1. Structure of the Nucleon and Nuclei in Lepton Scattering
Shunzo Kumano
Saga University
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
CTEQ6, JHEP 07 (2002) 012
GRV98, Eur. Phys. J. C5 (1998) 461
MRST02, hep-ph/
 factory

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

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 of g1
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 )
AAC, PRD 62 (2000)
“Spin content” DS
 factory

13. Quark spin content at a  factory

14. Comments on nuclear
PDFs (parton distribution functions)

15. 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

16. 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

17. 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 ?

18. Selected topic: “HERMES” effecctX '
L, T

19. “HERMES effect” (nuclear effect on R=L/T)
HERMES, Ackerstall el al., Phys. Rev. Lett. B 475 (2000) 386;
Erratum, hep-ex/ ,
CCFR/NuTeV, U.K.Yang et al., Phys.Rev.Lett. 87 (2001)
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)
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

20. Formalism

21. Formalism (continued)

22. 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

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 
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)