419 research outputs found
Scaling in many-body systems and proton structure function
The observation of scaling in processes in which a weakly interacting probe
delivers large momentum to a many-body system simply reflects the
dominance of incoherent scattering off target constituents. While a suitably
defined scaling function may provide rich information on the internal dynamics
of the target, in general its extraction from the measured cross section
requires careful consideration of the nature of the interaction driving the
scattering process. The analysis of deep inelastic electron-proton scattering
in the target rest frame within standard many-body theory naturally leads to
the emergence of a scaling function that, unlike the commonly used structure
functions and , can be directly identified with the intrinsic proton
response.Comment: 11 pages, 4 figures. Proceedings of the 11th Conference on Recent
Progress in Many-Body Theories, Manchester, UK, July 9-13 200
Radiative Corrections to Electron-Proton Scattering
The radiative corrections to elastic electron-proton scattering are analyzed
in a hadronic model including the finite size of the nucleon. For initial
electron energies above 8 GeV and large scattering angles, the proton vertex
correction in this model increases by at least two percent the overall factor
by which the one-photon exchange (Rosenbluth) cross section must be multiplied.
The contribution of soft photon emission is calculated exactly. Comparison is
made with the generally used expressions previously obtained by Mo and Tsai.
Results are presented for some kinematics at high momentum transfer.Comment: 31 pages, 4 figure
The dependence of the measured asymmetry : the test of the Bjorken sum rule
We analyse the proton and deutron data on spin dependent asymmetry
supposing the DIS structure functions and
have the similar -dependence. As a result, we have obtained
that at and
at , what is in the
best agreement with the Bjorken sum rule predictions.Comment: LaTeX, 5 pages, no figures, to be published in JETP Letter
DGLAP evolution extends the triple pole pomeron fit
We show that the triple pole pomeron model \cite{CMS} provides an initial
condition for a DGLAP evolution \cite{DGLAP} that produces a fit to high
experimental DIS data. We obtain good for initial scales down to 3
GeV. Values of the initial scale smaller than 1.45 GeV are ruled out at
the 90% confidence level.Comment: 8 pages, 6 figures, uses RevTex 4. Typos corrected, some points
clarifed and 1 figure adde
Higher Twist, Scaling, and Effective for Lepton Scattering in the Few GeV Region
We use a new scaling variable , and add low modifications to
GRV98 leading order parton distribution functions such that they can be used to
model electron, muon and neutrino inelastic scattering cross sections (and also
photoproduction) at both very low and high energies.Comment: 6 pages, 3 figures. To be published in J. Phys. G (Conf. Proceedings)
based on two talks by Arie Bodek at the NuFact conference, Imperial
College, London, England, July 200
Measurement of the proton and deuteron structure functions, F2p and F2d, and of the ratio sigma(L)/sigma(T)
The muon-proton and muon-deuteron inclusive deep inelastic scattering cross
sections were measured in the kinematic range 0.002 < x < 0.60 and 0.5 < Q2 <
75 GeV2 at incident muon energies of 90, 120, 200 and 280 GeV. These results
are based on the full data set collected by the New Muon Collaboration,
including the data taken with a small angle trigger. The extracted values of
the structure functions F2p and F2d are in good agreement with those from other
experiments. The data cover a sufficient range of y to allow the determination
of the ratio of the longitudinally to transversely polarised virtual photon
absorption cross sections, R= sigma(L)/sigma(T), for 0.002 < x < 0.12 . The
values of R are compatible with a perturbative QCD prediction; they agree with
earlier measurements and extend to smaller x.Comment: In this replacement the erroneously quoted R values in tables 3-6 for
x>0.12, and R1990 values in tables 5-6 for all x, have been corrected, and
the cross sections in tables 3-4 have been adapted. Everything else,
including the structure functions F2, remained unchanged. 22 pages, LateX,
including figures, with two .sty files, and three separate f2tab.tex files
for the F2-tables. Accepted for publication in Nucl.Phys.B 199
Rapid-onset dystonia-parkinsonism associated with the I758S mutation of the ATP1A3 gene: a neuropathologic and neuroanatomical study of four siblings
Rapid-onset dystonia-parkinsonism (RDP) is a movement disorder associated with mutations in the ATP1A3 gene. Signs and symptoms of RDP commonly occur in adolescence or early adulthood and can be triggered by physical or psychological stress. Mutations in ATP1A3 are also associated with alternating hemiplegia of childhood (AHC). The neuropathologic substrate of these conditions is unknown. The central nervous system of four siblings, three affected by RDP and one asymptomatic, all carrying the I758S mutation in the ATP1A3 gene, was analyzed. This neuropathologic study is the first carried out in ATP1A3 mutation carriers, whether affected by RDP or AHC. Symptoms began in the third decade of life for two subjects and in the fifth for another. The present investigation aimed at identifying, in mutation carriers, anatomical areas potentially affected and contributing to RDP pathogenesis. Comorbid conditions, including cerebrovascular disease and Alzheimer disease, were evident in all subjects. We evaluated areas that may be relevant to RDP separately from those affected by the comorbid conditions. Anatomical areas identified as potential targets of I758S mutation were globus pallidus, subthalamic nucleus, red nucleus, inferior olivary nucleus, cerebellar Purkinje and granule cell layers, and dentate nucleus. Involvement of subcortical white matter tracts was also evident. Furthermore, in the spinal cord, a loss of dorsal column fibers was noted. This study has identified RDP-associated pathology in neuronal populations, which are part of complex motor and sensory loops. Their involvement would cause an interruption of cerebral and cerebellar connections which are essential for maintenance of motor control. Electronic supplementary material The online version of this article (doi:10.1007/s00401-014-1279-x) contains supplementary material, which is available to authorized users
Determination of polarized parton distribution functions and their uncertainties
We investigate the polarized parton distribution functions (PDFs) and their
uncertainties by using the world data on the spin asymmetry A_1. The
uncertainties of the polarized PDFs are estimated by the Hessian method. The up
and down valence-quark distributions are determined well. However, the
antiquark distributions have large uncertainties at this stage, and it is
particularly difficult to fix the gluon distribution. The \chi^2 analysis
produces a positively polarized gluon distribution, but even \Delta g(x)=0
could be allowed according to our uncertainty estimation. In comparison with
the previous AAC (Asymmetry Analysis Collaboration) parameterization in 2000,
accurate SLAC-E155 proton data are added to the analysis. We find that the E155
data improve the determination of the polarized PDFs, especially the polarized
antiquark distributions. In addition, the gluon-distribution uncertainties are
reduced due to the correlation with the antiquark distributions. We also show
the global analysis results with the condition \Delta g(x)=0 at the initial
scale, Q^2=1 GeV^2, for clarifying the error correlation effects with the gluon
distribution.Comment: 9 pages, 15 eps figures, REVTeX, FORTRAN package is available at the
web site http://www-hs.phys.saga-u.ac.jp/aac.html. Replaced 3 eps figures in
Fig.
Isospin Dependence of Power Corrections in Deep Inelastic Scattering
We present results of a perturbative QCD analysis of deep inelastic
measurements of both the deuteron and proton structure functions. We evaluate
the theoretical uncertainty associated to nuclear effects in the deuteron, and
we extract simultaneously the isospin depedendence of: i)the higher twists
terms; ii) the ratio of the longitudinal to transverse cross sections; iii) the
ratio of the neutron to proton structure functions. The extraction of the
latter, in particular, has been at the center of an intense debate. Its
accurate determination is crucial both theoretically and for the interpretation
of the more precise neutrino experiments including the newly planned high
intensity 50 GeV proton synchrotron.Comment: 33 pages, 16 figure
Polarized Parton Distribution Functions in the Nucleon
Polarized parton distribution functions are determined by using world data
from the longitudinally polarized deep inelastic scattering experiments. A new
parametrization of the parton distribution functions is adopted by taking into
account the positivity and the counting rule. From the fit to the asymmetry
data A_1, the polarized distribution functions of u and d valence quarks, sea
quarks, and gluon are obtained. The results indicate that the quark spin
content is \Delta\Sigma=0.20 and 0.05 in the leading order (LO) and the
next-to-leading-order (NLO) MS-bar scheme, respectively. However, if x
dependence of the sea-quark distribution is fixed at small x by "perturbative
QCD" and Regge theory, it becomes \Delta \Sigma=0.24 ~ 0.28 in the NLO. The
small-x behavior cannot be uniquely determined by the existing data, which
indicates the importance of future experiments. From our analysis, we propose
one set of LO distributions and two sets of NLO ones as the
longitudinally-polarized parton distribution functions.Comment: 51 pages, REVTeX, aps.sty, aps12.sty, epsfig.sty, prabib.sty,
revtex.sty, revtex.cls, 17 eps figures. Submitted for publication. Email:
[email protected]
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