Double polarization measurements with the Crystal Barrel/TAPS experiment at ELSA

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1 Double polarization measurements with the Crystal Barrel/TAPS experiment at ELSA Results for π and η photoproduction Jan Hartmann for the CBELSA/TAPS collaboration HISKP, University of Bonn CB-ELSA 8/5/2 Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS / 6

2 Double polarization measurements with the Crystal Barrel/TAPS experiment at ELSA Introduction Motivation The Crystal Barrel/TAPS experiment 2 Results Transversely polarized target Longitudinally polarized target 3 Summary Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 2/ 6

3 Baryon Spectroscopy s [ev] σ/µb γp X 2 γp pπ + π γp pπ γp pπ π γp K + Λ γp pη E γ [ev] Partial wave analysis required to extract contributing amplitudes. measurement of single and double polarization observables Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 3/ 6

4 The Crystal Barrel/TAPS experiment Forward Detector as-cherenkov Polarized Target Crystal Barrel + Inner detector oniometer Tagging system TAPS Photon intensity monitor Beam Dump Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 4/ 6

5 The Crystal Barrel/TAPS experiment Forward Detector as-cherenkov Polarized Target Crystal Barrel + Inner detector oniometer Tagging system TAPS Crystal Barrel Photon intensity monitor Beam Dump Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 4/ 6

6 Meson Reconstruction # 5 π Reaction: γp pγγ 4 η [MeV] m γγ Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 5/ 6

7 The Crystal Barrel/TAPS experiment Forward Detector as-cherenkov Polarized Target Crystal Barrel + Inner detector oniometer Tagging system TAPS Target polarization Frozen Spin Target P [%] Photon intensity monitor Beam Dump // 4// // 8// date Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 6/ 6

8 circularly polarized: bremsstrahlung of longitudinally pol. electrons helicity transfer: / P e Polarized Photon Beams linearly polarized: coherent bremsstrahlung using diamond crystal crystal orientation defines plane of linear polarization P γ I rel E γ / E e measurement of electron polarization using Møller polarimeter P lin E γ [MeV] Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 7/ 6

9 Polarization Observables photoproduction of pseudoscalar mesons: all 3 single polarization observables 4 double polarization observables can be measured with the Crystal Barrel/TAPS experiment dσ dσ (θ, φ) = (θ) [ Pγ lin dω dω +P x +P y P z photon pol. target pol. axis x y z unpolarized σ T linear Σ H P circular F E ( P lin γ (+P lin Σ(θ) cos(2φ) H(θ) sin(2φ) + Pγ circ F (θ) ) γ P (θ) cos(2φ) T (θ) ) ( P lin γ (θ) sin(2φ) + Pγ circ E(θ) )] [] W.-T. Chiang, F. Tabakin, Phys. Rev. C 55 (997) Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 8/ 6

10 Beam Asymmetry Σ linearly polarized photon beam (angle of pol. plane: α = 45 ) unpolarized target N(φ) = P beam N N N + N = Σ cos(2(φ α)) γp pπ γp pη N 8 MeV < E γ < 9 MeV.8 χ 2 / ndf 27.9 / 7 Σ.542 ±.42 N 8 MeV < E γ < 9 MeV.8 χ 2 / ndf.69 / 7 Σ.2496 ± α φ π [ ] α φ η[ ] Note: target material butanol also small contribution from C Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 9/ 6

11 Σ π Photoproduction: Beam Asymmetry Σ 65 MeV < E γ < 683 MeV 683 MeV < E γ < 77 MeV 77 MeV < E γ < 75 MeV.5 75 MeV < E γ < 783 MeV.5 85 MeV < E γ < 883 MeV MeV < E γ < 87 MeV preliminary MeV < E γ < 97 MeV.5 87 MeV < E γ < 85 MeV MeV < E γ < 95 MeV our data RAAL data [2] Maid Said Bna cos θ π Note: target material butanol also small contribution from C [2] O. Bartalini et al., Eur. Phys. J. A 26, (25) Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS / 6

12 Target Asymmetry T unpolarized beam transversely polarized target (direction of pol.: β = 99 ) N(φ) = fp target N N N + N = T sin(φ β) γ p pπ γ p pη N 7 MeV < E γ < 8 MeV.5.4 χ 2 / ndf / 7 T ±.29 N 8 MeV < E γ < 9 MeV χ / ndf 9.97 / 7 T.668 ± β φ π [ ] β φ η[ ] Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS / 6

13 Recoil Polarization P and Observable H linearly polarized photon beam (angle of pol. plane: α = 45 ) transversely polarized target (direction of pol.: β = 99 ) N(φ) = (N N ) (N N ) fp beam P target (N + N ) + (N + N ) = (P sin(φ β) cos(2(φ α)) + H cos(φ β) sin(2(φ α))) γ p pπ γ p pη N 8 MeV < E γ < 9 MeV.4.3 χ 2 / ndf 7.24 / 6 P -.45 ±.8 H.26 ±.76 N 8 MeV < E γ < 9 MeV.4.3 χ 2 / ndf / 6 P.275 ±.22 H ± α 9β φ π [ ] α β φ η[ ] Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 2/ 6

14 Double Polarization Observable linearly polarized beam, longitudinally polarized target: dσ dσ (φ) = ( Pγ lin Σ cos(2φ) + Pγ lin P z sin(2φ) ) dω dω.8.6 E γ = 733 MeV.8.6 E γ = 767 MeV.8.6 E γ = 8 MeV.8.6 E γ = 833 MeV cosθ π cosθ π cosθ π cosθ π.8.6 E γ = 867 MeV.8.6 E γ = 9 MeV.8.6 E γ = 933 MeV.8.6 E γ = 967 MeV cosθ π cosθ π cosθ π cosθ π.8.6 E γ = MeV.8.6 E γ = 33 MeV.8.6 E γ = 67 MeV.8.6 E γ = MeV cosθ π cosθ π cosθ π cosθ π γ p pπ Maid Said Bna A. Thiel (Bonn) Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 3/ 6

15 Double Polarization Observable E circularly polarized beam, longitudinally polarized target: γ p pπ : N /2 N 3/2 M. ottschall (Bonn) Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 4/ 6

16 π Photoproduction: E circularly polarized beam, longitudinally polarized target:.8.6 E cosθ cosθ cosθ cosθ cosθ cosθ cosθ cosθ cosθ - cosθ - cosθ - cosθ cos θ π Maid Said Bna M. ottschall (Bonn) Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 5/ 6

17 Summary First double polarization data has been taken with the Crystal Barrel/TAPS experiment at ELSA: longitudinally or transversely polarized target linearly or circularly polarized photon beam Preliminary results shown for Target Asymmetry T Recoil Polarization P Double Polarization Observables E,, and H One step closer towards the complete experiment. The new results will be important input for PWA. Jan Hartmann Double polarization measurements with Crystal Barrel/TAPS 6/ 6