T and F in photoproduction in the S11(1535) region. production in threshold region S11(1535) and D13(1520) resonances

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1 T and F in photoproduction in the S11(1535) region production in threshold region S11(1535) and D13(1520) resonances Previous measurements Differential cross sections Polarisation observables S-D phase rotation Multipoles Target asymmetry T T and F measurement at MAMI-C? Count rate estimations Simulations Resolutions and statistical accuracy

2 Introduction Single meson production p p 0, p p Unpolarised target, linear polarised beam Polarised target, linear & circular polarised beam d = d {1 p lin cos(2 ) d pol d unpol d = d {1 p lin cos(2 )} d pol d unpol ptx plin H sin(2 ) ptx pcirc F pty T pty plin P cos(2 ) ptz plin G sin(2 ) ptz pcirc E} Polarised Frozen Spin Target available within 2009 Longitudinal (z) & transverse (x,y) target polarisation Combination with polarised beam Double polarisation observables Investigation of overlapping N resonances S11, P11, D13, F15,...

3 Multipoles in production production p p in threshold region: thres = 707 MeV < < 900 MeV = 90 corresponding to Wthres = 1485 MeV < W < 1602 MeV Important multipoles: E0 : dominated by S11(1535) E2, M2 : dominated by D13(1520) E1, M1 : background (Born,, ) = 90 Helicity multipoles: A0 = E0 A2 = (3M2 E2 )/2 B1 = E1 M1 B2 = E2 M2 EtaMAID (full) EtaMAID, S11(1535) only EtaMAID, D13(1520) only EtaMAID, Born,, only

4 Observables and multipoles Differential cross sections d /d : MAMI/TAPS: MeV, CBarrel/ELSA: MeV, PRL 74, 3736 (1995) PRL 94, (2005) Photon asymmetry : GRAAL: MeV, PRL 81, 1797 (1998) CBarrel/ELSA: MeV, EPJ A 33, 147 (2007) Target asymmetry T: PHOENICS: MeV, PRL 81, 534 (1998) Multipole structure: * A ] d /d ~ E0 2 2(3cos2 1) Re[E0 2 * S-D wave interference Term: E0 B2 * B ] ~ 3sin2 Re[E0 2 * Real in all isobar models: Im[E0 B2 ] 0 * B ] cos Im[E * B ]) T ~ 3sin (Im[E

5 Phase rotation Fit to PHOENICS data: * * B ]) T ~ 3sin (Im[E0 B1 ] cos Im[E0 2 Non-zero imaginary part of E0 B2 Large phase shift between S and D wave: Phase rotation Phase shift E0 B2 Magnitude B2

6 Target asymmetry T Standard isobar models SAID, default EtaMAID EtaMAID with ad-hoc integration of phase rotation Energy dependence of S-D phase shift? Large shift near threshold, still visible at W 1535 MeV, disappearing at W 1580 MeV?

7 Double-polarisation observable F Standard isobar models SAID, default EtaMAID EtaMAID with ad-hoc integration of phase rotation Less sensitivity to S-D phase shift No experimental data yet With circular polarised beam F for free

8 Model predictions for T and F SAID and EtaMAID models: Discrepancies between EtaMAID and SAID predictions T: F: Different behaviour at > 900 MeV Opposite sign? No data for F yet Only few data for T limited accuracy no data for > 1100 MeV Measurement of T and F at MAMI-C: Investigate S-D phase rotation in threshold region Higher accuracy and energy/angular resolutions for T Provide data for T and F up to = 1400 MeV Constraints for isobar models?

9 Count rate estimations Run conditions: Electron energy E0 = 1508 MeV or 1558 MeV Tagged photon energy range = MeV (224 tagger channels) at E0 = 1508 MeV. Electron count rate Ne = s-1 Tagging efficiency tag = 70% Photon flux N = s-1 Polarised target protons (2 cm butanol) Np = cm-2 Target polarisation Pp Average circular beam polarisation P Detection/reconstructruction efficiency CB = 0.3. trans = 0.8 circ = 0.6 analysing both 2 and Livetime t = 70% with DAQ at 800 events/sec 5600 reconstructed p p reactions/h 2.8M reconstructed p p reactions in 500h beam time

10 T simulations (EtaMAID) at ~500 h = MeV = MeV = MeV = MeV = MeV = MeV = MeV = MeV = MeV

11 F simulations (EtaMAID) at ~500 h = MeV = MeV = MeV = MeV = MeV = MeV = MeV = MeV = MeV

12 T and F simulations (EtaMAID) at ~500h Resolutions: Beam energy binning = 10 MeV Polar angle binning = 12 = 90 Statistical accuracy for T at = (90 6) : = MeV: T = = MeV: T = = MeV: T = = MeV: T = = 90 Statistical accuracy for F at = (90 6) : = MeV: F = = MeV: F = = MeV: F = = MeV: F = 0.066