GPDs @ JLab12 & EIC

1. GPDs @ JLab12 & EIC QCD workshop, 15/12/06

2. 1/ GPDs are a beautiful/rich theoretical tool but are very difficult to access/extract experimentally 2/ Very encouraging first experimental results coming out from JLab 6 GeV (and HERMES) where we develop/test the analysis techniques 3/ JLab@12 GeV and EIC are the ultimate facilities for a full study/definite extraction of GPDs

3. t g* x~xB g,M,... x ~ ~ H,E,H,E p p’ Beam or target spin asymmetries contain only ImT, i.e. GPDs at x = x and -x Cross sections and charge asymmetries measurements (ReT) Integral of GPDs over x

4. Ds 2s ep epg s+ - s- s+ + s- A = = Polarized beam, unpolarized target: ~ ~ x = xB/(2-xB) DsLU~ sinf{F1H+ x(F1+F2)H+kF2E}df H(x,x,t),H(x,x,t), E(x,x,t) k = -t/4M2 (BSA) Kinematical suppression Unpolarized beam, long. pol. target: ~ ~ H, H DsUL~ sinf{F1H+x(F1+F2)(H+ … }df (l)TSA Unpolarized beam, trans. pol. target: H, E DsUT~ sinf{k(F2H – F1E) + …..}df (t)TSA Global (polarized and unpolarized) data analysis, X-sec, asym., (p,n), (g,M), to extract the GPDs

5. 1/ GPDs are a beautiful/rich theoretical tool but are very difficult to access/extract experimentally 2/ Very encouraging first experimental results coming out from JLab 6 GeV (and HERMES) where we develop/test the analysis techniques 3/ JLab@12 GeV and EIC are the ultimate facilities for a full study/definite extraction

6. ep epg Hall A 6 GeV DVCS Bethe-Heitler GPDs Difference of polarized cross sections Unpolarized cross sections Thesis C. Muñoz-Camacho (Saclay), A. Camsonne (Clermont) : arXiv:nucl-ex/0607029

7. Twist-2terms dominate the cross section and are independent ofQ2in the explored kinematical domain • The contribution to the cross section oftwist-3terms issmalland isindependent of Q2in the limit of error bars Strong indication in favor of factorization already from Q2=2 GeV2 in the valence region

8. DVCS + BH cross sections and comparison to theoritical BH Thesis H.S. Jo (Orsay) Hall B 6 GeV 0.2<-t<0.4 0.4<-t<0.6 0.09<-t<0.2 PRELIMINARY 0.6<-t<1 1<-t<1.5 1.5<-t<2

9. en eng Thesis M. Mazouz (Grenoble) E03-106 n-DVCS P.Y. Bertin, C.E. Hyde-Wright, F. Sabatié, E. Voutier et al. Strong sensitivity to E PRELIMINARY

10. 1/ GPDs are a beautiful/rich theoretical tool but are very difficult to access/extract experimentally 2/ Very encouraging first experimental results coming out from JLab 6 GeV (and HERMES) where we develop/test the analysis techniques 3/ JLab@12 GeV and EIC are the ultimate facilities for a full study/definite extraction

11. EIC : gluons and sea quarks region JLab 12 GeV : valence quarks region Large phase space (x,t,Q2) High luminosity Valence region JLab12 EIC Sea/gluon region

12. Beam asymmetry@12 GeV IC in standard position – 80 days – 10^35 Lum – VGG model

13. A LU Sensitivity to GPD models BSA <xB> =0.2 <Q2> = 3.3 GeV2 <-t> = 0.45 GeV2 <xB> =0.2 <Q2> = 3.3 GeV2 <Q2> =3.3 GeV2 <-t> = 0.45 GeV2 TSA <xB> =0.36 <Q2> = 4.1 GeV2 <-t> = 0.52 GeV2 <xB> =0.36 <Q2> = 4.1 GeV2 <Q2> =4.1 GeV2 <-t> = 0.52 GeV2

14. Q2=5 GeV2 Exclusive r0 prod. with transversely polarized target 2D (Im(AB*))/p T A~ (2Hu +Hd) AUT = - r0 |A|2(1-x2) - |B|2(x2+t/4m2) - Re(AB*)2x2 B~ (2Eu + Ed) Asymmetry depends linearly on the GPD E, which enters Ji’s sum rule. r0 Goeke, Polyakov, Vdh, (2001) L=1035cm-2s-1 2000hrs

15. GPDs depend on3 variables (x,x,t) and only 2 are experimentally accessible (x,t): convolution issue and inevitable model dependence Need to measure over a large phase space several channels and observables which mutually constrain the GPDs parametrizations Very encouraging first experimental results coming out from JLab 6 GeV (twist-2 dominance, first constraints on GPD models, first –very preliminary- extractions of Ju, Jd,…) Ultimate facilities : JLab@12 GeV (valence quark region) and EIC (gluons and sea quarks region) Summary