1,617 research outputs found
The ATLAS liquid argon hadronic end-cap calorimeter: construction and selected beam test results
ATLAS has chosen for its Hadronic End-Cap Calorimeter (HEC) the copper-liquid
argon sampling technique with flat plate geometry and GaAs pre-amplifiers in
the argon. The contruction of the calorimeter is now approaching completion.
Results of production quality checks are reported and their anticipated impact
on calorimeter performance discussed. Selected results, such as linearity,
electron and pion energy resolution, uniformity of energy response, obtained in
beam tests both of the Hadronic End-Cap Calorimeter by itself, and in the ATLAS
configuration where the HEC is in combination with the Electromagnetic End-Cap
Calorimeter (EMEC) are described.Comment: 4 pages, 2 figures,IPRD04 conferenc
Energy versus electron transfer in organic solar cells: a comparison of the photophysics of two indenofluorene: fullerene blend films
In this paper, we compare the photophysics and photovoltaic device performance of two indenofluorene based polymers: poly[2,8-(6,6,12,12-tetraoctylindenofluorene)-co-4,7-(2,1,3-benzothiodiazole] (IF8BT) and poly[2,8-(6,6,12,12-tetraoctylindenofluorene)-co-5,5-(40,70-di-2-thienyl-20,10,30-benzothiodiazole] (IF8TBTT) blended with [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Photovoltaic devices made with IF8TBTT exhibit greatly superior photocurrent generation and photovoltaic efficiency compared to those made with IF8BT. The poor device efficiency of IF8BT/PCBM devices is shown to result from efficient, ultrafast singlet FâŹorster energy transfer from IF8BT to PCBM, with the resultant PCBM singlet exciton lacking sufficient energy to drive charge photogeneration. The higher photocurrent generation observed for IF8TBTT/PCBM devices is shown to result from IF8TBTTâs relatively weak, red-shifted photoluminescence characteristics, which switches off the polymer to fullerene singlet energy transfer pathway. As a consequence, IF8TBTT singlet excitons are able to drive charge separation at the polymer/fullerene interface, resulting in efficient photocurrent generation. These results are discussed in terms of the impact of donor/acceptor energy transfer upon photophysics and energetics of charge photogeneration in organic photovoltaic\ud
devices. The relevance of these results to the design of polymers for organic photovoltaic applications is also discussed, particularly with regard to explaining why highly luminescent polymers developed for organic light emitting diode applications often give relatively poor performance in organic photovoltaic devices
Advanced simulation code for alpha spectrometry
A Monte Carlo code, known as AASI, is developed for simulating energy spectra
in alpha spectrometry. The code documented here is a comprehensive package
where all the major processes affecting the spectrum are included. A unique
feature of the code is its ability to take into account coincidences between
the particles emitted from the source. Simulations and measurements highlight
the importance of coincidences in high-resolution alpha spectrometry. To show
the validity of the simulated results, comparisons with measurements and other
simulation codes are presented.Comment: 21 pages, 4 figures, to be published in Nucl. Instr. and Meth.
Surface roughness interpretation of 730 kg days CRESST-II results
The analysis presented in the recent publication of the CRESST-II results
finds a statistically significant excess of registered events over known
background contributions in the acceptance region and attributes the excess to
a possible Dark Matter signal, caused by scattering of relatively light WIMPs.
We propose a mechanism which explains the excess events with ion sputtering
caused by 206Pb recoils and alpha particles from 210Po decay, combined with
realistic surface roughness effects.Comment: 15 pages, 6 figures. v2: corrected quenching factor discussion. v3:
corrected references. v4: added reference
A High-resolution Scintillating Fiber Tracker With Silicon Photomultiplier Array Readout
We present prototype modules for a tracking detector consisting of multiple
layers of 0.25 mm diameter scintillating fibers that are read out by linear
arrays of silicon photomultipliers. The module production process is described
and measurements of the key properties for both the fibers and the readout
devices are shown. Five modules have been subjected to a 12 GeV/c proton/pion
testbeam at CERN. A spatial resolution of 0.05 mm and light yields exceeding 20
detected photons per minimum ionizing particle have been achieved, at a
tracking efficiency of more than 98.5%. Possible techniques for further
improvement of the spatial resolution are discussed.Comment: 31 pages, 27 figures, pre-print version of an article published in
Nuclear Instruments and Methods in Physics Research Section A, Vol. 62
A Scintillating Fiber Tracker With SiPM Readout
We present a prototype for the first tracking detector consisting of 250
micron thin scintillating fibers and silicon photomultiplier (SiPM) arrays. The
detector has a modular design, each module consists of a mechanical support
structure of 10mm Rohacell foam between two 100 micron thin carbon fiber skins.
Five layers of scintillating fibers are glued to both top and bottom of the
support structure. SiPM arrays with a channel pitch of 250 micron are placed in
front of the fibers. We show the results of the first module prototype using
multiclad fibers of types Bicron BCF-20 and Kuraray SCSF-81M that were read out
by novel 32-channel SiPM arrays from FBK-irst/INFN Perugia as well as
32-channel SiPM arrays produced by Hamamatsu. A spatial resolution of 88 micron
+/- 6 micron at an average yield of 10 detected photons per minimal ionizig
particle has been achieved.Comment: 5 pages, 7 figures, submitted as proceedings to the 11th Topical
Seminar on Innovative Particle and Radiation Detectors (IPRD08
A new design for the CERN-Fr\'ejus neutrino Super Beam
We present an optimization of the hadron focusing system for a low-energy
high-intensity conventional neutrino beam (Super-Beam) proposed on the basis of
the HP-SPL at CERN with a beam power of 4 MW and an energy of 4.5 GeV. The far
detector would be a 440 kton Water Cherenkov detector (MEMPHYS) located at a
baseline of 130 km in the Fr\'ejus site. The neutrino fluxes simulation relies
on a new GEANT4 based simulation coupled with an optimization algorithm based
on the maximization of the sensitivity limit on the mixing angle.
A new configuration adopting a multiple horn system with solid targets is
proposed which improves the sensitivity to and the CP violating
phase .Comment: 11 pages, 18 figures, 2 table
Liquid Xenon Detectors for Positron Emission Tomography
PET is a functional imaging technique based on detection of annihilation
photons following beta decay producing positrons. In this paper, we present the
concept of a new PET system for preclinical applications consisting of a ring
of twelve time projection chambers filled with liquid xenon viewed by avalanche
photodiodes. Simultaneous measurement of ionization charge and scintillation
light leads to a significant improvement to spatial resolution, image quality,
and sensitivity. Simulated performance shows that an energy resolution of <10%
(FWHM) and a sensitivity of 15% are achievable. First tests with a prototype
TPC indicate position resolution <1 mm (FWHM).Comment: Paper presented at the International Nuclear Physics Conference,
Vancouver, Canada, 201
The ATLAS discovery potential for MSSM neutral Higgs bosons decaying to a mu+mu- pair in the mass range up to 130 GeV
Results are presented on the discovery potential for MSSM neutral Higgs
bosons in the Mh-{max}scenario. The region of large tan beta, between 15 and
50, and mass between ~ 95 and 130 GeV is considered in the framework of the
ATLAS experiment at the Large Hadron Collider (LHC), for a centre-of-mass
energy = 14 TeV. This parameter region is not fully covered by the present data
either from LEP or from Tevatron. The h/A bosons, supposed to be very close in
mass in that region, are studied in the channel h/A -> mu+mu- accompanied by
two b-jets. The study includes a method to control the most copious background,
Zo -> mu+mu- accompanied by two b-jets. A possible contribution of the H boson
to the signal is also considered
Evaluation of measurement accuracies of the Higgs boson branching fractions in the International Linear Collider
Precise measurement of Higgs boson couplings is an important task for
International Linear Collider (ILC) experiments and will facilitate the
understanding of the particle mass generation mechanism.
In this study, the measurement accuracies of the Higgs boson branching
fractions to the and quarks and gluons, , were evaluated with the full International Large
Detector model (\texttt{ILD\_00}) for the Higgs mass of 120 GeV at the
center-of-mass (CM) energies of 250 and 350 GeV using neutrino, hadronic and
leptonic channels and assuming an integrated luminosity of ,
and an electron (positron) beam polarization of -80% (+30%).
We obtained the following measurement accuracies of the Higgs cross section
times branching fraction () for decay
of the Higgs into , , and ; as 1.0%, 6.9%, and 8.5% at
a CM energy of 250 GeV and 1.0%, 6.2%, and 7.3% at 350 GeV, respectively.
After the measurement accuracy of the cross section ()
was corrected using the results of studies at 250 GeV and their extrapolation
to 350 GeV, the derived measurement accuracies of the branching fractions
() to , , and gg were 2.7%, 7.3%, and 8.9% at
a CM energy of 250 GeV and 3.6%, 7.2%, and 8.1% at 350 GeV, respectively.Comment: 15 pages, 6 figure
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