869 research outputs found
SCINTILLA A European project for the development of scintillation detectors and new technologies for nuclear security
Europe monitors transits using radiation detectors to prevent illicit
trafficking of nuclear materials. The SCINTILLA project aims to develop a
toolbox of innovative technologies designed to address different usage cases.
This article will review the scope, approach, results of the first benchmark
campaign and future plans of the SCINTILLA project.Comment: To appear on the Proceedings of the 13th ICATPP Conference on
Astroparticle, Particle, Space Physics and Detectors for Physics
Applications, Villa Olmo (Como, Italy), 23--27 October, 2013, to be published
by World Scientific (Singapore
The Heavy Photon Search test detector
The Heavy Photon Search (HPS), an experiment to search for a hidden sector photon in fixed target electroproduction, is preparing for installation at the Thomas Jefferson National Accelerator Facility (JLab) in the Fall of 2014. As the first stage of this project, the HPS Test Run apparatus was constructed and operated in 2012 to demonstrate the experiment\u27s technical feasibility and to confirm that the trigger rates and occupancies are as expected. This paper describes the HPS Test Run apparatus and readout electronics and its performance. In this setting, a heavy photon can be identified as a narrow peak in the e(+)e(-) invariant mass spectrum above the trident background or as a narrow invariant mass peak with a decay vertex displaced from the production target, so charged particle tracking and vertexing are needed for its detection. In the HPS Test Run, charged particles are measured with a compact forward silicon microstrip tracker inside a dipole magnet. Electromagnetic showers are detected in a PbW0(4) crystal calorimeter situated behind the magnet, and are used to trigger the experiment and identify electrons and positrons. Both detectors are placed close to the beam line and split top bottom. This arrangement provides sensitivity to low mass heavy photons, allows clear passage of the unscattered beam, and avoids the spray of degraded electrons coming from the target. The discrimination between prompt and displaced e(+)e(-) pairs requires the first layer of silicon sensors be placed only 10 cm downstream of the target. The expected signal is small, and the trident background huge, so the experiment requires very large statistics. Accordingly, the HPS Test Run utilizes high-rate readout and data acquisition electronics and a fast trigger to exploit the essentially 100% duty cycle of the CEBAF accelerator at JLab. (C) 2014 The Authors. Published by Elsevier B.V
Spin observables for pion photoproduction on the deuteron in the (1232)-resonance region
Spin observables for the three charge states of the pion for the pion
photoproduction reaction on the deuteron, , with polarized
photon beam and/or oriented deuteron target are predicted. For the beam-target
double-spin asymmetries, it is found that only the longitudinal asymmetries
and do not vanish, whereas all the circular
and the other longitudinal asymmetries do vanish. The sensitivity of spin
observables to the model deuteron wave function is investigated. It has been
found that only and are sensitive to the model deuteron wave
function, in particular in the case of -production above the
-region, and that other asymmetries are not.Comment: 16 pages, 8 figures, accepted for publication in J. Phys. G: Nucl.
Part. Phy
Spin Sum Rules and the Strong Coupling Constant at large distance
We present recent results on the Bjorken and the generalized forward spin
polarizability sum rules from Jefferson Lab Hall A and CLAS experiments,
focusing on the low part of the measurements. We then discuss the
comparison of these results with Chiral Perturbation theory calculations. In
the second part of this paper, we show how the Bjorken sum rule with its
connection to the Gerasimov-Drell-Hearn sum, allows us to conveniently define
an effective coupling for the strong force at all distances.Comment: Contribution to proceedings for the Workshop on Spin Structure at
Long Distance (Newport News, March 2009
Photoproduction of K+ K- Meson Pairs on the Proton
The exclusive reaction γp → pK+K− was studied in the photon energy range 3.0–3.8 GeV and momentum transfer range 0.6 \u3c −t\u3c 1.3 GeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20 pb−1. The reaction was isolated by detecting the K+ and the proton in CLAS, and reconstructing the K− via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the ϕ meson in the P wave, evidence for S − P interference was found. The differential production cross sections dσ=dt for individual waves in the mass range of the ϕ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the t-dependent cross section of the S-wave contribution to the elastic K+K− photoproduction has been measured
Systematic Regge theory analysis of omega photoproduction
Systematic analysis of available data for -meson photoproduction is
given in frame of Regge theory. At photon energies above 20 GeV the
reaction is entirely dominated by Pomeron exchange.
However, it was found that Pomeron exchange model can not reproduce the
and data at high energies
simultaneously with the same set of parameters. The comparison between
and data indicates a large room for meson exchange contribution to
-meson photoproduction at low energies. It was found that at low
energies the dominant contribution comes from and -meson exchanges.
There is smooth transition between the meson exchange model at low energies and
Regge theory at high energies.Comment: 7 pages, 8 figures, revtex
Dark photon production through positron annihilation in beam-dump experiments
High energy positron annihilation is a viable mechanism to produce dark
photons (). This reaction plays a significant role in beam-dump
experiments using experiments using multi-GeV electron-beams on thick targets
by enhancing the sensitivity to production. The positrons produced
by the electromagnetic shower can produce an via non-resonant () and resonant ()
annihilation on atomic electrons. For visible decays, the contribution of
resonant annihilation results in a larger sensitivity with respect to limits
derived by the commonly used -strahlung in certain kinematic regions.
When included in the evaluation of the E137 beam-dump experiment reach,
positron annihilation pushes the current limit on downwards by a
factor of two in the range 33 MeV/c MeV/c.Comment: 9 pages, 7 figure
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