proton form factors

Egle TOMASI-GUSTAFSSONCEA DSM DapniaJLab May 22008 1

Proton Form Factors

QQ22lele1 GeV1 GeV22

F2F2

F1F1

Over a period of time lasting at least 2000 years Man has puzzled over and sought

an understanding of the composition of matterhellip


Electromagnetic Hadron Form Factors Electromagnetic Hadron Form Factors in Space and Time-like regions in Space and Time-like regions

Egle Tomasi-GustafssonSaclay France

JLab May 2 2008


PLANPLANExperimental view

ndash space-like (ep-scattering)ndash time-like (e+e- or pp annihilation)

Model Independent Statementsndash Symmetry properties of fundamental interactionsndash Kinematical constraints

Models and lsquoexactrsquo calculations Radiative corrections


Hadron Electromagnetic Form factorsHadron Electromagnetic Form factors

ndash Characterize the internal structure of a particle

( point-like)

ndash Elastic form factors contain information on the

hadron ground state

ndash In a P- and T-invariant theory the EM structure of a

particle of spin S is defined by 2S+1 form factors

ndash Neutron and proton form factors are different

ndash Deuteron 2 structure functions but 3 form factors

ndash Playground for theory and experiment


Space-like and time-like regionsSpace-like and time-like regions

bullFFs are analytical functionsbullIn framework of one photon exchange FFs are functions of the

momentum transfer squared of the virtual photon t = q2 = -Q2

ScatterinScatteringg

e- + h =gt e- + h e+ + e- =gt h + h

_

AnnihilationAnnihilation

_

Form factors are real in the space-like region complex in the time-like region

tlt0 tgt0


Crossing SymmetryCrossing Symmetry

Scattering and annihilation channels

- Described by the same amplitude

- function of two kinematical variables s and t

p2 rarr ndash p2

k2 rarr ndash k2

- which scan different kinematical regions


Proton Form Factors


Proton Form Factors Ratio

POLARIZATION ExpJlab E93-027 E99-007 SpokepersonsCh Perdrisat V Punjabi M Jones E Brash M Jones et al Phys Rev Lett 841398 (2000)O Gayou et al Phys Rev Lett 88092301 (2002)V Punjabi et al Phys Rev C 71 055202 (2005)

Linear deviation from dipole GEpGMp

Jlab Super RosenbluthIA Qattan et alPRL 94 142301 (2005)

Jlab E04-108019 NOW running

SLAC RosenbluthL Andivahis PRD505491 (1994)


The Rosenbluth separation (1950)The Rosenbluth separation (1950)

bullElastic ep cross section (1 exchange)

bull point-like particle Mott

Linearity of the reduced cross section


The Rosenbluth separation The Rosenbluth separation

The dynamics is contained in FFs

Q2

The kinematics energies angles

The reaction mechanism

Holds for 1 exchange only


Rosenbluth separationRosenbluth separation

=05=02

=08

Contribution of the electric term

hellipto be compared to the absolute value of the error on and to the size and dependence of RC

ET-G Phys Part Nucl Lett 4 281 (2007)


The polarization induces a term in the cross section proportional to GE GM

Polarized beam and target or

polarized beam and recoil proton polarization

The polarization method (1967)The polarization method (1967)


Neutron Form Factors




The reaction d(eersquon)p - Ax

Select quasi-elastic kinematics

Pol electron beam pol target orneutron polarimeter

Large dependence ofasymmetry on GEn

GI Gakh A P Rekalo E T-G Annals of Physics 319 150 (2005)

+ d n + p

DWF

GEn

GEp

FSI



-The KHARKOV model - Impulse Approximation - Deuteron structure - Kinematics proton spectator - Polarization observables



FSI

DWF

Does not depend on beam helicity

+ d n + pGEn

ET-G GI Gakh A P Rekalo M P Rekalo PRC70025202 (2004)

The reaction d(eersquon)p ndash AxAz

Generalization of the polarization method

Asymmetry ratio

A(01)T ndashLT SFs(WQ2)


GEn from the deuteron

bullGEn gt GEp starting from 2 GeV2

E T-G and M P Rekalo Europhys Lett 55 188 (2001)


The nucleon form factors

VDM IJLF IachelloPLB 43 191 (1973)

Extended VDM (G-K 92) ELLomon PRC 66 045501 2002)

HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton

E T-G F Lacroix Ch Duterte GI Gakh EPJA 24 419 (2005)


STATUS on EM Form factors

Space-like region

1) standard dipole function for the nucleon magnetic FFs GMp and GMn

2) linear deviation from the dipole function for the electric proton FF GEp

3) contradiction between polarized and unpolarized measurements

4) non vanishing electric neutron FF GEn


Nucleon models

bullSkyrme Models (Soliton)bullVector Dominance Models (G-K IJLhellip)bullPerturbative QCDbull(Relativistic) Constituent Quark ModelbullDi-quark modelsbullGPDbullhelliphellip





HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region


Time-like observables | GE| 2 and | GM| 2

As in SL region- Dependence on q2 contained in FFs- Even dependence on cos2exchange- No dependence on sign of FFs- Enhancement of magnetic term

but TL form factors are complex

A Zichichi S M Berman N Cabibbo R Gatto Il Nuovo Cimento XXIV 170 (1962)B Bilenkii C Giunti V Wataghin Z Phys C 59 475 (1993)G Gakh ET-G Nucl Phys A761120 (2005)


Time-Like Region

E T-G F Lacroix C Duterte GI Gakh EPJA 24 419 (2005)

VDM IJLF IachelloPLB43 191 (1973)

Extended VDM (G-K 92) ELLomon PRC66 045501(2002)

lsquoQCD inspiredrsquo

proton

neutron



Time-like region

1) No individual determination of GE and GM2) Assume GE=GM (valid only at threshold) VMD or

pQCD inspired parametrizations (for p and n)

3) TL nucleon FFs are twice larger than SL FFs 4) Recent data from Babar (radiative return)

bull interesting structures in the Q2 dependence of GM(=GE)

bull GMneGE

=03 GeV is the QCD scale parameter

A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A

Double spin observables


Models in TL Region (polarization)

VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz

E T-G F Lacroix C Duterte GI Gakh EPJA 24 419(2005)


Time-Like Region GE versus GM

GE=0

GE=GM

GE=GD

E T-G and M P Rekalo Phys Lett B 504 291 (2001)

Asym

| GM| 2

Cross section at 900


Perspectives in Time-Like region

Frascati

Panda

GE = GM

CEA DSM Dapnia

Facilty for Antiproton and Ion Research (GSI Darmstadt Germany)

- Proton linac (injector)- 2 synchrotons (30 GeV p)- A number of storage rings Parallel beams operation

Physics Polarization Staging Signals Timeline


Towards a unified description of Hadron Form factors

to clarify

- zero of GEp

- asymptotic properties

- reaction mechanism


Comparison BABAR-LEAR

q2 (GeV2)

Analytical Expression for R(q2)Dispersion Relations (S Pacetti)

Space-like Time-like


Phragmegraven-Lindeloumlf theorem

Asymptotic properties for analytical functions

E T-G and G Gakh Eur Phys J A 26 265 (2005)

=005 01

If f(z) a as z along a straight line and f(z) b as z along another straight line and f(z) is regular and bounded in the angle between then a=b and f(z) a uniformly in the angle




Applies to NN and NNInteraction (Pomeranchuk theorem )t=0 not a QCD regime

Connection with QCD asymptoticsGM (TL)

GM (SL)

GE (SL)


Reaction mechanism1-2 interference


Two-photon exchange

Different results with different experimental methods

- Both methods based on the same formalism

- Experiments repeated

New mechanism

bull1-2 ~ =e24=1137

bull1970rsquos Gunion Levhellip


eeplusmn plusmn + p+ prarr rarr eeplusmnplusmn + p+ p

1 exchange

bull Two EM form factorsbull Real (in SL region)bull Functions of one variable (t)bull Describe e+ and e- scattering

2 exchange

bull Three structure functionsbull Complexebull Functions of TWO variables (st)bull Different for e+ and e- scattering

4 spin frac12 fermions rarrrarr 16 amplitudes in the general caseT-invariance of EM interaction identity of initial and final states helicity conservation unitarity


Model independent considerations for eeplusmnplusmn N scattering

Determination of EM form factors in presence of 2 exchange

-electron and positron beams

- longitudinally polarized - in identical kinematical

conditions

M P Rekalo E T-G EPJA (2004) Nucl Phys A (2003)



If no positron beamhellip

Either three T-odd polarization observableshellip

bullAy unpolarized leptons transversally polarized target (or Py outgoing nucleon polarization with unpolarized leptons unpolarized target )bullDepolarization tensor (Dab) dependence of the b-component of the final nucleon polarization on the a-component of the nucleon target with longitudinally polarized leptonsor five T-even polarization observableshellip

among dsd Pxe) Pz(e) Dxx Dyy Dzz DxzM P Rekalo E T-G EPJA (2004) Nucl Phys A (2003)


1g

1-2 interference

21

M P Rekalo E T-G and D Prout Phys Rev C60 042202 (1999)


The 1-2 interference destroys the linearity

of the Rosenbluth plot


11-2-2 interference (e-d) interference (e-d)


CA DA



From the data

deviation from linearity

ltlt 1

Parametrization of 2-contribution for e+p

E T-G G Gakh Phys Rev C 72 015209 (2005)

)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange

bullThe 2 amplitude is expected to be mostly imaginary

bullIn this case the 1-2 interference is more important in time-like region as the Born amplitude is complex


TL unpolarized cross section

bullInduces four new termsbullOdd function of bullDoes not contribute at =90deg

2contribution

e+ +e- p + p

E T-G G Gakh NPA (2007)


bullProperties of the TPE amplitudes with respect to the transformation cos = - cos ie -

(equivalent to non-linearity in Rosenbluth fit)

bullBased on these properties one can remove or single out TPE contribution

Symmetry relationsSymmetry relations



bullDifferential cross section at complementary angles

Symmetry relations

The DIFFERENCE enhances the 2 contribution

The SUM cancels the 2 contribution


Radiative Return (ISR)

s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +


Angular distribution

Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19

A=001A=001plusmnplusmn002002

Mpp=24-3Mpp=24-3

E T-G EA Kuraev S Bakmaev S Pacetti Phys Lett B (2008)


Radiative Corrections to the dataRadiative Corrections to the data

Slope negative if

- RC can reach 40 on - Declared error ~1- Same correction for GE and GM

- Have a large -dependence- Affect the slope

The slope is negative starting from 2-3 GeV2

el=meas RC

slope


Reduced cross section and RCReduced cross section and RCData from L Andivahis et al Phys Rev D50 5491 (1994)

Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2

Radiative Corrected data

Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)


Scattered electron energy

All orders of PT needed beyond Mo amp Tsai approximation

Initial state emission

final state emission

Quasi-elastic scattering

3

Y0

Not so smallShift to LOWER Q2


Radiative Corrections (SF method)

Polarization data

JLab data

SLAC data

Yu Bystricky EAKuraev E T-G Phys Rev C75 015207 (2007)


Instead of Conclusionshellip

bullFundamental measurement the electric and the magnetic distributions of the proton are different in SL region What about TL Separation of GE and GM

via angular dependence of differential cross section

bull Clarify reaction mechanism 2- exchange by model independent symmetry requirements

bull Unified description in TL and SL region zero of GEp

bull Asymptotic properties QCD and analyticity

Model independent propertiesModel independent properties Lessons from QED Lessons from QED


The work presentedhere was initiated in a collaboration with Prof M P REKALO


Experimental correlationExperimental correlation

el=meas RC

Q2 gt 2 GeV2 Q2 lt 2 GeV2

RC()

only published values




Q2 lt 2 GeV2

Correlation (ltRCbull)



The Pauli and Dirac Form Factors

Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279

The electromagnetic current in terms of the Pauli and Dirac FFs

Related to the Sachs FFs


Two Photon Exchange

No exact calculation for ep scattering

( inelastic intermediate states)

but

electron-muon scattering

constitutes an upper limit


Interference of 1 2 exchange

bullExplicit calculation for structureless proton ndash The contribution is small for unpolarized and

polarized ep scatteringndash Does not contain the enhancement factor L ndash The relevant contribution to K is ~ 1

EAKuraev V Bytev Yu Bystricky ET-G Phys Rev D74 013003 (1076)


QED versus QCD

Imaginary part of the 2Imaginary part of the 2 amplitude amplitude

electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2


Structure Function method

bullSF method applied to QED processes calculation of radiative corrections with precision of 01

bullTakes into account the dynamics of the process

bullFormulated in terms of parton densities (leptons antileptons photons)

bullMany applications to different processes

E A Kuraev and VS Fadin Sov J of Nucl Phys 41 466 (1985)

Electron SF probability to lsquofindrsquo electron in the initial electron with energy fraction x and virtuality up to Q2

Lipatov equations (1975)


Unpolarized Cross sectionUnpolarized Cross section

Born +dipole FFs(=unpolarized experiment+MoampTsai)

SF (with dipole FFs)SF+2 exchange

Q2=3 GeV2

Q2=5 GeV2 SF change the slope

Q2=1 GeV2

2 exchange very small


Polarization ratioPolarization ratio

Born SFSF+2 exchange

=60deg

2 destroys linearity


=80deg

=20deg

Yu Bystricky EAKuraev E T-G Phys Rev C 75 015207 (2007)


Electromagnetic Hadron Form Factors Electromagnetic Hadron Form Factors in Space and Time-like regions in Space and Time-like regions

Egle Tomasi-GustafssonSaclay France

JLab May 2 2008









( point-like)


hadron ground state











e- + h =gt e- + h e+ + e- =gt h + h

_


_


tlt0 tgt0






p2 rarr ndash p2

k2 rarr ndash k2



Proton Form Factors
















Q2






=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg










( point-like)


hadron ground state











e- + h =gt e- + h e+ + e- =gt h + h

_


_


tlt0 tgt0






p2 rarr ndash p2

k2 rarr ndash k2



Proton Form Factors
















Q2






=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg







e- + h =gt e- + h e+ + e- =gt h + h

_


_


tlt0 tgt0






p2 rarr ndash p2

k2 rarr ndash k2



Proton Form Factors
















Q2






=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg







p2 rarr ndash p2

k2 rarr ndash k2



Proton Form Factors
















Q2






=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Proton Form Factors
















Q2






=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg

















Q2






=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




=05=02

=08



















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg

















+ d n + p

DWF

GEn

GEp

FSI






FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg







FSI

DWF


+ d n + pGEn




Asymmetry ratio










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg










HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Space-like region






Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Nucleon models






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg






HohlerNPB 114 505 (1976)

BostedPRC 51 409 (1995)

Electric Magneticne

utro

npr

oton



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Time-like region







Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg








Time-Like Region





proton

neutron



Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Time-like region





bull GMneGE


A(p) = 563 GeV4 A(n) = 7715 GeV4

)](ln[ 2222

ss

AGM


Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Spin Observables

Analyzing power A




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




VDM IJL

Ext VDM


R

Ay Axx Ayy

Axz

Azz




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




GE=0

GE=GM

GE=GD


Asym

| GM| 2




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Frascati

Panda

GE = GM

CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg


CEA DSM Dapnia






to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




to clarify

- zero of GEp





q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




q2 (GeV2)







=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg






=005 01







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg







GM (SL)

GE (SL)




Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg





Two-photon exchange




New mechanism

bull1-2 ~ =e24=1137




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




1 exchange


2 exchange








conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg







conditions









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg









1g

1-2 interference

21








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg








CA DA



From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




From the data


ltlt 1



)(1

1)( 2)(2 QfQF a

2222

22

]1[ a

Dγ(a)

m[GeV]Q

GC)(Qf


Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Two-Photon exchange






2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg





2contribution

e+ +e- p + p










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg










Symmetry relations





s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




s

m

x

sin

xx

x)xs(W

s

m

s

Ex)m)(ppee()xs(W

s

m

cosddm

)ppee(d

e

2

22

122

2

2

2

2

e+ +e- p + p +



Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Mpp=1877-19Mpp=1877-19

Mpp=24-3Mpp=24-3


Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Mpp=1877-19Mpp=1877-19


Mpp=24-3Mpp=24-3




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Slope negative if




el=meas RC

slope



Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Q2=175 GeV2

Q2=5 GeV2

Q2=325 GeV2

Q2=4 GeV2

Q2=25 GeV2

Q2=7 GeV2

Q2=6 GeV2


Raw data without RC

Slope from P M

E T-G G Gakh PRC 72 015209 (2005)







3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg








3

Y0




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Polarization data

JLab data

SLAC data














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg














el=meas RC


RC()





Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Q2 lt 2 GeV2





Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg




Normalization

F1p(0)=1 F2p(0)= κp

GEp(0)=1 GMp(0)=μp=279




Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



Two Photon Exchange



but









QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg








QED versus QCD


electronproton


QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg



QED versus QCD

Q2=005 GeV2

Q2=12 GeV2

Q2=2 GeV2














Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg















Q2=3 GeV2


Q2=1 GeV2





=60deg



=80deg

=20deg





=60deg



=80deg

=20deg


proton form factors

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