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Structure of the Nucleon and Nuclei in Lepton Scattering

Structure of the Nucleon and Nuclei in Lepton Scattering. Shunzo Kumano Saga University kumanos@cc.saga-u.ac.jp http://hs.phys.saga-u.ac.jp 第４回研究会「ミューオン蓄積リングを使った ニュートリノ源とそれが拓く物理」 May 16-17, 2003, TMU, Japan Contents  Introduction to

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Structure of the Nucleon and Nuclei in Lepton Scattering

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  1. Structure of the Nucleon and Nucleiin Lepton Scattering Shunzo Kumano Saga University kumanos@cc.saga-u.ac.jp http://hs.phys.saga-u.ac.jp 第４回研究会「ミューオン蓄積リングを使った ニュートリノ源とそれが拓く物理」 May 16-17, 2003, TMU, Japan Contents Introduction to -nucleon, -nucleus interactions  Selected topic: “HERMES effect” May 17, 2003

  2. Why nucleonic & nuclear structure at a  factory? (1) basic interest to understand hadron structure perturbative & non-perturbative QCD (2) practical purpose: to describe hadron cross sections precisely For hadron reactions with Q2>1 GeV2 , accurate PDFs (parton distribution functions) are needed.For example, heavy-ion reactions quark-gluon plasma signature exotic events at large Q2 physics “beyond current framework” neutrino reactions n +Fe, n +p, n + O (neutrino properties) …

  3. Recent unpolarized distributions see http://durpdg.dur.ac.uk/hepdata/pdf.html • CTEQ6, JHEP 07 (2002) 012 • GRV98, Eur. Phys. J. C5 (1998) 461 • MRST02, hep-ph/0211080  factory

  4. m X – q ± W p n N m Neutrino deep inelastic scattering (CC)

  5. Neutrino-quark scattering (CC)

  6. in parton model (CC) valence-quark distributions

  7. Neutrino deep inelastic scattering (NC) Neutrino-quark scattering (NC)

  8. High-energy spin physics in neutrino scattering

  9. Polaried neutrino-proton scattering (CC) new structure functions g3, g4, g5 Confusing definitions of g3, g4, g5 from J. Blumlein & M. Kochelev, NP, B498 (1997) 285. 0 at Q2>>M2

  10. Role of  factory in spin physics Polarized valence-quark and sea-quark (strange, charm) distributions can be investigated in detail.

  11. polarized parton distributions status of proton-spin issue polarized e/-proton scattering  measurement ofg1 proton, deuteron,3He g1 data with isospin symmetry  valence and sea polarization quark spin content experimentally rest of the spin ???

  12. Parton distributions (Q2=1 GeV2 ) “Spin content” DS AAC, PRD 62 (2000) 034017  factory

  13. Quark spin content at a  factory

  14. Comments on nuclear PDFs (parton distribution functions)

  15. 1.2 EMC J NMC J 1.1 E139 H J E665 J F J J F H H 1 J J J J J J H F J J J F J H J J 0.9 H H F H J J J J F J 0.8 0.7 0.001 0.01 0.1 1 • parton distributions in nuclei Nuclear modification of F2A /F2D is well known in electron/muon scattering. Fermi motion x shadowing original EMC finding

  16. typical distributions 1.2 valence 1.1 1 0.9 sea 0.8 gluon 0.7 0.6 2 2 Q = 1 GeV 0.5 0.001 0.01 0.1 1 x Nuclear corrections for Ca

  17. 1.2 preliminary without DY data 1.1 1 valence 0.9 F3Ca/F3D 0.8  factory (F3) 0.7 valence shadowing ? 0.6 0.5 0.001 0.01 0.1 1 x Valence-quark distributions in nuclei • Nuclear modification of F3 cannot be investigated at this stage due to lack of accurate deuteron data. • accurate F3A/F3D data are valuable • for determining the shadowing model • for determining accurate nuclear parton • distributions

  18. X ' L, T p Selected topic: “HERMES” effecct

  19. “HERMES effect” (nuclear effect on R=L/T) HERMES, Ackerstall el al., Phys. Rev. Lett. B 475 (2000) 386; Erratum, hep-ex/0210067, 0210068. CCFR/NuTeV, U.K.Yang et al., Phys.Rev.Lett. 87 (2001) 251802. Theoretical studies e.g. by Miller, Brodsky, and Karliner, in Phys. Lett. B 481, 245 (2000). (2000) (2002)-preprint M. Ericson and SK, Phys. Rev. C67 (2003) 022201 Nuclear modification of transverse-longitudinal ratio does exist in medium and large x regions. Mechanisms (1) transverse nucleon motion  T-L admixtureof nucleon structure functions (2) binding and Fermi-motion effects in the spectral function

  20. Formalism

  21. Formalism (continued)

  22. 0.4 2 2 Q = 1 GeV 0.3 R 0.2 R 14 N R 2 N 10 GeV 0.1 2 100 GeV 0 0 0.2 0.4 0.6 0.8 1 x 1.1 2 2 Q = 1 GeV 2 10 GeV 2 1.05 100 GeV 1 without L-T mixing 0.95 0 0.2 0.4 0.6 0.8 1 x Results admixture effects

  23. Summary on “the HERMES effect” (1) After the HERMES (CCFR/NuTeV) re-analysis, people tend to lose interest in the nuclear effect on R. However, we claim that nuclear modification should exist in medium and large x regions. (2) Physical origin transverse-longitudinal admixture due to the transverse Fermi motion binding and Fermi motion effects in the spectral function (3) Need future experimental investigations JLab, EIC, NuMI,  factory, …

  24. Summary Short baseline physics of  factory  reactions with the nucleon and nuclei validity of present “nucleon” (Fe!) structure functions sum rules, pQCD, non-pQCD PDFs nuclear medium effects quark spin content  newspin structure functions … These studies have influence on QCD (hadron models) heavy-ion physics finding new physics beyond the current theoretical framework neutrino properties (long baseline physics) …

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