General-mass treatment for deep inelastic scattering at NNLO in CTEQ PDF analysis

ORAL

Abstract

We present an NNLO realization of the general mass scheme S-ACOT-$\chi$ for the treatment of heavy-flavour production in neutral current deep-inelastic scattering. Practical implementation of the NNLO calculation is illustrated on the example of semi-inclusive structure functions $F_{2c}(x,Q)$ and $F_{Lc}(x,Q)$. In a modern global QCD analysis of parton distribution functions (PDFs), several factors are comparable in magnitude to next-to-next-to-leading order (NNLO) radiative contributions in the QCD coupling strength $\alpha_s$. Among these factors, dependence of QCD cross sections on masses of heavy quarks, $m_c$ and $m_b$, can be significant. Global fits are sensitive to two types of mass effects, kinematical suppression of production of c and b quarks near respective mass thresholds in deep inelastic scattering (DIS), and large radiative contributions to collinear production of $\bar{c} c$ or $\bar{b}b$ pairs at large collider energy. It is therefore natural to evaluate all fitted cross sections in a ``general-mass'' (GM) factorization scheme, which assumes that the number of (nearly) massless quark flavors varies with energy, and at the same time includes dependence on heavy-quark masses in relevant kinematical regions. The S-ACOT-$\chi$ scheme that we present, is motivated by the QCD factorization theorem for DIS with massive quarks and we show it is valid to all orders of $\alpha_s$.

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Authors

  • Marco Guzzi

    Southern Methodist University

  • Allan Headley

    Texas A\&M, Sam Houston State University, Southern Methodist University, Dept of Physics, Texas Tech University, Depts of Cell Physiology and Molecular Biophysics, Texas Tech University HSC, Texas Tech University, Lee College, Texas A\&M University, Texas A\&M Univ.-Commerce, University of North Texas, Texas A\&M University and Princeton University, Princeton University, The University of North Texas, University of Texas at Austin, Center for High Energy Density Science, University of Texas at Austin, Institute for Fusion Studies, University of Texas at Austin, UT Arlington, Stephen F. Austin State University, Texas A&M University--Commerce, University of Texas at Dallas, University of Texas at El Paso, Department of Physics, The University of Texas at Dallas, Department of Physics and Astronomy, Francis Marion University, University of Texas at Brownsville, Texas State University--San Marcos, UTSA, Northwestern University, Rice University, Abilene Christian University, Texas Southern University, Department of Physics, Southern Methodist University, Dallas, Texas A\&M University Cyclotron Institute, Sciprint.org, University of Texas MD Anderson Cancer Center, University of Texas at San Antonio, Paschal High School, Fort Worth, TX, Department d'Enginyeria Electronica, Universitat Autonoma de Barcelona, Department of Physics, Texas State University at San Marcos, Texas State University at San Marcos, Angelo State University, Texas State University-San Marcos, Department of Surgery, The University of Texas Southwestern Medical Center, Dallas, TX 75390, Department of Medicine, Baylor College of Medicine, Department of Bioengineering, Rice University, Department of Physics and Astronomy, Rice University, Department of Surgery, University of Texas Southwestern Medical Center, University of Texas at Dallas, Physics, Viginia State University, Jefferson Laboratory, Trinity University, LIGO, UTB-TSC, Mount Holyoke College, Texas A&M University, Electrical and Computer Engineering, TAMU, American Institute of Physics, University of Texas at Arlington, Texas Christian University, Fort Worth, TX, University of Pennsylvania, Philadelphia, PA, University of Missouri-Columbia, Columbia, MO, Paine College, Augusta, GA, Univ. of Edinburgh, INFN-LNS, INFN LNS CATANIA ITALY, Arkansas Technical University, AR, USA, Cyclotron Institute Texas A\&M University College Station Usa, and Heather Galloway, Texas State University--San Marcos

  • Allan Headley

    Texas A\&M, Sam Houston State University, Southern Methodist University, Dept of Physics, Texas Tech University, Depts of Cell Physiology and Molecular Biophysics, Texas Tech University HSC, Texas Tech University, Lee College, Texas A\&M University, Texas A\&M Univ.-Commerce, University of North Texas, Texas A\&M University and Princeton University, Princeton University, The University of North Texas, University of Texas at Austin, Center for High Energy Density Science, University of Texas at Austin, Institute for Fusion Studies, University of Texas at Austin, UT Arlington, Stephen F. Austin State University, Texas A&M University--Commerce, University of Texas at Dallas, University of Texas at El Paso, Department of Physics, The University of Texas at Dallas, Department of Physics and Astronomy, Francis Marion University, University of Texas at Brownsville, Texas State University--San Marcos, UTSA, Northwestern University, Rice University, Abilene Christian University, Texas Southern University, Department of Physics, Southern Methodist University, Dallas, Texas A\&M University Cyclotron Institute, Sciprint.org, University of Texas MD Anderson Cancer Center, University of Texas at San Antonio, Paschal High School, Fort Worth, TX, Department d'Enginyeria Electronica, Universitat Autonoma de Barcelona, Department of Physics, Texas State University at San Marcos, Texas State University at San Marcos, Angelo State University, Texas State University-San Marcos, Department of Surgery, The University of Texas Southwestern Medical Center, Dallas, TX 75390, Department of Medicine, Baylor College of Medicine, Department of Bioengineering, Rice University, Department of Physics and Astronomy, Rice University, Department of Surgery, University of Texas Southwestern Medical Center, University of Texas at Dallas, Physics, Viginia State University, Jefferson Laboratory, Trinity University, LIGO, UTB-TSC, Mount Holyoke College, Texas A&M University, Electrical and Computer Engineering, TAMU, American Institute of Physics, University of Texas at Arlington, Texas Christian University, Fort Worth, TX, University of Pennsylvania, Philadelphia, PA, University of Missouri-Columbia, Columbia, MO, Paine College, Augusta, GA, Univ. of Edinburgh, INFN-LNS, INFN LNS CATANIA ITALY, Arkansas Technical University, AR, USA, Cyclotron Institute Texas A\&M University College Station Usa, and Heather Galloway, Texas State University--San Marcos

  • Allan Headley

    Texas A\&M, Sam Houston State University, Southern Methodist University, Dept of Physics, Texas Tech University, Depts of Cell Physiology and Molecular Biophysics, Texas Tech University HSC, Texas Tech University, Lee College, Texas A\&M University, Texas A\&M Univ.-Commerce, University of North Texas, Texas A\&M University and Princeton University, Princeton University, The University of North Texas, University of Texas at Austin, Center for High Energy Density Science, University of Texas at Austin, Institute for Fusion Studies, University of Texas at Austin, UT Arlington, Stephen F. Austin State University, Texas A&M University--Commerce, University of Texas at Dallas, University of Texas at El Paso, Department of Physics, The University of Texas at Dallas, Department of Physics and Astronomy, Francis Marion University, University of Texas at Brownsville, Texas State University--San Marcos, UTSA, Northwestern University, Rice University, Abilene Christian University, Texas Southern University, Department of Physics, Southern Methodist University, Dallas, Texas A\&M University Cyclotron Institute, Sciprint.org, University of Texas MD Anderson Cancer Center, University of Texas at San Antonio, Paschal High School, Fort Worth, TX, Department d'Enginyeria Electronica, Universitat Autonoma de Barcelona, Department of Physics, Texas State University at San Marcos, Texas State University at San Marcos, Angelo State University, Texas State University-San Marcos, Department of Surgery, The University of Texas Southwestern Medical Center, Dallas, TX 75390, Department of Medicine, Baylor College of Medicine, Department of Bioengineering, Rice University, Department of Physics and Astronomy, Rice University, Department of Surgery, University of Texas Southwestern Medical Center, University of Texas at Dallas, Physics, Viginia State University, Jefferson Laboratory, Trinity University, LIGO, UTB-TSC, Mount Holyoke College, Texas A&M University, Electrical and Computer Engineering, TAMU, American Institute of Physics, University of Texas at Arlington, Texas Christian University, Fort Worth, TX, University of Pennsylvania, Philadelphia, PA, University of Missouri-Columbia, Columbia, MO, Paine College, Augusta, GA, Univ. of Edinburgh, INFN-LNS, INFN LNS CATANIA ITALY, Arkansas Technical University, AR, USA, Cyclotron Institute Texas A\&M University College Station Usa, and Heather Galloway, Texas State University--San Marcos