1. Investigating the Conjectured Nucleon Deformation at Low Q2 at the Mainz Microtron N.F. Sparveris Department of Physics, University of Athens and Institute of Accelerating Systems and Applications, Athens, Greece for the Mainz N-Δ Collaboration (Athens, MIT, Mainz, RIKEN, U. Kentucky, U.Zagreb, U. Ljubljiana) Electromagnetic Interactions with Nucleons and Nuclei Milos, September 2005

2. Overview Mainz Measurements: Η(e,e’p)π o measurements at low Q 2 region (0.06 – 0.20 (GeV/c) 2 ) 855 MeV polarized electron beam High precision measurements involving in- and out of - plane detection Experiment performed in 2 stages (spring 2003 & fall 2003) Objective: Observables: cross sections  extract: responses (LT, TT, LT’, L+T)  quadrupole strengths (CMR and EMR) Measure with high precision EMR and CMR Ratios Investigate the role of the pion cloud at the low Q 2 region Preliminary results for the responses and the quadrupole amplitudes will be presented

3. u d u ud u γ * Μ1, Ε2, C2 Μ 1+, Ε 1+, S 1+ π o p(qqq) I = J = 938 MeV Δ(qqq) I = J = 1232 MeV Ν  Δ(1232) Spherical  M1 Deformed  M1, E2, C2 Deformation signal

4. p 00 Extracting the response functions cross section measurements at various azimouthal angles Η(e,e’p)π o

5. … precise Response measurements… and extensive mapping versus θ Response functions

6. Ν  Δ program @ Mainz Spectrometer A detecting electrons (in plane) Spectrometer B detecting protons (can go up to 10 o out of plane) Spectrometer C detecting electrons (luminosity monitor) Maximum E beam = 855 MeV Maximum I beam = 25 μA CW beam Focus on the low Q 2 region in an attempt to understand the effect of the mesonic cloud on the responses “Mainz Ν  Δ collaboration” (IASA (Athens), MIT,, Mainz..) sequential measurements:

7. Q 2 (GeV/c) 2 W (MeV)Θ pq (deg.) April 20030.06012320 - 40 “0.12712320 - 60 “0.20012320 - 60 October 20030.060W - scan0 “0.200W - scan0 “0.06011550 - 26 Mainz Ν  Δ measurements

8. Phase space sequential measurements

9. (Mainz)(Bates) Results: Q 2 = 0.06 (GeV/c) 2

10. PRELIMINARY S.Stave PhD

11. Results: Q 2 = 0.20 (GeV/c) 2

12. PRELIMINARY Results: Q 2 = 0.127 (GeV/c) 2

13. Latest Compilation of Bates Data @ Q 2 = 0.127 (GeV/c) 2

14. CMR

15. EMR

16. M 1+

17. Conclusions & outlook CMR Preliminary results indicate CMR around (-5 ± 0.5) % for both the Q 2 =0.06 GeV 2 & 0.20 GeV 2 Results at all Mainz Q 2 points will be finalized this year. Precise values for the quadrupole strengths will be extracted at Q 2 =0.06 (GeV/c) 2 and 0.20 (GeV/c) 2 The CMR and EMR results at Q 2 =0.06 (GeV/c) 2 and 0.20 (GeV/c) 2 will be evaluated along with the corresponding values at Q 2 =0.127 (GeV/c) 2 (Bates/Mainz) in order to understand the Q 2 dependence of the quadrupole strengths at the low Q 2 region. The LT’ results at Q2=0.127 (GeV/c) 2 are expected to enrich the world data base at this Q 2. Provide more constrains to background amplitudes at this Q 2.