16 March 2009 EuNPC, Bochum 1

Kaon Photoproduction Results from CLAS

D. G. Ireland

2

“Missing” Baryon Resonances

3

Resonance Hunting…

Mostly done with N scattering or photoproductionMissing resonances may decay through other channels

Total Cross-sections+ differential cross-sections+ Partial Wave Analysis + ...

0.5 1.0 1.5

Cro

ss s

ecti

on

E (GeV)

P33

N(1440)P11

N(1520)D13

N(1535)S11

(1600)P33

4

Meson Photoproduction Cross Sections

5

Evidence for new resonance?

With D13

Without D13

Mart & Benhold, Phys. Rev. C 61 012201(R) (1999)

6

Transversity Amplitudes

b1 = 1/2[(S1 + S2) + i(N - D)] p

K }} p

K }} p

K }} p

K }}

b2 = 1/2[(S1 + S2) - i(N - D)]

b3 = 1/2[(S1 - S2) - i(N + D)]

b4 = 1/2[(S1 - S2) + i(N + D)]

N, S1,S2, D: Helicity Amplitudes

7

Experimental Observables

8

p →K Reaction Kinematics

proton

zy

x

z

y

x

zy

x

p

. .c m

K

proton

K+

zzzz

yy

xxxx

CPOP

TPP

CPOP

Pd

d

cos2sincos

2coscoscos

cos2sincos

2cos10

Cross Section without target polarisationHyperon is self-analysing

9

CEBAF at Jefferson Laboratory

10

CLAS

11

Tagged Photons at CLAS

• E = E0 – E’

• Circular Polarisation: polarised electron beam, amorphous radiator

• Linear polarisation: Crystal (diamond) radiator

12

p →K Cross Section Measurements

R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

13

Recoil Polarisation

proton

zy

x

z

y

x

zy

x

p

. .c m

K

proton

K+

zzzz

yy

xxxx

CPOP

TPP

CPOP

Pd

d

cos2sincos

2coscoscos

cos2sincos

2cos10

Hyperon is self-analysing

14

Recoil Polarisation (P) p→K

Guidal, Laget, VanderhaeghenGuidal, Laget, Vanderhaeghen

GENTGENT Kaon-MAIDKaon-MAID

J. McNabb J. McNabb et alet al. (CLAS) Phys. Rev. C . (CLAS) Phys. Rev. C 6969, 042201 (2004)., 042201 (2004).

15

Beam-Recoil Double Polarisation (Cx’,Cz’)

proton

zy

x

z

y

x

zy

x

p

. .c m

K

proton

K+

zzzz

yy

xxxx

CPOP

TPP

CPOP

Pd

d

cos2sincos

2coscoscos

cos2sincos

2cos10

Hyperon is self-analysing

16

Polarisation

2 2 2x zR P C C

→ fully polarised

R. Bradford et al., Phys. Rev. C 75, 035205 (2007).

17

Photon Beam Asymmetry ()

proton

zy

x

z

y

x

zy

x

p

. .c m

K

proton

K+

zzzz

yy

xxxx

CPOP

TPP

CPOP

Pd

d

cos2sincos

2coscoscos

cos2sincos

2cos10

18

Linear Polarisation analysis

Photon Linear Polarisation Particle ID

Thesis work of Craig Paterson (Glasgow)

19

p →K Photon Beam Asymmetry

20

p →K Photon Beam Asymmetry

PREL

IMIN

ARY

21

p →K Photon Beam Asymmetry

PREL

IMIN

ARY

22

Beam-Recoil Double Polarisation (x,Oz)

proton

zy

x

z

y

x

zy

x

p

. .c m

K

proton

K+

zzzz

yy

xxxx

CPOP

TPP

CPOP

Pd

d

cos2sincos

2coscoscos

cos2sincos

2cos10

23

p →K Extracting Ox and Oz

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p →K Beam-Recoil Ox and Oz

O x

PREL

IMIN

ARY

O z

PREL

IMIN

ARY

25

Experimental Observables

26

Outlook – Deuterium Target

• Data taking completed

• Currently being analysed

• Data on quasifree neutron and proton

• Circular and Linear Polarisation

27

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…

28

Conclusions

Kaon Photoproduction results from CLAS:

• Published results: , P, Cx, Cz

• Preliminary results: , T, Ox, Oz

In the near future:

• Same set of results for 2H target (quasifree neutron and proton)

• “Complete” results (FROST)

Next few years:

• Complete set on 2H and p (HDIce)

29

Backup Slides…

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Resonances in Quark Models

31

Kaon Photoproduction

32

Contributing Processes

+ channel coupling…

33

Helicity Amplitudes

N No overall helicity flip = |–p |

p

K }}S1 Single helicity flip

p

K }}S2 Single helicity flip

p

K }}D Double helicity flip

p

K }}

34

Cross Section Measurements

R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

35

Cross Section Measurements

R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

36

Cross Section Measurements

R. Bradford et al., Phys. Rev. C 73, 035202 (2006).

37

Beam-Recoil Double Polarisation Cz

R. Bradford et al., Phys. Rev. C 75, 035205 (2007).

Saclay, Argonne, PittsburghSaclay, Argonne, Pittsburgh

Bonn, Giessen, GatchinaBonn, Giessen, GatchinaKaon-MAIDKaon-MAID

Regge+ResonanceRegge+Resonance GENTGENT

Shklyar Shklyar Lenske Lenske MoselMosel

38

Beam-Recoil Double Polarisation Cx

GENTGENT

Saclay, Argonne, PittsburghSaclay, Argonne, Pittsburgh

Bonn, Giessen, GatchinaBonn, Giessen, Gatchina

Kaon-MAIDKaon-MAID

Regge+ResonanceRegge+Resonance

Shklyar Lenske Shklyar Lenske MoselMosel

R. Bradford et al., Phys. Rev. C 75, 035205 (2007).

39

Photon Beam Asymmetry

40

Photon Beam Asymmetry

PREL

IMIN

ARY

41

Photon Beam Asymmetry

PREL

IMIN

ARY

42

Recoil - Comparison

g8b

Prev CLAS

GRAAL

~Factor of 4 increase in statistics from best previous measurements

PREL

IMIN

ARY