LEDA / Lepton Scattering on Hadrons

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

• Hypernuclear Spectroscopy

: 12

C

and 16 O, 9 Be(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

(

nuclear medium 208 Pb(e,e’p) 207 Tl

)

in the

E

LECTROproduction of

H

ypernuclei at

J

efferson

Lab H

ypernuclei 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)

.

e’ e

• 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 p L K + new experimental approach: alternative to the hadronic induced reactions studied so far.

• Hyperon formation in

neutron stars

controlled by the attractive hyperon nucleon interaction which can be extracted from

hypernuclear data

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

LEDA

experiment is planning to complete a

systematic study of high resolution spectroscopy

on light and medium heavy nuclei

12 C(e,e’K)

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

12 B L

Signal Bckgnd

 7

16 O(e,e’K) 16 N

L  L

( -interaction here is in p-state, Data will help in improving the model parameters Spin-Orbit term of

L

poorly known N interaction potential) …. 9 Be(e,e’p) 9 Li

L

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 Septum magnets RICH detector and ( INFN contribution ), important devices for other experiments (parity, GDH..) and planned ( Pb Parity, Transversity ..)) Models of elementary reactions fail in reproducing the data

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

Happex : “strangeness content of proton” Parity-violating electron scattering on proton and 4 He Interference with Electromagnetic amplitude makes Neutral Current accessible Strange form factors Longitudinal spin asymmetry violates parity (polarized e-, unpolarized p) G E s G M s = -0.12

±

= 0.62

±

0.29

0.32

.

anticipated precision Would imply that 7% of nucleon magnetic moment is

Strange

Improving precsion Q 2 ~0.1 GeV 2

LEDA contribution for experiments in Hall A

(performed and planned)

Superconducting Septum magnets 12.5

°

section) 6

°

(>Mott cross

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

RICH detector unambiguous K identification



Ch

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:

 

e

  +

Z

z 0 2 

A LR

  

R R

   

L L

PWIA     1  4 sin 2 

W



F n F p

       

e



As effective probe of

neutron form factor F

n (Q 2 )

Accurate neutron radius determination

Experimental Aspects • CEBAF 80% Polarized Electron Beam • Lead Foil Target • Hall A Standard Spectrometers + Septum Magnets

Single Spin Asymmetry of

3

He(e,e’h

±

)X on DIS

First Time Measurement of neutron Transverse Target Single Spin Asymmetry :

A UT

 

h l

, 

S l

   1

S T

 

Sivers A UT

  

l h



l h

, 

S l

, 

l S

sin        

h l l h l h

 , 

l S

, 

l S



S l

       

A Collins UT

sin  

h l

 

S l



h

 

K

Physics Motivations:

• Nucleon Spin Structure

: information on (poorly know) (unknown) angular momentum transverse quark spin contribution to the nucleon spin

• Non-perturbative QCD

: clean Q 2 evolution non-singlet transverse quark distribution and function provides a Experimental Aspects

• CEBAF High Density Electron Beam • High Density

Transversely polarized 3 He target almost pure polarized neutron

• RICH Detector

identification for scattered hadron (p/K)

• 26 International Institutions involved • Approved

rating experiment (Jlab) with highest

• Expected to run 2

nd for 1 month semester of 2007

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

Impulse Approximation Limitation to 208 Pb(e,e’p) 207 Tl reaction K. Aniol, A. Saha, J. M. Udias and G. Urciuoli Spokepersons

Identifying correlations and relativistic effects in the nuclear medium

The experiment will use 208 Pb, a doubly magic, complex nuclei, a textbook case for the shell model, measuring 208 Pb(e,e’p) 207 Tl cross sections at true quasielastic kinematics and at both sides of q.

This has

never been done before for A>16 nucleus

Quasielastic kinematics: x B = 1, q = 1 GeV/c , ω = 0.433

Nikhef data at x B ~ 0.18

GeV/c Determine momentum distributions: Determine Transverse-Longitudinal Asymmetry A TL : 0 < p

A TL

 miss       < 500 MeV/c   0 0             (1) First measurements in quasielastic kinematics on the paradigmatic shell model nucleus, 208 Pb at high Q 2 . Accurate spectroscopic factors for separated shells will be obtained at several values of Q 2 .

(2) Strength for p miss > 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 A functions.

TL for the five low lying states of 207 Tl will be measured. A TL helps distinguishing between relativistic and nonrelativistic structure of the wave

E94-107 Hall A Experiment Vs. KEK-E369

12 C(e,e’K) 12 B L 12 C(   ,K + ) 12 C L H. Hotchi

et al.

, Phys. Rev. C 64 (2001) 044302 Statistical significance of core excited states:

Signal

 7

Bckgnd



E94-107

Hall A Experiment Vs.

FINUDA

(at Da  ne) 12 C(e,e’K) 12 B L 12 C(K ,   ) 12 C L Statistical significance of core excited states:

Signal

 7

Bckgnd



E94-107 Hall A Experiment Vs. HallC E89-009

12 C(e,e’K) 12 B L 12 C(e,e’K) 12 B L

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

New analysis

Statistical significance of core excited states:

Signal

 7

Bckgnd



E94-107 Hall A Experiment: status of

12 B

L

data

12 C(e,e’K) 12 B L

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 : Statistical significance of core excited states

:

Signal

 7

Bckgnd

the data are already of good quality extremely … to be published soon



Happex: “strangeness content of nucleon through Parity-violating electron scattering on proton and 4 He .

Interference with Electromagnetic amplitude makes Neutral Current accessible Longitudinal spin asymmetry violates parity (polarized e-, unpolarized p)

World Data

Anticipated Precision from 2005 run G E s G M s = -0.12

±

= 0.62

±

0.29

0.32

Would imply that 7% of nucleon magnetic moment is Strange Q 2 ~0.1 GeV 2