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Bertone V, Britzger D, Camarda S, Cooper-Sarkar A, Geiser A, Giuli F, Glazov A, Godat E, Kusina A, Luszczak A, Lyonnet F, Olness F, Plačakytė R, Radescu V, Schienbein I, Zenaiev O. Impact of the heavy-quark matching scales in PDF fits. THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS 2017; 77:837. [PMID: 31997936 PMCID: PMC6956874 DOI: 10.1140/epjc/s10052-017-5407-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 11/22/2017] [Indexed: 06/09/2023]
Abstract
We investigate the impact of displaced heavy-quark matching scales in a global fit. The heavy-quark matching scale μ m determines at which energy scale μ the QCD theory transitions from N F toN F + 1 in the variable flavor number scheme (VFNS) for the evolution of the parton distribution functions (PDFs) and strong couplingα S ( μ ) . We study the variation of the matching scales, and their impact on a global PDF fit of the combined HERA data. As the choice of the matching scale μ m effectively is a choice of scheme, this represents a theoretical uncertainty; ideally, we would like to see minimal dependence on this parameter. For the transition across the charm quark (fromN F = 3 to 4), we find a largeμ m = μ c dependence of the global fit χ 2 at NLO, but this is significantly reduced at NNLO. For the transition across the bottom quark (fromN F = 4 to 5), we have a reducedμ m = μ b dependence of the χ 2 at both NLO and NNLO as compared to the charm. This feature is now implemented in xFitter 2.0.0, an open source QCD fit framework.
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Affiliation(s)
- The xFitter Developers’ Team:
- Department of Physics and Astronomy, VU University, 1081 HV Amsterdam, The Netherlands
- Nikhef Theory Group Science Park 105, 1098 XG Amsterdam, The Netherlands
- DESY Hamburg, Notkestraße 85, 22609 Hamburg, Germany
- CERN, 1211 Geneva 23, Switzerland
- University of Oxford, 1 Keble Road, Oxford, OX1 3NP UK
- SMU Physics, Box 0175, Dallas, TX 75275-0175 USA
- Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble Alpes, CNRS/IN2P3, 53 avenue des Martyrs, 38026 Grenoble, France
- Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Kraków, Poland
- T.Kosciuszko Cracow University of Technology, 30-084 Kraków, Poland
- Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - V. Bertone
- Department of Physics and Astronomy, VU University, 1081 HV Amsterdam, The Netherlands
- Nikhef Theory Group Science Park 105, 1098 XG Amsterdam, The Netherlands
| | - D. Britzger
- DESY Hamburg, Notkestraße 85, 22609 Hamburg, Germany
| | | | | | - A. Geiser
- DESY Hamburg, Notkestraße 85, 22609 Hamburg, Germany
| | - F. Giuli
- University of Oxford, 1 Keble Road, Oxford, OX1 3NP UK
| | - A. Glazov
- DESY Hamburg, Notkestraße 85, 22609 Hamburg, Germany
| | - E. Godat
- SMU Physics, Box 0175, Dallas, TX 75275-0175 USA
| | - A. Kusina
- Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble Alpes, CNRS/IN2P3, 53 avenue des Martyrs, 38026 Grenoble, France
- Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Kraków, Poland
| | - A. Luszczak
- T.Kosciuszko Cracow University of Technology, 30-084 Kraków, Poland
| | - F. Lyonnet
- SMU Physics, Box 0175, Dallas, TX 75275-0175 USA
| | - F. Olness
- SMU Physics, Box 0175, Dallas, TX 75275-0175 USA
| | - R. Plačakytė
- Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - V. Radescu
- DESY Hamburg, Notkestraße 85, 22609 Hamburg, Germany
- CERN, 1211 Geneva 23, Switzerland
| | - I. Schienbein
- Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble Alpes, CNRS/IN2P3, 53 avenue des Martyrs, 38026 Grenoble, France
| | - O. Zenaiev
- DESY Hamburg, Notkestraße 85, 22609 Hamburg, Germany
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