3,359 research outputs found
First operation of a double phase LAr Large Electron Multiplier Time Projection Chamber with a two-dimensional projective readout anode
We have previously reported on the construction and successful operation of
the novel double phase Liquid Argon Large Electron Multiplier Time Projection
Chamber (LAr LEM-TPC). This detector concept provides a 3D-tracking and
calorimetric device capable of adjustable charge amplification, a promising
readout technology for next-generation neutrino detectors and direct Dark
Matter searches. In this paper, we report on the first operation of a LAr
LEM-TPC prototype - with an active area of 1010 cm and 21 cm drift
length - equipped with a single 1 mm thick LEM amplifying stage and a two
dimensional projective readout anode. Cosmic muon events were collected, fully
reconstructed and used to characterize the performance of the chamber. The
obtained signals provide images of very high quality and the energy loss
distributions of minimum ionizing tracks give a direct estimate of the
amplification. We find that a stable gain of 27 can be achieved with this
detector configuration corresponding to a signal-over-noise ratio larger than
200 for minimum ionizing tracks. The decoupling of the amplification stage and
the use of the 2D readout anode offer several advantages which are described in
the text.Comment: 25 pages, 17 figure
THE INVESTMENT POTENTIAL OF THE TERRITORY AND METHODS OF ITS DETERMINATION
The article considers approaches to the definition of the investment potential of the area, and offers an original way of constructing outline map on the basis of the investment potential of the proposed investment index.В статье рассматриваются подходы к определению инвестиционного потенциала территории, и предлагается оригинальный способ построения карты-схемы инвестиционного потенциала на основе предложенного инвестиционного индекса.Сборник выпущен при поддержке Фонда содействия развитию УрФУ имени первого Президента России Б.Н. Ельцин
A search for light dark matter in XENON10 data
We report results of a search for light (<10 GeV) particle dark matter with
the XENON10 detector. The event trigger was sensitive to a single electron,
with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear
recoil energy. Considering spin-independent dark matter-nucleon scattering, we
exclude cross sections \sigma_n>3.5x10^{-42} cm^2, for a dark matter particle
mass m_{\chi}=8 GeV. We find that our data strongly constrain recent elastic
dark matter interpretations of excess low-energy events observed by CoGeNT and
CRESST-II, as well as the DAMA annual modulation signal.Comment: Manuscript identical to v2 (published version) but also contains
erratum. Note v3==v2 but without \linenumber
Hemilability of phosphine-thioether ligands coordinated to trinuclear Mo3S4 cluster and its effect on hydrogenation catalysis
Ligand-exchange reactions of [Mo3S4(tu)8(H2O)]Cl44H2O (tu = thiourea) with
(PhCH2CH2)2PCH2CH2SR ligands, where R = Ph (PS1), pentyl (PS2) or Pr (PS3) afford new
complexes isolated as [Mo3S4Cl3(PS1)3]PF6 ([1]PF6), [Mo3S4Cl3(PS2)3]PF6 ([2]PF6) and
[Mo3S4Cl3(PS3)3]PF6 ([3]PF6) salts in 30-50% yields as the major reaction products. The crystal
structures of [1]PF6 and [2]PF6 were determined by X-ray diffraction (XRD) analysis. Each of
the three phosphine-thioether ligands is coordinated in a bidentate chelating mode to a different
molybdenum atom of the Mo3S4 trinuclear cluster, herewith all the phosphorus atoms of the
phosphino-thioether ligand are located trans to the capping sulfur (3-S). A second product that
forms in the reaction of [Mo3S4(tu)8(H2O)]Cl44H2O with PS1 corresponds to the neutral
[Mo3S4Cl4(PS1)2(PS1*)] complex. Its XRD analysis reveals both bidentate (PS1) and
monodentate (PS1*) coordinating modes of the same ligand. In the latter mode the phosphinethioether
is coordinated to a Mo atom only via the P atom. All compounds were characterized by
1H, 31P{1H} NMR, electrospray-ionization (ESI) mass spectrometry and cyclic voltammetry
(CV). Reactions of [1]PF6, [2]PF6 and [3]PF6 with an excess of Bu4NCl in CD2Cl2 were followed
by 31P{1H} NMR. The spectra indicate equilibrium between cationic [Mo3S4Cl3(PSn)3]
+
and
neutral [Mo3S4Cl4(PSn)2(PSn*)] (n = 1, 2) species. The equilibrium constants were determined
as 2.5 ± 0.2103
, 43 ± 2 М
-1
and 30 ± 2 М
-1
(at 25°C) for [1]PF6, [2]PF6 and [3]PF6, indicating
quantitative differences in hemilabile behavior of the phosphino-thioether ligands, depending on
the substituent at sulfur. Clusters [1]PF6, [2]PF6 and [3]PF6 were tested as catalysts in reduction
of nitrobenzene to aniline with Ph2SiH2 under mild conditions. Significant differencies in the
catalytic activity were observed, which can be attributed to different hemilabile behavior of the
PS1 and PS2/PS3 ligands
Measurement of single electron emission in two-phase xenon
We present the first measurements of the electroluminescence response to the
emission of single electrons in a two-phase noble gas detector. Single
ionization electrons generated in liquid xenon are detected in a thin gas layer
during the 31-day background run of the ZEPLIN-II experiment, a two-phase xenon
detector for WIMP dark matter searches. Both the pressure dependence and
magnitude of the single-electron response are in agreement with previous
measurements of electroluminescence yield in xenon. We discuss different
photoionization processes as possible cause for the sample of single electrons
studied in this work. This observation may have implications for the design and
operation of future large-scale two-phase systems.Comment: 11 pages, 6 figure
Measurement of the decay form factors in the OKA experiment
A precise measurement of the vector and axial-vector form factors difference
in the decay is presented.
About 95K events of are selected in
the OKA experiment. The result is .
Both errors are smaller than in the previous measurements.Comment: 9 pages, 8 figure
Prospects for at CERN in NA62
The NA62 experiment will begin taking data in 2015. Its primary purpose is a
10% measurement of the branching ratio of the ultrarare kaon decay , using the decay in flight of kaons in an unseparated
beam with momentum 75 GeV/c.The detector and analysis technique are described
here.Comment: 8 pages for proceedings of 50 Years of CP
Single electron emission in two-phase xenon with application to the detection of coherent neutrino-nucleus scattering
We present an experimental study of single electron emission in ZEPLIN-III, a
two-phase xenon experiment built to search for dark matter WIMPs, and discuss
applications enabled by the excellent signal-to-noise ratio achieved in
detecting this signature. Firstly, we demonstrate a practical method for
precise measurement of the free electron lifetime in liquid xenon during normal
operation of these detectors. Then, using a realistic detector response model
and backgrounds, we assess the feasibility of deploying such an instrument for
measuring coherent neutrino-nucleus elastic scattering using the ionisation
channel in the few-electron regime. We conclude that it should be possible to
measure this elusive neutrino signature above an ionisation threshold of
3 electrons both at a stopped pion source and at a nuclear reactor.
Detectable signal rates are larger in the reactor case, but the triggered
measurement and harder recoil energy spectrum afforded by the accelerator
source enable lower overall background and fiducialisation of the active
volume
ChPT tests at the NA48 and NA62 experiments at CERN
The NA48/2 Collaboration at CERN has accumulated unprecedented statistics of
rare kaon decays in the Ke4 modes: Ke4(+-) ()
and Ke4(00) () with nearly one percent
background contamination. The detailed study of form factors and branching
rates, based on these data, has been completed recently. The results brings new
inputs to low energy strong interactions description and tests of Chiral
Perturbation Theory (ChPT) and lattice QCD calculations. In particular, new
data support the ChPT prediction for a cusp in the invariant mass
spectrum at the two charged pions threshold for Ke4(00) decay. New final
results from an analysis of about 400 rare
decay candidates collected by the NA48/2 and NA62 experiments at CERN during
low intensity runs with minimum bias trigger configurations are presented. The
results include a model-independent decay rate measurement and fits to ChPT
description.Comment: XIIth International Conference on Heavy Quarks and Leptons 2014,
Mainz, German
Recent NA48/2 and NA62 results
The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented
statistics of rare kaon decays in the modes: () and ()
with nearly one percent background contamination. It leads to the improved
measurement of branching fractions and detailed form factor studies. New final
results from the analysis of 381 rare decay
candidates collected by the NA48/2 and NA62 experiments at CERN are presented.
The results include a decay rate measurement and fits to Chiral Perturbation
Theory (ChPT) description.Comment: Prepared for the Proceedings of "Moriond QCD and High Energy
Interactions. March 22-29 2014." conferenc
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