Status N* photoproduction with CLAS
Eugene PasyukJefferson Lab
CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
2E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
Resonance status for N* and Δ*
• Nearly half the states have only fair or poor evidence!
• Most states need more work to learn details
• Are there missing states?
3E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
Baryon Resonance Spectrum
Masses, widths, and coupling constants not well known for many resonances
Most models predict more resonance states than observed
N*
S. Capstik and W. Roberts
Lattice QCD
Mass(π) = 396 MeV
R.G. Edwards et al. Phys. Rev. D84 074508 (2011)
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From the Experiment to Theory
Experimentcross section,
spin observables
TheoryLQCD,
quark models,QCD sum rules,
…
Reaction Theorydynamical frameworks
Amplitude analysis→multipole amplitudes
→phase shifts
(single) dσ/dΩ,Σ,P,T(beam-target) E,F,G,H,(beam-recoil) Cx,Cz,Ox,Oz,(target-recoil) Lx,Lz, Tx,Tz,
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Polarization observables in pseudoscalar meson production4 Complex amplitudes: 16 real polarization observables.Complete measurement from 8 carefully chosen observables. πN has large cross section but in KY recoil is self-
analysing
I. S. Barker, A. Donnachie, J. K. Storrow, Nucl. Phys. B95 347 (1975).
πN KYrecoil targ
γ γ targ recoil
☻☻☻
☻
linearly polarized photons
☻☻☻☻☻☻
longitudinally polarized target
☻☻☻☻☻☻
circ polarized photons
☻☻☻☻☻☻☻☻☻☻☻☻
transversely polarized target
Complete, andover-determined
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CEBAF Large Acceptance Spectrometer 1997-2012
Torus magnet6 superconducting coils
Gas Cherenkov counterse/ separation, 256 PMTs
Time-of-flight countersplastic scintillators, 684 photomultipliers
Drift chambers35,000 cells
target + start counter
Electromagnetic calorimetersLead/scintillator, 1296 photomultipliers
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12/18/2012
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Polarized pohoton beamC
ircu
lar
pola
riza
tion
Circular polarization from 100% polarized electron beam
Linearly polarized photons: coherent bremsstrahlung on oriented diamond crystal
Circularly polarized beam produced by longitudinally polarized electrons
H. Olsen and L.C. Maximon, Phys. Rev. 114, 887 (1959)
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FROST
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HDIce polarized target Polarized at very high
magnetic field and very low temperature
Transferred to in-beam cryostat
Spin can be moved between H and D with RF transitions
All material can be polarized with small background
12E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
What we measure with CLAS
γp→π0p, π+n γp→ηp γp→η’p γp→KY (K+Λ, K+Σ0, K0Σ+) γp→π+π-p ωp, ρp, ϕp ….
γn→π-p γn→π+π-n γn→Σ-K+ , ΛK0
…..
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Single pion production
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Σ for γp → nπ+
60 1200 60 1200
DU12CM12MAIDBbGa
M. Dugger et al.Paper under collaboration review
g8b
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Σ for γ p → p π0
M. Dugger et al.
DU12CM12MAIDBbGa
Paper under collaboration review
g8b
16E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
Changes in couplings
Solution A1/2 A3/2
D(1700)3/2- DU12 132 ± 5 108 ± 5CM12 105 ± 5 92 ± 4BnGa 160 ± 20 165 ± 25MD07 226 210PDG12 104 ± 15 85 ± 22
D(1905)5/2+ DU12 20 ± 2 -49 ± 5CM12 19 ± 2 -38 ± 4BnGa 25 ± 5 -49 ± 4MD07 18 -28PDG12 26 ± 11 -45 ± 20
Those are both **** states!
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E for γ p → p π0
• Early stage results• Predictions agree
better at lower energies
(new)
M. Dugger et al.
g9a
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E for γ p → n π+
S. Strauch
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
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PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
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PRELIMINARY PRELIMINARY PRELIMINARY
Predictions worse at higher energies above 1.7 GeV
SAIDSAID (new fit)MAID
Cos(θπc.m.)
W = 1.25 GeV W = 1.27 GeV
W = 1.29 GeV W = 1.31 GeV W = 1.33 GeV W = 1.35 GeV
W = 1.47 GeVW = 1.45 GeV
W = 1.43 GeVW = 1.41 GeVW = 1.39 GeVW = 1.37 GeV
W = 1.49 GeV W = 1.51 GeV W = 1.53 GeV W = 1.55 GeV W = 1.57 GeV W = 1.59 GeV
W = 1.71 GeVW = 1.69 GeVW = 1.67 GeVW = 1.65 GeVW = 1.63 GeVW = 1.61 GeV
W = 1.73 GeVW = 1.75 GeV W = 1.77 GeV W = 1.81 GeV W = 1.83 GeV W = 1.9 GeV
W = 2.19 GeVW = 2.13 GeVW = 2.07 GeV
W = 2.02 GeVW = 1.98 GeVW = 1.94 GeV
W=1.73 GeV
Analysis note is being written
g9a
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T for γ p → n π+
(new)
(new)
(new)
M. Dugger et al.
g9b
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F for γ p → n π+
• Agreement with predictions get much worse at higher energies
• SAID13 are predictions based on preliminary fits to CLAS pion Σ measurements
(new) (new)
(new)
M. Dugger et al.
g9b
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Σ for γ n → p π-
D. Sokhan
preliminary
Curve - SAIDRed GRAALMagenta and Blue - Erevan 9 out of 40 angular bins are shown
Bins 0.04 in cos and 20 MeV in W
g13
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E for γn(p) → pπ-(p) g14
T. Kagea
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η photoproduction
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P. Collins
Σ for γp → pη
SAIDMAID
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY PRELIMINARY
PRELIMINARY
PRELIMINARYPRELIMINARY
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PRELIMINARY
preliminary
Analysis under working group review
g8b
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E for for γp → pη
I. Senderovich
g9a
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G for for γp → pη
I. Senderovich
g9a
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T for for γp → pη
R. Tucker
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F for for γp → pη
R. Tucker
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KY production
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D. G. Ireland, K. Livingston, B. McKinnon, C. A. Paterson
Σ , Ox , Oz for γ p → K+ Λ g8b
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Σ , Ox , Oz for γ p → K+ Σ0
D. G. Ireland, K. Livingston, B. McKinnon, C. A. Paterson
g8b
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T for γ p → K+ Λ and γ p → K+Σ0
D. G. Ireland, K. Livingston, B. McKinnon, C. A. Paterson
Due to the self-analyzing nature of the , determine many observables using only a linearly polarized beam
Direct measurements of TA4 – N. Walford
g8b
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W=1725 MeVEγ=1117 MeV
W=2125 MeVEγ=1938 MeV
W=2025 MeVEγ=1717 MeV
W=1975 MeVEγ=1610 MeV
W=1925 MeVEγ=1506 MeV
W=1875 MeVEγ=1405 MeV
W=1825 MeVEγ=1306 MeV
W=1775 MeVEγ=1210 MeV
W=2275 MeVEγ=2290 MeV
W=2225 MeVEγ=2170 MeV
W=2175 MeVEγ=2053 MeV
W=1675 MeVEγ=1027 MeV
T for γp→K+Λ
N. Walford
preliminary
★-CLASBnGakaonMAID
g9b
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W=1725 MeVEγ=1117 MeV
W=2125 MeVEγ=1938 MeV
W=2075 MeVEγ=1826 MeV
W=2025 MeVEγ=1717 MeV
W=1975 MeVEγ=1610 MeV
W=1925 MeVEγ=1506 MeV
W=1875 MeVEγ=1405 MeV
W=1825 MeVEγ=1306 MeV
W=1775 MeVEγ=1210 MeV
W=2275 MeVEγ=2290 MeV
W=2225 MeVEγ=2170 MeV
W=2175 MeVEγ=2053 MeV
T for γp → K+Σ0
N. Walford
preliminary
★-CLASBnGakaonMAID
g9b
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F for γp→K+Λ
N. Walford
★-CLASBnGakaonMAID
preliminary
g9b
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+- photoproduction
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Photoproduction of π+π-p states • Dominates photoproduction cross section for W >1.6 GeV • 64 observables• 28 independent relations related to helicity amplitude magnitudes• 21 independent relations related to helicity amplitude phases• Results in 15 independent numbers
Could be used for search of resonances that decay into other resonances
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Cross section for γp →pπ+π-
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IS for pπ+π-
E=1900-1950 MeV W=2120 MeV
One of 20 energy bins Charles Hanretty
Linearly polarized photons, unpolarized target
g8b
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I for pπ+π-
S. Strauch et al., PRL. 95, 162003 (2005) W. Roberts and T. Oed, PRC 71, 055201 (2005)A. Fix and H. Arenhovel, EPJA 25, 115 (2005) S. Park
g9a
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Pz for pπ+π-
W. Roberts and T. Oed, PRC 71, 055201 (2005)A. Fix and H. Arenhovel, EPJA 25, 115 (2005) S. Park
g9a
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Pz for pπ+π-
W. Roberts and T. Oed, PRC 71, 055201 (2005)A. Fix and H. Arenhovel, EPJA 25, 115 (2005) S. Park
g9a
43E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
Comparison with model: Pcz
preliminary
A. Fix and H. Arenhovel, EPJA 25, 115 (2005)
Y. Mao
g9a
44
Comparison with model: Psz
preliminary
Y. Mao
A. Fix and H. Arenhovel, EPJA 25, 115 (2005)
E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
g9a
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Summary of meson photoproduction σ Σ T P E F G H Tx Tz Lx Lz Ox Oz Cx Cz
Proton target
pπ0 ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓
nπ+ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓
pη ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓
pη’ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K+Λ ✔ ✓ ✓ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔
K+Σ0 ✔ ✓ ✓ ✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✔ ✔
K0*Σ+
✔ ✓ ✓ ✓ ✓ ✓ ✓ ✓
“Neutron” targetpπ- ✔ ✓ ✓ ✓ ✓ ✓ ✓
K+Σ- ✓ ✓ ✓ ✓ ✓ ✓ ✓
K0Λ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
K0Σ0 ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓
✔ - published ✔ - acquired
46E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
Summary Data collection with proton and deuteron targets is
complete “complete (or nearly complete) measurement” in
pseudoscalar meson photoproduction is in the can In many cases these are the first measurements. In most cases model predictions do not agree with
the data at higher energies Phenomenological and theoretical analyses will have
to deal with tenths of thousands of data points for various observables in different final states.
Setting up close collaboration with Bonn-Gatchina group.
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Extras
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Polarization observables in pseudoscalar meson production
g14 – E06-101: polarized gamma beams on polarized HD
• Circular and Linear polarized photons• flux up to 108 s-1 tagged (low bkg)• Longitudinally polarized solid HD• P(D) ~ 22%; lifetimes ~ 2 yr• Nov/11 – May/12: 14 billion triggers
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R Values for the
The appears 100% polarized when created with a fully polarized beam.
2 2 2x zR P C C + +
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Average R values
Energy and angle averages are consistent with unity.
No model predicted this CLAS result.
1 .0 1 0 .0 1R = ±
53E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
Model of effective Lagrangian approach
About the model:•Calculates diff-cross section by using transition amplitudes
•Amplitudes are determined by all the double-pion diagrams
53
• The diagrams above show the decay from N* resonances.
• Include resonances:
Diagrams of N* for the reaction γN → ππN
Other decays:• N-Born terms• Δ-Born terms
Examples of 2-fold differential g p → p + - cross sections2-fold cross sections within the CLAS acceptance.
Nine one-fold and 18 two-fold differential cross sections have become available for the first time in W-bins of 25 MeV width.
One-fold differential g p → p + - cross sections Blue dots: experimental data within the CLAS acceptanceBlack dots: accounting for the contributions from inefficient areas employing phase space approximationRed dots: extrapolating cross sections into inefficient areas within the framework of the JM model
Two approaches for cross section extrapolation provided close results
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recoil polarization P
excitation function
g11: W=1.7 – 2.8 GeV(unpolarized beam & target)
M.E. McCracken et al., PRC 81, 025201 (2010)
γp→K+Λ: cross section and P
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γp→K+Λ: Cx/Cz
Bradford et al. PRC 75, 035205 (2007),
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Comparison with other measurements
Experiment
Final State
W range (Gev)
S P T Ox Oz
CLAS g11K 1.62 – 2.84 N Y N N N
KS 1.69 – 2.84 N Y N N N
LEPSK 1.94 – 2.30 Y N N N N
KS 1.94 – 2.30 Y N N N N
GRAALK 1.64 – 1.92 Y Y Y Y Y
KS 1.74 – 1.92 Y Y N N N
CLAS g8K 1.71 – 2.19 Y Y Y Y Y
KS 1.75 – 2.19 Y Y Y Y Y
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Comparison with other measurements
LEPS LEPS
CLAS g8 CLAS g8
GRAAL
GRAAL
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Beam Asymmetry Comparison
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Beam Asymmetry Comparison
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Beam Asymmetry Comparison
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Beam-Recoil Comparison
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Beam Asymmetry Comparison
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Beam Asymmetry
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Target Asymmetry
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Beam-Recoil, Ox
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Beam-Recoil, Oz
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Beam Asymmetry
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Target Asymmetry
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Beam-Recoil, Ox
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Beam-Recoil, Oz
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Σ for γ p → p π0
DU12CM12MAIDBbGa
M. Dugger et al.
74E. Pasyuk CLAS 3rd Euroworkshop Glasgow, UK, June 20-22, 2013
W=1725 MeVEγ=1117 MeV
W=2125 MeVEγ=1938 MeV
W=2075 MeVEγ=1826 MeV
W=2025 MeVEγ=1717 MeV
W=1975 MeVEγ=1610 MeV
W=1925 MeVEγ=1506 MeV
W=1875 MeVEγ=1405 MeV
W=1825 MeVEγ=1306 MeV
W=1775 MeVEγ=1210 MeV
W=2275 MeVEγ=2290 MeV
W=2225 MeVEγ=2170 MeV
W=2175 MeVEγ=2053 MeV
W=1675 MeVEγ=1027 MeV
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T for γ p → K+ Λ
N. Walford
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Preliminary results: integrated cross section at W from 1.6 to 2.8 GeV
SAPHIR(2005)&ABBHHM(1969)
JLAB g11a within CLAS acceptance
JLAB g11aaccept. corr. applied
Systematic errors from accept. corr. procedure ~8-20%
Integrated cross sections for γp → p π+π -
E .Golovach
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Differential cross sections for γp → pπ+π-
Blues dots:Measured cross sections within the CLAS acceptance.
Blue line: JM model* prediction within the CLAS acceptance.Black line: JM model results for 100% acceptance.
Black dots: Estimated cross sections when the contribution from inefficient area was obtained employing phase space approximation.
*Mokeev et al. PRC 80 (2009) 045212
E .Golovach
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Differential cross sections for γp → pπ+π-
Blues dots:Measured cross sections within the CLAS acceptance.
Black dots: Estimated cross sections when the contribution from inefficient area was obtained employing phase space approximation.
E .Golovach