7,948 research outputs found
Ambiguities of theoretical parameters and CP/T violation in neutrino factories
We study the optimal setup for observation of the CP asymmetry in neutrino
factory experiments --- the baseline length, the muon energy and the analysis
method. First, we point out that the statistical quantity which has been used
in previous works doesn't represent the CP asymmetry. Then we propose the more
suitable quantity, , which is sensitive to the CP
asymmetry. We investigate the behavior of with ambiguities of
the theoretical parameters. The fake CP asymmetry due to the matter effect
increases with the baseline length and hence the error in the estimation of the
fake CP asymmetry grows with the baseline length due to the ambiguities of the
theoretical parameters. Namely, we lose the sensitivity to the genuine
CP-violation effect in longer baseline.Comment: 8pages, 2figures, Talk given by J. Sato at Joint U.S. / Japan
Workshop on New Initiatives in Muon Lepton Flavor Violation and Neutrino
Oscillation with High Intense Muon and Neutrino Sources, Honolulu, Hawaii,
2-6 Oct 200
LHC Tests of Light Neutralino Dark Matter without Light Sfermions
We address the question how light the lightest MSSM neutralino can be as dark
matter candidate in a scenario where all supersymmetric scalar particles are
heavy. The hypothesis that the neutralino accounts for the observed dark matter
density sets strong requirements on the supersymmetric spectrum, thus providing
an handle for collider tests. In particular for a lightest neutralino below 100
GeV the relic density constraint translates into an upper bound on the Higgsino
mass parameter in case all supersymmetric scalar particles are heavy. One
can define a simplified model that highlights only the necessary features of
the spectrum and their observable consequences at the LHC. Reinterpreting
recent searches at the LHC we derive limits on the mass of the lightest
neutralino that, in many cases, prove to be more constraining than dark matter
experiments themselves.Comment: 22 pages, 8 figure
Suzaku observations of X-ray excess emission in the cluster of galaxies A3112
We analysed the Suzaku XIS1 data of the A3112 cluster of galaxies in order to
examine the X-ray excess emission in this cluster reported earlier with the
XMM-Newton and Chandra satellites. The best-fit temperature of the intracluster
gas depends strongly on the choice of the energy band used for the spectral
analysis. This proves the existence of excess emission component in addition to
the single-temperature MEKAL in A3112. We showed that this effect is not an
artifact due to uncertainties of the background modeling, instrument
calibration or the amount of Galactic absorption. Neither does the PSF scatter
of the emission from the cool core nor the projection of the cool gas in the
cluster outskirts produce the effect. Finally we modeled the excess emission
either by using an additional MEKAL or powerlaw component. Due to the small
differencies between thermal and non-thermal model we can not rule out the
non-thermal origin of the excess emission based on the goodness of the fit.
Assuming that it has a thermal origin, we further examined the Differential
Emission Measure (DEM) models. We utilised two different DEM models, a Gaussian
differential emission measure distribution (GDEM) and WDEM model, where the
emission measure of a number of thermal components is distributed as a
truncated power law. The best-fit XIS1 MEKAL temperature for the 0.4-7.0 keV
band is 4.7+-0.1 keV, consistent with that obtained using GDEM and WDEM models.Comment: 8 pages, 10 figures, accepted to A&
Large gauge invariant non-standard neutrino interactions
Theories beyond the Standard Model must necessarily respect its gauge
symmetry. This implies strict constraints on the possible models of
non-standard neutrino interactions, which we analyze. The focus is set on the
effective low-energy dimension six and eight operators involving four leptons,
decomposing them according to all possible tree-level mediators, as a guide for
model building. The new couplings are required to have sizeable strength, while
processes involving four charged leptons are required to be suppressed. For
non-standard interactions in matter, only diagonal tau-neutrino interactions
can escape these requirements and can be allowed to result from dimension six
operators. Large non-standard neutrino interactions from dimension eight
operators alone are phenomenologically allowed in all flavour channels and
shown to require at least two new mediator particles. The new couplings must
obey general cancellation conditions both at the dimension six and eight
levels, which result from expressing the operators obtained from the mediator
analysis in terms of a complete basis of operators. We illustrate with one
example how to apply this information to model building.Comment: 34 pages, 4 figures, 5 tables. Final version in PR
X-ray observations and mass determinations in the cluster of galaxies Cl0024+17
We present a detailed analysis of the mass distribution in the rich and
distant cluster of galaxies Cl0024+17. X-ray data come from both a deep
ROSAT/HRI image of the field (Bohringer et al. 1999) and ASCA spectral data.
Using a wide field CCD image of the cluster, we optically identify all the
faint X-ray sources, whose counts are compatible with deep X-ray number counts.
In addition we marginally detect the X-ray counter-part of the gravitational
shear perturbation detected by Bonnet et al. (1994) at a 2.5 level. A
careful spectral analysis of ASCA data is also presented. In particular, we
extract a low resolution spectrum of the cluster free from the contamination by
a nearby point source located 1.2 arcmin from the center. The X-ray temperature
deduced from this analysis is keV at the 90%
confidence level. The comparison between the mass derived from a standard X-ray
analysis and from other methods such as the Virial Theorem or the gravitational
lensing effect lead to a mass discrepancy of a factor 1.5 to 3. We discuss all
the possible sources of uncertainties in each method of mass determination and
give some indications on the way to reduce them. A complementary study of
optical data is in progress and may solve the X-ray/optical discrepancy through
a better understanding of the dynamics of the cluster.Comment: Revised version, accepted in Astronomy and Astrophysics (Main
Journal). Few changes in the discussio
Single-dot spectroscopy via elastic single-electron tunneling through a pair of coupled quantum dots
We study the electronic structure of a single self-assembled InAs quantum dot
by probing elastic single-electron tunneling through a single pair of weakly
coupled dots. In the region below pinch-off voltage, the non-linear threshold
voltage behavior provides electronic addition energies exactly as the linear,
Coulomb blockade oscillation does. By analyzing it, we identify the s and p
shell addition spectrum for up to six electrons in the single InAs dot, i.e.
one of the coupled dots. The evolution of shell addition spectrum with magnetic
field provides Fock-Darwin spectra of s and p shell.Comment: 7 pages, 3 figures, Accepted for publication in Phys. Rev. Let
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