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 -nucleon, -nucleus interactions  Selected topic: “HERMES effect” May 17, 2003

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) …

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

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

Neutrino-quark scattering (CC)

in parton model (CC) valence-quark distributions

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

High-energy spin physics in neutrino scattering

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

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

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

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

Quark spin content at a  factory

Comments on nuclear PDFs (parton distribution functions)

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

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

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 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 0.001 0.01 0.1 x valence preliminary without DY data F3Ca/F3D  factory (F3) valence shadowing ?

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

“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 admixture of nucleon structure functions (2) binding and Fermi-motion effects in the spectral function

Formalism

Formalism (continued)

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

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, …

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  new spin 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)