Author
D. F. Geesaman
Bio: D. F. Geesaman is an academic researcher from Argonne National Laboratory. The author has contributed to research in topics: Proton & Scattering. The author has an hindex of 10, co-authored 18 publications receiving 572 citations.
Topics: Proton, Scattering, Inelastic scattering, Neutron, Muon
Papers
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University of Illinois at Chicago1, University of Maryland, College Park2, Lawrence Livermore National Laboratory3, Massachusetts Institute of Technology4, Fermilab5, University of Pennsylvania6, University of Washington7, University of Wuppertal8, Max Planck Society9, Ohio University10, Harvard University11, University of Freiburg12, Argonne National Laboratory13, Hungarian Academy of Sciences14, University of California, San Diego15, Northwestern University16
TL;DR: The first precise measurements of F 2 in the low x and Q 2 range of the data were taken at Fermilab experiment 665 during 1991-1992 using liquid hydrogen and deuterium targets as discussed by the authors.
Abstract: The proton and deuteron structure functions F{sub 2}{sup p} and F{sub 2}{sup d} measured in inelastic muon scattering with an average beam energy of 470 GeV. The data were taken at Fermilab experiment 665 during 1991-1992 using liquid hydrogen and deuterium targets. The F{sub 2} measurements are reported in the range 0.0008 < x < 0.6 and 0.2 < Q{sup 2} < 75 GeV{sup 2}. These are the first precise measurements of F{sub 2} in the low x and Q{sub 2} range of the data. The E665 data overlap in x with the HERA data, and there is a smooth connection in Q{sup 2} between the two data sets. At high Q{sup 2} the E665 measurements are consistent with QCD-evolved leading twist structure function models. The data are qualitatively described by structure function models incorporating the hadronic nature of the photon at low Q{sup 2}. The Q{sup 2} and the W dependence of the data measure the transition in the nature of the photon between a point-probe at high Q{sup 2} and a hadronic object at low Q{sup 2}.
174 citations
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Los Alamos National Laboratory1, Oak Ridge National Laboratory2, New Mexico State University3, Fermilab4, Abilene Christian University5, Texas A&M University6, Argonne National Laboratory7, Georgia State University8, Illinois Institute of Technology9, Louisiana State University10, Valparaiso University11, University of Texas at Austin12
TL;DR: In this paper, the Drell-Yan cross section ratio was measured in Fermilab E866, which led to the first determination of {bar d}(x)/{bar u} (x), and the integral of the proton over the range 0.02-0.345.
Abstract: The Drell-Yan cross section ratios, {sigma}(p+d)/{sigma}(p+p), measured in Fermilab E866, have led to the first determination of {bar d}(x)/{bar u}(x), {bar d}(x){minus}{bar u}(x), and the integral of {bar d}(x){minus}{bar u}(x) for the proton over the range 0.02{le}x{le}0.345. The E866 results are compared with predictions based on parton distribution functions and various theoretical models. The relationship between the E866 results and the NMC measurement of the Gottfried integral is discussed. The agreement between the E866 results and models employing virtual mesons indicates that these non-perturbative processes play an important role in the origin of the {bar d},{bar u} asymmetry in the nucleon sea. {copyright} {ital 1998} {ital The American Physical Society}
93 citations
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California Institute of Technology1, Lawrence Livermore National Laboratory2, American University3, University of Wisconsin-Madison4, Massachusetts Institute of Technology5, Argonne National Laboratory6, California State University, Los Angeles7, Stanford University8, University of Colorado Boulder9, Rensselaer Polytechnic Institute10
TL;DR: The A-dependence of the quasielastic A(e,e'p) reaction has been studied at SLAC with ^2H, C, Fe, and Au nuclei at momentum transfers Q 2 = 1, 3, 5, and 6.8 (GeV/c)2 as discussed by the authors.
81 citations
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University of Illinois at Chicago1, Max Planck Society2, University of Maryland, College Park3, University of Hamburg4, Stanford University5, Lawrence Livermore National Laboratory6, Massachusetts Institute of Technology7, Fermilab8, Fidelity Investments9, University of Pennsylvania10, Rockefeller University11, University of Washington12, University of Wuppertal13, University of Wisconsin-Madison14, Ohio University15, Texas A&M University16, Columbia University17, Harvard University18, University of Freiburg19, Heidelberg University20, Argonne National Laboratory21, College of William & Mary22, National Kaohsiung Normal University23, Florida State University24, Los Alamos National Laboratory25, University of California, San Diego26, University of Colorado Boulder27, Linear Technology28, California Institute of Technology29, University of Oxford30, Northwestern University31, Yale University32, New Mexico State University33, Thomas Jefferson National Accelerator Facility34, CERN35, Hoffmann-La Roche36
TL;DR: In this article, the diffractive production of ρ0(770 @#@) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV2 and 20 GeV < 420 GeV.
Abstract: The diffractive production of ρ0(770 @#@) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV2
< Q2
< 20 GeV2 and 20 GeV < ? < 420 GeV. The data were obtained in the Fermilab fixed-target experiment E665 with primary muons of 470 GeV energy. Results are presented on the Q2, x and ? dependence of the cross section, on the shape of the ρ+ρt -
mass spectrum, on the slope of the diffraction peak and on the production and decay angular distributions of the ρ0(770). The cross section for diffractive production of ρ0 by virtual photons on protons depends mainly on Q2. At fixed Q2, no significant dependence on x or ? is observed. The extrapolation to Q2 = 0 yields a photoproduction cross section of (10.30 ± 0.33) μb. The slope of the t′ distribution has a value of (7.0 ± 0.2) GeV−2, with a tendency to decrease as Q2 increases. The production and decay angular distributions of the ρ0 depend strongly on Q2 and are consistent with s-channel helicity conservation. The ratio R = σ
l
/σ
t
deduced from the decay angular distributions rises strongly with Q2, passing the value of 1 at Q2
≈ 2 GeV2.
53 citations
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University of Colorado Boulder1, California Institute of Technology2, Argonne National Laboratory3, Lawrence Livermore National Laboratory4, American University5, University of Maryland, College Park6, University of Wisconsin-Madison7, Massachusetts Institute of Technology8, University of Michigan9, Thomas Jefferson National Accelerator Facility10, California State University, Los Angeles11, Stanford University12, University of Illinois at Urbana–Champaign13, Old Dominion University14, University of Pennsylvania15, Rensselaer Polytechnic Institute16, Kent State University17, Northwestern University18
TL;DR: In this paper, the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90° was measured.
Abstract: Measurements were performed for the photodisintegration cross section of the deuteron for photon energies from 1.6 to 2.8 GeV and center-of-mass angles from 37° to 90°. The measured energy dependence of the cross section at θ_(cm)=90° is in agreement with the constituent counting rules.
45 citations
Cited by
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TL;DR: In this paper, the authors presented an updated leading-order, next-to-leading order and next-next-ordering order parton distribution function (MSTW 2008) determined from global analysis of hard-scattering data within the standard framework of leading-twist fixed-order collinear factorisation in the $\overline{\mathrm{MS}}$¯¯$¯¯¯¯¯
Abstract: We present updated leading-order, next-to-leading order and next-to-next-to-leading order parton distribution functions (“MSTW 2008”) determined from global analysis of hard-scattering data within the standard framework of leading-twist fixed-order collinear factorisation in the $\overline{\mathrm{MS}}$
scheme. These parton distributions supersede the previously available “MRST” sets and should be used for the first LHC data taking and for the associated theoretical calculations. New data sets fitted include CCFR/NuTeV dimuon cross sections, which constrain the strange-quark and -antiquark distributions, and Tevatron Run II data on inclusive jet production, the lepton charge asymmetry from W decays and the Z rapidity distribution. Uncertainties are propagated from the experimental errors on the fitted data points using a new dynamic procedure for each eigenvector of the covariance matrix. We discuss the major changes compared to previous MRST fits, briefly compare to parton distributions obtained by other fitting groups, and give predictions for the W and Z total cross sections at the Tevatron and LHC.
3,546 citations
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TL;DR: In this paper, the authors presented LO, NLO and NNLO sets of parton distribution functions (PDFs) of the proton determined from global analyses of the available hard scattering data.
Abstract: We present LO, NLO and NNLO sets of parton distribution functions (PDFs) of the proton determined from global analyses of the available hard scattering data. These MMHT2014 PDFs supersede the 'MSTW2008' parton sets, but they are obtained within the same basic framework. We include a variety of new data sets, from the LHC, updated Tevatron data and the HERA combined H1 and ZEUS data on the total and charm structure functions. We also improve the theoretical framework of the previous analysis. These new PDFs are compared to the 'MSTW2008' parton sets. In most cases the PDFs, and the predictions, are within one standard deviation of those of MSTW2008. The major changes are the [Formula: see text] valence quark difference at small [Formula: see text] due to an improved parameterisation and, to a lesser extent, the strange quark PDF due to the effect of certain LHC data and a better treatment of the [Formula: see text] branching ratio. We compare our MMHT PDF sets with those of other collaborations; in particular with the NNPDF3.0 sets, which are contemporary with the present analysis.
1,238 citations
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TL;DR: In this article, the authors give an overview of the theory for generalized parton distributions and their role in small-x physics, and present strategies for phenomenological analysis, including the use of these quantities for describing soft contributions to exclusive processes at large energy and momentum transfer.
941 citations
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TL;DR: In this paper, the authors investigate the interplay between uncertainties on strong coupling and uncertainties on parton distribution functions (PDFs), and provide eigenvector PDF sets with different fixed α-676 S petertodd values.
Abstract: We determine the uncertainty on the strong coupling α
S
due to the experimental errors on the data fitted in global analysis of hard-scattering data, within the standard framework of leading-twist fixed-order collinear factorisation in the $\overline{\mathrm{MS}}$
scheme, finding that α
S
(M
2
)=0.1202
−0.0015
+0.0012
at next-to-leading order (NLO) and α
S
(M
2
)=0.1171
−0.0014
+0.0014
at next-to-next-to-leading order (NNLO). We do not address in detail the issue of the additional theory uncertainty on α
S
(M
2
), but an estimate is ±0.003 at NLO and at most ±0.002 at NNLO. We investigate the interplay between uncertainties on α
S
and uncertainties on parton distribution functions (PDFs). We show, for the first time, how both these sources of uncertainty can be accounted for simultaneously in calculations of cross sections, and we provide eigenvector PDF sets with different fixed α
S
values to allow further studies by the general user. We illustrate the application of these PDF sets by calculating cross sections for W, Z, Higgs boson and inclusive jet production at the Tevatron and LHC.
500 citations
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TL;DR: It is shown that the experimental data from HERA in the region x<0.01 confirm the expectations of this scaling over a very broad region of Q(2), and it is suggested that the geometric scaling is more general than the saturation model.
Abstract: We observe that the saturation model of deep inelastic scattering predicts a geometric scaling of the total gamma(*)p cross section in the region of small Bjorken variable x. The geometric scaling in this case means that the cross section is a function of only one dimensionless variable tau = Q(2)R(2)(0)(x), where the function R(0)(x) decreases with decreasing x. We show that the experimental data from HERA in the region x<0.01 confirm the expectations of this scaling over a very broad region of Q(2). We suggest that the geometric scaling is more general than the saturation model.
455 citations