Vector-Meson Photoproduction

Transcription

1 Vector-Meson Photoproduction PWA ATHOS 2015 Ashburn, VA Hartmut Schmieden Physikalisches Institut Universität Bonn Germany why vecor mesons? ELSA status ω, ϕ, K* double polarization γ + p p + ω ELSA Summary & Conclusions 1

2 Why vector mesons? search for (missing) resonances understand internal resonance dynamics medium modifications VMD: photoproduction elastic vm nucleon scattering NN potential (ω) ω & ϕ: isospin filters for s-ch. resonances K* required for complete picture 1.49 p η 1.7 p ω 1.90 p η' 1.96 p ϕ K* Λ K + Λ(1520) cm energy / GeV 2

3 Production Mechanism basically similar for other vm's figure taken from Williams et al. (CLAS) PR C80 (2009) ! to disentangle for resonance analysis 3

4 Completeness spin-1 meson 3 polarization states determine 24 amplitudes 1 phase but: more information accessible than in pseudoscalar production decay angular distributions polarized unpolarized beam asymm. G, G bachelor linpol. beam-target asymm. E 4 beam-target helicity asymm.

5 5

6 ELSA experimental areas beamline E beamline S HPH-Kick-off March 2014 p. 5 D. Elsner 6

7 CB/TAPS setup BoFrost pol. target ph ~ 82% τ ~ 300 h 7

8 γ + p p + ω J. Barth et al. (SAPHIR collab.), Eur. Phys. J. A 18 (2003) 117 SAPHIR ELSA Eγ = GeV unpol. t-dependence x-sec total x-sec unpolarized SDME's (dσ/dt) / (µb/gev 2 ) diffractive resonance? t t min / GeV 2 8

9 γ + p p + ω data: V. Vegna et al. (GRAAL) arxiv: also shown Frank Klein et al. (CBELSA) Phys. Rev. D 78 (2008) model: Q. Zhao et al., Phys. Rev. C 58 & 63 no resonances s-channel resonances confirms resonance contributions near threshold 9

10 γ + p p + ω Williams et al. (CLAS) PR C80 (2009) [PWA paper] 10

11 γ + p p + ω Williams et al. (CLAS) PR C80 (2009) [PWA paper] 11

12 γ + p p + ω Williams et al. (CLAS) PR C80 (2009) unpolarized SDME's 12

13 γ + p p + ω A. Wilson et al. (CBELSA) submitted to Phys. Lett. B lin. polarized SDME's Bonn-Gatchina PWA 13

14 γ + p p + ω H. Eberhardt et al. (CBELSA/TAPS) arxiv: beam-target double polarization longitudinally polarized target w/ circular beam polarization linear 14

15 γ + p p + ω MAMI near threshold VMD scatt. length consistent with previous theoretical results: (0.82 ± 0.03) fm I. Strakovsky et al. (MAMI-A2) arxiv:

16 γ + d ω + X V. Vegna et al. (GRAAL) arxiv: quasifree neutron different! quasifree proton 16

17 Resonance extractions from "ω"-pwa Bonn-Gatchina PWA E. Klempt, priv. comm. Penner & Mosel, PR C 66 GRAAL dominant CLAS PWA dominant CLAS PWA suggestive CLAS PWA strong CLAS PWA + 1 new resonance > 2 GeV 17

18 γ + p p + ϕ ideal mixing π/η-exchange s-ch. resonances } OZI suppressed pure Pomeron exchange "bump" structure t-channel effect? N* contribution? cc effect? LEPS figure taken from T. Mibe et al. (LEPS), Phys. Rev. Lett. 95 (2005) SAPHIR: J. Barth et al. (SAPHIR), Eur. Phys. J. A 17 (2003)

19 γ + p p + ϕ ϕ K + K charged mode B. Dey et al. (CLAS) PR C89 (2014) confirmation of earlier findings w/ tremendously improved statistics 19

20 γ + p p + ϕ H.-Y. Ryu, et al., Prog. Theor. Exp. Phys (2014) 023D03 arxiv: K Λ(1520), K* Λ(1116), K Λ(1116) similar: S. Ozaki et al., Phys. Rev. C 80 (2009) from B. Dey et al. 20

21 γ + p p + ϕ H.-Y. Ryu, et al., Prog. Theor. Exp. Phys (2014) 023D03 arxiv: describes "bump" KΛ(1520) box unfortunately log-scale 21

22 γ + p p + ϕ H.-Y. Ryu, et al., Prog. Theor. Exp. Phys (2014) 023D03 arxiv: S. Ozaki et al., PR C80 (2009) & erratum: PR C (2010) KΛ(1520) or ϕn "molecule" w/ ss N*(~2250MeV, δ ~ 100 MeV) J P = 1/2 describes "bump" KΛ(1520) box unfortunately log-scale 22

23 γ + p p + ϕ ϕ K 0 S K0 L neutral mode H. Seraydaryan et al. (CLAS) PR C89 (2014) bump persists! 23

24 γ + p p + ϕ s-channel resonance(s)?? J = 3/2 resonance parity + or m = 2.08 GeV width ~ 0.5 GeV A 1/2 /A 3/2 = not D 13 (2080) large s-content strong coupling to ω and KΛ 3/2 + resonance t t-channel 3/2 A. Kiswandhi and S.N. Yang, Phys. Rev. C 86 (2012)

25 γ + p K* + Y ( * ) production mechanism s-quark exchange figure from S.-H. Kim, A. Hosaka, H.-C. Kim Phys. Rev. D 90 (2014)

26 γ + p K* + Y K* + Λ K* 0 Σ + K* + Λ K* 0 data Hleiqawi et al. (CLAS) Nanova et al. (CBELSA) sensitivity to κ exchange W. Tang et al.[clas], Phys. Rev. C 87 (2013)

27 γ + p K* + Y : resonance contributions S.-H. Kim, A. Hosaka, H.-C. Kim Phys. Rev. D 90 (2014) essential important for K* + Λ off proton negligible for K* 0 Λ off neutron 27

28 γ + p K S 0 + Σ + K* most forward bin <θ K cm > = 0.83 R. Ewald et al. (CBELSA), PLB 713 (2012) full: present data open: Castelijns et al. 28

29 γ + p K S 0 + Σ + R. Ewald et al. (CBELSA), PLB 713 (2012) full: present data open: Castelijns et al. 29

30 γ + p K S 0 + Σ + K* Σ + cross section added M. Nanova et al., EPJ A35 (2008) 333 R. Ewald et al. (CBELSA), PLB 713 (2012) full: present data open: Castelijns et al. 30

31 γ + p K S 0 + Σ + K* Σ + cross section added M. Nanova et al., EPJ A35 (2008) 333 K* K K π R. Ewald et al. (CBELSA), PLB 713 (2012) N Λ/Σ 31

32 γ + p K S 0 + Σ + interpretation A. Ramos & E. Oset, Phys. Lett. B727 (2013) 287 vectormeson-baryon dynamics structure N*(2080)(3/2 ) / N*(2090)(1/2 ) [removed from PDG] delicate interference K*Λ / K*Σ channels K 0 Σ 0 off neutron target to test proton neutron 32

33 BGO-OD ELSA tagger OD spectrometer w/ tracking & tof BGO calorimeter w/ pid & tracking 33

34 BGO-OD ELSA l unique combination of central calorimetry with l high resolution forward spectrometer l complementary to other setups Crystal Barrel /TAPS CLAS SPring8 tagger OD spectrometer w/ tracking & tof BGO calorimeter w/ pid & tracking 34

35 BGO-OD ELSA 35

36 BGO-OD commissioning results Missing mass: γ p X γ γ [MeV] 1500 Neutral meson reconstruction in the BGO Two γ invariant mass [MeV] β Charged particle ID in the Forward Spectrometer Momentum (p) [MeV] Counts Fit to π 0 peak Mean = 137 MeV σ = 15 MeV Fit to η peak Mean = 528 MeV σ = 31 MeV Counts Missing mass from protons, p < 1GeV M η M ω M η Two γ invariant mass [MeV] Missing mass: γp p X [Mev] 36

37 BGO-OD K + id β 1.1 β forward spec With Calculated β p [MeV/c] p [MeV/c] 1000 Simulated data Experimental data Fitted K lifetime 11 ns BGO ball Energy of decay sub-cluster [MeV] Time between incident and decay sub-cluster [ns] 37

38 BGO-OD forward spectrometer: (γ K + ) missing mass No extra selection cuts 120 Energy deposition in the BGO < 250 MeV Missing (hyperon) mass [MeV] Missing (hyperon) mass [MeV] Energy deposition in the BGO < 250 MeV & π 0 reconstructed π 0 reconstructed in the BGO Λ(1116) Σ(1193) Σ(1385) Λ(1405) Λ(1520) Missing (hyperon) mass [MeV] Missing (hyperon) mass [MeV] 38

39 Summary & Conclusions ps + vector meson photoproduction complete picture high precision unpolarized data ω: single & double polarization ϕ: Pomeron-dominated, but bump at threshold resonance / coupled ch. effect? K*: high precision data first resonance extraction coupling to other channels? more polarization data needed neutron target! } PWA resonance extraction 39