Kaon Photoproduction Results from CLAS

Transcription

1 Kaon Photoproduction Results from CLAS D. G. Ireland 9-13 November 2009 INT-Jlab Workshop on Hadron Spectroscopy 0

2 Missing Baryon Resonances 1

3 Resonance Hunting Total Cross-sections + differential cross-sections + Partial Wave Analysis +... Cross section Δ(1232)P 33 N(1440)P 11 N(1520)D 13 N(1535)S 11 Δ(1600)P Eγ (GeV) Mostly done with πn scattering or photoproduction Missing resonances may decay through other channels 2

4 Meson Photoproduction Cross Sections 3

5 Evidence for new resonance? With D 13 Without D 13 Mart & Benhold, Phys. Rev. C (R) (1999) 4

6 Transversity Amplitudes r γ p } Λ K r γ p } Λ K r γ p } Λ K r γ p } Λ K b 1 = 1 / 2 [(S 1 + S 2 ) + i(n - D)] b 2 = 1 / 2 [(S 1 + S 2 ) - i(n - D)] b 3 = 1 / 2 [(S 1 -S 2 ) - i(n + D)] b 4 = 1 / 2 [(S 1 -S 2 ) + i(n + D)] N, S 1,S 2, D: Helicity Amplitudes 5

7 Experimental Observables 6

8 γp KΛ Reaction Kinematics ˆx ẑ K+ γ r ŷ cm.. Θ K + proton Λ r ˆx ŷ ẑ ˆx ŷ π ẑ Θ p proton Hyperon is self-analysing dσ = σ { 0 1 Pγ Σ cos 2φ dω α cosθ P O sin 2φ α cosθ PC + α cosθ x y α cosθ P O z γ P γ x α cosθ z y P T γ x cos 2φ sin 2φ α cosθ PC Cross Section without target polarisation z o o x z } 7

9 CLAS at Jefferson Laboratory Hall B 8

10 Tagged Photons at CLAS E γ = E 0 E Circular Polarisation: polarised electron beam, amorphous radiator Linear polarisation: Crystal (diamond) radiator 9

11 γp KΛ Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, (2006). 10

12 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, (2006). 11

13 γp KΣ Cross Section Measurements B. Dey (CMU) 12

14 Information Content of Data Assuming perfect differential cross section measurement (one bin in W, θ CM ) Rescale transversity amplitudes: a i = b b i b2 + b3 + b4 2 What is the remaining uncertainty in the amplitudes? Quantify with Entropy: ( a ) log P( ) H P i 2 a i = 13

15 Differential Cross Section only 14

16 Recoil Polarisation ˆx ẑ K+ γ r ŷ cm.. Θ K + proton Λ r ˆx ŷ ẑ ˆx ŷ π ẑ Θ p proton Hyperon is self-analysing dσ = σ { 0 1 Pγ Σ cos 2φ dω α cosθ P O sin 2φ α cosθ PC + α cosθ x y α cosθ P O z γ P γ x α cosθ z y P T γ x cos 2φ sin 2φ α cosθ PC z o o x z } 15

17 Recoil Polarisation (P) γp KΛ GENT Kaon-MAID Guidal, Laget, Vanderhaeghen J. McNabb et al. (CLAS) Phys. Rev. C 69, (2004). 16

18 Differential Cross Section + Recoil (LARGE) 17

19 Beam-Recoil Double Polarisation (C x,c z ) ˆx ẑ K+ γ r ŷ cm.. Θ K + proton Λ r ˆx ŷ ẑ ˆx ŷ π ẑ Θ p proton Hyperon is self-analysing dσ = σ { 0 1 Pγ Σ cos 2φ dω α cosθ P O sin 2φ α cosθ PC + α cosθ x y α cosθ P O z γ P γ x α cosθ z y P T γ x cos 2φ sin 2φ α cosθ PC z o o x z } 18

20 Λ Polarisation R P + C + C x z Λ fully polarised R. Bradford et al., Phys. Rev. C 75, (2007). 19

21 Differential Cross Section + Recoil (LARGE) + Cx (LARGE) + Cz (LARGE) 20

22 Photon Beam Asymmetry (Σ) ˆx ẑ K+ γ r ŷ cm.. Θ K + proton Λ r ˆx ŷ ẑ π dσ = σ dω 0 { 1 P γ Σ cos 2φ ˆx ŷ ẑ Θ p proton α cosθ P O + α cosθ x y α cosθ P O z γ P γ x z sin 2φ α cosθ PC α cosθ y P T γ x cos 2φ sin 2φ α cosθ PC z o o x z } 21

23 Linear Polarisation analysis Photon Linear Polarisation Particle ID Λ Σ 0 Thesis work of Craig Paterson (Glasgow) 22

24 γp KΛ Photon Beam Asymmetry 23

25 γp KΛ Photon Beam Asymmetry 24

26 γp KΛ Photon Beam Asymmetry 25

27 Differential Cross Section + Beam Asymmetry (LARGE) 26

28 Recoil - Comparison ~Factor of 4 increase in statistics from best previous measurements g8b Prev CLAS GRAAL 27

29 Beam-Recoil Double Polarisation (Ο x,o z ) ˆx ẑ K+ γ r ŷ cm.. Θ K + proton Λ r ˆx ŷ ẑ π dσ = σ dω 0 { 1 P γ Σ cos 2φ ˆx ŷ ẑ Θ p proton α cosθ P O + α cosθ x y α cosθ P O z γ P γ x z sin 2φ α cosθ PC α cosθ y P T γ x cos 2φ sin 2φ α cosθ PC z o o x z } 28

30 γp KΛ Beam-Recoil O x and O z 29

31 Positivity Constraints: P 2 + O x2 + O z 2 - Full polarization at forward angles - Not repeated over full kinematic range - More relations can be tested (P 2 + O x 2 +Oz 2 ) 1/2 30

32 Differential Cross Section + Recoil (LARGE) + Ox (LARGE) + Oz (LARGE) 31

33 Differential Cross Section + Beam Asymmetry (LARGE) Recoil (LARGE) + Target (LARGE) 32

34 Outlook Deuterium Target G10. Unpolarized photons on Deuterium 1 st measurement of σ for the γ n K + Σ - Sergio Anefalos Pereira, INFN. Detect π - n, K + Σ from π - n inv. mass G13. Circularly and linearly polarized photons on Deuterium γ n K + Σ - analysis for polarization observables underway. Edwin Munevar, GWU

35 Outlook Deuterium Target γp (n) > Κ + Λ 0 (n) Russell Johnstone, Glasgow Cosθ cm ( ) Each plot is 200MeV photon energy bin MeV Σ 0 Data taking completed Currently being analysed Data on quasifree neutron and proton Circular and Linear Polarisation Λ 0 34

36 Outlook Deuterium Target G13 1 st measurement of Beam Asymmetry γn (p) > Κ 0 s Λ0 (p) Neil Hassall, Glasgow Single, and double polarization observables in progress 35

37 Outlook FROzen Spin Target (FROST) Target can be longitudinally or transversely polarised Complete measurement possible First part of run complete Undergoing calibration Second period to run soon 36

38 Complete Measurement KY photon target recoil 37

39 Conclusions Kaon Photoproduction results from CLAS: Published results: σ, P, C x, C z Preliminary results: Σ, T, O x, O z In the near future: Same set of results for 2 H target (quasifree neutron and proton) Complete results (FROST) Next few years: Complete set on 2 H and p (HDIce) 38

40 Backup Slides 39

41 B. Dey (CMU) 40

42 B. Dey (CMU) 41

43 B. Dey (CMU) 42

44 B. Dey (CMU) 43

45 B. Dey (CMU) 44

46 CLAS 45

47 g8b: July 2005 Polarized photon energy range: GeV Events (single charged particle in CLAS): 10 billion preliminary results: π 0 p, Mike Dugger, ASU CLAS data SAID Beam Asymmetry Σ High statistics. Good agreement with previous measurement. We have P well determined. From Brem. Calculation and pin results we expect 3% systematic error in P

48 Resonances in Quark Models 47

49 Kaon Photoproduction 48

50 Experimental Observables 49

51 Contributing Processes + channel coupling 50

52 Helicity Amplitudes r γ p } Λ K r γ p } Λ K r γ p } Λ K r γ p } Λ K N S 1 S 2 D No overall helicity flip = γ (p Λ) Single helicity flip Single helicity flip Double helicity flip 51

53 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, (2006). 52

54 Cross Section Measurements R. Bradford et al., Phys. Rev. C 73, (2006). 53

55 Beam-Recoil Double Polarisation C z Regge+Resonance GENT Saclay, Argonne, Pittsburgh Kaon-MAID Bonn, Giessen, Gatchina Shklyar Lenske Mosel R. Bradford et al., Phys. Rev. C 75, (2007). 54

56 Beam-Recoil Double Polarisation C x Saclay, Argonne, Pittsburgh Bonn, Giessen, Gatchina Shklyar Lenske Mosel Regge+Resonance GENT Kaon-MAID R. Bradford et al., Phys. Rev. C 75, (2007). 55

57 Photon Beam Asymmetry 56

58 Photon Beam Asymmetry 57

59 Photon Beam Asymmetry 58

60 K production on n. Deuterium target G13 1 st measurement of Beam Asymmetry γn (p) > Κ 0 s Σ 0 (p) Neil Hassall, Glasgow Single, and double polarization observables in progress

61 Differential Cross Section + Recoil (small) 60

62 γp KΛ: Extracting O x and O z 61

63 Outlook Deuterium Target G13 γn (p) > Κ 0 s Λ0 (p) γn (p) > Κ 0 s Σ 0 (p) Neil Hassall, Glasgow 62