PHOTON 2017 CERN 24052017 Generalized Parton Distributions and

PHOTON 2017, CERN, 24/05/2017 Generalized Parton Distributions and Deep Virtual Compton Scattering Michel Guidal (IPN Orsay)

y ep a e. X (DIS) (Parton Distribution Functions: PDF) z x

y ep a e. X (DIS) (Parton Distribution Functions: PDF) z x y ep a ep (elastic) (Form Factors: FFs) z x

y ep a e. X (DIS) (Parton Distribution Functions: PDF) z x y ep a ep (elastic) ep a epg (DVCS) (Form Factors: FFs) z z x x

y ep a e. X (DIS) (Parton Distribution Functions: PDF) z x y ep a ep (elastic) (Form Factors: FFs) ep a epg (DVCS) ep a ep. X (SIDIS) z z (Generalized Parton Distributions: GPDs) (Transverse Momentum Dependent PDFs: TMDs) z x x x

In the light-cone frame: x+x : relative longitudinal momentum of initial quark x-x : relative longitudinal momentum of final quark t=D 2 : total squared momentum transfer to the nucleon (transverse component: ) (also Q 2 -dependence but LO and LT framework in the following)

GPDs or the tomography of the nucleon Hu(x, b ) y z x x -1 b (Ge. V ) Ji’s sum rule 2 Jq = x(H+E)(x, ξ, 0)dx

g f e’ e leptonic plane hadronic plane x= x. B/(2 -x. B) DVCS Bethe-Heitler N’ GPDs F 1, F 2 k=-t/4 M 2 Polarized beam, unpolarized target (BSA) : ~-k. F 2 E}df Ds. LU ~ sinf Im{F 1 H + x(F 1+F 2)H Unpolarized beam, longitudinal target (l. TSA) : ~ 1+F 2)(H + x. B/2 E) –xk. F 2 E+…}df ~ Ds. UL ~ sinf. Im{F 1 H+x(F Polarized beam, longitudinal target (Bl. TSA) : ~ 1+F 2)(H + x. B/2 E)…}df Ds. LL ~ (A+Bcosf)Re{F 1 H+x(F Unpolarized beam, transverse target (t. TSA) : Ds. UT ~ cosf. Im{k(F 2 H – F 1 E) + …. . }df CFFs ~ , E } Im{Hp, H p p ~ Im{Hp, Hp} ~ Re{Hp, Hp} Im{Hp, Ep}

Hq(x, x, t) but only x and t experimentally accessible

JLab Hall A JLab CLAS DVCS BSA DVCS B-pol. X-section DVCS unpol. X-section DVCS l. TSA HERMES DVCS BSA, l. TSA, t. TSA, BCA DVCS unpol. and B-pol. X-sections

From data to GPDs (CFFs): Deconvolution/ Fitting algorithms of CFFs from (BH+DVCS) amplitudes

M. G. , H. Moutarde, M. Vanderhaeghen Rept. Prog. Phys. 76 (2013) 066202

New recent data from JLab: CLAS coll. PRL 115 (2015), 212003 Hall A coll. PRC 92 (2015), 055202 CLAS coll. PRL 114 (2015), 032001 CLAS coll. PRD 91 (2015), 052014 R. Dupré, M. G. , M. Vanderhaeghen Phys. Rev. D 95 (2017) 011501

If Up to (model-dependent) « deskewing effects » (a few percent) : this formula involves: While we extract: Need to estimate: (assuming )

HERMES JLab « Integrated » radius from elastic form factor F 1:

GPDs contain a wealth of information on nucleon structure and dynamics: space-momentum quark correlation, orbital momentum, pion cloud, pressure forces within the nucleon, … Large flow of new observables being released and new data expected soon (JLab 6, JLab 12, COMPASS) (Other DVCS-related processes planned for JLab 12 Ge. V (TCS, DVMP, DDVCS, …) First new insights on nucleon structure already emerging from current data with new fitting algorithms Theory developments: higher twists, target mass corrections, NLO corrections, …

BACK-UP

The Bethe-Heitler process

M. Boer, MG J. Phys. G 42 (2015) 3, 034023

(M. Burkhardt) If However, this formula involves: While we extract: Need to estimate: (assuming )

for

The axial charge (Him) appears to be more « concentrated » than ~ the electromagnetic charge (Him) Confirmed by CLAS A_UL and A_LL data: Phys. Rev. D 91 (2015) 5, 052014

~ Examples of correlation between HIm and HIm Polarized beam, unpolarized target (BSA) : ~-k. F 2 E}df Ds. LU ~ sinf Im{F 1 H + x(F 1+F 2)H

for