818 research outputs found
A Bayesian technique for improving the sensitivity of the atmospheric neutrino L/E analysis
This paper outlines a method for improving the precision of atmospheric
neutrino oscillation measurements. One experimental signature for these
oscillations is an observed deficit in the rate of charged-current
interactions with an oscillatory dependence on , where
is the neutrino propagation distance, and is the neutrino
energy. For contained-vertex atmospheric neutrino interactions, the
resolution varies significantly from event to event. The
precision of the oscillation measurement can be improved by incorporating
information on resolution into the oscillation analysis. In
the analysis presented here, a Bayesian technique is used to estimate the
resolution of observed atmospheric neutrinos on an
event-by-event basis. By separating the events into bins of
resolution in the oscillation analysis, a significant improvement in
oscillation sensitivity can be achieved.Comment: 12 pages, 7 figures, submitted to Nucl. Instrum. Methods A,
accompanies arXiv:1208.2915 [hep-ex
Atmospheric Neutrino Problem in Maximally-Mixed Three Generations of Neutrinos
Motivated by the indication that both the atmospheric and the solar neutrino
puzzles may simultaneously be solved by (vacuum as well as matter-induced
resonant) oscillations of two generations of neutrinos with large mixing, we
have analyzed the data on the atmospheric and solar neutrinos assuming that all
{\it three} neutrinos are maximally mixed. It is shown that the values of obtained from the two-generation analyses are still valid even in
the three-generation scheme, i.e. the two puzzles can be solved simultaneously
if for the atmospheric
neutrinos and for solar
neutrinos in the maximally mixed three-generation scheme.Comment: Revtex file, 11 pages + 3 figures (included). The postscript file of
text and figures is available at
ftp://toxd01.to.infn.it/pub/giunti/1994/dftt-54-94/dftt-54-94.ps.
Precise Calculation of the Relic Density of Kaluza-Klein Dark Matter in Universal Extra Dimensions
We revisit the calculation of the relic density of the lightest Kaluza-Klein
particle (LKP) in the model of Universal Extra Dimensions. The Kaluza-Klein
(KK) particle spectrum at level one is rather degenerate, and various
coannihilation processes may be relevant. We extend the calculation of
hep-ph/0206071 to include coannihilation processes with all level one KK
particles. In our computation we consider a most general KK particle spectrum,
without any simplifying assumptions. In particular, we do not assume a
completely degenerate KK spectrum and instead retain the dependence on each
individual KK mass. As an application of our results, we calculate the
Kaluza-Klein relic density in the Minimal UED model, turning on coannihilations
with all level one KK particles. We then go beyond the minimal model and
discuss the size of the coannihilation effects separately for each class of
level 1 KK particles. Our results provide the basis for consistent relic
density computations in arbitrarily general models with Universal Extra
Dimenions.Comment: 44 pages, 19 figures, typeset in JHEP styl
Gravitational Coupling and Dynamical Reduction of The Cosmological Constant
We introduce a dynamical model to reduce a large cosmological constant to a
sufficiently small value. The basic ingredient in this model is a distinction
which has been made between the two unit systems used in cosmology and particle
physics. We have used a conformal invariant gravitational model to define a
particular conformal frame in terms of large scale properties of the universe.
It is then argued that the contributions of mass scales in particle physics to
the vacuum energy density should be considered in a different conformal frame.
In this manner, a decaying mechanism is presented in which the conformal factor
appears as a dynamical field and plays a key role to relax a large effective
cosmological constant. Moreover, we argue that this model also provides a
possible explanation for the coincidence problem.Comment: To appear in GR
Filtering out the cosmological constant in the Palatini formalism of modified gravity
According to theoretical physics the cosmological constant (CC) is expected
to be much larger in magnitude than other energy densities in the universe,
which is in stark contrast to the observed Big Bang evolution. We address this
old CC problem not by introducing an extremely fine-tuned counterterm, but in
the context of modified gravity in the Palatini formalism. In our model the
large CC term is filtered out, and it does not prevent a standard cosmological
evolution. We discuss the filter effect in the epochs of radiation and matter
domination as well as in the asymptotic de Sitter future. The final expansion
rate can be much lower than inferred from the large CC without using a
fine-tuned counterterm. Finally, we show that the CC filter works also in the
Kottler (Schwarzschild-de Sitter) metric describing a black hole environment
with a CC compatible to the future de Sitter cosmos.Comment: 22 pages, 1 figure, discussion extended, references added, accepted
by Gen.Rel.Gra
Oviposition Preference and Offspring Performance In Container Breeding Mosquitoes: Evaluating the Effects of Organic Compounds and Laboratory Colonisation
1. The preference–performance hypothesis (PPH) predicts that organisms lacking parental care should oviposit in habitats that optimise offspring performance. Preference–performance relationships were investigated for the Asian tiger mosquito (Aedes albopictus Skuse) and the southern house mosquito (Culex quinquefasciatus Say) (Diptera: Culicidae), two medically important container-breeding species, in response to an organic chemical blend mimicking decaying plant matter. Additionally, the effects of long-term laboratory colonisation of Cx. quinquefasciatus using wild and laboratory strains were evaluated.
2. Oviposition bioassays were conducted by releasing gravid mosquitoes into field enclosures with automobile tires containing low and high concentrations of the chemical blend, and water controls. The offspring were then reared in water collected from the tires in which they were deposited.
3. Aedes albopictus and wild Cx. quinquefasciatus laid more eggs in the chemical blend than water controls but did not differentiate between the low and high concentrations. Conversely, laboratory Cx. quinquefasciatus only preferred the high concentration to the low concentration. No statistical associations between oviposition preference and larval survival were found, as the chemical blend did not affect survivorship of either species.
4. The oviposition preference for the chemical blend over water controls suggests that both species oviposit in the best available resource environment, but further studies are needed before conclusions regarding preference–performance relationships can be drawn.
5. It was found that long-term laboratory colonisation affects the oviposition behaviour in Cx. quinquefasciatus, suggesting that behavioural studies on laboratory strains are not always applicable to wild populations
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