Kaon Production on the Nucleon

D. G. Ireland

MENU Rome, September 30 – October 4, 2013

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Kaon Photoproduction

very high momentum

transfer (pQCD)

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Baryon Summary Table (PDG 2008)

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Baryon Summary Table (PDG 2012)

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“Missing” Baryon Resonances

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Resonances in Quark Models

Baryon Spectrum on the Lattice

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Excited state baryon spectroscopy from lattice QCD.Edwards, Dudek, Richards, Wallace Phys. Rev. D 84, 074508 (2011)

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Resonance Hunting…

Mostly done with pN scatteringMissing resonances may decay through other channels

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

Meson Photoproduction Cross Sections

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Jefferson Lab

CLAS

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*g p →KY Electroproduction

p

proton

Hyperon is self-analysing

Cross Section:

… with electron polarization…

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*g p →KL Separated Structure Functions

D. Carman et al. (CLAS), Phys. Rev. C 87, 025204, 2013

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*g p →KS Separated Structure Functions

D. Carman et al. (CLAS), Phys. Rev. C 87, 025204, 2013

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*g p →KL Q2 Dependence

D. Carman et al. (CLAS), Phys. Rev. C 87, 025204, 2013

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*g p →KS Q2 Dependence

D. Carman et al. (CLAS), Phys. Rev. C 87, 025204, 2013

gp →KL Photoproduction

proton

zy

x

z

y

x

zy

x

p

. .c m

K

proton

K+

Hyperon is self-analysing

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CLAS results γp→K+Λ → K+pπ-

Bonn-Gatchina Coupled Channel Analysis, A.V. Anisovich et al, EPJ A48, 15 (2012)

(Includes nearly all new photoproduction data)

M. McCracken et al. (CLAS), Phys. Rev. C 81, 025201, 2010

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CLAS results γp→K+Λ → K+pπ-

Bonn-Gatchina Coupled Channel Analysis, A.V. Anisovich et al, EPJ A48, 15 (2012)

(Includes nearly all new photoproduction data)

M. McCracken et al. (CLAS), Phys. Rev. C 81, 025201, 2010 R. Bradford et al. (CLAS), Phys.Rev. C75, 035205, 2007

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Fit to K+Λ with PDG2010 states < 2 GeV

EBAC group: Kamano, Nakamura, Lee, Sato (2012) Includes ***, **** states

PDG states insufficient to fit KΛ data

1965 1965

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Evidence for new N* states and couplings

StateN((mass)JP

PDG 2010 PDG 2012 KΛ KΣ Nγ

N(1710)1/2+ ***(not seen in

GW analysis)

*** *** ** ***

N(1880)1/2+ ** ** * **

N(1895)1/2- ** ** * ***

N(1900)3/2+ ** *** *** ** ***

N(1875)3/2- *** *** ** ***

N(2150)3/2- ** ** **

N(2000)5/2+ * *** ** * **

N(2060)5/2- *** ** ***

Bonn-Gatchina Analysis – A.V. Anisovich et al., EPJ A48, 15 (2012)(First coupled-channel analysis that includes nearly all new photoproduction data)

Ref: Scaling and Resonances in Elementary K+L Photoproduction [R.A. Schumacher and M.M. Sargsian, Phys. Rev. C 83, 025207 (2011)]

Compute coherent total amplitude:

Fit to observed angular distributions:

Test various resonance sets vs. mass

Free parameters: mass, width, couplings

Spin observables neglected

Sensitive to smaller contributions to reaction

Structure appears when scaling utilised.

N* K+L Amplitude Analysis

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Linearly Polarized Photons

Diamond radiator mountedon target ladder

Radiator in goniometer

Alignment checked byobserving symmetric

“Stonehenge Plot”

Polarization determined by fit to coherent bremsstrahlung

spectrum

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FROzen Spin Target (FROST)

Target can be longitudinally or transversely polarised[See talk by Barry Ritchie]

Transversity Amplitudes

b1 = < | M | > p

K } p

K } p

K } p

K }

b2 = < | M | >

b3 = < | M | ‖ >

b4 = < | M | ‖>

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Observables

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Imaging Multi-dimensional Objects

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Imaging Multi-dimensional Objects

?

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Comparison with other measurements

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Experiment Final State W range (Gev)

S P T Ox Oz

CLAS g11KL 1.62 – 2.84 N Y N N N

KS 1.69 – 2.84 N Y N N N

LEPSKL 1.94 – 2.30 Y N N N N

KS 1.94 – 2.30 Y N N N N

GRAALKL 1.64 – 1.92 Y Y Y Y Y

KS 1.74 – 1.92 Y Y N N N

CLAS g8KL 1.71 – 2.19 Y Y Y Y Y

KS 1.75 – 2.19 Y Y Y Y Y

Comparison with other measurements

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LEPS LEPS

CLAS g8 CLAS g8

GRAAL

GRAAL

Beam Asymmetry Comparison

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Preliminary

Beam-Recoil Comparison

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Preliminary

Beam Asymmetry Comparison

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Preliminary

Summary

• CLAS has measured a large set of data involving Kaon production

• Electroproduction: • Separated structure functions• Q2 dependence – information on form factors• Needs theoretical work

• Photoproduction: • Cross sections and recoil polarizations sensitive to N* physics• Exact interpretation of N* spectrum still ambiguous

• Outlook: • More polarization data to come (electro- and photo-production)• Results from (quasi-free) neutron• Full set of observables in KL and KS in resonance region• Exciting prospect for N* physics (with results from other channels)

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