1. LEDA / Lepton Scattering on Hadrons
Member of the Hall A Collaboration at Jefferson Lab, leadership on:
Hypernuclear Spectroscopy: 12C and 16O,9Be(preliminary) high quality data available. First publication soon. Extension to heavier hypernuclei under evaluation
Good results on Parity (Happex) and Spin structure of neutron
3 experiments approved in January (high rate)
PREX: measurement of neutron skin in Lead
Transversity: one experiment approved on nucleon spin structure
Correlation and relativistic effects ( 208Pb(e,e’p)207Tl) in the nuclear medium

2. ELECTROproduction of Hypernuclei at Jefferson Lab
Hypernuclei are bound states of nucleons with a strange baryon (Lambda hyperon). Hypernuclear physics accesses information on the nature of the force between nucleons and strange baryons. A hypernucleus is a “laboratory” to study nucleon-hyperon interaction (L-N interaction).
The characteristics of the Jefferson Lab. electron beam, and those of the experimental equipments, offer a unique opportunity to study hypernuclear spectroscopy via electromagnetic induced reactions. A new experimental approach: alternative to the hadronic induced reactions studied so far. K+ e e’ p L
Ebeam ~ 4GeV
Hall A facility:
Standard HRS spectrometers
2 Septum Magnets for small angle
RICH detector for superior p / K / identification
Hyperon formation in neutron stars is controlled by the attractive hyperon-nucleon interaction which can be extracted from hypernuclear data
LEDA experiment is planning to complete a systematic study of high resolution spectroscopy on light and medium- heavy nuclei

3. Preliminary Preliminary
First RESULTS on 12C and 16O, 9Be nuclear targets:
12C(e,e’K)12BL
16O(e,e’K)16NL
Preliminary
~ 400 KeV
Preliminary
-interaction here is in p-state, poorly known…. Data will help in improving the model parameters (Spin-Orbit term of N interaction potential)
9Be(e,e’p)9LiL
Energy resolution ~ 700 KeV
the best achieved in hypernuclear production experiments, (improving) down to
first clear evidence of excited core states at ~2.5 and 6.5 MeV with high statistical significance
(possible because of the RICH detector and Septum magnets (INFN contribution), important devices for other experiments (parity, GDH..) and planned(Pb Parity, Transversity..))
Preliminary
~ 400 KeV
Models of elementary reactions fail in reproducing the data
(Red, Bennhold-Mart (K MAID)) (Blue Saclay-Lyon (SLA))

4. . anticipated precision
Happex: “strangeness content of proton”
Parity-violating electron scattering on proton and 4He Strange form factors
Interference with Electromagnetic amplitude makes Neutral Current accessible
Longitudinal spin asymmetry violates parity (polarized e-, unpolarized p)
. anticipated precision
GEs = ± 0.29
GMs = 0.62 ± 0.32
Would imply that 7% of nucleon magnetic moment is Strange
Q2~0.1 GeV2
Improving precision

5. Pion rejection factor ~ 1000
LEDA contribution for experiments in Hall A (performed and planned)
Superconducting Septum magnets
12.5° ° (>Mott cross section)
RICH detector unambiguous K identification
Pion rejection factor ~ 1000

6. PREX: Parity Violating Electron Scattering on Pb
Investigation of the nucleonic matter properties
Equation of state of neutron rich matter
Symmetry energy of dense matter
Strong connection with neutron star properties
Clean Measurement of neutron skin of lead
by Left/Right Electroweak Cross Section Asymmetry: z
As effective probe of neutron form factor Fn(Q2)
Accurate neutron radius determination
Experimental Aspects
CEBAF 80% Polarized Electron Beam
Lead Foil Target
Hall A Standard Spectrometers + Septum Magnets

7. Single Spin Asymmetry of 3He­(e,e’h±)X on DIS
First Time Measurement of neutron Transverse Target Single Spin Asymmetry:
Physics Motivations:
Nucleon Spin Structure: information on (poorly know) transverse quark spin and (unknown) angular momentum contribution to the nucleon spin
Non-perturbative QCD: non-singlet transverse quark distribution function provides a clean Q2 evolution
26 International Institutions involved
Approved experiment (Jlab) with highest rating
Expected to run 2nd semester of 2007 for 1 month
Experimental Aspects
CEBAF High Density Electron Beam
High Density Transversely polarized 3He target almost pure polarized neutron
RICH Detector for scattered hadron (p/K) identification
Complementary to existing data (HERMES and COMPASS mainly) and unique for the coming years

8. Impulse Approximation Limitation to 208Pb(e,e’p)207Tl reaction
Identifying correlations and relativistic effects in the nuclear medium
K. Aniol, A. Saha, J. M. Udias and G. Urciuoli Spokepersons
The experiment will use 208Pb, a doubly magic, complex nuclei, a textbook case for the shell model, measuring 208Pb(e,e’p)207Tl cross sections at true quasielastic kinematics and at both sides of q.
This has never been done before for A>16 nucleus
Quasielastic kinematics:
xB = 1, q = 1 GeV/c , ω = GeV/c
Determine momentum distributions:
0 < pmiss < 500 MeV/c
Determine Transverse-Longitudinal Asymmetry ATL:
Nikhef data at xB ~ 0.18
First measurements in quasielastic kinematics on the paradigmatic shell model nucleus, 208Pb at high Q2. Accurate spectroscopic factors for separated shells will be obtained at several values of Q2.
Strength for pmiss > 300 MeV/c will give insight into nuclear structure issues and will settle the long standing question about the amount of long range correlations. They will be seen for the first time, if they are there.
A new observable ATL for the five low lying states of 207Tl will be measured. ATL helps distinguishing between relativistic and nonrelativistic structure of the wave functions.

9. E94-107 Hall A Experiment Vs. KEK-E369
12C(e,e’K)12BL
12C(p+,K+)12CL
H. Hotchi et al., Phys. Rev. C 64 (2001)
Statistical significance of core excited states:

10. E94-107 Hall A Experiment Vs. FINUDA (at Dane)
12C(e,e’K)12BL
12C(K- , p-)12CL
Statistical significance of core excited states:

11. E94-107 Hall A Experiment Vs. HallC E89-009
12C(e,e’K)12BL
12C(e,e’K)12BL
Miyoshi et al., PRL 90 (2003)
New analysis
Statistical significance of core excited states:

12. E94-107 Hall A Experiment: status of 12B data
12C(e,e’K)12BL
Energy resolution is ~ 750 keV with not fully optimized optics for momenta reconstruction
Work is in progress to further improve the resolution, hence the signal/noise ratio
more checks and tuning have to be done, …but :
the data are already of extremely good quality
… to be published soon
Statistical significance of core excited states: