LEDA / Lepton Scattering on Hadrons

• 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

Member of the Hall A Collaboration at Jefferson Lab, leadership on:

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.

Ebeam ~ 4GeV

K+

ee’

pL

• 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

Hall A facility:• Standard HRS spectrometers• 2 Septum Magnets for small angle• RICH detector for superior p / K / identification

First RESULTS on 12C and 16O, 9Be nuclear targets:

12C(e,e’K)12B12C(e,e’K)12B

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 thanks to the RICH detector and Septum magnets (INFN contribution), important devices for other experiments (parity, GDH..) and planned(Pb Parity, Transversity..)

16O(e,e’K)16N

16O(e,e’K)16N

Signal

Bckgnd 7

-interaction here is in p-state, poorly known…. Data will help in improving the model parameters (Spin-Orbit term of N interaction potential)

-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)9Li

9Be(e,e’p)9Li

Models of elementary reactions fail in reproducing the data

(Red, Bennhold-Mart (K MAID)) (Blue Saclay-Lyon (SLA))

Models of elementary reactions fail in reproducing the data

(Red, Bennhold-Mart (K MAID)) (Blue Saclay-Lyon (SLA))

~ 400 KeV

~ 400 KeV

Q2~0.1 GeV2

Happex: “strangeness content of proton”

Parity-violating electron scattering on proton and 4He Strange form factors

. anticipated precision

Interference with Electromagnetic amplitude makes Neutral Current

accessible

Longitudinal spin asymmetry violates parity (polarized e-, unpolarized p)

GEs = -0.12 ± 0.29

GMs = 0.62 ± 0.32

Would imply that 7%7% of nucleon magnetic moment

is Strange

Improving precision

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Pion rejection factor ~ 1000

Superconducting Septum magnets

RICH detector unambiguous K identification

LEDA contribution for experiments in Hall A (performed and planned)

12.5° 6 ° (>Mott cross section)

PREX: Parity Violating Electron Scattering on PbInvestigation 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 leadby Left/Right Electroweak Cross Section Asymmetry:

2

22

PWIA

sin41QF

QFA

p

nW

LR

LRLR

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

z

Single Spin Asymmetry of 3He (e,e’h±)X on DIS

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

Complementary to existing data (HERMES and COMPASS mainly) and unique for the

coming years

First Time Measurement of neutron Transverse Target Single Spin Asymmetry:

lS

lh

CollinsUT

lS

lh

SiversUT

SlS

lhUT

AA

A lS

lh

lS

lh

lS

lh

lS

lh

T

sinsin

,,,

,,1

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

• 26 International Institutions involved

• Approved experiment (Jlab) with

highest rating

• Expected to run 2nd semester of 2007

for 1 month

K

h

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

(1) 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.

(2) 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.

(3) 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.

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:

Impulse Approximation Limitation to 208Pb(e,e’p)207Tl reaction

0

0TLA

Nikhef data at xB ~ 0.18

H. Hotchi et al., Phys. Rev. C 64 (2001) 044302 H. Hotchi et al., Phys. Rev. C 64 (2001) 044302

E94-107 Hall A Experiment Vs. KEK-E369

12C(e,e’K)12B12C(e,e’K)12B 12C(,K+)12C

12C(,K+)12C

Statistical significance of core excited states:

Signal

Bckgnd 7

E94-107 Hall A Experiment Vs. FINUDA (at Dane)

12C(e,e’K)12B12C(e,e’K)12B 12C(K-, )12C

12C(K-, )12C

Statistical significance of core excited states:

Signal

Bckgnd 7

E94-107 Hall A Experiment Vs. HallC E89-00912C(e,e’K)12B

12C(e,e’K)12B 12C(e,e’K)12B12C(e,e’K)12B

Miyoshi et al., PRL 90 (2003) 232502.

New analysis

Statistical significance of core excited states:

Signal

Bckgnd 7

E94-107 Hall A Experiment: status of 12B data12C(e,e’K)12B

12C(e,e’K)12B

Statistical significance of core excited states:

Signal

Bckgnd 7

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