511 research outputs found
Transparency of 0.2% GdCl3 Doped Water in a Stainless Steel Test Environment
The possibility of neutron and neutrino detection using water Cerenkov
detectors doped with gadolinium holds the promise of constructing very large
high-efficiency detectors with wide-ranging application in basic science and
national security. This study addressed a major concern regarding the
feasibility of such detectors: the transparency of the doped water to the
ultraviolet Cerenkov light. We report on experiments conducted using a 19-meter
water transparency measuring instrument and associated materials test tank.
Sensitive measurements of the transparency of water doped with 0.2% GdCl3 at
337nm, 400nm and 420nm were made using this instrument. These measurements
indicate that GdCl3 is not an appropriate dopant in stainless steel constructed
water Cerenkov detectors.Comment: 17 pages, 11 figures, corrects typos, changes formatting, adds error
bars to figure
Evidence for Mikheyev-Smirnov-Wolfenstein effects in solar neutrino flavor transitions
We point out that the recent data from the Sudbury Neutrino Observatory,
together with other relevant measurements from solar and reactor neutrino
experiments, convincingly show that the flavor transitions of solar neutrinos
are affected by Mikheyev-Smirnov-Wolfenstein (MSW) effects. More precisely, one
can safely reject the null hypothesis of no MSW interaction energy in matter,
despite the fact that the interaction amplitude (formally treated as a free
parameter) is still weakly constrained by the current phenomenology. Such a
constraint can be improved, however, by future data from the KamLAND
experiment. In the standard MSW case, we also perform an updated analysis of
two-family active oscillations of solar and reactor neutrinos.Comment: 8 pages + 5 figyre
Weak and Electromagnetic Nuclear Decay Signatures for Neutrino Reactions in SuperKamiokande
We suggest the study of events in the SuperKamiokande neutrino data due to
charged- and neutral-current neutrino reactions followed by weak and/or
electromagnetic decays of struck nuclei and fragments thereof. This study could
improve the prospects of obtaining evidence for production from oscillations and could augment the data sample used to disfavor
oscillations.Comment: 7 pages, latex, to appear in Phys. Rev. Let
Neutrino Masses, Mixing and Oscillations
Basics of neutrino oscillations is discussed. Importance of time-energy
uncertainty relation is stressed. Neutrino oscillations in the leading
approximation and evidence for neutrino oscillations are briefly summarized.Comment: A report at the International School of Nuclear Physics ``Neutrino in
Cosmology, in Astro, Particle and Nuclear Physics'' Erice, Italy, Sept.
16-24, 200
Outer Membrane Vesicles of Helicobacter pylori TK1402 are Involved in Biofilm Formation
<p>Abstract</p> <p>Background</p> <p><it>Helicobacter pylori </it>forms biofilms on glass surfaces at the air-liquid interface in <it>in vitro </it>batch cultures; however, biofilms of <it>H. pylori </it>have not been well characterized. In the present study, we analyzed the ability of <it>H. pylori </it>strains to form biofilms and characterized the underlying mechanisms of <it>H. pylori </it>biofilm formation.</p> <p>Results</p> <p>Strain TK1402 showed strong biofilm forming ability relative to the other strains in Brucella broth supplemented with 7% FCS. The strong biofilm forming ability of TK1402 is reflected the relative thickness of the biofilms. In addition, outer membrane vesicles (OMV) were detected within the matrix of only the TK1402 biofilms. Biofilm formation was strongly correlated with the production of OMV in this strain. We further observed that strain TK1402 did not form thick biofilms in Brucella broth supplemented with 0.2% β-cyclodextrin. However, the addition of the OMV-fraction collected from TK1402 could enhance biofilm formation.</p> <p>Conclusion</p> <p>The results suggested that OMV produced from TK1402 play an important role in biofilm formation in strain TK1402.</p
Minimalistic Neutrino Mass Model
We consider the simplest model which solves the solar and atmospheric
neutrino puzzles, in the sense that it contains the smallest amount of beyond
the Standard Model ingredients. The solar neutrino data is accounted for by
Planck-mass effects while the atmospheric neutrino anomaly is due to the
existence of a single right-handed neutrino at an intermediate mass scale
between 10^9 GeV and 10^14 GeV. Even though the neutrino mixing angles are not
exactly predicted, they can be naturally large, which agrees well with the
current experimental situation. Furthermore, the amount of lepton asymmetry
produced in the early universe by the decay of the right-handed neutrino is
very predictive and may be enough to explain the current baryon-to-photon ratio
if the right-handed neutrinos are produced out of thermal equilibrium. One
definitive test for the model is the search for anomalous seasonal effects at
Borexino.Comment: 19 pages, 3 figures, references added, results unchange
Neutral-Current Atmospheric Neutrino Flux Measurement Using Neutrino-Proton Elastic Scattering in Super-Kamiokande
Recent results show that atmospheric oscillate with eV and , and that
conversion into is strongly disfavored. The Super-Kamiokande (SK)
collaboration, using a combination of three techniques, reports that their data
favor over . This distinction
is extremely important for both four-neutrino models and cosmology. We propose
that neutrino-proton elastic scattering () in water
\v{C}erenkov detectors can also distinguish between active and sterile
oscillations. This was not previously recognized as a useful channel since only
about 2% of struck protons are above the \v{C}erenkov threshold. Nevertheless,
in the present SK data there should be about 40 identifiable events. We show
that these events have unique particle identification characteristics, point in
the direction of the incoming neutrinos, and correspond to a narrow range of
neutrino energies (1-3 GeV, oscillating near the horizon). This channel will be
particularly important in Hyper-Kamiokande, with times higher rate.
Our results have other important applications. First, for a similarly small
fraction of atmospheric neutrino quasielastic events, the proton is
relativistic. This uniquely selects (not ) events,
useful for understanding matter effects, and allows determination of the
neutrino energy and direction, useful for the dependence of oscillations.
Second, using accelerator neutrinos, both elastic and quasielastic events with
relativistic protons can be seen in the K2K 1-kton near detector and MiniBooNE.Comment: 10 pages RevTeX, 8 figure
Properties of Fermion Mixings in Intersecting D-brane Models
We consider the Yukawa couplings for quarks and leptons in the context of
Pati-Salam model using intersecting D-brane models where the Yukawa coupling
matrices are rank one in a simple choice of family replication. The CKM mixings
can be explained by perturbing the rank 1 matrix using higher order terms
involving new Higgs fields available in the model. We show that the near
bi-large neutrino mixing angles can be naturally explained, choosing the light
neutrino mass matrix to be type II seesaw dominant. The predicted value of
U_{e3} is in the range \simeq 0.05-0.15. In the quark sector, V_{cb} is
naturally close to the strange/bottom quark mass ratio and we obtain an
approximate relation V_{ub} V_{cb} \simeq (m_s/m_b)^2 V_{us}. The geometrical
interpretations of the neutrino mixings are also discussed.Comment: 17 pages, 3 figure
Total neutrino and antineutrino nuclear cross sections around 1 GeV
We investigate neutrino-nucleus interactions at energies around 1 GeV. In
this regime, the main contributions to the cross sections come from
quasi-elastic and production processes. Our formalism, based on the
Impulse Approximation is well suited to describe both types of interactions. We
focus on a series of important nuclear effects in the interaction of electron
neutrinos with , also relevant to future -Beams. Our results
show that the Fermi gas model, widely used in data analysis of neutrino
experiments, overestimates the total cross sections by as much as 20 %.Comment: 30 pages, 15 figure
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