2,957 research outputs found
Radiative tail from the quasielastic peak in deep inelastic scattering of polarized leptons off polarized He-3
The contribution of the radiative tail from the quasielastic peak to low
order radiative correction to deep inelastic scattering of polarized leptons by
polarized He was calculated within the sum rules formalism and -scaling
hypothesis. Numerical analysis was carried out under the conditions of HERMES
experiment.Comment: 10 pages, 3 figure
Higher twists in polarized DIS and the size of the constituent quark
The spontaneous breaking of chiral symmetry implies the presence of a
short-distance scale in the QCD vacuum, which phenomenologically may be
associated with the "size" of the constituent quark, rho ~ 0.3 fm. We discuss
the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon
operators determining the leading power (1/Q^2-) corrections to the moments of
the nucleon spin structure functions. We argue that the flavor-nonsinglet
twist-4 matrix element, f_2^{u - d}, has a sizable negative value of the order
rho^{-2}, due to the presence of sea quarks with virtualities ~ rho^{-2} in the
proton wave function. The twist-3 matrix element, d_2, is not related to the
scale rho^{-2}. Our arguments support the results of previous calculations of
the matrix elements in the instanton vacuum model. We show that this
qualitative picture is in agreement with the phenomenological higher-twist
correction extracted from an NLO QCD fit to the world data on g_1^p and g_1^n,
which include recent data from the Jefferson Lab Hall A and COMPASS
experiments. We comment on the implications of the short-distance scale rho for
quark-hadron duality and the x-dependence of higher-twist contributions.Comment: 8 pages, 4 figure
SoLid : Search for Oscillations with Lithium-6 Detector at the SCK-CEN BR2 reactor
Sterile neutrinos have been considered as a possible explanation for the recent reactor and Gallium anomalies arising from reanalysis of reactor flux and calibration data of previous neutrino experiments. A way to test this hypothesis is to look for distortions of the anti-neutrino energy caused by oscillation from active to sterile neutrino at close stand-off (similar to 6-8m) of a compact reactor core. Due to the low rate of anti-neutrino interactions the main challenge in such measurement is to control the high level of gamma rays and neutron background.
The SoLid experiment is a proposal to search for active-to-sterile anti-neutrino oscillation at very short baseline of the SCK center dot CEN BR2 research reactor.
This experiment uses a novel approach to detect anti-neutrino with a highly segmented detector based on Lithium-6. With the combination of high granularity, high neutron-gamma discrimination using 6LiF:ZnS(Ag) and precise localization of the Inverse Beta Decay products, a better experimental sensitivity can be achieved compared to other state-of-the-art technology. This compact system requires minimum passive shielding allowing for very close stand off to the reactor. The experimental set up of the SoLid experiment and the BR2 reactor will be presented. The new principle of neutrino detection and the detector design with expected performance will be described. The expected sensitivity to new oscillations of the SoLid detector as well as the first measurements made with the 8 kg prototype detector deployed at the BR2 reactor in 2013-2014 will be reported
Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton
Double-polarization observables in the reaction have been measured at . The experiment
was performed at the spectrometer setup of the A1 Collaboration using the 855
MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil
proton polarimeter. From the double-polarization observables the structure
function is extracted for the first time, with the value , using the low-energy theorem
for Virtual Compton Sattering. This structure function provides a hitherto
unmeasured linear combination of the generalized polarizabilities of the
proton
The HERMES Dual-Radiator Ring Imaging Cerenkov Detector
The construction and use of a dual radiator Ring Imaging Cerenkov(RICH)
detector is described. This instrument was developed for the HERMES experiment
at DESY which emphasizes measurements of semi-inclusive deep-inelastic
scattering. It provides particle identification for pions, kaons, and protons
in the momentum range from 2 to 15 GeV, which is essential to these studies.
The instrument uses two radiators, C4F10, a heavy fluorocarbon gas, and a wall
of silica aerogel tiles. The use of aerogel in a RICH detector has only
recently become possible with the development of clear, large homogeneous and
hydrophobic aerogel. A lightweight mirror was constructed using a newly
perfected technique to make resin-coated carbon-fiber surfaces of optical
quality. The photon detector consists of 1934 photomultiplier tubes for each
detector half, held in a soft steel matrix to provide shielding against the
residual field of the main spectrometer magnet.Comment: 25 pages, 23 figure
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