1. Shape of Hadrons Athens 27.-29. April 2006 Real Photon Experiments  M. Kotulla E2/M1 @ MAMI and LEGS magnetic dipole moment of the   

2. Nucleon Structure

3. first excited State precise electro- and photoproduction data:  magnetic dipole transition M1  electric quadrupole transition E2  Coulomb quadrupole transition C2 incoming photon: M1, E2, C2 outgoing pion: N   transition  intrinsic

4. methods:  isospin decomposition:  most sensitive: shape of angular distribution beam asymmetry at 90°  E 1 + M 1 +  multipol analysis, dispersion relation  R EM Extraction

5. DAPHNE @ MAMI

6. TAPS @ MAMI 6  62, 1  138 detectors with individual veto detector, solid angle: ~0.40  4  sr MAMI 1999-2000 100cm beam

7. LEGS setup

8. Photon Asymmetry

9. Differential Cross Sections

10. Comparison LEGS - MAMI

11. P 33 Partial Waves (MAMI)

12. MAMI Results:  DAPHNE measurement: C || /(12A || ) dispersion relation analysis multiplol ana (S,P waves + Born) LEGS Results:  multipol analysis (up to F waves + Born) R. Beck et al., PRC 61 031204 (2000)G. Blanpied et al., PRC 64 025203 (2001) R EM  for comparison: deuteron

13. The Beamline LH 2 CB (inside 2MWPCs, PID) TAPS  beam production runs 22.6.2004-4.4.2005 CB:   672 NaI(Tl)  covers 20° - 160°  TAPS:   510 BaF 2  covers 1° - 20° 

14. Photon Asymmery 15% of total statistics Photon Asymmetry  :  @400MeV:   CBT =0.619  0.015   Leukel =0.592  0.036  @420MeV:   CBT =0.632  0.015   Leukel =0.591  0.033 E. Downie preliminary

15.   Magnetic Moment p p   ´´  measurement:  excitation of the  + and identification of the    ´p state  reaction description necessary M1, (E2), M3  ´  transition p   p ´´ p p  ´´  basic principle  resonance:  isolated excited state of the nucleon  lifetime  ~ 20 -23 s    M.Kotulla et al., PRL 89, 272001 (2002) PDG2004    = (2.7  2.2  3)  N

16. Reaction Description Pascalutsa, Vanderhaeghen PRL 94 102003 (2005) M. Kotulla et al., PRL 89, 272001 (2002) Recent progress:  chiral effective field theory ansatz V. Pascalutsa, M. Vanderhaeghen PRL 94 102003 (2005)  systematic ansatz (NLO) error estimation  rescattering: MDM acquires real and imaginary part

17.   (1232) MDM cross sections:  angular distribution of  ´  comparison: pioneering experiment (TAPS1999)   = (2.7  2.2  3)   M.K. et al., PRL 89, 272001 (2002)  preliminary Crystal Ball / TAPS data much higher precision new Crystal Ball / TAPS Data   (1232) MDM experiment:   p     ´p  exclusive measurement  kinematical overdetermination  identification checks preliminary B. Boillat

18. new Crystal Ball / TAPS Data checks:  photon beam asymmetry p  meson p ´´ E. Downie  =0.619  0.015 S. Schumann preliminary

19. Summary    magnetic moment  pioneering experiment TAPS@MAMI1999 (proof of principle)  new (CB/TAPS) measurement is currently being analyzed much higher precision  reaction calculation (systematic ansatz): chiral effective field theory  Outlook: experiment feasible S 11 + (1535):  p   ´  p S 11 0 (1535):  n   ´  n(LD 2 target) N  R EM :  precise data from MAMI and LEGS very good agreement in photon asymmetry slight deviation in (differential) cross sections