Helicity Dependent Cross Sections in Meson Photoproduction off Quasi-Free Protons and Neutrons

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1 Helicity Dependent Cross Sections in Meson Photoproduction off Quasi-Free Protons and Neutrons Frankfurt, March 7 th 24 DPG Frühjahrstagung A2

2 Outline Introduction Motivation Double Polarization Observable E Experiment 2 η - Analysis 3 2π - Analysis 4 Conclusion

3 Motivation different resonance contributions to proton and neutron 5 σ[µb] 5 γn ηn σ n /σ p σ p (3/2)*σ n σ p, free W[GeV] 2 2 H, this work 2 H, Jaegle et al..6.8 W[GeV] σ [µb] σ(pπ π )n σ(nπ π )p n MAID γn 2π N σ n /σ p W [MeV] W [MeV] D. Werthmüller et al., Phys. Rev. Lett., 232 M. Oberle et al., in preparation use polarization observables to identify amplitudes and quantum numbers

4 Double Polarization Observable E circularly polarized beam P γ longitudinally polarized target P T Observable Spin Orientation σ /2 σ 3/2,, measure the asymmetry: E = σ /2 σ 3/2 σ /2 +σ 3/2 = σ /2 σ 3/2 2σ tot

5 Double Polarization Observable E polarized deuterium dbutanol: C 4 D 9 OD 2 ways to measure E: w/o carbon: E = σ /2 σ 3/2 2σ tot with carbon: E = σ /2 σ 3/2 σ /2 +σ 3/2

6 Double Polarization Observable E polarized deuterium dbutanol: C 4 D 9 OD 2 ways to measure E: w/o carbon: E = σ /2 σ 3/2 2σ tot with carbon: E = σ /2 σ 3/2 σ /2 +σ 3/2 dbutanol Carbon η/h July 3 9 days - 25 Feb 4 5 days 3 days 3 Jan/Feb lin. pol., trigger,...

7 Experiment: Setup Circularly polarised tagged photon beam TAPS MWPC PID Crystal Ball: Highly segmented sphere made of NaI target NaI PID: Cylinder of scintillation counters surrounds target, charged particle detector BaF2 Veto CB TAPS: Forward wall, BaF 2 & PbWO 4 crystals geometrical acceptance close to 4π

8 η-analysis

9 Reaction Identification neutral and charged particles: σ p σ n γp ηp γn ηn η 2γ 2n & c 3n η 6γ 6n & c 7n find best combination with χ 2 test: η 2γ (σ n ): χ 2 = (m k(γγ) m η) 2 ( m k (γγ)) 2 k =,...,3 η 6γ: χ 2 = 3 k= (m k (γγ) m π ) 2 ( m k (γγ)) 2

10 Background Suppression Coplanarity: φ = φ N φ η Counts [a.u.].5 σ p η 2γ σ p η 6γ σ n η 2γ σ n η 6γ.5 cut on ±2 σ φ [ ]

11 Background Suppression Missing Mass: M = P Beam +P N P η ) m N 69 MeV 89 MeV 9 MeV 29 MeV 39 MeV Counts [a.u.].5 69 MeV.5 89 MeV 9 MeV 29 MeV 39 MeV m [MeV] cut on ±.5 σ

12 Pulse Shape Analysis (TAPS) Photon : 3σ nucleon: exclusion zone ]85,38[ MeV

13 Other identification possibilities 8 γ TAPS 5 4 p TAPS E [MeV] 6 4 E [MeV] ToF [ns] 5 5 ToF [ns] 5 4 n TAPS 8 p CB E [MeV] 3 2 E [MeV] ToF [ns] E [MeV]

14 Invariant Mass Distributions Counts [a.u.] 69 MeV 89 MeV 9 MeV 29 MeV 37 MeV.5 69 MeV 89 MeV 9 MeV 29 MeV.5 69 MeV.5 89 MeV 9 MeV 29 MeV 37 MeV 37 MeV m γγ [MeV] integrate m γγ (E,cos(θ)) 2γ: MeV 6γ: 5-6 MeV normalize with photon flux detection efficiency correction (MC) nucleon detection efficiency correction (hydrogen data) γ +p η +p γ +p π +π + +n

15 η Asymmetries - Preliminary E σ /2 σ 3/2 On Neutron On Proton E E W [MeV] W [MeV] [µb] σ /2 [µb] σ / W [MeV] W [MeV] MAID [µb] σ 3/2 [µb] σ 3/2 BnGa W [MeV] W [MeV]

16 2π -Analysis

17 2π Asymmetries - Preliminary (Manuel Dieterle PhD work) On Proton E E σ /2 σ 3/ W [MeV] [µb] σ / W [MeV] [µb] σ 3/ W [MeV] On Neutron E W [MeV] σ /2 [µb] W [MeV] MAID σ 3/2 [µb] W [MeV]

18 Conclusion preliminary asymmetries for η and 2π η bump only in σ /2 : S, P resonance? 2π : To do: first bump in σ3/2 : D 3 (52) (p & n) second bump F5 (675) (p), D 5 (68) (n)? check normalization, trigger efficiency, nucleon efficiency,... use final target polarization values second approach: carbon subtraction more statistics is available: analyze Feb 4 beamtime (negative target polarization)

19 Thanks for your attention This work is supported by:

20 Appendix η-analysis

21 Appendix η Asymmetries E γ - Preliminary On Proton E E σ /2 σ 3/ E γ [MeV] [µb] σ / E γ [MeV] [µb] σ 3/ E γ [MeV].2 On Neutron E E γ [MeV] [µb] σ / E γ [MeV] [µb] σ 3/ E γ [MeV]

22 Appendix de/dω [/sr] MeV 73 MeV 75 MeV 77 MeV 79 MeV 8 MeV 83 MeV 85 MeV 87 MeV 89 MeV 9 MeV 93 MeV 95 MeV 97 MeV 99 MeV 7 MeV 9 MeV MeV 9 MeV 2 MeV 23 MeV 3 MeV 33 MeV 35 MeV MeV 3 MeV 3 MeV 5 MeV 25 MeV 27 MeV 37 MeV 39 MeV cos(θ η ) 5 MeV 7 MeV 29 MeV

23 Appendix de/dω [/sr] MeV 73 MeV 75 MeV 77 MeV 79 MeV 8 MeV 83 MeV 85 MeV 87 MeV 89 MeV 9 MeV 93 MeV 95 MeV 97 MeV 99 MeV 7 MeV 9 MeV MeV 9 MeV 2 MeV 23 MeV 3 MeV 33 MeV 35 MeV MeV 3 MeV 3 MeV 5 MeV 25 MeV 27 MeV 37 MeV 39 MeV cos(θ η ) 5 MeV 7 MeV 29 MeV

24 Appendix de/dω [/sr] MeV 55 MeV 55 MeV 525 MeV 535 MeV 548 MeV 562 MeV 578 MeV 592 MeV 68 MeV 622 MeV 638 MeV 652 MeV 668 MeV 682 MeV 742 MeV 832 MeV 758 MeV 848 MeV 772 MeV 862 MeV 698 MeV 788 MeV 882 MeV cos(θ* η ) 72 MeV 82 MeV 728 MeV 88 MeV

25 Appendix de/dω [/sr] MeV 55 MeV 55 MeV 525 MeV 535 MeV 548 MeV 562 MeV 578 MeV 592 MeV 68 MeV 622 MeV 638 MeV 652 MeV 668 MeV 742 MeV 832 MeV 758 MeV 848 MeV 682 MeV 772 MeV 862 MeV 698 MeV 788 MeV 882 MeV cos(θ* η ) 72 MeV 82 MeV 728 MeV 88 MeV

26 Appendix 2π -Analysis

27 Appendix MAID Proton Neutron

28 Appendix 2π Background Suppression Coplanarity: Counts [a.u.].5 σ p η 2γ σ n η 2γ φ [ ] cut on ±2 σ

29 Appendix π Invariant Mass Missing Mass: 475 MeV 775 MeV 75 MeV 375 MeV 435 MeV Counts [a.u.] MeV 775 MeV 75 MeV 375 MeV 435 MeV m [MeV] cut on ±.5 σ

30 Appendix 2π Background Suppression Invariant Mass: 475 MeV 775 MeV 75 MeV 375 MeV 45 MeV.5 Counts [a.u.] 475 MeV 775 MeV 75 MeV 375 MeV 45 MeV [MeV] m γγ