Latest results from GRAAL collaboration presented by Valentina Vegna

1. Workshop on the Physics of Excited Nucleon – NSTAR 2009, Beijing Latest results from GRAAL collaboration presented by Valentina Vegna on behalf of the GRAAL Collaboration Università degli Studi di Roma “Tor Vergata” and INFN Sezione di Roma Tor Vergata • the GRAAL experimental set-up; •  and 0photoproduction on quasi-free neutron; • K+and K+0 photoproduction on free proton; • in memoriam of Eid Hourany.

2. Meson Photoproduction at GRAAL GRAAL/ESRF • Beam Asymmetry Measurements for accessible reactions: • polarized photon beam; • large acceptance apparatus; • tagged photon beam. s (mb) E (GeV) ’threshold K threshold  threshold

3. g gL Eg e- Ee,me EL E’e, me e- 16 MeV FWHM GRAAL Polarized and Tagged Photon Beam green line UV line Ee= 6 GeV EL= 2.41 eV (green line, l = 514 nm) EL= 3.53 eV (U.V. line, l = 351 nm) Egmax= 1.1 GeV Egmax= 1.5 GeV Tagger Energy Spectrum Energy Resolution

4. GRAAL Detector NOT IN SCALE • Photon detection (energy resolution 3% FWHM at 1 GeV); • Charged particle identification (protons - pions); • Energy measurement for protons; • Neutron detection (and energy measurement in forward direction).

5.  Measurement at GRAAL Experimental Distribution at fixed E and mCM:

6.  Photoproduction on Quasi-Free Nucleon in Deuteron A.Fantini et al., Phys.Rev.C 78, 015203 (2008) 3 1 • Selection cuts: Preselection: 2 neutral cluster detected in BGO (invariant mass  (0.35-0.7) GeV/c2); 1 neutron or 1 proton (in the central or in the forward detectors); no other particles. 2 • Kinematic Analysis: • Two-body nature of each reaction step:

7.  in  Photoproduction on qfp and fp A.Fantini et al., Phys.Rev.C 78, 015203 (2008) qfp fp MAID2001 - fp reggeized model - qfp MAID2001 - qfp • at low energies: dependence • with increasing energy: forward-backward asymmetry

8.  in  Photoproduction on qfn A.Fantini et al., Phys.Rev.C 78, 015203 (2008) qfn reggeized model MAID2001 : symmetric behaviour : peak in forward direction : symmetric behaviour

9.  in  Photoproduction on qfp and qfn A.Fantini et al., Phys.Rev.C 78, 015203 (2008) qfn qfp • up to 1.05 GeV: • qfn quite close to qfn; • above 1.05 GeV: • P11(1670); • S11(1650)-P11(1710).

10. 0 Photoproduction on Quasi-Free Nucleon in Deuteron R. Di Salvo, to be submitted 3 1 Pre-selection: 2 neutral cluster detected in BGO (invariant mass  (0.09-0.20) GeV/c2); 1 neutron or 1 proton (in the central or in the forward detectors); no other particles (quasi-free kine). • Selection cuts: 2 • Kinematical Analysis: • Two-body nature of each reaction step:

11.  in 0 Photoproduction on qfp and fp R. Di Salvo, to be submitted fp qfp

12.  in 0 Photoproduction on qfn R. Di Salvo, to be submitted qfn MAID2007 MAID2007 new

13. in 0 Photoproduction on qfn Multipole extraction in MAID2007 Real part Immaginary part MAID2007 qfn mod MAID2007 qfn

14.  in 0 Photoproduction on qfp and qfn R. Di Salvo, to be submitted qfn qfp MAID2007 “new” for neutron MAID2007 “new” for proton

15. K+ and K+0Photoproduction on Free Proton A.Lleres et al., EPJ A 31, 79-93 (2007) 3 1 • Selection cuts: • Energy balance; • Charged particles mass; • Missing mass ; • Energy of the  from  decay. Preselection: 3 tracks + at most 1 neutral cluster detected in BGO (no neutral particle: K+; 1 neutral particle: K+0) 2 4 Check:  decay length • Kinematic Analysis: • Three-body kinematics; • Two-body nature of each reaction step;

16.  in K+ and K+0 Photoproduction A.Lleres et al., EPJ A 31, 79-93 (2007) GRAAL GRAAL Ghent Isobar Published Bonn coupled channel Saclay New Bonn coupled channel Bonn coupled channel

17. GRAAL CLAS Ghent Isobar Saclay Bonn coupled channel P in K+ Photoproduction A.Lleres et al., EPJ A 31, 79-93 (2007) From  and P measurements: • Saclay Model: • Ghent Isobar Model: • Reggeized Model: • Bonn Coupled Channel Model:

18. S1 S3 S4 S2 S2 S3 S4 S1 Formalism for Recoil Observables in K+ Photoproduction

19. Double Polarization Observables in K+ Photoproduction A.Lleres et al., EPJ A 39, 149-161 (2009) GRAAL GRAAL GI RPR GI RPR Bonn Gatchina Bonn Gatchina

20. T in K+ Photoproduction A.Lleres et al., EPJ A 39, 149-161 (2009) From Ox, Oz and T extractions: • Ghent Isobar RPR Model: • Bonn Gatchina Model: GRAAL GI RPR Bonn Gatchina

21. Comparison with CLAS A.Lleres et al., EPJ A 39, 149-161 (2009)

22. Conclusions •  photoproduction on nucleon: • measurement of  in the energy range from 0.7 to 1.5 GeV; • qfp is similar to fp: it suggests that qfn is similar tofn; • the energy dependence of qfp and qfn is very similar up to 1.05 GeV; • above 1.05 GeV, qfp is forward peaked while qfn looks more symmetric around CM = 90°; • above 1.05 GeV and backward angles, qfn is substantially higher than qfp; • 0 photoproduction on nucleon: • measurement of  in the energy range from 0.5 to 1.5 GeV; • qfpis similar to fp : it suggests that qfn is similar to fn; • qfp and qfn are very similar for low values of 0* but differ a lot with increasing of 0*; • K+ photoproduction: • systematic measurements of , P, Ox, Oz and T in the energy range from 0.9 to 1.5 GeV; • comparisons with 4 different models confirm the necessity to introduce new or poorly known resonances in the 1900 MeV mass region: P13and/or D13; • we need only one additional double-polarization observable to extract helicity amplitudes.

23. In memory of Dr. Eid Hourany Dr Eid HOURANY died in October 2008 at the age of 67. He had been involved as the leader of the Orsay team in the GRAAL venture since the beginning and constructed the scintillating wall of the GRAAL detection system. He has been a talented experimentalist able to analyse complex data. In the last few years, he has analyzed almost alone, « exotic » final states as: Nπ0π0, Nπ0η, Nω and extracted from the GRAAL data very innovative information. The quality of the GRAAL physics production is largely indebted to his constantly demanding attitude.

24. Double 0 photoproduction ...on the neutron ...on the proton P.R.L. 90 (2003) Phys.Lett.B 651 (2007)

25.  photoproduction on the proton P.R.L. 96 (2006)

26. 3-body phase space Döring, Oset, Strottman (2006) Simultaneous  and0 photoproduction P.R.L. 100 (2008)

27. Thanks a lotfor your attention

28. 0 Photoproduction: Re-calculation of 0 C.M. R. Di Salvo, to be submitted Deviation of the Lorentz Boost Axis Re-calculation of 0C.M.

29.  Photoproduction: Selected Events Fantini et al., Phys.Rev.C 78, 015203 (2008) neutron proton central region forward region Total exstimated background

30.  Photoproduction: Check Fantini et al., Phys.Rev.C 78, 015203 (2008) Check on the validity of: 3-parameters fit: Similiar results for  beam asymmetry; Higer 2; The quality of fits gets worse.

31. P0 in K+0 Photoproduction u , unity vector along the direction of  emission in the 0 rest frame

32. K+ Photoproduction : Efficiency Dependence for N+ and N- Lleres et al., EPJ A 31, 79-93 (2007) via Monte Carlo simulation Detection efficiencies and correction factors depend on the input values of Ox , Oz and T: iterative method (3 iterations).

33. Internal Check A.Lleres et al., EPJ A 39, 149-161 (2009)

34.  Photoproduction: theoretical models for comparisons Fantini et al., Phys.Rev.C 78, 015203 (2008)

35. Models in K photoproduction off free protons SACLAY G.I. BCC GRPR