Measurements of p(e, e’π +)n in the ∆(1232) and higher resonances for Q2≤4.9GeV2

N* 2005 Meeting Kijun ParkN* 2005 Meeting Kijun Park

Physics MotivationPhysics Motivation KinematicsKinematics Experiments & Analysis ProcessExperiments & Analysis Process ResultsResults

Cross Section & AsymmetryCross Section & Asymmetry Structure functions & Photocoupling AmplitudeStructure functions & Photocoupling Amplitude

SummarySummary

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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 ?

History of History of Roper Resonance Roper Resonance

Photocoupling Photocoupling AmplitudeAmplitude

Various Q2 dependences for transition form-factors are predicted by different models.

Roper signature has been clearly seen in πN and γN reactions. The unresolved low mass of P11(1440)

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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

Kinematic variable

Single pion Single pion ElectroproductionElectroproduction

Unpol. Xsection w/ one-photon exchange approx.

Asymmetry

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E1-6 Data (Oct.2001-Jan.2002)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)

E1-6 Data Kinematic Coverage

Kinematic Kinematic

Bins Bins

= 58,800= 58,800

Q2[GeV2]

W[GeV] W[GeV]

MMx[GeV]Q2[GeV2]

W[GeV] W[GeV]

MMx[GeV]

Q2[GeV2]

W[GeV] W[GeV]

MMx[GeV]Q2[GeV2]

W[GeV] W[GeV]

MMx[GeV]

Particle ID (Particle ID (e-,π ++))

Electron ID : q<0, fiducial , EC, Nphe , vertex cutPion ID : q>0, fiducial, TOF mass, vertex cut

Kinematic Correction (Kinematic Correction (e-,π ++))

Applied to both Experimental, MC data

Acceptance Correction [AC]Acceptance Correction [AC]AC calculated by GSIM

Radiative Correction [RC]Radiative Correction [RC]RC done by ExcluRad (PRD 66, A. Afanasev)

Bin Centering Correction [BCC]Bin Centering Correction [BCC]BCC performed by Models(MAID03, Sato-Lee)

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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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W=1.23GeV, Q2=2.05GeV2 W=1.40GeV, Q2=2.05GeV2

MAID00

MAID03

DMTSL

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MAID00

MAID03

SL04SL

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MAID00

MAID03

SL04SL

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MAID00

MAID03

SL04SL

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//

MAID00

MAID03

DMTMAID98

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Quark Models

This Work

GWU (VPI) pion photoproduction

RPP estimation

ηelectro-, photo- production IM, DR

π electro- production IM, DR

π -2π analysis

Relativistic Quark ModelNon-relativistic Quark ModelBonn, DESY, NINA, Jlab(η)

Light-front calculation

q3G hybrid state

re-analyze the old data MAINZ

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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 extracte

d.

The Cross Section and Beam Spin Asymmetry are fitted to extract the Transition Form Factors and compared with present predictions.

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BACKUP SLIDES

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I. The hadrons constitute most of the visible matter.II. The contribution of the current quark masses into total

baryon mass is very small; most of the hadron mass comes from strong interactions.

III. Investigation of the spectrum and the internal structure of the hadrons provides information about the underlying strong interactions.

IV. One of the physics goals of the JLab is to investigate the strong interactions in the confinement regime.

Why we are interested in Why we are interested in Hadron Physics ??Hadron Physics ??

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Elastic 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 res

onance states.

Electron Electron ScatteringScattering

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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.

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.

Quark Quark ModelModel

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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

*

N

N*

El, Ml ,Sl

A1/2, A3/2,S1/2

Electroproduction Electroproduction AmplitudesAmplitudes

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One of the first observed baryon resonances.

Spin J=3/2 and isospin I=3/2. From angular momentum and parity co

nservation 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.

e

e /*

e

e /*

More sophisticated models allow for explicit pion degrees of freedom (pion cloud).

pion cloud can also introduce E1+ and S1+ contributions.

M1

P(938) J=1/2

(1232) J=3/2

∆∆(1232)Resonan(1232)Resonancece

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e-

Particle ID (Particle ID (e-,π ++))

Θπ =20o

φπ

θπ

φπ

Fiducial Volume cutFiducial Volume cut

((e-,π ++))

Kinematic Kinematic CutsCuts

π+

p

ph

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Mass of Proton from elastic Mass of Neutron from nπ +

Kinematic Kinematic CorrectionCorrectionss

After Kine. Corr. For GSIM Vertex Corr. & Cut

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Angle dependent RC W dependent RC

AC & RC AC & RC CorrectionsCorrections

σ = 0.0372 σ = 0.0368

tvertextvertex

Acceptance vs. PHICM

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Ratio between elastic cross section and Bosted FFP(Rad) vs. electron angle

Elastic Cross Section

Inelastic Cross Section

Q2 dependence of inelastic cross section @ W=1.21GeV

W dependence of inelastic cross section @ Q2=2.5GeV2

Bin correction by sub-binning from two models @ W=1.23GeV, CSCM=0.1, two Q2 bins

NormalizatioNormalizationn

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Electron Beam Asymmetry

Asymmetry in W=1.39GeV @ Q2=1.72, 2.05GeV2& Compare to calculation from five different Physics Models

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Electron Beam Asymmetry

Asymmetry in W=1.39GeV @ Q2=2.44, 2.91GeV2& Compare to calculation from five different Physics Models

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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 3.0σ→3.5σ

Resol. 1.4%

Pion fiducial cut ( -10% width)

Width 3.3%

Missing mass cut 3.0σ→2.0σ

Resol. 1.0%

Vertex cut ( -5% cut)

Width 1.0%

LH2 target Density/Length

< 1.0%

Radiative Corr. MAID00/03 Evnt ratio < 0.4%

Acceptance Corr. MAID00/03 Evnt ratio < 1.0%

Total 6.3%

Systematic Systematic UncertaintiesUncertainties

Tot. sys.

pi fidu .sys.

e PID. sys.e fidu. sys.

MMx. sys.Z-vtx. sys.

pi PID. sys.

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5-th Structure Function

σLTP @ W =1.39GeV in five different Q2 bins

& Compare to calculation from Physics Models

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/ / * / *0 1 1 2 2

/ * *0 1 1 1 0 0 1 1

/ * *1 1 1 1 1 1 1

/ * *2 2 2 1 1 2

(cos ) (cos )

Im[( 3 ) ( 2 ) ]

6 Im[( ) ]

12 Im[( ) 2 ]

LTP D D P D P

D M M E S E S S

D M M E S E S

D M E S E S

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Legendre moment as function of W[GeV]

D0/(W),D1

/ (W) : fit from Pl=2,3,4(cosθ)

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Model comparison MAID2000 & 2003

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Dependence of S1/2 , A1/2

MAID2003

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Dependence of S1/2 , A1/2 MAID2003 Q2=2.GeV2

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Dependence of S1/2 , A1/2 MAID2003 Q2=2.GeV2

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Dependence of S1/2 , A1/2 MAID2003 Q2=2.GeV2

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σLTP vs. W @ Q2=1.72GeV2, CSCM<0.

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σLTP vs. W @ Q2=1.72GeV2, CSCM>0.

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σLTP vs. W @ Q2=2.05GeV2, CSCM<0.

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σLTP vs. W @ Q2=2.05GeV2, CSCM>0.

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σLTP vs. W @ Q2=2.44GeV2, CSCM<0.

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σLTP vs. W @ Q2=2.44GeV2, CSCM>0.

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σLTP vs. W @ Q2=2.91GeV2, CSCM<0.

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σLTP vs. W @ Q2=2.91GeV2, CSCM>0.

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Legendre moment as function of W[GeV]D0

/(W),D1/ (W) :MAID2003

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Legendre moment vs. Q2 at P11(1440)

D0/(Q2) D1

/ (Q2) D0/(Q2) D1

/ (Q2)Various Models MAID2003

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D0/(W), D1

/ (W), D0/(Q2), D1

/(Q2)

Legendre moment as function of W, Legendre moment as function of W, QQ22

σLTP = D0/+D1

/P1(cosθ)+D2/P2(cosθ)

W dependence Q2 dependence

A1/2 sensitive to imaginary part of M1- ,S1-