1. October 12, 2005 @ Tallahassee, FL
Measurements of p(e, e’π +)n in the ∆(1232) and higher resonances for Q2≤4.9GeV2
October 12, Tallahassee, FL
Physics Motivation
Kinematics
Experiments & Analysis Process
Results
Cross Section & Asymmetry
Structure functions & Photocoupling Amplitude
Summary
N* 2005 Meeting Kijun Park

2. History of Roper Resonance
Physics Motivation ?
History of Roper Resonance
Roper signature has been clearly seen in
πN and γN reactions.
The unresolved low mass of P11(1440)
Close, Capstick, Simula : CQM
→ N=2 radially excited state
Cano-Gonzalez : A system consisting of a hard quark core & vector meson cloud
Li-Burkert : A hybrid states with q3G
P11(1440) is a pentaquark state ? ?
Various Q2 dependences for transition form-factors are predicted by different models.
Photocoupling Amplitude
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3. Single pion Electroproduction
Kinematics
Single pion Electroproduction
Kinematic variable
Unpol. Xsection w/ one-photon exchange approx.
s-channel
t-channel
Physics motivation
Study of Resonance to understand Nucleon Structure
Most Studies for NΔ(1232) and NN*(1535) using pπ0, pρ channels
States with I=1/2 couple more to the nπ+ than pπ0
Cross Section & Asymmetry gives us information on resonances in excited states
Asymmetry
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4. Experimental Data E1-6 Data (Oct.2001-Jan.2002) Kinematic Bins
E1-6 Data Kinematic Coverage
E1-6 Data (Oct.2001-Jan.2002)
5.754GeV polarized e- & LH2
~7M nπ+ trigger after MMx cut
W[GeV]
1.1 ~ 1.8
0.02(35)
Q2[GeV2]
1.72 ~ 4.92
Variable(7)
CSCM
-1.0 ~ 1.0
0.2(10)
PHICM
0. ~ 360.O
15O(24)
Kinematic
Bins
= 58,800
Particle ID (e-,π+)
Electron ID : q<0, fiducial , EC, Nphe , vertex cut
Pion ID : q>0, fiducial, TOF mass, vertex cut
Kinematic Correction (e-,π+)
Applied to both Experimental, MC data
Acceptance Correction [AC]
AC calculated by GSIM
Radiative Correction [RC]
RC done by ExcluRad (PRD 66, A. Afanasev)
Bin Centering Correction [BCC]
BCC performed by Models(MAID03, Sato-Lee)
High quality electron beam polarization, stable target status during e1-6
The same Kinematic correction technique applied to both MC, real data
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5. Cross section vs. PHICM , W
Cross section as function of φ*
@ W=1.23GeV, CSCM= 0.1, Different Q2 bins
Cross section as function of W
@ CSCM= 0.1 , 0.3
φ* =67.5 o, 142.5o
Different Q2 bins
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6. Asymmetry vs. PHICM W=1.23GeV, Q2=2.05GeV2 W=1.40GeV, Q2=2.05GeV2
MAID00
MAID03
DMT SL
W=1.23GeV, Q2=2.05GeV2
W=1.40GeV, Q2=2.05GeV2
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7. Structure Function :
MAID00
MAID03
SL04 SL
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8. Structure Function :
MAID00
MAID03
SL04 SL
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9. Structure Function :
MAID00
MAID03
SL04 SL
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10. /
Structure Function :
MAID00
MAID03
DMT
MAID98
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11. A 1/2 S 1/2 Photo-coupling Amp. ; preliminary
Quark Models
Light-front calculation
preliminary
q3G hybrid state
π-2π analysis
π electro- production IM, DR
ηelectro-, photo- production IM, DR
RPP estimation
GWU (VPI) pion photoproduction
This Work
Relativistic Quark Model
Non-relativistic Quark Model
Bonn, DESY, NINA, Jlab(η)
re-analyze the old data MAINZ
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12. Photo-coupling Amp. ; A 1/2 A 3/2 S 1/2 preliminary 10/12/05
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13. Summary
Differential Cross Section has been measured first time completely over all angular range in 1.1 < W < 1.8GeV at high 1.7 < Q2 < 4.9GeV2
Electron Beam Asymmetry has been measured in same kinematic region.
Measurement of Cross Section and Asymmetry have been compared to recent physics models such as MAID’s, Sato-Lee, DMT etc.
σT+εLσL , σTT , σLT , σLT / Structure Functions have been extracted.
The Cross Section and Beam Spin Asymmetry are fitted to extract the Transition Form Factors and compared with present predictions.
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14. BACKUP SLIDES
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15. Why we are interested in Hadron Physics ??
The hadrons constitute most of the visible matter.
The contribution of the current quark masses into total baryon mass is very small; most of the hadron mass comes from strong interactions.
Investigation of the spectrum and the internal structure of the hadrons provides information about the underlying strong interactions.
One of the physics goals of the JLab is to investigate the strong interactions in the confinement regime.
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16. Electron Scattering Elastic Scattering Deep Inelastic Scattering
Target stays intact and holds.
A good tool to study the ground state of the nucleon
Deep Inelastic Scattering
Energy transfer is large, target is broken apart.
A good tool to study the quark-gluon content of the nucleon at small distances.
Resonance excitation
The target is excited into a single bound system.
Allows us to study the internal structure of the ground and the excited states, and very useful for the exclusive reactions.
Key : Nπ decay channels of the intermediate excited states.
This analysis covers not only Δ(1232) but high resonance states.
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17. Quark Model Quarks are fundamental particle of hadrons.
Quarks interact with each other through eight gluon fields in QCD : SU(3) gauge theory
QCD has a complicate picture for solution at long distances.
In the constituent quark model the nucleon consists of 3 “fat” ~300 MeV constituent quarks in a confining potential.
Presence of Color tensor forces, such as spin-spin interaction, which can break the spherical symmetry of the ground state.
May be too simplified, other degrees of freedom, such as pions, may be needed.
Nucleon consists 3 constituent quarks (~300MeV) in a confined potential in constituent quark model.
Presence of Color tensor forces ; spin-spin interaction (Break the spherical symmetry of the ground state)
Simplified other degrees of freedom (pions) may be needed.
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18. Electroproduction Amplitudes
The electroproduction of an excited state can be described in terms of 3 photocoupling amplitudes A1/2, A3/2 and S1/2 .
Describable pion electroproduction using multipole amplitude El, Ml and Sl .
l : the orbital angular momentum in Nπ system.
The ± sign indicates how the spin of proton couples to the orbital momentum.
For each resonance there is one-to-one connection between multipole and helicity amplitudes. p g* N N*
El, Ml ,Sl
A1/2, A3/2,S1/2
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19. One of the first observed baryon resonances.
Spin J=3/2 and isospin I=3/2.
From angular momentum and parity conservation γN  Δ transition can be induced by E2, M1 and C2 multipoles.
SU(6)xO(3) symmetric quark model describes γN  Δ transition as a single quark spin flip.
If SU(6)xO(3) spatial wave functions are pure L=0, then γN  Δ transition can only be induced by j=1 photons, i.e. only M1+ allowed.
D-waves in the wave function will allow for E1+ and S1+ contributions.
∆(1232)Resonance
g M1
P(938) J=1/2
D(1232) J=3/2
e / e
More sophisticated models allow for explicit pion degrees of freedom (pion cloud).
pion cloud can also introduce E1+ and S1+ contributions.
e / e
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20. Kinematic Cuts e- π+ p φπ Particle ID (e-,π+) ph Fiducial Volume cut
Particle identification as an electron
Θπ=20o φπ θπ
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21. Kinematic Corrections
Mass of Proton from elastic
Mass of Neutron from nπ+
Kinematic Corrections
Vertex Corr. & Cut
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After Kine. Corr. For GSIM

22. AC & RC Corrections DATA GSIM σ = 0.0372 σ = 0.0368 tvertex
W dependent RC
Angle dependent RC
Acceptance vs. PHICM
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23. Normalization Elastic Cross Section
Ratio between elastic cross section and Bosted FFP(Rad) vs. electron angle
Inelastic Cross Section
W dependence of
inelastic cross section
@ Q2=2.5GeV2
Normalization
Bin correction by sub-binning from two models
@ W=1.23GeV, CSCM=0.1, two Q2 bins
Q2 dependence of inelastic cross section @ W=1.21GeV
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24. Electron Beam Asymmetry
Asymmetry in Q2=1.72, 2.05GeV2
& Compare to calculation from five different Physics Models
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25. Electron Beam Asymmetry
Asymmetry in Q2=2.44, 2.91GeV2
& Compare to calculation from five different Physics Models
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26. Systematic Uncertainties
Criteria
Avg.
Electron identification (S.F.) 3.0σ→3.5σ
Resol.
4.1%
Electron fiducial cut ( -10% width)
Width
2.3%
Pion identification σ→3.5σ
1.4%
Pion fiducial cut ( -10% width)
3.3%
Missing mass cut σ→2.0σ
1.0%
Vertex cut ( -5% cut)
LH2 target Density/Length
< 1.0%
Radiative Corr MAID00/03
Evnt ratio
< 0.4%
Acceptance Corr MAID00/03
Total
6.3%
Tot. sys.
e PID. sys.
e fidu. sys.
pi PID. sys.
pi fidu .sys.
Z-vtx. sys.
MMx. sys.
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27. 5-th Structure Function
σLTP @ W =1.39GeV in five different Q2 bins
& Compare to calculation from Physics Models
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28. 10/12/05
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29. D0/(W),D1/ (W) : fit from Pl=2,3,4(cosθ)
Legendre moment as function of W[GeV]
D0/(W),D1/ (W) : fit from Pl=2,3,4(cosθ)
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30. Model comparison MAID2000 & 2003
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31. Dependence of S1/2 , A1/2 MAID2003
Main sensitivity came from M1-, S1-
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32. Dependence of S1/2 , A1/2 MAID2003 Q2=2.GeV2
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33. Dependence of S1/2 , A1/2 MAID2003 Q2=2.GeV2
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34. Dependence of S1/2 , A1/2 MAID2003 Q2=2.GeV2
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35. σLTP vs. W @ Q2=1.72GeV2, CSCM<0.
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36. σLTP vs. W @ Q2=1.72GeV2, CSCM>0.
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37. σLTP vs. W @ Q2=2.05GeV2, CSCM<0.
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38. σLTP vs. W @ Q2=2.05GeV2, CSCM>0.
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39. σLTP vs. W @ Q2=2.44GeV2, CSCM<0.
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40. σLTP vs. W @ Q2=2.44GeV2, CSCM>0.
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41. σLTP vs. W @ Q2=2.91GeV2, CSCM<0.
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42. σLTP vs. W @ Q2=2.91GeV2, CSCM>0.
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43. D0/(W),D1/ (W) :MAID2003 Legendre moment as function of W[GeV]
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44. Legendre moment vs. Q2 at P11(1440)
Various Models
MAID2003
D0/(Q2) D1/ (Q2)
D0/(Q2) D1/ (Q2)
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45. Legendre moment as function of W, Q2
σLTP = D0/+D1/P1(cosθ)+D2/P2(cosθ)
D0/(W), D1/ (W), D0/(Q2), D1/(Q2)
D0, D1 have dominant dependence of M1-, S1-
A1/2 sensitive to imaginary part of M1- ,S1-
W dependence
Q2 dependence
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