BARYON FORM FACTORS

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BARYON FORM FACTORS

• TWO GAMMA EXCHANGE RESOLVED THE DISCREPANCY
  BETWEEN THE DATA OBTAINED BY ROSENBLUTH
  SEPARATION AND POLARIZATION TRANSFER FOR GE(p)
• QUALITY DATA ON N(1440), N(1535) and some higher
  N TRANSITION FORM FACTORS
• CONSISTENT RESULTS FOR THE STRANGENESS FORM
  FACTORS OF THE PROTON FROM SAMPLE, HAPPEX, A4 AND
  G0. CHALLENGE FOR THEORY
• CLEAR INDICATIONS FOR LONG RANGE PION CLOUD IN
  ALL NUCLEON FORM FACTORS
• PRECISION DATA ON GE(n)
• NEW PRECISION DATA FOR gP (p)
• FORM FACTORS --- DVCS --- PARTON DISTRIBUTIONS

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NEXT FEW YEARS

• NEW DATA ON THE FORM FACTORS IN THE
• TIME LIKE REGION OF Q2
• GLUON POLARIZATION
• TRANSVERSITY COMPASS-II, FAIR

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THEORISTS FORM FACTORS

• CALCULATE FROM CURRENT MATRIX ELEMENTS
• GE(Q2) (1t)1/2 lt1/2, Q/2 I0 1/2, -Q/2gt
• GM(Q2) (11/t)1/2 lt1/2, Q/2 Ix 1/2, -Q/2gt
• t Q2/4 M2)
• ELECTRIC FORM FACTORS IN THE BREIT FRAME
• GE(Q2) ? d3R eiQR ?(R),
• GM(Q2) ? d3R eiQR (1/2) ltj, j r j(R) j, jgt
• in the Breit frame, where Q0 0
• GOVERNING SINGULARITIES IN TIME-LIKE REGION

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EXPERIMENTALISTS FORM FACTORSSPACE-LIKE Q2

• DIFFERENTIAL CROSS SECTION
• ds/dO sM (GE2tGM2) /(1t)2t GM2 tan2 ?/2
• One-photon exchange approximation
• forward-backward Rosenbluth separation
• SPIN POLARIZATION TRANSFER
• GE/GM - ( Pt / Pl ) (E E)/2 M tan ?/2
• no forward-backward separation, but instrumental
  challenge

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EXPERIMENTALISTS FORM FACTORSTIME-LIKE Q2
M. Mirazita et al. 2005
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AXIAL FORM FACTOR RELATION TO PION DECAY LO ChPT
(PCAC)
B. Juliá-Díaz et al., PRC 70
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EXOTIC FORM FACTORS

• THE STRANGENESS FORM FACTORS
• CONTRIBUTION FROM SS- PAIRS
• THE ANAPOLE FORM FACTOR
• AXIAL PART IN ELECTROMAGNETIC CURRENT
• J? (GF/Mp2) FA(Q2)(Q2??-Q? Q? ??)?5
• arises from PV quark interactions
• TRANSVERSITY
• ltP?q-(0) ????q(0)Pgt ? qP? S? P? S?

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I.A.Qattan et al, PRL 94, 142301 (2005)
GEp/GMp EXPERIMENT
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TWO PHOTON EXCHANGE
P. Guichon M. Vanderhaeghen PRL 91,
142303 (2003)
Need only a 6 correction in the ? dependent term
in the differential cross section from TPE to
resolve the discrepancy
? 1/12(1?) tan2 (?/2)
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HADRONIC CALCULATIONBlunden et al, PRL 91,
142304 (2003)nucl/th0506039
nucl-th/0506039
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THE ?(1232) CONTRIBUTIONIS SMALL !S. Kondratyuk
et al, nucl-th/0506026
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PARTONIC CALCULATIONA.V.Afanasev et al, PRD
72,013008 (2005)
Ratio of e- to e scattering decisive!
Expt planned at Novosibirsk
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GE ON THE LATTICE
ISOVECTOR FORM FACTOR C. Alexandrou
(2005) PRELIMINARY
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GM ON THE LATTICE
ISOVECTOR FORM FACTOR C. Alexandrou
(2005) PRELIMINARY
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GE(n)
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LONG RANGE STRUCTURE IN THE NUCLEON FORM FACTORS
J. Friedrich Th. Walcher, EPJA A17, 607 (2003)
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THE PION CLOUD
THE PION CLOUD
J.Friedrich Th. Walcher, EPJA A17, 607 (2003)
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POINCARÉ COVARIANT QUARK MODELS

• GENERATORS OF POINCARÉ TRANSFORMATIONS
• H, P, J, K K boosts
• CHOICE OF KINEMATIC SUBGROUP
• INSTANT FORM KINEMATICS P, J, KH
  O(3)
• LIGHT FRONT KINEMATICS P, K, JH
  O(1,2)
• POINT FORM KINEMATICS J, K, PH
  SO(1,3)

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SU(6) quark model for instant, point and
front form kinematics fitted wave functions
B. Julia-Diaz, D.O.R F. Coester PRC 69, 035212
(2004)
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BARYON PHENOMENOLOGY WITH DIFFERENT KINEMATICS

• B. Juliá-Díaz, F. Coester DOR, PRC C69 (2004)
  035212
• SU(6) spin-isospin wave functions x (1 P2/4
  b2)-a
• hyperspherical momentum P
  ((4/3)(p12p22p32))1/2

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GE(n) Foldy term
rn2exp -0.1161 0.0022 fm2, rn2 Foldy -0.126
fm2
solid instant, dotted point dashed front
S 2 instant,point, 1 front
Consistent quark model demands covariant treatment
of the boosts
1-2 mixed symmetry S-state Sufficient to fix the
qqq quark model
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GROUND STATE WAVE FUNCTION ANDCONFINING POTENTIAL
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Point form quark model form factors R.F.Wagenbrunn
et al, hep-ph/0509047
Very small matter radius r2 0.1 fm2
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AXIAL INDUCED PSEUDOSCALAR FORM FACTORS

• J? GA(Q2) ???5 i (Q?/2 M) GP (Q2) ?5 ?a
• gP(Q2) (m?/ 2 M) GP(Q2)
• MUON CAPTURE Q2 - m?2

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PROBLEM RESOLUTION

• ChPT gP 8.3 0.2
• N. Kaiser, PRC 67, 027002 (2003)
• TRIUMF RMC
• gP 12.2 1.1
• D. H. Wright, PRC 57, 373 (1998)
• New result on ortho-para transition in µ-
  molecular H factor 2.7
• gP 10.6 1.1
• J.H.D. Clarke et al nucl-ex/0509025
• ( Triumf RMC)

- Introduces problems with earlier data
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Quark model results for GA and GP
MA1.077 0.039 GeV/c2 A.Liesenfeld et al, PL B
468, 20 (1999)
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?(1232) ! ? N

• qqq quark model underestimates the
• transtion form factor by 30
• ? Pion cloud and/or sea-quarks

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? N - ? COUPLED CHANNEL CALCULATION
Sato-Uno-Lee PRC 67, 065201 (2003)
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Coupled channel \pi-N-\Delta model
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HADRONIC COUPLED CHANNELS ?-N-? MODEL
T. Sato and T.-S. H. Lee Nucl-th/0404025
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Bates, CLAS, PDG
I.Aznauryuan, ANL talk 2005
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I.Aznauryuan, ANL talk 2005
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N? TRANSITION FORM FACTOR ACCORDING TO QCD
LATTICE CALCULATION
C. Alexandrou et al, PRL 94, 020601 (2005)
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C. Alexandrou et al., hep-lat/0509140
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Effective field theory NV. Pascalutsa and M.
Vanderhaeghen,hep-ph/0508060
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N(1440) HELICITY AMPLITUDES
I.Aznauryuan, ANL talk 2005
PRD C71, 015201 (2005)
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N(1535) HELICITY AMPLITUDESI.G.Aznauryan (CLAS),
PRD C71, 015201 (2005)
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STRANGENESS FORM FACTORS
?, Z0
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E. J. Beise et al, Prog. Part. Phys. 54, 289
(2005)
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D. Armstrong K.Carter, CERN Courier 45, 8 (2005)
GO PRL 95, 092001 (2005), A4 Prog.Part.Nucl.Phys
. 55, 320 (2005)
SAMPLE PLB 583, 79 (2004), HAPPEX PRC 69,
065501 (2004)
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BUT µs GMs(0) SHOULD BE NEGATIVE !

• ASYMMETRIC LONG RANGE FLUCTUATION
• PSEUDOSCALAR MESON LOOP

K
P?
e
-e/3 (strange quark)
?, S0
lt K ?0 T pgt lt? q gt
POSITIVE MAGNETIC MOMENT CONTRIBUTION ?
NO ... MULTIPLY BY 3 (lt s- ?µ sgt
NEGATIVE GMs !
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D.Beck and R.D.McKeown, Ann Rev Nucl Part Sci 51,
189 (2001)
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• K,K loops in the chiral quark model
• µs - 0.046 nm
• L. Hannelius DOR, PRC 62, 045204 (2000)
• QCD Lattice calculation with chiral extrapolation
• µs - 0.046 0.019 nm
• D.B.Leinweber al, PRL 94, 212001 (2005)
• tremendous challenge for future experiments

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SPIN DEPENDENT HYPERFINE INTERACTIONLOWERS
ANTISYMMETRIC SPIN STATES

• ltS0 ?1?2 S0gt -3
• ltS1 ?1?2 S1gt 1
• COLOR MAGNETIC HF INTERACTION
• V (2? / 9 m2) ?s ?1 ?2 ?(r)
• FLAVOR-SPIN INTERACTION ...fits the expt
  spectrum
• V? C? ?ij ?Fi?Fj ?i ?j , C? 30
• NUCLEON ltN ? ?i?jNgt -2
• lt ? ?i?j ?i ?jNgt 10

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The
is in the S-state, Not K? like!
B.S.Zou DOR, PRL 95, 072001 (2005)
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Fenice/ADONE
GM(p) FOR TIME LIKE Q2
E835/FNAL
M. Mirazita et al, INFN preprint (2005)
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GM(p) FOR TIME LIKE Q2
M. Mirazita et al, INFN preprint (2005)
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GM (n) FOR TIME LIKE Q2
M. Mirazita et al, INFN preprint (2005)
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GM(n) Vector meson pole scalar meson
pole phenomenology
F. Iachello Q. Wan, PRC 69, 055204 (2004)
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SUMMARY

• TWO PHOTON EXCHANGE AFFECTS ROSENBLUTH
• SEPARATION OF GE , GM
• ALL FORM FACTORS INDICATE PION CLOUD
• STRUCTURE IN BARYONS
• QCD LATTICE CALCULATIONS APPROACH
• EMPIRICAL NUCLEON FORM FACTORS
• REALISTIC ChPT EXTRAPOLATION TO SMALL QUARK MASS
  ESSENTIAL
• THE COMPONENT IN THE PROTON IS NOT A
• K? FLUCTUATION