1,408 research outputs found
Possible, alternative explanations of the T2K observation of the nu_e appearance from an initial nu_mu
An alternative explanation to the emergence of sin^2(2 theta_13) > 0 is
discussed. It is pointed out that the recorded T2K events might have been due
to some other new physics in the neutrino sector, related to the LSND/MiniBooNE
sterile neutrino anomalies, for which there is nowadays a growing evidence. The
presently running ICARUS detector with the CNGS beam will be able to
distinguish between these two possible sources of the effectComment: 5 pages, 1 figur
On particle production for high energy neutrino beams
Analytical formulae for the calculation of secondary particle yields in p-A
interactions are given. These formulae can be of great practical importance for
fast calculations of neutrino fluxes and for designing new neutrino beam-lines.
The formulae are based on a parameterization of the inclusive invariant cross
sections for secondary particle production measured in p-Be interactions. Data
collected in different energy ranges and kinematic regions are used. The
accuracy of the fit to the data with the empirical formulae adopted is within
the experimental uncertainties. Prescriptions to extrapolate this
parameterization to finite targets and to targets of different materials are
given. The results obtained are then used as an input for the simulation of
neutrino beams. We show that our approach describes well the main
characteristics of measured neutrino spectra at CERN. Thus it may be used in
fast simulations aiming at the optimisation of the proposed long-baseline
neutrino beams at CERN and FNAL. In particular we will show our predictions for
the CNGS beam from CERN to Gran Sasso.Comment: 18 pages, 10 figures. Submitted to The European Physics Journal
Genotypic and Phenotypic Heterogeneity in Alicyclobacillus acidoterrestris: A Contribution to Species Characterization.
Alicyclobacillus acidoterrestris is the main cause of most spoilage problems in fruit juices
and acidic products. Since soil borne species often contaminate fruit juices and do not need
strict extreme requirements for survival, it is a great concern to investigate whether and how
soil species could evolve from their ecological niches in microbial community to new environments as fruit juices. In this study, 23 isolates of thermo-acidophilic, spore-forming bacteria from soil were characterized by cultural and molecular methods. In addition, 2 strains
isolated from a spoilage incident in pear juice were typed. Strains phenotyping showed that
they could be grouped into 3 different clusters, and some isolates showed identical or quite
similar patterns. Analyzing pH and temperature ranges for growth, the majority of strains
were able to grow at values described for many species of Alicyclobacillus. Qualitative utilization of lysine, arginine and indole production from tryptophan revealed, for the first time,
deamination of lysine and decarboxylation of arginine. Resistance to 5% NaCl as well as
the ability to hydrolyze starch and gelatin, nitrate reduction, catalase and oxidase activities
confirmed literature evidences. Examining of 16S rRNA, showed that isolates were divided
into three blocks represented by effectively soil species and strains that are moving from
soil to other possible growing source characterized by parameters that could strongly influence bacterial survival. RAPD PCR technique evidenced a great variability in banding patterns and, although it was not possible to obtain genotypically well-distinguished groups, it
was feasible to appreciate genetic similarity between some strains. In conclusion, the investigation of a microbial community entails a combination of metagenomic and classic culturedependent approaches to expand our knowledge about Alicyclobacillus and to look for new
subspecies
Constant-q data representation in Neutron Compton scattering on the VESUVIO spectrometer
Standard data analysis on the VESUVIO spectrometer at ISIS is carried
out within the Impulse Approximation framework, making use of the West
scaling variable y. The experiments are performed using the
time-of-flight technique with the detectors positioned at constant
scattering angles. Line shape analysis is routinely performed in the
y-scaling framework, using two different (and equivalent) approaches:
(I) fitting the parameters of the recoil peaks directly to fixed-angle
time-of-flight spectral (2) transforming the time-of-flight spectra into
fixed-angle y spectra, referred to as the Neutron Compton Profiles, and
then fitting the line shape parameters. The present work shows that
scattering signals from different fixed-angle detectors can be collected
and rebinned to obtain Neutron Compton Profiles at constant wave vector
transfer, q, allowing for a suitable interpretation of data in terms of
the dynamical structure factor, S(q, w). The current limits of
applicability of such a procedure are discussed in terms of the
available q-range and relative uncertainties for the VESUVIO
experimental set up and of the main approximations involved. (C) 2008
Elsevier B.V. All rights reserved
Hybrid Superconducting Neutron Detectors
A new neutron detection concept is presented that is based on superconductive
niobium (Nb) strips coated by a boron (B) layer. The working principle of the
detector relies on the nuclear reaction 10B+n + 7Li ,
with and Li ions generating a hot spot on the current-biased Nb strip
which in turn induces a superconducting-normal state transition. The latter is
recognized as a voltage signal which is the evidence of the incident neutron.
The above described detection principle has been experimentally assessed and
verified by irradiating the samples with a pulsed neutron beam at the ISIS
spallation neutron source (UK). It is found that the boron coated
superconducting strips, kept at a temperature T = 8 K and current-biased below
the critical current Ic, are driven into the normal state upon thermal neutron
irradiation. As a result of the transition, voltage pulses in excess of 40 mV
are measured while the bias current can be properly modulated to bring the
strip back to the superconducting state, thus resetting the detector.
Measurements on the counting rate of the device are presented and the future
perspectives leading to neutron detectors with unprecedented spatial
resolutions and efficiency are highlighted.Comment: 8 pages 6 figure
A new search for anomalous neutrino oscillations at the CERN-PS
The LSND experiment has observed a 3.8 sigma excess of anti-nu_e events from
an anti-nu_mu beam coming from pions at rest. If confirmed, the LSND anomaly
would imply new physics beyond the standard model, presumably in the form of
some additional sterile neutrinos. The MiniBooNE experiment at FNAL-Booster has
further searched for the LSND anomaly. Above 475 MeV, the nu_e result is
excluding the LSND anomaly to about 1.6 sigma but it introduces an unexplained,
new 3.0 sigma anomaly at lower energies, down to 200 MeV. The nu_e data have so
far an insufficient statistics to be conclusive with LSND's anti-nu_e. The
present proposal at the CERN-PS is based on two strictly identical LAr-TPC
detectors in the near and far positions, respectively at 127 and 850 m from the
neutrino (or antineutrino) target and focussing horn, observing the
electron-neutrino signal. This project will benefit from the already developed
technology of ICARUS T600, well tested on surface in Pavia, without the need of
any major R&D activity and without the added problems of an underground
experiment (CNGS-2). The superior quality of the Liquid Argon imaging TPC and
its unique electron - pi-zero discrimination allow full rejection of the NC
background, without efficiency loss for electron neutrino detection. In two
years of exposure, the far detector mass of 600 tons and a reasonable
utilization of the CERN-PS with the refurbished previous TT7 beam line will
allow to collect about 10^6 charged current events, largely adequate to settle
definitely the LSND anomaly.Comment: 23 pages, 17 figures, added watermark, better referencin
Facility for fast neutron irradiation tests of electronics at the ISIS spallation neutron source
The VESUVIO beam line at the ISIS spallation neutron source was set up for neutron irradiation tests in the neutron energy range above 10 MeV. The neutron flux and energy spectrum were shown, in benchmark activation measurements, to provide a neutron spectrum similar to the ambient one at sea level, but with an enhancement in intensity of a factor of 107. Such conditions are suitable for accelerated testing of electronic components, as was demonstrated here by measurements of soft error rates in recent technology field programable gate arrays
Proton momentum distribution in a protein hydration shell
The momentum distribution of protons in the hydration shell of a
globular protein has been measured through deep inelastic neutron
scattering at 180 and 290 K, below and above the crossover temperature
T-c=1.23T(g), where T-g=219 K is the glass transition temperature. It is
found that the mean kinetic energy of the water hydrogens shows no
temperature dependence, but the measurements are accurate enough to
indicate a sensible change of momentum distribution and effective
potential felt by protons, compatible with the transition from a single
to a double potential well. This could support the presence of tunneling
effects even at room temperature, playing an important role in
biological function
Search for Neutron Flux Generation in a Plasma Discharge Electrolytic Cell
Following some recent unexpected hints of neutron production in setups like
high-voltage atmospheric discharges and plasma discharges in electrolytic
cells, we present a measurement of the neutron flux in a configuration similar
to the latter. We use two different types of neutron detectors,
poly-allyl-diglicol-carbonate (PADC, aka CR-39) tracers and Indium disks. At
95% C.L. we provide an upper limit of 1.5 neutrons cm^-2 s^-1 for the thermal
neutron flux at ~5 cm from the center of the cell. Allowing for a higher energy
neutron component the largest allowed flux is 64 neutrons cm^-2 s^-1. This
upper limit is two orders of magnitude smaller than what previously claimed in
an electrolytic cell plasma discharge experiment. Furthermore the behavior of
the CR-39 is discussed to point our possible sources of spurious signals.Comment: 4 pages, 3 figure
- …