650 research outputs found
The Persint visualization program for the ATLAS experiment
The Persint program is designed for the three-dimensional representation of
objects and for the interfacing and access to a variety of independent
applications, in a fully interactive way. Facilities are provided for the
spatial navigation and the definition of the visualization properties, in order
to interactively set the viewing and viewed points, and to obtain the desired
perspective. In parallel, applications may be launched through the use of
dedicated interfaces, such as the interactive reconstruction and display of
physics events. Recent developments have focalized on the interfacing to the
XML ATLAS General Detector Description AGDD, making it a widely used tool for
XML developers. The graphics capabilities of this program were exploited in the
context of the ATLAS 2002 Muon Testbeam where it was used as an online event
display, integrated in the online software framework and participating in the
commissioning and debug of the detector system.Comment: 9 pages, 10 figures, proceedings of CHEP200
Perturbative QCD Analysis of Local Duality in a fixed W^2 Framework
We study the global Q^2 dependence of large x, F_2 nucleon structure function
data, with the aim of providing a perturbative-QCD based, quantitative analysis
of parton-hadron duality. As opposed to previous analyses at fixed x, we use a
framework in fixed W^2. We uncover a breakdown of the twist-4 approximation
with a renormalon type improvement at O(1/Q^4) which, by affecting the initial
evolution of parton distributions, will have consequences for pQCD analyses
also at large x and very large Q^2.Comment: RevTex4, 8 pages, 3 figure
Structure Functions of the Nucleon in a Statistical Model
Deep inelastic scattering is considered in a statistical model of the
nucleon. This incorporates certain features which are absent in the standard
parton model such as quantum statistical correlations which play a role in the
propagation of particles when considering Feynman diagrams containing internal
lines. The inclusion of the corrections in our numerical
calculations allows a good fit to the data for . The fit
corresponds to values of temperature and chemical potential of approximately
GeV and GeV. The latter values of parameters, however,
give rise, for all , to a large value for .Comment: 16 pages TeX, 11 figures available as Postscript files, University of
Bielefeld preprint BI-TP 93/3
Parton-Hadron Duality: Resonances and Higher Twists
We explore the physics of the parton-hadron duality in the nucleon structure
functions appearing in lepton-nucleon scattering. We stress that the duality
allows one to extract the higher-twist matrix elements from data in the
resonance region, and learn about the properties of resonances if these matrix
elements are known. As an example, we construct the moments of
for the low and medium region, and from which we study the interplay
between higher twists and the resonance contributions.Comment: 7 pages with 4 figures and 1 table, REVTeX, MIT-CTP-234
Bloom-Gilman duality of inelastic structure functions in nucleon and nuclei
The Bloom-Gilman local duality of the inelastic structure function of the
proton, the deuteron and light complex nuclei is investigated using available
experimental data in the squared four-momentum transfer range from 0.3 to 5
(GeV/c)**2. The results of our analysis suggest that the onset of the
Bloom-Gilman local duality is anticipated in complex nuclei with respect to the
case of the protonand the deuteron. A possible interpretation of this result in
terms of a rescaling effect is discussed with particular emphasis to the
possibility of reproducing the damping of the nucleon-resonance transitions
observed in recent electroproduction data off nuclei.Comment: revised version, to appear in Physical Review
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
On the value of from the analysis of the SLAC/BCDMS deep inelastic scattering data
We performed NLO QCD analysis of the nonsinglet part of the combined
SLAC/BCDMS data on with the extraction of and high twist
contribution. It was shown that the value of obtained in the
analysis is sensitive to the statistical inference procedures dealing with
systematic errors on the data. The fit with the complete account of
point-to-point correlations of the data gave the value of
, to be compared with the previously
reported value of . This new value of
is compatible with the LEP measurements and the world average. The
high twist contribution being strongly anti-correlated with the value of
became lower than it was previously reported.Comment: 9 pages, LATEX, 2 figures (PS), report-no added, English improved,
misprints corrected, minor changes of the tex
Power Corrections and Renormalons in Deep Inelastic Structure Functions
We study the power corrections (infrared renormalon contributions) to the
coefficient functions for non-singlet deep inelastic structure functions due to
gluon vacuum polarization insertions in one-loop graphs. Remarkably, for all
the structure functions , , and , there are only two such
contributions, corresponding to and power corrections. We
compute their dependence on Bjorken . The results could be used to model the
dominant higher-twist contributions.Comment: Latex 2e, 9 pages including 2 Postscript figure
Power corrections in the longitudinal and transverse structure functions of proton and deuteron
Power corrections to the Q**2 behaviour of the low-order moments of both the
longitudinal and transverse structure functions of proton and deuteron have
been investigated using available phenomenological fits of existing data in the
Q**2 range between 1 and 20 (GeV/c)**2. The Natchmann definition of the moments
has been adopted for disentangling properly target-mass and dynamical
higher-twist effects in the data. The leading twist has been treated at
next-to-leading order in the strong coupling constant and the effects of higher
orders of the perturbative series have been estimated using a
renormalon-inspired model. The contributions of (target-dependent) multiparton
correlations to both 1/Q**2 and 1/Q**4 power terms have been determined in the
transverse channel, while the longitudinal one appears to be consistent with a
pure infrared renormalon picture in the whole Q**2-range between 1 and 20
(GeV/c)**2. Finally, the extracted twist-2 contribution in the deuteron turns
out to be compatible with the hypothesis of an enhanced d-quark parton
distribution at large x.Comment: revised version with only minor changes, to appear in Nuclear Physics
On the Role of Higher Twist in Polarized Deep Inelastic Scattering
The higher twist corrections to the spin dependent proton and
neutron structure functions are extracted in a model
independent way from experimental data on and found to be
non-negligible. It is shown that the NLO QCD polarized parton densities
determined from the data on g1, including higher twist effects, are in good
agreement with those found earlier from our analysis of the data on g1/F1 and
A1 where higher twist effects are negligible. On the contrary, the LO QCD
polarized parton densities obtained from the data on g1, including higher
twist, differ significantly from our previous results.Comment: 18 pages, latex, 6 figures, final version which will be published in
Phys. Rev. D, fig. 5 is changed, misprints in Table 2 are remove
- …