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

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

Preliminary Preliminary First RESULTS on 12C and 16O, 9Be nuclear targets: 12C(e,e’K)12BL 16O(e,e’K)16NL 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 ~ 750 KeV the best achieved in hypernuclear production experiments, to be improved down to ~ 500 KeV) 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 Models of elementary reactions fail in reproducing the data (Red, Bennhold-Mart (K MAID)) (Blue Saclay-Lyon (SLA))

. 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 = -0.12 ± 0.29 GMs = 0.62 ± 0.32 Would imply that 7% of nucleon magnetic moment is Strange Q2~0.1 GeV2 Improving precsion

Pion rejection factor ~ 1000 LEDA contribution for experiments in Hall A (performed and planned) Superconducting Septum magnets 12.5° 6 ° (>Mott cross section) RICH detector unambiguous K identification Pion rejection factor ~ 1000

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

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

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 = 0.433 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.

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) 044302 Statistical significance of core excited states:

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:

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) 232502. New analysis Statistical significance of core excited states:

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:

Would imply that 7% of nucleon magnetic moment is Strange Happex: “strangeness content of nucleon through Parity-violating electron scattering on proton and 4He. Longitudinal spin asymmetry violates parity (polarized e-, unpolarized p) Interference with Electromagnetic amplitude makes Neutral Current accessible Anticipated Precision from 2005 run World Data GEs = -0.12 ± 0.29 GMs = 0.62 ± 0.32 Would imply that 7% of nucleon magnetic moment is Strange Q2~0.1 GeV2