Kaon Production on the Nucleon D. G. Ireland MENU Rome, September 30 – October 4, 2013.
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Kaon Production on the Nucleon D. G. Ireland MENU Rome, September 30 – October 4, 2013
Transcript of Kaon Production on the Nucleon D. G. Ireland MENU Rome, September 30 – October 4, 2013.
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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