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 ${\cal O}(\alpha_{s})$ corrections in our numerical calculations allows a good fit to the data for $x\geq 0.25$. The fit corresponds to values of temperature and chemical potential of approximately $T=0.067$ GeV and $\mu=0.133$ GeV. The latter values of parameters, however, give rise, for all $x$, to a large value for $R=\sigma_{L}/\sigma_{T}$.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 $F_2(x, Q^2)$ for the low and medium $Q^2$ 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 αs\alpha_s 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 $F_2$ with the extraction of $\alpha_s$ and high twist contribution. It was shown that the value of $\alpha_s$ 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 $\alpha_s(M_Z)=0.1180\pm0.0017 (68$, to be compared with the previously reported value of $\alpha_s(M_Z)=0.113\pm0.003 (99$. This new value of $\alpha_s$ is compatible with the LEP measurements and the world average. The high twist contribution being strongly anti-correlated with the value of $\alpha_s$ 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 $F_1$, $F_2$, $F_3$ and $g_1$, there are only two such contributions, corresponding to $1/Q^2$ and $1/Q^4$ power corrections. We compute their dependence on Bjorken $x$. 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 $h^N(x)/Q^2$ to the spin dependent proton and neutron structure functions $g_1^N(x, Q^2)$ are extracted in a model independent way from experimental data on $g_1^N$ 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