747 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
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
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
New hadrons as ultra-high energy cosmic rays
Ultra-high energy cosmic ray (UHECR) protons produced by uniformly
distributed astrophysical sources contradict the energy spectrum measured by
both the AGASA and HiRes experiments, assuming the small scale clustering of
UHECR observed by AGASA is caused by point-like sources. In that case, the
small number of sources leads to a sharp exponential cutoff at the energy
E<10^{20} eV in the UHECR spectrum. New hadrons with mass 1.5-3 GeV can solve
this cutoff problem. For the first time we discuss the production of such
hadrons in proton collisions with infrared/optical photons in astrophysical
sources. This production mechanism, in contrast to proton-proton collisions,
requires the acceleration of protons only to energies E<10^{21} eV. The diffuse
gamma-ray and neutrino fluxes in this model obey all existing experimental
limits. We predict large UHE neutrino fluxes well above the sensitivity of the
next generation of high-energy neutrino experiments. As an example we study
hadrons containing a light bottom squark. These models can be tested by
accelerator experiments, UHECR observatories and neutrino telescopes.Comment: 17 pages, revtex style; v2: shortened, as to appear in PR
Ultra-High Energy Neutrino Fluxes and Their Constraints
Applying our recently developed propagation code we review extragalactic
neutrino fluxes above 10^{14} eV in various scenarios and how they are
constrained by current data. We specifically identify scenarios in which the
cosmogenic neutrino flux, produced by pion production of ultra high energy
cosmic rays outside their sources, is considerably higher than the
"Waxman-Bahcall bound". This is easy to achieve for sources with hard injection
spectra and luminosities that were higher in the past. Such fluxes would
significantly increase the chances to detect ultra-high energy neutrinos with
experiments currently under construction or in the proposal stage.Comment: 11 pages, 15 figures, version published in Phys.Rev.
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