A pivotal year for Generalized Parton Distributions Pivotal year - PowerPoint PPT Presentation

A pivotal year for Generalized Parton Distributions Pivotal year for GPDs J. Ball, G. Charles, B. Moreno, H. Moutarde, F. Sabati´ e, 2011 situation S. Procureur GPDs and DVCS Leading twist, leading order Irfu/SPhN, CEA-Saclay Selected data Status of GPD analysis Hadron 2011 - 14 / 06 / 2011 Extraction methods Universality Key results 2011 situation 1 Future orientations COMPASS-II JLab’s 12 GeV Status of GPD analysis of data 2 upgrade Spin observables on an EIC The PROPHET package Future orientations 3 Conclusions H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 1 / 16

Generalized Parton Distributions. Viewing nucleon structure in 3d. Pivotal year DIS for GPDs e − Parton Distributions e − 2011 situation γ , Q 2 GPDs and DVCS γ Q 2 Leading twist, leading order Selected data Status of GPD X p analysis Extraction methods Universality nucleon Key results Future orientations COMPASS-II JLab’s 12 GeV upgrade Spin observables on an EIC The PROPHET package Conclusions H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 2 / 16

Generalized Parton Distributions. Viewing nucleon structure in 3d. DVCS Generalized Pivotal year e − for GPDs Parton Distributions e − γ , Q 2 γ , Q 2 2011 situation γ Q 2 GPDs and DVCS γ Leading twist, leading order b y Selected data p Status of GPD p analysis Extraction t methods nucleon b x Universality Key results Future Correlation of the longitudinal momentum and the orientations COMPASS-II transverse position of the struck quark. JLab’s 12 GeV upgrade Spin observables on an EIC The PROPHET package Conclusions H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 2 / 16

Generalized Parton Distributions. Viewing nucleon structure in 3d. DVCS DVMP Pivotal year e − e − for GPDs e − e − 2011 situation γ Q 2 γ Q 2 GPDs and DVCS γ Leading twist, π, ρ, . . . leading order Selected data p p Status of GPD p p analysis Extraction t t methods Universality Key results Future Correlation of the longitudinal momentum and the orientations COMPASS-II transverse position of the struck quark. JLab’s 12 GeV upgrade 3-dimensional description of the nucleon. Spin observables on an EIC Insights on : The PROPHET package spin structure, Conclusions energy-momentum structure. H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 2 / 16

Generalized Parton Distributions. Viewing nucleon structure in 3d. DVCS e − DVMP Pivotal year e − for GPDs e − e − π, ρ, . . . γ 2011 situation γ , Q 2 γ , Q 2 GPDs and DVCS factorization factorization Leading twist, leading order x + ξ x − ξ x + ξ x − ξ Selected data Status of GPD analysis p p p p Extraction methods t t Universality Key results Future orientations Correlation of the longitudinal momentum and the COMPASS-II JLab’s 12 GeV transverse position of the struck quark. upgrade Spin observables 3-dimensional description of the nucleon. on an EIC The PROPHET Insights on : package spin structure, Conclusions energy-momentum structure. H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 2 / 16

Generalized Parton Distributions. Viewing nucleon structure in 3d. Pivotal year DVCS e − Generalized for GPDs e − Parton Distributions γ 2011 situation γ , Q 2 γ , Q 2 γ , Q 2 H ( x , ξ, t ) GPDs and DVCS Leading twist, factorization E ( x , ξ, t ) leading order Selected data x + ξ x − ξ b y ˜ H ( x , ξ, t ) Status of GPD ˜ analysis E ( x , ξ, t ) Extraction p p methods nucleon Universality t b x Key results Future orientations Obtain this 3d picture from DVCS / DVMP measurements ? COMPASS-II JLab’s 12 GeV singlet pion valence transverse upgrade quarks spin quarks, gluons cloud C. Weiss, Spin observables xP on an EIC slower The PROPHET b AIP Conf. package longitud. Proc. 1149, Conclusions s e e r n s v a t r quarks move 150 (2009) faster x < 0.01 x ~ 0.1 x ~ 0.3 (a) (b) (c) H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 2 / 16

DVCS described by 4 Compton Form Factors. Approximations : quark sector, leading twist and leading order. Pivotal year Example : GPD F = H , E ( − ) or ˜ H , ˜ E (+). for GPDs � +1 2011 situation � � 1 1 GPDs and DVCS F = dx F ( x , ξ, t ) ξ − x − i ǫ ∓ Leading twist, ξ + x − i ǫ leading order − 1 Selected data Status of GPD analysis Integration yields real and imaginary parts to F : Extraction methods Universality Key results Compton Form Factor at Leading Order Future orientations � +1 COMPASS-II � 1 1 � JLab’s 12 GeV upgrade = dx F ( x , ξ, t ) Re F P ξ − x ∓ Spin observables ξ + x on an EIC − 1 The PROPHET � � package Im F = π F ( ξ, ξ, t ) ∓ F ( − ξ, ξ, t ) Conclusions Existence of dispersion relations at fixed t . H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 3 / 16

(Part of) Selected DVCS measurements. Fine kinematic binning, large kinematic coverage, several observables. JLab Hall A : helicity-dependent and independent cross sections Pivotal year for GPDs C. Mu˜ noz Camacho et al. , Phys. Rev. Lett. 97 , 262002 (2006) 2011 situation Restricted kinematic range, highly-precise helicity-dependent GPDs and DVCS Leading twist, cross sections. leading order Selected data Status of GPD analysis JLab Hall B : Beam Spin Asymmetries Extraction methods Universality F.-X. Girod et al. , Phys. Rev. Lett. 100 , 162002 (2008) Key results Wide kinematic range, precise BSAs. Future orientations COMPASS-II JLab’s 12 GeV upgrade Spin observables Hermes : BSAs, BCAs, TSAs on an EIC The PROPHET package A. Airapetian et al. , JHEP 0806 , 017 (2008) Conclusions D. Zeiler et al. , arXiv:0810.5007 [hep-ex] Restricted kinematic range, several different observables. H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 4 / 16

(Part of) Selected DVCS measurements. Fine kinematic binning, large kinematic coverage, several observables. JLab Hall A : helicity-dependent and independent cross sections Pivotal year for GPDs C. Mu˜ noz Camacho et al. , Phys. Rev. Lett. 97 , 262002 (2006) 2011 situation Restricted kinematic range, highly-precise helicity-dependent GPDs and DVCS Leading twist, cross sections. leading order Selected data Status of GPD analysis JLab Hall B : Beam Spin Asymmetries Extraction methods Universality F.-X. Girod et al. , Phys. Rev. Lett. 100 , 162002 (2008) Key results Wide kinematic range, precise BSAs. Future orientations COMPASS-II JLab’s 12 GeV upgrade Spin observables Hermes : BSAs, BCAs, TSAs (Update in progress) on an EIC The PROPHET package A. Airapetian et al. , JHEP 0806 , 017 (2008) Conclusions D. Zeiler et al. , arXiv:0810.5007 [hep-ex] Restricted kinematic range, several different observables. H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 4 / 16

Overview of current extraction methods. Problems : Model dependence ? Degrees of freedom ? Extrapolations ? Pivotal year Local fits for GPDs Take each kinematic bin independantly of the others. 2011 situation GPDs and DVCS Extraction of Re H , Im H , . . . as independent parameters. Leading twist, leading order Selected data Status of GPD Global fit analysis Extraction Take all kinematic bins at the same time. Use a methods Universality parametrization of GPDs or CFFs. Key results Future orientations COMPASS-II Hybrid : Local / global fit JLab’s 12 GeV upgrade Combine two previous methods to estimate model dependence. Spin observables on an EIC The PROPHET package Neural networks Conclusions Already used ofr PDF fits. In progress for GPDs. H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 5 / 16

Overview of current extraction methods. Problems : Model dependence ? Degrees of freedom ? Extrapolations ? Pivotal year Local fits for GPDs Take each kinematic bin independantly of the others. 2011 situation Extraction of Re H , Im H , . . . as independent parameters. GPDs and DVCS Leading twist, leading order Selected data Status of GPD analysis Extraction ~ methods H Im (x B =.25,t) H Im (x B =.25,t) � or ◦ : Universality Key results ”7-CFF” fit Future results. orientations COMPASS-II ♦ : ” H − ˜ H ” fit JLab’s 12 GeV upgrade Spin observables results. on an EIC The PROPHET package + : VGG. Conclusions M. Guidal, Phys. Lett. B689 (2010) 156 H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 5 / 16

Overview of current extraction methods. Problems : Model dependence ? Degrees of freedom ? Extrapolations ? Pivotal year Global fit for GPDs Take all kinematic bins at the same time. Use a 2011 situation parametrization of GPDs or CFFs. GPDs and DVCS Leading twist, leading order Selected data Without Hall A Status of GPD analysis data. Extraction t � � 0.28 GeV 2 methods � HALL A With Hall A 4 Universality Q 2 � 2 GeV 2 � CLAS Im � � x B ,t,Q 2 �� Π Key results data. � CLAS Future 3 � � CLAS orientations △ : neural COMPASS-II JLab’s 12 GeV 2 � HERMES � network. � � upgrade � � � Spin observables � � on an EIC � � : ”7-CFF” fit � 1 � The PROPHET � package � results. Conclusions 0 ⋄ : ” H − ˜ 0.10 0.15 0.20 0.25 0.30 0.35 H ”. x B K. Kumericki and D. M¨ uller, Exclusive 2010 ◦ : hybrid fits. H. M outarde (Irfu/SPhN, CEA-Saclay) Hadron 2011 - 14 / 06 / 2011 5 / 16