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Exploring the Structure of Nucleons: A Comprehensive Overview

Dive into the fundamental questions surrounding nucleons, their imaging techniques, and impact on high-energy physics. Discover approaches, experimental efforts, and connections with other fields in this illuminating exploration.

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Exploring the Structure of Nucleons: A Comprehensive Overview

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  1. WG.9: Working Group on International Cooperation in Nuclear Physics (ICNP) The Structure of the Nucleon CPHT Cédric Lorcé August 29, Riken Tokyo Office, Tokyo, Japan

  2. Outline • Fundamental questions • Hadron imaging • Impact onotherfields • Currentpictures • Conclusions

  3. Fundamental questions about the nucleon Nucleons are key building blocks of all matteraround us, and yetwe do not know thatmuch about them ! Origin of mass and spin ? Mproton = Mquarks + Ekinetic + Einteraction ~ 2% ~ 98% Higgsboson Strong interaction Proton Quarks

  4. Fundamental questions about the nucleon But also … Size ? Shape ? Structure ? 2010

  5. Approaches to the problem Hadron spectroscopy Latticeprediction of light mesonspectrum [J. Dudeket al. (2011)] • Mesonspectrumbetterknownthan baryon spectrum • Missingresonances (other production channel ?) • Exotic states (glueballs, hybrids, tetraquarks, pentaquarks, …) • Nature (bound state, molecule, mixing, …)

  6. Approaches to the problem Hadron imaging « Quantum billiard » Charge distribution [Carlson, Vanderhaeghen (2008)] Electron Proton • Large number of distributions (charge, spin, flavor, momentum, …) • Requires high luminositiesIntensityfrontier • Essential input for high-energyphysics (electroweak, BSM, darkmatter, …)

  7. 1D imaging Parton distribution functions (PDFs) Electrocardiogram [PDG (2016)] Perturbative QCD evolution Momentum fraction Deepinelasticscattering (DIS)

  8. 3D imaging Transverse momentumPDFs (TMDs) 3D model of heart Polarizedtarget Unpolarizedtarget Courtesy of A. Bacchetta Semi-inclusive DIS (SIDIS)

  9. 1+2D imaging GeneralizedPDFs (GPDs) 1+2D model of heartbeat Nucleon transverse extent [Dupré et al. (2017)] x-dissected charge distribution Sea quarks & gluons Pion cloud Valence quarks Deeplyvirtual Compton scattering (DVCS)

  10. 3+2D imaging TMDs PDFs GPDs Momentumtransfer

  11. 3+2D imaging TMDs PDFs FFs GPDs Charges Formfactors Elasticscattering

  12. 3+2D imaging GTMDs TMDs PDFs FFs GPDs Charges GeneralizedTMDs Phase-space (Wigner) distribution [Meissner, Metz, Schlegel (2009)] [C.L., Pasquini, Vanderhaeghen (2011)]

  13. Rich spin structure TMDs GPDs Quark polarization Spin-orbit Nucleonpolarization Spin-spin [C.L., Pasquini (2016)]

  14. Multipoledecomposition UU LU [C.L., Pasquini (2016)]

  15. Multipoledecomposition UU LU Density mode Inflation mode Orbital mode Spiral mode [C.L., Pasquini (2016)]

  16. Experimental efforts

  17. Impact on high-energyphysics Main uncertainty on precision SM and BSM studiescomesfromPDFs [Forte, Watt (2013)] [LHeCStudy Group (2012)]

  18. Impact on high-energyphysics GPDs and TMDsoffer new opportunities Gluon TMD contributions to Higgs production Multiple parton scattering [Boer et al. (2012)] [Diehl et al. (2012)] Gluon linearpolarization ratio Double PDF GPD2 GPD1

  19. Connections withotherfields Quantum optics Twistedbeams of photons and electrons Solid-state physics Spin Hall effect Astrophysics Hydrodynamicalpicture General relativity Gravitational memory effect quark pressure gluon pressure Before After

  20. Back to the fundamental questions Nucleonmomentumdecomposition Phenomenological extraction [Harland-Lang et al. (2015)] Pq 54,6(5) % Latticeestimate [Alexandrouet al. (2017)] 27,3(2,3) % PG Pq 74(10) %

  21. Back to the fundamental questions Nucleonmassdecomposition Phenomenological extraction [Gao et al. (2015)] 11(1) % Em Eq 33(1) % Latticeestimate [Bali et al. (2016)] [Alexandrouet al. (2017)] 29,1(1,5) % Em Eq 33,7(7,5) % EG 20,5(1,7) %

  22. Back to the fundamental questions Nucleonmassdecomposition Trace decomposition Ji’sdecomposition New decomposition [Shifmanet al. (1978)] [Ji (1995)] [C.L. (2017)] ~ 11% ~ 11% ~ 11% ~ 33% ~ 33% ~ 14% Em Em Em ~ 22% Ea Eq Eq Ea Ea EG EG ~ 42% ~ 89% ~ 34% Trace anomaly

  23. Back to the fundamental questions Nucleonspindecomposition Phenomenological extraction [Nocera et al. (2014)] [DSSV (2014)] 25(10) % Sq SG 40(?) % Latticeestimate [Alexandrouet al. (2017)] Lq Sq 42,4(9,0) % 39,8(3,2) % JG 27,2(?) %

  24. Back to the fundamental questions Reviews: [Leader, C.L. (2014)] [Wakamatsu (2014)] [Liu, C.L. (2016)] Nucleonspindecomposition Kineticdecomposition Canonical decomposition [Ji (1997)] [Wakamatsu (2010)] [Jaffe, Manohar (1990)] [Chen et al. (2008)] [Hatta (2012)] ~ 20% ~ 25% ~ 25% ~ 29% Lq Sq Sq Lq LG LG ~ 15% SG SG ~ 6% ~ 40% ~ 40% « Outside » the nucleon « Inside » the nucleon Struck quark Chromo Lorentz force [Burkardt (2013)] [Burkardt, C.L. (in preparation)]

  25. Hot topics for the near future • Gluon distributions • Orbital angularmomentum • QCD trace anomaly • Transverse polarizationeffects • Saturation effects • Higher-twists effects • Quark flavordecomposition • Medium modifications • … Lattice QCD

  26. Conclusions • Understandingnucleon structure is a fundamentalproblem • Nucleonimagingoffers key insight • Rich spin structure withnumerouseffects • Gluon contributions and OAM stillmissing • Electron-ion collider and Lattice QCD willplay an essential role • Connections withotherfieldsshouldbefurtherexplored !

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