Matthias Burkardt

New Mexico State University, Las Cruces, New Mexico, United States

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Publications (107)177.8 Total impact

  • Matthias Burkardt
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    ABSTRACT: The interaction-dependent part of the x2 moment of the twist-3 polarized parton distribution g2(x) is related to the transverse force acting on the active quark in deep-inelastic scattering off a transversely polarized nucleon immediately after it has absorbed the virtual photon. Similarly, the x2 moment of the chirally odd twist-3 unpolarized parton distribution e(x) can be related to the transverse force experienced by a transversely polarized quark ejected from a transversely polarized nucleon.
    Physical Review D 12/2013; · 4.69 Impact Factor
  • Lekha Adhikari, Matthias Burkardt
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    ABSTRACT: Fourier transforms of GPDs describe the distribution of partons in the transverse plane. The 2nd moment of GPDs has been identified by X.Ji with the angular momentum (orbital plus spin) carried by the quarks - a fundamental result that is being widely utilized in the spin decomposition of a longitudinally polarized nucleon. However, I will demonstrate that, despite the above results, the Fourier transform of the 2nd moment of GPDs does not describe the distribution of angular momentum in the transverse plane for a longitudinally polarized target.
    07/2013;
  • Matthias Burkardt
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    ABSTRACT: Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum due to final state interactions as it leaves the target in a DIS experiment.
    03/2013;
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    ABSTRACT: We present calculations of the magnetic moment and magnetic polarisability of the neutron from the background field method. The calculations are performed on $32^3\times64$ dynamical lattices generated by the PACS-CS collaboration and made available via the ILDG. We consider uniform fields quantised by the periodic spatial volume. We explore different approaches for improving the quality of the fits used in the results. Also included are initial results for the magnetic moment of the lowest lying negative parity nucleon states.
    12/2012;
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    Matthias Burkardt
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    ABSTRACT: Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar.We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
    Physical review D: Particles and fields 05/2012; 88(1).
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    ABSTRACT: This report is based on a ten-week program on "Gluons and the quark sea at high-energies", which took place at the Institute for Nuclear Theory in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. This report is organized around four major themes: i) the spin and flavor structure of the proton, ii) three-dimensional structure of nucleons and nuclei in momentum and configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.
    08/2011;
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    ABSTRACT: This report is based on a ten-week program on "Gluons and the quark sea at high-energies", which took place at the Institute for Nuclear Theory in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. This report is organized around four major themes: i) the spin and flavor structure of the proton, ii) three-dimensional structure of nucleons and nuclei in momentum and configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC.
    07/2011;
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    Hikmat BC, Matthias Burkardt
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    ABSTRACT: We compare the orbital angular momentum of the 'quark' in the scalar diquark model as well as that of the electron in QED (to order {\alpha}) obtained from the Jaffe-Manohar de- composition to that obtained from the Ji relation. We estimate the importance of the vector potential in the definition of orbital angular momentum.
    Few-Body Systems 02/2011; · 1.05 Impact Factor
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    ABSTRACT: We present a summary of a recent workshop held at Duke University on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions. The transverse momentum dependent parton distribution functions (TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation functions, were discussed extensively at the Duke workshop. In this paper, we summarize first the theoretical issues concerning the study of partonic structure of hadrons at a future electron-ion collider (EIC) with emphasis on the TMDs. We then present simulation results on experimental studies of TMDs through measurements of single spin asymmetries (SSA) from semi-inclusive deep-inelastic scattering (SIDIS) processes with an EIC, and discuss the requirement of the detector for SIDIS measurements. The dynamics of parton correlations in the nucleon is further explored via a study of SSA in D (`D) production at large transverse momenta with the aim of accessing the unexplored tri-gluon correlation functions. The workshop participants identified the SSA measurements in SIDIS as a golden program to study TMDs in both the sea and valence quark regions and to study the role of gluons, with the Sivers asymmetry measurements as examples. Such measurements will lead to major advancement in our understanding of TMDs in the valence quark region, and more importantly also allow for the investigation of TMDs in the sea quark region along with a study of their evolution.
    European Physical Journal A 01/2011; 47(3). · 2.04 Impact Factor
  • 01/2011;
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    Matthias Burkardt, Hikmat BC, Abdullah Jarrah
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    ABSTRACT: Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, are exhibit a significant deviation from axial symmetry when the target and/or quark is transversely polarized. From this deformation, we present an intuitive derivation of the Ji relation. In a scalar diquark model and in QED, we compare the Ji and Jaffe-Manohar decompositions of the nucleon spin. Using the MIT bag model, we estimate spectator effects through the presence of the gluon vector potential in the definitions of the quark orbital angular momentum. Comment: invited talk at MENU2010, Williamsburg, May 31 - June 4
    11/2010;
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    Matthias Burkardt
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    ABSTRACT: Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark are transversely polarized. Connections between this deformation and transverse single-spin asymmetries as well as with quark-gluon correlations are discussed. The sign of transverse deformation of impact parameter dependent parton distributions in a transversely polarized target can be related to the sign of the contribution from that quark flavor to the nucleon anomalous magnetic moment. Therefore, the signs of the Sivers function for $u$ and $d$ quarks, as well as the signs of quark-gluon correlations embodied in the polarized structure function $g_2$ can be understood in terms of the proton and neutron anomalous magnetic moments.
    Few-Body Systems 11/2010; · 1.05 Impact Factor
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    Matthias Burkardt, Abdullah Jarrah
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    ABSTRACT: Using the MIT bag model, we study the contribution from the gluon vector potential due to the spectators to the orbital angular momentum of a quark in the bag model. For $\alpha_s = {\cal O}(1)$, this spectator contribution to the quark orbital angular momentum in the gauge-covariant Ji decomposition is of the same order as the non gauge-covariant quark orbital angular momentum and its magnitude is larger for $d$ than for $u$ quarks and negative for both. Comment: 5 pages
    11/2010;
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    M Burkardt
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    ABSTRACT: Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark are transversely polarized. Connections between this deformation and single-spin asymmetries as well as with quark-gluon correla-tions are discussed. The information content of the DVCS amplitude at fixed Q 2 can be condensed into GPDs along the 'diagonal' x = ξ plus D-form factor.
    10/2010;
  • Matthias Burkardt
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    ABSTRACT: Polarized structure functions at low Q{sup 2} have the physical interpretation of (generalized) spin polarizabilities. At high Q{sup 2}, the polarized parton distribution g{sub 2}(x) provides access to quark-gluon correlations in the nucleon. We discuss the interpretation of the x{sup 2} moment of g-bar{sub 2}(x) as an average transverse force on quarks in deep-inelastic scattering from a transversely polarized target. Qualitative connections with generalized parton distributions are emphasized. The x{sup 2} moment of the chirally-odd twist-3 parton distribution e(x) provides information on the dependence of the average transverse force on the transversity of the quark.
    AIP Conference Proceedings. 07/2009; 1155(1).
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    Matthias Burkardt
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    ABSTRACT: Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when target and/or quark are transversely polarized. In combination with the final state interactions, this transverse deformation provides a natural mechanism for naive-T odd transverse single-spin asymmetries in semi-inclusive DIS. The deformation of PDFs in impact parameter space can also be related to the transverse force acting on the active quark in polarized DIS at higher twist. Comment: 4 pages, invited talk at CIPANP09
    07/2009;
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    Matthias Burkardt
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    ABSTRACT: Polarized structure functions at low $Q^2$ have the physical interpretation of (generalized) spin polarizabilities. At high $Q^2$, the polarized parton distribution $g_2(x)$ provides access to quark-gluon correlations in the nucleon. We discuss the interpretation of the $x^2$ moment of $\bar{g}_2(x)$ as an average transverse force on quarks in deep-inelastic scattering from a transversely polarized target. Qualitative connections with generalized parton distributions are emphasized. The $x^2$ moment of the chirally-odd twist-3 parton distribution $e(x)$ provides information on the dependence of the average transverse force on the transversity of the quark. Comment: 9 pages, invited talk at `Spin Structure at Low $Q^2$', Jefferson Lab, March 2009
    05/2009;
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    Matthias Burkardt
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    ABSTRACT: The beam charge asymmetry helps to isolate the real part of the deeply virtual Compton scattering (DVCS) amplitude. It is discussed what information can be gained both from the real and imaginary part of the DVCS amplitude. Comment: 5 pages, 2 figures, invited talk at `Workshop on Positrons at Jefferson Lab'
    05/2009;
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    Matthias Burkardt
    [Show abstract] [Hide abstract]
    ABSTRACT: Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark is transversely polarized. In combination with the final state interactions, this transverse deformation provides a natural mechanism for naive-T odd transverse single-spin asymmetries in semi-inclusive DIS. The deformation can also be related to the transverse force acting on the active quark in polarized DIS at higher twist. Comment: 9 pages, Proceedings Spin 2008
    02/2009;
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    M. Burkardt, C A Miller, W.-D. Nowak
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    ABSTRACT: The proton is a composite object with spin one-half, understood to contain highly relativistic spin one-half quarks exchanging spin-one gluons, each possibly with significant orbital angular momenta. While their fundamental interactions are well described by Quantum ChromoDynamics (QCD), our standard theory of the strong interaction, nonperturbative calculations of the internal structure of the proton based directly on QCD are beginning to provide reliable results. Most of our present knowledge of the structure of the proton is based on experimental measurements interpreted within the rich framework of QCD. An area presently attracting intense interest, both experimental and theoretical, is the relationship between the spin of the proton and the spins and orbital angular momenta of its constituents. While remarkable progress has been made, especially in the last decade, the discovery and investigation of new concepts have revealed that much more remains to be learned. This progress is reviewed and an outlook for the future is offered. Comment: 104 pages, 43 figures, intended for non-experts, accepted by Rep. Progr. Phys.; references updated, typos corrected, minor changes in text
    Reports on Progress in Physics 12/2008; · 13.23 Impact Factor

Publication Stats

2k Citations
177.80 Total Impact Points

Institutions

  • 1995–2013
    • New Mexico State University
      • Department of Physics
      Las Cruces, New Mexico, United States
  • 2002
    • University of Maryland, College Park
      • Department of Physics
      College Park, MD, United States
  • 2001
    • University of Cambridge
      Cambridge, England, United Kingdom
  • 1996
    • TRIUMF
      Vancouver, British Columbia, Canada
  • 1994–1995
    • University of Washington Seattle
      • Institute for Nuclear Theory
      Seattle, WA, United States
  • 1992–1995
    • Massachusetts Institute of Technology
      • Center for Theoretical Physics
      Cambridge, MA, United States
  • 1991–1992
    • Stanford University
      • SLAC National Accelerator Laboratory
      Palo Alto, California, United States
  • 1988–1989
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Institute of Theoretical Physics
      Erlangen, Bavaria, Germany