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Highlights on hadron physics at CLAS
K. HicksJAEA SeminarMay 18, 2012
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JAEA Seminar 2
Outline
• Meson-Baryon Cloud (MBC) Effects– New results on baryon photocouplings– Need for coupled-channels analysis
• Spectroscopy of baryons and mesons– New and future analysis of KL– New data: 2p, K*Y, KY*, etc.
• Future upgrade to CLAS12– Probe transition from MBC to quark core.
2012 May 18
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JAEA Seminar 3
quar
k m
ass (
GeV
)
Quark mass extrapolated to the chiral limit, where q is the momentum variable of the tree-level quark propagator (curve=DSE, data=LQCD).
LQCD, DSE and …meson dressed quark
confinement
current quark
p,r,w… resolutionlow
high
Hadron Structure with Electromagnetic Probes
N,N*,D,D*…
3q-core+MB-cloud
3q-core
pQCD
2012 May 18
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JAEA Seminar 4
NΔ Transition Form Factor (GM) from EBAC analysis
In the relativistic QM framework, the bare-core contribution is well described by the three-quark component of the wavefunction.
One third of G*M at low Q2 is due
to contributions from meson–baryon (MB) dressing:
bare quark core
Q2=5GeV2
CLASHall A Hall CMAMIBates
Meson-BaryonCloudEffect
The area of Q2<7.0 GeV2 is far from pQCD domain
B.Julia-Diaz et al., PRC 69, 035212 (2004)
2012 May 18
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JAEA Seminar 5
Partial wave (LSJ) amplitude of a b reaction:
Reaction channels:
Transition potentials:
coupled-channels effect
Dynamical coupled-channels model of EBAC
Meson-exchange potentials(Derived from Lagrangians) bare N* states
For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)
2012 May 18
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JAEA Seminar 6
Partial wave (LSJ) amplitude of a b reaction:
Reaction channels:
Transition potentials:
coupled-channels effect
Dynamical coupled-channels model of EBAC
exchange potentialsof ground state
mesons and baryonsbare N* states
For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)
core
meson cloud
meson
baryon
Physical N*s will be a “mixture” of the two pictures:
2012 May 18
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JAEA Seminar 7
Jefferson Lab Today
Large acceptance spectrometer electron/photon beams
Hall B
B
A
C2012 May 18
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JAEA Seminar 8
Radiative Decay of Strange Baryons
2012 May 18
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JAEA Seminar 9
General Motivation
• Electromagnetic interactions are the cleanest way to access information on wavefunctions.– For strange baryons, the EM coupling can only be
studied by measuring the decay.• SU(6) wavefunctions provide a zeroth-order
prediction for M1 transitions.– SU(6) symmetry provides a link between N* and
Y* radiative decays: constrain SU(6) symmetries.
2012 May 18
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JAEA Seminar 10
U-spin: connects D and S* decays
• SU(3) has three equal symmetries:– I-spin: exchange of u and d quarks– U-spin: exchange of d and s quarks– V-spin: exchange of u and s quarks
• With respect to known symmetries:– I-spin conserves chiral symmetry (mass)– U-spin conserves EM symmetry (charge)– V-spin conserves neither chiral nor EM symmetry
2012 May 18
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JAEA Seminar 11
Group structure of U-spin:
2012 May 18
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JAEA Seminar 12
How is this useful?
2012 May 18
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JAEA Seminar 13
CLAS result
2012 May 18
~10% uncert.
PhD thesis, Dustin Keller
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JAEA Seminar 14
Predictions from other models
2012 May 18
Experiment: 660 +/- 60 479 +/- 73
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JAEA Seminar 15
Interpretation
• Meson-Baryon Cloud effects are substantial for the Y* resonances also.– U-spin relation works better than CQM, etc.
• We can now make a prediction for S*+ decay.– The Wigner-Eckart theorem requires that the
branching ratios D+ pg and D0 ng are equal.– U-spin predicts a ratio:
2012 May 18
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JAEA Seminar 16
New CLAS result
2012 May 18
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JAEA Seminar 17
The MBC in electroproduction
2012 May 18
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JAEA Seminar 18
N* electrocouplings from analyses of exclusive channels
γv
N N’N*,△
A3/2, A1/2, S1/2
GM, GE, GC
p, h, pp,..
N
p, h, pp,..
N’
+*
• Separation of resonant/non-resonant contributions
• N* ‘s can couple to various exclusive channels with entirely different non-resonant amplitudes, while their electrocouplings should remain the same.
• Consistent results from the analyses of Np and Npp electroproduction channels show that model uncertainties are under control.
Resonant amplitudes Non-resonant amplitudes
2012 May 18
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JAEA Seminar 19
Npp CLAS (New!) preliminary.
Np CLAS
Good agreement between the Np and Npp channels. N* electrocouplings are measurable and model independent.
I. Aznauryan,V. Burkert, et al., PRC 80,055203 (2009).
A1/2S1/2
A3/2
F15(1685)
A3/2
P11(1440) P11(1440)
D13(1520)
Np worldV. Burkert, et al., PRC 67,035204 (2003).
Np Q2=0, PDG.
Np Q2=0, CLAS
M. Dugger, et al., PRC 79,065206 (2009).
gvNN* electrocouplings from Np/Npp production
2012 May 18
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JAEA Seminar 20
High lying resonance electrocouplings from p+p-p Δ(1700)D33
A1/2
A3/2 S1/2
Electrocouplings of S31(1620), S11(1650), F35(1685), D33(1700) ,and P13(1720) states were obtained for the first time from p+p-p electroproduction data .
Npp CLAS preliminary.
Np worldV.D.Burkert, et al., PRC 67,035204 (2003).
Np Q2=0, PDG.
Np Q2=0, CLAS
M.Dugger, et al., PRC 79,065206 (2009).
2012 May 18
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JAEA Seminar 21
Mystery of P11(1440) structure is solved
Quark models:I. Aznauryan LC
S. Capstick LC
Relativistic covariant approach byRamalho & Gross
The electrocouplings are consistent with P11(1440) structure as combination: a) quark core as a first radial excitation of the nucleon, and b) meson-baryon dressing.
EBAC-DCC MB dressing (absolute values).
A1/2
S1/2
MBC effects could explain the data at low Q2.2012 May 18
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JAEA Seminar 22
Coupled-channels effect in various reactions
Fullc.c. effect of ppN(pD,rN,sN) & hN off
Full
Fullc.c effect off
c.c. effect of ppN(pD,rN,sN) & hN off
Pion photoproductions
Pion electroproductions
Double pion productions
EBAC2012 May 18
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JAEA Seminar 23
Lineshape of the L(1405)
2012 May 18
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JAEA Seminar 242012 May 18
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JAEA Seminar 252012 May 18
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JAEA Seminar 262012 May 18
K. Moriya & R. Schumacher (CMU/IU) (CMU)
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JAEA Seminar 27
Interpretation
• For a baryon resonance with a single pole, isospin symmetry S+p- = S-p+.
• The data favor a dynamically-generated resonance (two-pole solution Sp and NK).– Evidence of MB coupled-channels effects?
2012 May 18
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JAEA Seminar 28
Spectroscopy with KY, K*Y and KY*
2012 May 18
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JAEA Seminar 29
Quark Model Classification of N*
D(1232)
D13(1520)S11(1535)
Roper P11(1440)
+ q³g
+ q³qq
+ N-Meson
+ …New P11, P13, or D13 states?
2012 May 18
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JAEA Seminar 30
Amplitude Uncertainty in gp K+L
CLAS (g1c, g11a) and GRAAL s, Cx’, Cz’, s , P and S, T, P, Ox’, Oz’
Real parts of the PWA multipolesBoGa (dot-dashed), MAID (dashed), SAID (dotted), JSLT (solid)
A. S
ando
rfi e
t al.,
J. P
hys.
G 3
8 (2
011)
053
001
2012 May 18
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JAEA Seminar 31
Process is described by 4 complex, parity conserving amplitudes 8 well-chosen measurements are needed to determine amplitude For hyperon finals state 16 observables will be measured in CLAS large ➠redundancy in determining the photo-production amplitudes allows many ➠cross checks 8 observables measured in reactions without recoil polarization
weak decay has large analyzing power
γp→K+Λ
FROST/HD gN pN, hN, KL, KS, Npp
2012 May 18
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JAEA Seminar 32
K*+Y Photoproduction
Motivation:1. Search for higher-mass N* resonances 2. Compare with KY and K*0Y a. K*Y coupling sensitive to K0(800).
b. K0(800) is part of the scalar nonet.c. K0(800) has not been directly observed.
g
p
N*Y
K*
Oh and Kim, Phys Rev C 74, 015208(2006).
2012 May 18
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JAEA Seminar 33
Differential cross sections of K*+Λ:
Preliminary result
2.1 ---2.7 GeV1.5 --- 2.1 GeV
2012 May 18
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JAEA Seminar 34
Differential cross sections of K*+ Σ0:
Preliminary result
1.7 --- 2.3 GeV 2.3 --- 2.9 GeV
2012 May 18
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L++ +*Kpg
Total Cross Sections
Preliminary result
0* S++ +Kpg
2012 May 18 35JAEA Seminar
PhD thesis of Wei Tang
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2012 May 18 JAEA Seminar 36
P. Mattione, Rice/CMU
Preliminary
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JAEA Seminar 37
Meson Spectroscopy
2012 May 18
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JAEA Seminar 382012 May 18
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JAEA Seminar 39
New: Scalar Mesons from gp KsKsp
2012 May 18
4-p Invariant mass (GeV)
CLAS g11Eg
max=3.8CLAS g12Eg
max=5.7
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JAEA Seminar 40
The future: CLAS12
2012 May 18
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JAEA Seminar 41
CLAS12
Luminosity > 1035 cm-2s-1
Hermeticity Polarization
Baryon Spectroscopy Elastic Form Factors N to N* Form Factors GPDs and TMDs DIS and SIDIS Nucleon Spin Structure Color Transpareny …
Central Detector
Forward Detector
1m
CLAS12
2012 May 18
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M. Battaglieri
Forward Photon Tagger for Spectroscopy
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JAEA Seminar 43
A new N* regime at Q2>3.5 GeV2?
Data appear to reach aplateau at Q2>3.5 GeV2, but conclusive tests require higher Q2 P11
D13
S11
Transition to photon interactions with dressed quarks?
2012 May 18
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JAEA Seminar 44
Resonance Transitions at 12 GeV
CLAS12 projected
Experiment E12-09-003 will extend access to transition FF for many prominent states in the range to Q2=12GeV2.
quar
k m
ass (
GeV
)
Electromagnetic form factors are sensitive to the effective quark mass.
At 12 GeV we probe the transition from “dressed quarks” to elementary quarks.
accessibleat 6 GeV
accessibleat 12 GeV
2012 May 18
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JAEA Seminar 45
Summary
• The Meson-Baryon Cloud has significant effects on photon coupling observables– We cannot ignore coupled-channel effects!
• There are precise new data on KY, K*Y, KY*– This will help the search for missing resonances– K* data will determine the role of the K0(800).
• PWA for mesons: exotics & scalar mixing• Future: CLAS12: transition to current quarks.
2012 May 18
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JAEA Seminar 46
Backup Slides
2012 May 18
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JAEA Seminar 47
t-dependence of f(1500)
2012 May 18