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Djukanovic D, Ottnad K, Wilhelm J, Wittig H. Strange Electromagnetic Form Factors of the Nucleon with N_{f}=2+1 O(a)-Improved Wilson Fermions. PHYSICAL REVIEW LETTERS 2019; 123:212001. [PMID: 31809157 DOI: 10.1103/physrevlett.123.212001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 08/19/2019] [Indexed: 06/10/2023]
Abstract
We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the coordinated lattice simulation ensembles with N_{f}=2+1 flavors of O(a)-improved Wilson fermions and an O(a)-improved vector current. Several source-sink separations are investigated in order to estimate the excited-state contamination. We calculate the form factors on six ensembles with lattice spacings in the range of a=0.049-0.086 fm and pion masses in the range of m_{π}=200-360 MeV, which allows for a controlled chiral and continuum extrapolation. In the computation of the quark-disconnected contributions, we employ hierarchical probing as a variance-reduction technique.
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Affiliation(s)
- D Djukanovic
- Helmholtz Institute Mainz, Staudingerweg 18, D-55128 Mainz, Germany
| | - K Ottnad
- Helmholtz Institute Mainz, Staudingerweg 18, D-55128 Mainz, Germany
- PRISMA+ Cluster of Excellence and Institute for Nuclear Physics, Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55128 Mainz, Germany
| | - J Wilhelm
- PRISMA+ Cluster of Excellence and Institute for Nuclear Physics, Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55128 Mainz, Germany
| | - H Wittig
- Helmholtz Institute Mainz, Staudingerweg 18, D-55128 Mainz, Germany
- PRISMA+ Cluster of Excellence and Institute for Nuclear Physics, Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55128 Mainz, Germany
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Yang YB, Liang J, Bi YJ, Chen Y, Draper T, Liu KF, Liu Z. Proton Mass Decomposition from the QCD Energy Momentum Tensor. PHYSICAL REVIEW LETTERS 2018; 121:212001. [PMID: 30517795 DOI: 10.1103/physrevlett.121.212001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Indexed: 06/09/2023]
Abstract
We report results on the proton mass decomposition and also on related quark and glue momentum fractions. The results are based on overlap valence fermions on four ensembles of N_{f}=2+1 domain wall fermion configurations with three lattice spacings and three volumes, and several pion masses including the physical pion mass. With fully nonperturbative renormalization (and universal normalization on both quark and gluon), we find that the quark energy and glue field energy contribute 32(4)(4)% and 36(5)(4)% respectively in the MS[over ¯] (modified minimal substraction) scheme at μ=2 GeV. A quarter of the trace anomaly gives a 23(1)(1)% contribution to the proton mass based on the sum rule, given 9(2)(1)% contribution from the u, d, and s quark scalar condensates. The u, d, s, and glue momentum fractions in the MS[over ¯] scheme are in good agreement with global analyses at μ=2 GeV.
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Affiliation(s)
- Yi-Bo Yang
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jian Liang
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Yu-Jiang Bi
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
| | - Ying Chen
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Terrence Draper
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Keh-Fei Liu
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
| | - Zhaofeng Liu
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
- School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China
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Precision measurement of the weak charge of the proton. Nature 2018; 557:207-211. [DOI: 10.1038/s41586-018-0096-0] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 04/05/2018] [Indexed: 11/09/2022]
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Abstract
We report the results on the proton mass decomposition and also on the related quark and glue momentum fractions. The results are based on overlap valence fermions on four ensembles of Nf = 2 + 1 DWF configurations with three lattice spacings and volumes, and several pion masses including the physical pion mass. With 1-loop pertur-bative calculation and proper normalization of the glue operator, we find that the u, d, and s quark masses contribute 9(2)% to the proton mass. The quark energy and glue field energy contribute 31(5)% and 37(5)% respectively in the MS scheme at µ = 2 GeV. The trace anomaly gives the remaining 23(1)% contribution. The u, d, s and glue momentum fractions in the MS scheme are consistent with the global analysis at µ = 2 GeV.
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Abstract
I discuss recent lattice QCD studies of the gluon structure of hadrons and light nuclei. After very briefly highlighting new determinations of the gluon contributions to the nucleon’s momentum and spin, presented by several collaborations over the last year, I describe first calculations of gluon generalised form factors. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic gluon degrees of freedom, and I present the first evidence for such effects, based on lattice QCD calculations. The planned Electron-Ion Collider, designed to access gluon structure quantities, will have the capability to test this prediction, and measure a range of gluon observables including generalised gluon distributions and transverse momentum dependent gluon distributions, within the next decade.
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