Meson Physics with Crystal Ball at MAMI

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1 Meson Physics with Crystal Ball at MAMI Institute for Nuclear Physics University Mainz

2 Outline Crystal Ball Set-up at MAMI ' Cross Sections Transition Form Factor from e+e- Revisited T and F Asymmetry in Photoproduction Summary

3 Outline Crystal Ball Set-up at MAMI ' Cross Sections Transition Form Factor from e+e- Revisited T and F Asymmetry in Photoproduction Summary

4 Mainz Microtron Ee-<1604 MeV E<0.1 MeV MESA High current (110 A) High polarisation (85%) Duty factor 100% ~7000 h/year running experiments

5 Experiments at MAMI MESA A2: Real Photon Experiments: - Glasgow tagging spectrometer - Crystal Ball / TAPS hermetic photon spectrometer - Meson Factory PRISMA/SFB 1044: - Dark Photon Search - El.-weak Mixing Angle A1: Electron Scattering: - focusing magnetic spectrometers - neutron detection, spin precession - Kaon spectrometer (KAOS/A1)

6 Real Photons in A2 Data form CLAS, SAPHIR E =E0-Ee- Ethr 1447 MeV High energy resolution: E 2MeV at Ee-=883 MeV E 4MeV at Ee-=1558 MeV Linearly and circularly polarised photon-beam Tagging range: 5.1 to 93% of E Maximum energy tagged for E =1604 MeV is 1491 MeV

7 End-Point-Tagger Installation of EPT during 2012 EPT Same working principle as main tagging spectrometer E MeV E 2.5MeV Non-permanent installation infront of main Tagger

8 4 -Setup Crystal Ball: 672 NaI(Tl) crystals 93,3% of total solid angle Each crystal equipped with PMT 2% = E E /GeV 0.25 t = 2.5 ns FWHM =2 3 = 2 3 sin TAPS: Up to 510 BaF2 crystals Polar acceptance: 4-20 t = 0.5 ns FWHM 0,79 % = 1,8 % E E / GeV

9 Targets LH2/lD2 used for high rate meson production ( / ') - Length: 3cm, 5cm, 10cm l3he/l4he Polarised Butanol/D-Butanol - Transverse and longitudinal polarisation - Lenght: 2 cm - Dynamic Nuclean Polarisation - Max. Polarisation: 90% - Holding filed: 0.44 T - Relaxation time: ~1000h Solid Targets

10 Outline Crystal Ball Set-up at MAMI ' Cross Sections Transition Form Factor from e+e- Revisited T and F Asymmetry in Photoproduction Summary

11 ' 0 0 Invariant Mass y in ar y lim in ar in im Pr e Pr el y y E =1570±10 MeV Pr el im in ar ar in lim E =1530±10 MeV y y E =1510±10 MeV ar in lim Pr e E =1550±10 MeV Pr e lim Pr e Pr el im in ar ar in lim Pr e E =1490±10 MeV E =1470±10 MeV ar y E =1450±10 MeV y E =1430±10 MeV S. Prakhov (UCLA) P. Ott (Mainz)

12 ' Cross Section Using ' 0 0 E =1450±10 MeV E =1470±10 MeV E =1490±10 MeV E =1510±10 MeV Preliminary Preliminary Preliminary Preliminary E =1570±10 MeV Preliminary Preliminary Preliminary in ar y E =1550±10 MeV Pr el im E =1530±10 MeV tot S. Prakhov (UCLA) P. Ott (Mainz)

13 ' Programme Status now: EPT successfully in operation Preliminary result for photoproduction cross section near threshold Preliminary result for ' 0 0 Dalitz plot (limited statistics) MC background studies for ' e+e- and first glance at data DAQ Improvement: New trigger system (FPGA based) Faster DAQ PCs Factor of 2 in speed gained Sep. 2013: Further DAQ upgrade Additional factor of 2 in speed? Next ' Production: EPT installation in beam in summer/fall 2014 Beamtime estimate underway Measure with x4 speed and longer period Goal: 400,000 ' 0 0 (Dalitz plot analysis) ~ ' e+e- (Transition Form Factor) A. Denig, M. Ostrick, P. Ott, S. Prakhov, M. Unverzagt, S. Wagner

14 Outline Crystal Ball Set-up at MAMI ' Cross Sections Transition Form Factor from e+e- Revisited T and F Asymmetry in Photoproduction Summary

15 Previous Analysis of TFF H. Berghäuser et al. (A2-Collaboration), Phys. Rev. B 701 (2011) Based on kinematic cuts Small amount of data Limited photoproduction energy range -2 = (1.92±0.35stat±0.13syst) GeV-2

16 New Analysis of TFF Based on kinematic fitting 3x more data Full photoproduction range accessible at MAMI used 18,000 events (no proton requirement: 22,000 events) m(e+e-)=45±5 MeV Preliminary m(e+e-)=285±5 MeV Preliminary Solid line: Pole-approximation fit Normalisation and as free parameters Preliminary

17 New Result on TFF S. Prakhov, M. Unverzagt et al., to be submitted to Phys. Rev. soon Preliminary -2 = (1.95±0.15stat±0.05syst) GeV-2 preliminary A2, 2011: H. Berghäuser et al., Phys. Rev. B 701 (2011) NA60, In-In: R. Arnaldi et al., Phys. Lett. B 677 (2009) 260. TL calculation: C. Terschlüsen, Diploma thesis, University Gießen, Padé-approximants: R. Escribano, P. Masjuan, P. Sanchez-Puertas, in preparation.

18 Outline Crystal Ball Set-up at MAMI ' Cross Sections Transition Form Factor from e+e- Revisited T and F Asymmetry in Photoproduction Summary

19 Polarisation Observables T and F Disentangle Multipoles (complete experiment), perform PWAs s-d wave interference in T for, isobar models predict zero interference Dominated by Born,, Dominated by D13(1520) Dominated by S11(1535) Double polarisation observable F not measured yet

20 Transverse Target Asymmetry T for Red points: Balck points: Black line: Blue line: Red line: Green line: CB 2010/11 PHOENICS Pr el im in ar y Bock et al., Phys. Rev. Lett. 81, 534 (1998) MAID-2003, isobar model MAID-2003, reggeized isobar model BG SAID Victor Kashevarov (Mainz)

21 Double Polarisation Observable F for Black line: Blue line: Red line: MAID-2003, isobar model MAID-2003, reggeized isobar model BG Pr el im in ar y First time measurement with Crystal Ball! Victor Kashevarov (Mainz)

22 Outline Crystal Ball Set-up at MAMI ' Cross Sections Transition Form Factor from e+e- Revisited T and F Asymmetry in Photoproduction Summary

23 Summary ' production at MAMI possible now - Preliminary results on ' photoproduction cross section - First glances on ' 0 0 Dalitz plot and ' Transition Form Factor New determination of the Transition Form Factor in e+e- - More than one order of magnitude more than previous A2 analysis - Soon to be published Polarisation observables with Crystal Ball - Precise determintation of Target Asymmetry T (preliminary) - First determination of Double Polarisation Observable F (preliminary) 12 years physics programme funded through DFG (SFB 1044) - Broad physics programme including Light Meson Dynamics Transition Form Factors of pseudoscalar Mesons Polarisation Observables (long. and trans. Pol. target)