888 research outputs found
Living between languages: The politics of translation in Leila Aboulela’s Minaret and Xiaolu Guo’s A Concise Chinese-English Dictionary for Lovers
This is the author's final draft post-refereeing as published in The Journal of Commonwealth Literature 2012 47: 207 DOI:10.1177/0021989412440433. The online version of this article can be found at: http://jcl.sagepub.com/content/47/2/20
Inclusive Dielectron Cross Sections in p+p and p+d Interactions at Beam Energies from 1.04 to 4.88 GeV
Measurements of dielectron production in p+p and p+d collisions with beam
kinetic energies from 1.04 to 4.88 GeV are presented. The differential cross
section is presented as a function of invariant pair mass, transverse momentum,
and rapidity. The shapes of the mass spectra and their evolution with beam
energy provide information about the relative importance of the various
dielectron production mechanisms in this energy regime. The p+d to p+p ratio of
the dielectron yield is also presented as a function of invariant pair mass,
transverse momentum, and rapidity. The shapes of the transverse momentum and
rapidity spectra from the p+d and p+p systems are found to be similar to one
another for each of the beam energies studied. The beam energy dependence of
the integrated cross sections is also presented.Comment: 15 pages and 16 figure
Dielectron Cross Section Measurements in Nucleus-Nucleus Reactions at 1.0 A GeV
We present measured dielectron production cross sections for Ca+Ca, C+C,
He+Ca, and d+Ca reactions at 1.0 A GeV. Statistical uncertainties and
systematic effects are smaller than in previous DLS nucleus-nucleus data. For
pair mass < 0.35 GeV/c2 : 1) the Ca+Ca cross section is larger than the
previous DLS measurement and current model results, 2) the mass spectra suggest
large contributions from pi0 and eta Dalitz decays, and 3) dsigma/dM is
proportional to ApAt. For M > 0.5 GeV/c2 the Ca+Ca to C+C cross section ratio
is significantly larger than the ratio of ApAt values.Comment: Submitted to Physical Review Letters. Further analysis information
will be posted on our web pages -- http://macdls.lbl.gov Figure 1 has been
redrawn to make more legible. Text modified to support redrawn figur
NLO corrections to ultra-high energy neutrino-nucleon scattering, shadowing and small x
We reconsider the Standard Model interactions of ultra-high energy neutrinos
with matter. The next to leading order QCD corrections are presented for
charged-current and neutral-current processes. Contrary to popular
expectations, these corrections are found to be quite substantial, especially
for very large (anti-) neutrino energies. Hence, they need to be taken into
account in any search for new physics effects in high-energy neutrino
interactions. In our extrapolation of the parton densities to kinematical
regions as yet unexplored directly in terrestrial accelerators, we are guided
by double asymptotic scaling in the large Q^2 and small Bjorken x region and to
models of saturation in the low Q^2 and low x regime. The sizes of the
consequent uncertainties are commented upon. We also briefly discuss some
variables which are insensitive to higher order QCD corrections and are hence
suitable in any search for new physics.Comment: 21 pages, LaTeX2e, uses JHEP3.cls (included), 8 ps files for figures
published versio
The Air Microwave Yield (AMY) experiment - A laboratory measurement of the microwave emission from extensive air showers
The AMY experiment aims to measure the microwave bremsstrahlung radiation
(MBR) emitted by air-showers secondary electrons accelerating in collisions
with neutral molecules of the atmosphere. The measurements are performed using
a beam of 510 MeV electrons at the Beam Test Facility (BTF) of Frascati INFN
National Laboratories. The goal of the AMY experiment is to measure in
laboratory conditions the yield and the spectrum of the GHz emission in the
frequency range between 1 and 20 GHz. The final purpose is to characterise the
process to be used in a next generation detectors of ultra-high energy cosmic
rays. A description of the experimental setup and the first results are
presented.Comment: 3 pages -- EPS-HEP'13 European Physical Society Conference on High
Energy Physics (July, 18-24, 2013) at Stockholm, Swede
The MIDAS telescope for microwave detection of ultra-high energy cosmic rays
We present the design, implementation and data taking performance of the
MIcrowave Detection of Air Showers (MIDAS) experiment, a large field of view
imaging telescope designed to detect microwave radiation from extensive air
showers induced by ultra-high energy cosmic rays. This novel technique may
bring a tenfold increase in detector duty cycle when compared to the standard
fluorescence technique based on detection of ultraviolet photons. The MIDAS
telescope consists of a 4.5 m diameter dish with a 53-pixel receiver camera,
instrumented with feed horns operating in the commercial extended C-Band (3.4
-- 4.2 GHz). A self-trigger capability is implemented in the digital
electronics. The main objectives of this first prototype of the MIDAS telescope
- to validate the telescope design, and to demonstrate a large detector duty
cycle - were successfully accomplished in a dedicated data taking run at the
University of Chicago campus prior to installation at the Pierre Auger
Observatory.Comment: 13 pages, 18 figure
Neutrino searches at the Pierre Auger Observatory
The surface detector array of the Pierre Auger Observatory is sensitive to ultra-high energy neutrinos in the cosmic radiation. Neutrinos can interact in the atmosphere close to ground (down-going) and, for tau neutrinos, through the Earth-skimming mechanism (up-going) where a tau lepton is produced in the Earth crust that can emerge and decay in the atmosphere. Both types of neutrino-induced events produce an inclined particle air shower that can be identified by the presence of a broad time structure of signals in the water-Cherenkov detectors. We discuss the neutrino identification criteria used and present the corresponding limits on the diffuse and point-like source fluxes
The East-West method: an exposure-independent method to search for large scale anisotropies of cosmic rays
The measurement of large scale anisotropies in cosmic ray arrival directions
at energies above 10^13 eV is performed through the detection of Extensive Air
Showers produced by cosmic ray interactions in the atmosphere. The observed
anisotropies are small, so accurate measurements require small statistical
uncertainties, i.e. large datasets. These can be obtained by employing ground
detector arrays with large extensions (from 10^4 to 10^9 m^2) and long
operation time (up to 20 years). The control of such arrays is challenging and
spurious variations in the counting rate due to instrumental effects (e.g. data
taking interruptions or changes in the acceptance) and atmospheric effects
(e.g. air temperature and pressure effects on EAS development) are usually
present. These modulations must be corrected very precisely before performing
standard anisotropy analyses, i.e. harmonic analysis of the counting rate
versus local sidereal time. In this paper we discuss an alternative method to
measure large scale anisotropies, the "East-West method", originally proposed
by Nagashima in 1989. It is a differential method, as it is based on the
analysis of the difference of the counting rates in the East and West
directions. Besides explaining the principle, we present here its mathematical
derivation, showing that the method is largely independent of experimental
effects, that is, it does not require corrections for acceptance and/or for
atmospheric effects. We explain the use of the method to derive the amplitude
and phase of the anisotropy and we demonstrate its power under different
conditions of detector operation
Nuclear Recoil Identification in a Scientific Charge-Coupled Device
Charge-coupled devices (CCDs) are a leading technology in direct dark matter
searches because of their eV-scale energy threshold and high spatial
resolution. The sensitivity of future CCD experiments could be enhanced by
distinguishing nuclear recoil signals from electronic recoil backgrounds in the
CCD silicon target. We present a technique for event-by-event identification of
nuclear recoils based on the spatial correlation between the primary ionization
event and the lattice defect left behind by the recoiling atom, later
identified as a localized excess of leakage current under thermal stimulation.
By irradiating a CCD with an AmBe neutron source, we demonstrate
identification efficiency for nuclear recoils with energies keV,
where the ionization events were confirmed to be nuclear recoils from topology.
The technique remains fully efficient down to 90 keV, decreasing to 50 at 8
keV, and reaching () at 1.5--3.5 keV. Irradiation with a Na
-ray source shows no evidence of defect generation by electronic
recoils, with the fraction of electronic recoils with energies keV that
are spatially correlated with defects .Comment: 9 pages, 7 figure
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