77 research outputs found
Observation of exclusive DVCS in polarized electron beam asymmetry measurements
We report the first results of the beam spin asymmetry measured in the
reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry
with a sin(phi) modulation is observed, as predicted for the interference term
of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The
amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and
leading-twist pQCD, the alpha is directly proportional to the imaginary part of
the DVCS amplitude.Comment: 6 pages, 5 figure
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
tex
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV
Differential cross sections for the reaction gamma p -> eta-prime p have been
measured with the CLAS spectrometer and a tagged photon beam with energies from
1.527 to 2.227 GeV. The results reported here possess much greater accuracy
than previous measurements. Analyses of these data indicate for the first time
the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710)
resonances, known to couple strongly to the eta N channel in photoproduction on
the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure
Measurement of the Deuteron Structure Function F2 in the Resonance Region and Evaluation of Its Moments
Inclusive electron scattering off the deuteron has been measured to extract
the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer
(CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement
covers the entire resonance region from the quasi-elastic peak up to the
invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum
transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous
measurements of the proton structure function F2 and cover a similar
two-dimensional region of Q2 and Bjorken variable x. Determination of the
deuteron F2 over a large x interval including the quasi-elastic peak as a
function of Q2, together with the other world data, permit a direct evaluation
of the structure function moments for the first time. By fitting the Q2
evolution of these moments with an OPE-based twist expansion we have obtained a
separation of the leading twist and higher twist terms. The observed Q2
behaviour of the higher twist contribution suggests a partial cancellation of
different higher twists entering into the expansion with opposite signs. This
cancellation, found also in the proton moments, is a manifestation of the
"duality" phenomenon in the F2 structure function
First measurement of direct photoproduction on the proton
We report on the results of the first measurement of exclusive
meson photoproduction on protons for GeV and GeV. Data were collected with the CLAS detector at the Thomas
Jefferson National Accelerator Facility. The resonance was detected via its
decay in the channel by performing a partial wave analysis of the
reaction . Clear evidence of the meson
was found in the interference between and waves at GeV. The -wave differential cross section integrated in the mass range of
the was found to be a factor of 50 smaller than the cross section
for the meson. This is the first time the meson has been
measured in a photoproduction experiment
Exclusive meson electroproduction from hydrogen at CLAS
The longitudinal and transverse components of the cross section for the reaction were measured in Hall B at Jefferson
Laboratory using the CLAS detector. The data were taken with a 4.247 GeV
electron beam and were analyzed in a range of from 0.2 to 0.6 and of
from 1.5 to 3.0 GeV. The data are compared to a Regge model based on
effective hadronic degrees of freedom and to a calculation based on Generalized
Parton Distributions. It is found that the transverse part of the cross section
is well described by the former approach while the longitudinal part can be
reproduced by the latter.Comment: 6 pages, 4 figure
Beam Spin Asymmetries in DVCS with CLAS at 4 .8 GeV
We report measurements of the beam spin asymmetry in Deeply Virtual Compton
Scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector
at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin
asymmetry has been measured in a wide range of kinematics, 1(GeV/c)
(GeV/c), , and 0.1 (GeV/c)
(GeV/c), using the reaction \pEpX. The number of
H and H events are separated in
each bin by a fit to the line shape of the H
distribution. The validity of the method was studied in detail using
experimental and simulated data. It was shown, that with the achieved missing
mass squared resolution and the available statistics, the separation of DVCS-BH
and events can reliably be done with less than 5% uncertainty. The
- and -dependences of the moments of the asymmetry are
extracted and compared with theoretical calculations
Modulating mitophagy in mitochondrial disease
Mitochondrial diseases may result from mutations in the maternally-inherited mitochondrial DNA (mtDNA) or from mutations in nuclear genes encoding mitochondrial proteins. Their bi-genomic nature makes mitochondrial diseases a very heterogeneous group of disorders that can present at any age and can affect any type of tissue. The autophagic-lysosomal degradation pathway plays an important role in clearing dysfunctional and redundant mitochondria through a specific quality control mechanism termed mitophagy. Mitochondria could be targeted for autophagic degradation for a variety of reasons including basal turnover for recycling, starvation induced degradation, and degradation due to damage. While the core autophagic machinery is highly conserved and common to most pathways, the signaling pathways leading to the selective degradation of damaged mitochondria are still not completely understood. Type 1 mitophagy due to nutrient starvation is dependent on PI3K (phosphoinositide 3-kinase) for autophagosome formation but independent of mitophagy proteins, PINK1 (PTEN-induced putative kinase 1) and Parkin. Whereas type 2 mitophagy that occurs due to damage is dependent on PINK1 and Parkin but does not require PI3K. Autophagy and mitophagy play an important role in human disease and hence could serve as therapeutic targets for the treatment of mitochondrial as well as neurodegenerative disorders. Therefore, we reviewed drugs that are known modulators of autophagy (AICAR and metformin) and may effect this by activating the AMP-activated protein kinase signaling pathways. Furthermore, we reviewed data available on supplements, such as Coenzyme Q and the quinone idebenone, that we assert rescue increased mitophagy in mitochondrial disease by benefiting mitochondrial function
Accelerated simulation technique for low bit error probability estimation of rapid single flux quantum logic cells
The elevated operating temperatures of high-Tc superconductor (HTS) rapid single flux quantum (RSFQ) logic cells lead to higher thermal noise and this can be a major limiting factor in the development of working circuits of this kind. Determining the thermally induced bit error probability (BEP) of a circuit is therefore extremely important. If the BEP of a circuit is high enough it can be directly measured by running a circuit simulation over many clock cycles and counting the faulty bits. However, the BEP's required are very low and these simulations take enormous amounts of time. We propose a general method that can be applied to any circuit, to quickly and easily determine its BEP, without requiring the identification of any specific error-prone junctions or the understanding, application and solving of any complicated and computationally intensive mathematical formulas. By varying the temperature that a circuit is simulated at, the amount of noise introduced into the system can be controlled: the higher the temperature, the more noise introduced, and the higher the observed BEP. The BEP is measured at various higher-than-normal temperatures where it can be measured quickly and relatively accurately, and a parametric model is then fitted to the data collected that describes the BEP as a function of temperature. Extrapolation of this model estimates the BEP at the required operating temperature. © 2007 IEEE.Conference Pape
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