this scenario, neutrons
with lower energy decay before reaching the Earth and produce a detectable flux
in a 1 km^3 neutrino telescope. The initial flavor composition of these
neutrinos, \phi(\bar\nu_e):\phi(\bar\nu_\mu):\phi(\bar\nu_\tau)=1:0:0, offers
the opportunity to perform a combined \bar\nu_\mu/\bar\nu_\tau appearance and
\bar\nu_e disappearance experiment. The observable ratio
\phi(\bar\nu_\mu)/\phi(\bar\nu_e+\bar\nu_\tau) of fluxes arriving on Earth
depends appreciably on the 13-mixing angle \theta_13 and the leptonic CP phase
\delta_CP, opening thus a new experimental avenue to measure these two
quantities.Comment: 4 pages, 2 eps figures. Enlarged discussion, references added.
Matches version to appear in PR
The Galactic magnetic field as spectrograph for ultra-high energy cosmic rays
We study the influence of the regular component of the Galactic magnetic
field (GMF) on the arrival directions of ultra-high energy cosmic rays
(UHECRs). We find that, if the angular resolution of current experiments has to
be fully exploited, deflections in the GMF cannot be neglected even for E=10^20
eV protons, especially for trajectories along the Galactic plane or crossing
the Galactic center region. On the other hand, the GMF could be used as a
spectrograph to discriminate among different source models and/or primaries of
UHECRs, if its structure would be known with sufficient precision. We compare
several GMF models introduced in the literature and discuss for the example of
the AGASA data set how the significance of small-scale clustering or
correlations with given astrophysical sources are affected by the GMF. We point
out that the non-uniform exposure to the extragalactic sky induced by the GMF
should be taken into account estimating the significance of potential
(auto-)correlation signals.Comment: 11 pages, 8 figures; minor corrections, enlarged discussion, contains
an extended review on Galactic magnetic field compared to published version,
to appear in Astroparticle Physic
Analysis of atmospheric neutrino oscillations in three-flavor neutrinos
We analyze the atmospheric neutrino experiments of Super-Kamiokande (830-920
live days) using the three-flavor neutrino framework with the mass hierarchy
m_1 nearly equal m_2 << m_3. We study the sub-GeV, multi- GeV neutrinos and
upward through-going and stopping muons zenith angle distributions taking
account of the Earth matter effects thoroughly. We obtain the allowed regions
of mass and mixing parameters Delm^2_{23}, theta_{13} and theta_{23}.
Delm^2_{23} is restricted to 0.002-0.01eV^2 and theta_{13}<13degrees,
35degrees<theta_{23}<55degrees in 90% C.L. For theta_{12}, there is no
difference between the large angle solar neutrino solution and small one. From
chi^2 fit, the minimum chi^2=55(54DOF) is obtained at
Delm^2_{23}=4x10^(-3)eV^2, theta_{13}=10degrees and theta_{23} =45degrees.Comment: 16 pages, 3 figures, LaTe
Tagging single muons and other long-flying relativistic charged particles by ultra-fast timing in air Cherenkov telescopes
Atmospheric air Cherenkov telescopes are successfully used for ground-based,
very high-energy (VHE) gamma ray astronomy. Triggers from the so-called single
muon and other long-flying relativistic charged particle events are an unwanted
background for the Cherenkov telescope. Because of low rate at TeV energies the
muon background is unimportant. It is much more intense for telescopes with
high photon sensitivity and low energy threshold. Below a few hundred GeV
energy, the so-called muon background becomes so intense, that it can
deteriorate the sensitivity of telescopes (the so-called muon-wall problem).
From general considerations it can be anticipated that the signature of these
particles should be a light pulse with a narrow time structure. In fact,
simulations show that the pulses from muons have a very narrow time profile
that is well below the time resolutions of nearly all currently operating
telescopes. In this report we elaborate on the time profile of Cherenkov light
from the so-called single muons and show that a telescope with ultra-fast time
response can open a new dimension allowing one to tag and to reject those
events.Comment: Accepted by Astroparticle Physic
Effects to Scalar Meson Decays of Strong Mixing between Low and High Mass Scalar Mesons
We analyze the mass spectroscopy of low and high mass scalar mesons and get
the result that the coupling strengths of the mixing between low and high mass
scalar mesons are very strong and the strengths of mixing for scalar
mesons and those of I=0 scalar mesons are almost same. Next, we analyze the
decay widths and decay ratios of these mesons and get the results that the
coupling constants for which represents the coupling of high
mass scalar meson -> two pseudoscalar mesons are almost same as the
coupling for the I=0. On the other hand, the coupling constant for
which represents the low mass scalar meson -> are far
from the coupling constant for I=0. We consider a resolution for this
discrepancy. Coupling constant for glueball -> is smaller than
the coupling . is .Comment: 15 pages, 6 figure
Study of the performance and capability of the new ultra-fast 2 GSample/s FADC data acquisition system of the MAGIC telescope
In February 2007 the MAGIC Air Cherenkov Telescope for gamma-ray astronomy
was fully upgraded with an ultra fast 2 GSamples/s digitization system. Since
the Cherenkov light flashes are very short, a fast readout can minimize the
influence of the background from the light of the night sky. Also, the time
structure of the event is an additional parameter to reduce the background from
unwanted hadronic showers. An overview of the performance of the new system and
its impact on the sensitivity of the MAGIC instrument will be presented.Comment: Contribution to the 30th ICRC, Merida Mexico, July 2007 on behalf of
the MAGIC Collaboratio
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