12 GeV upgrade of Jefferson Lab Franck Sabatié CEA Saclay Franck Sabatié CEA Saclay  JLab from 6 to 12 GeV  New equipments  The physics program  Generalized Parton Distributions  Deeply Virtual Compton Scattering  Experiments from 6 to 12 GeV Focus: the Generalized Parton Distribution program

A B C Continuous electron beam - Energy from 0.8 to 6 GeV - Duty factor 100% - Beam polar ~85% - Delivers 3 halls simultaneously Jefferson Lab today

CHL-2 Enhance equipment in existing halls Add new hall Upgrading JLab from 6 to 12 GeV

9 GeV tagged polarized photons and a 4  hermetic detector D Super High Momentum Spectrometer (SHMS) at high luminosity and forward angles C High Resolution Spectrometer (HRS) Pair, and specialized large installation experiments A CLAS12 with new detectors and higher luminosity (10 35 /cm 2 -s) B New equipments for GeV beam

… and construction has started ! Making Progress - Construction crews have started to remove trees as work on the $310 million 12 GeV Upgrade gains momentum. Hall D, the lab's fourth experimental hall, will be constructed in the cleared area. The upgrade is scheduled for completion in Now at : Critical Decision Three (CD-3)

Search for exotic mesons & the origin of confinement (Hall D) Studies of the nucleon structure using: Generalized Parton Distributions, semi-inclusive DIS, high-x studies Physics of nuclei (modification of partonic structure in dense medium, …) Tests of the Standard Model (PV electron scattering, indirect searches for new physics) Physics topics with 12 GeV Jefferson Lab Most of these topics are covered by talks in this conference !

Search for exotic mesons & the origin of confinement (Hall D) Studies of the nucleon structure using: Generalized Parton Distributions Generalized Parton Distributions, semi-inclusive DIS, high-x studies Physics of nuclei (modification of partonic structure in dense medium, …) Tests of the Standard Model (PV electron scattering, indirect searches for new physics) Physics topics with 12 GeV Jefferson Lab

Non-local, Diagonal Deep Inelastic Scattering Local, Off-diagonal Elastic scattering Hofstadter (1958) Taylor et al. (1969)  p, s p’, s’ q  p, s q X 2 Im   p, s qq Optical theorem and factorization Forward Compton Amplitude The electromagnetic probe for the nucleon structure

A natural extension: non-local, off-diagonal matrix elements x + ξ x - ξ P - Δ/2P + Δ/2 GPD (x, ξ,t) The structure of the nucleon can be described by 4 Generalized Parton Distributions : (x + ξ) and (x - ξ) : longitudinal momentum fractions of quarks : Vector : H (x, ξ,t) : Tensor : E (x, ξ,t) : Axial-Vector : H (x, ξ,t) : Pseudoscalar : E (x, ξ,t) ~ ~ Mueller (1995)

* Q hard 2 large t = Δ 2 low –t process : -t << Q hard 2 Ji, Radyushkin (1996) x + ξ x - ξ P - Δ/2P + Δ/2 GPD (x, ξ,t) at large Q 2 : QCD factorization theorem hard exclusive processes can be described by 4 Generalized Parton Distributions: (x + ξ) and (x - ξ) : longitudinal momentum fractions of quarks : Vector : H (x, ξ,t) : Tensor : E (x, ξ,t) : Axial-Vector : H (x, ξ,t) : Pseudoscalar : E (x, ξ,t) ~ ~ And its golden process : Deeply Virtual Compton Scattering

Why Generalized Parton Distributions are the way to go ! Elastic Scattering transverse quark distribution in coordinate space DIS longitudinal quark distribution in momentum space DES (GPDs) f ully-correlated quark distribution in both coordinate and momentum space GPDs yield 3-dim quark structure of the nucleon Burkardt (2000, 2003) Belitsky, Ji, Yuan (2003)

Properties, applications  first moments : nucleon electroweak form factors ξ-independence : Lorentz invariance P - Δ/2P + Δ/2 Δ Pauli Dirac axial pseudo-scalar  forward limit : ordinary parton distributions unpolarized quark distributions polarized quark distributions : do NOT appear in DIS … new information They contain what we know already through sum rules and kinematical limits: Form Factors, parton distributions

Through the space-momentum correlation, they give access to the Orbital Angular Momentum (OAM) carried by partons inside the nucleon : Finally an end to the spin crisis ? Properties, applications Ji’s sum rule : Related to momentum fraction carried by quarks Best accessible using transverse polarized target. While waiting, neutron DVCS is sensitive to E Moments of GPDs are calculable in Lattice QCD. Lowest moments have already been computed for valence quarks.

They contain what we know already through sum rules and kinematical limits: Form Factors, parton distributions Through the space-momentum correlation, they give access to the Angular Orbital Momentum (AOM) carried by partons inside the nucleon : Finally an end to the spin crisis ? Using the same correlation, nucleon tomography and even 3D-imaging can be envisioned ! x b ┴ (fm) Properties, applications M. Burkardt, M. Diehl (2002) sea quarks

3D-imaging (full  dependence needed !) Z r┴r┴ GPDs as Wigner distribution can be used to picture quarks in the proton The associated Wigner distribution is a function of position r and Feynman momentum x: f(r,x) One can plot the Wigner distribution as a 3D function at fixed x A GPD model satisfying known constraint: A. Belitsky, X. Ji, and F. Yuan (2003)

Collins, Freund GPDs from Theory to Experiment Theory x+  x-  t GPDs Handbag Diagram   Physical process   Experiment   Factorization theorem states: In the suitable asymptotic limit, the handbag diagram is the leading contribution to DVCS. Q 2 and large at x B and t fixed but it’s not so simple… 1. Needs to be checked !!! 2. The GPDs enter the DVCS amplitude as an integral over x: - GPDs appear in the real part through a PP integral over x - GPDs appear in the imaginary part but at the line x= 

Experimental observables linked to GPDs Experimentally, DVCS is undistinguishable with Bethe-Heitler However, we know FF at low t and BH is fully calculable Using a polarized beam on an unpolarized target, 2 observables can be measured: At low energy, |T DVCS | 2 supposed small Ji, Kroll, Guichon, Diehl, Pire, …

e -’  p e-e- ** hadronic plane leptonic plane  Into the harmonic structure of DVCS |T BH | 2 Interference term BH propagators  dependence Belitsky, Mueller, Kirchner

6 GeV breakthroughs and results in a nutshell Hall A Measurement of difference and sum of cross-sections for proton and neutron

A UL A LU (90°) Hall B Q² xBxB 6 GeV breakthroughs and results in a nutshell Measurement of A LU and A UL on the proton

Extension of the Hall A experiments - 88 days on H target (BSA) - L ≈ 4x , 8.8 and 11 GeV Exclusivity ensured by high resolution - DVCS², twist-2, twist-3 separation - Test of factorization at different x B

Unpolarized cross sections Polarized cross sections difference  Access the real and imaginary parts of T DVCS separately Expected accuracy (only a few bins)

H1, ZEUS JLab Upgrade H1, ZEUS 12 GeV 27 GeV 200 GeV W = 2 GeV HERMES COMPASS Strategy for the CLAS12 detector in Hall B The CLAS12 detector covers a large kinematical domain, especially at high-x

Measuring DVCS using all polarization settings ! Depending on the experiment, measurement of  and  or CLAS12 will have access to beam and target polarizations (both L and T) With polarized beam and unpolarized target: With unpolarized beam and Longitudinally polarized target: With unpolarized beam and Transversely polarized target:

Expected accuracy for sin  term in A LU as a function of t

Projected results Spatial Image Extraction of the GPD H(x=  ) from projected CLAS12 data

Summary The JLab 12 GeV Upgrade has well defined physics goals of fundamental importance for the future of hadron physics, addressing in new and revolutionary ways the quark and gluon structure of mesons, nucleons, and nuclei by –accessing Generalized Parton Distributions –exploring the valence quark structure of the nucleon –understanding quark confinement and hadronization processes –extending nucleon elastic and transition Form Factors to short distances –mapping the spectrum of gluonic excitations of mesons –searching for physics beyond the Standard Model through parity violation Design of accelerator and equipment upgrades are underway Construction has begun ! Accelerator shutdown scheduled for 2012 Upgrade completion scheduled in 2015

Nucleon Valence Structure (SIDIS, High X, etc): C. Keppel, V. Burkert, H. Gao, G. Cates, A. Puckett, X. Zhan, Z-E. Meziani, J-P. Chen GPD related: P. Nadel-Turowski, M. Burkardt, D. Hamilton, V. Guzey Spectroscopy and Exotics : M. Shepherd, D. Lawrence Nuclei: A. Daniel, M. Olson, P. Monaghan, R. Schiavilla, M. Iodice PV with electrons: P. King, A. Thomas, P. Souder, E. Beise In sessions: Nuclear and Nucleon Structure 1 to 9 Plenary 7 Hadronic and Spin Physics 4 Hadron Spectroscopy and Exotics 5 New Facilities and Instrumentation 4 by order of appearance … (I may have forgotten a few !) More information on JLab 6 and 12 physics in this conference

BACKUP

Published non-dedicated results on A LU and A UL PRL 97, (2006) JLab/Hall B - E1 & HERMES JLab/Hall B - Eg1 Both results show, with a limited statistics, a sin  behavior (necessary condition for handbag dominance) In the A LU result, DD models (VGG) tend to over-estimate the data A LU A UL CLAS: PRL 87, (2001) HERMES: PRL 87, (2001)

E experimental setup 75% polarized 2.5uA electron beam 15cm LH2 target Left Hall A HRS with electron package 11x12 block PbF2 electromagnetic calorimeter 5x20 block plastic scintillator array 50 days of beam time in the fall 2004, at 2.5  A

Difference of cross-sections Corrected for real+virtual RC Corrected for efficiency Corrected for acceptance Corrected for resolution effects Checked elastic ~1% Twist-2 Twist-3 Extracted Twist-3 contribution small ! PRL97, (2006)

Q 2 dependence and test of scaling =0.26 GeV 2, =0.36 No Q 2 dependence using BMK separation: strong indication for scaling behavior and handbag dominance Twist-2 Twist-3 Twist 4+ contributions are smaller than 10% PRL97, (2006) Supposedly mostly H (~80%)

Total cross-section Corrected for real+virtual RC Corrected for efficiency Corrected for acceptance Corrected for resolution effects Extracted Twist-3 contribution small ! PRL97, (2006) but impossible to disentangle DVCS 2 from the interference term !

DVCS on the neutron in JLab/Hall A: E LD 2 target fb-1 x B =0.36, Q 2 =1.9 GeV 2 MODEL-DEPENDENT Ju-Jd extraction

E1-DVCS with CLAS : a dedicated DVCS experiment in Hall B ~50 cm Inner Calorimeter + Moller shielding solenoid Beam energy: ~5.8 GeV Beam Polarization:75-85% Integ. Luminosity:45 fb -1 2nd half of data under analysis M  (GeV 2 )

E1-DVCS kinematical coverage and binning W 2 > 4 GeV 2 Q 2 > 1 GeV 2

Integrated over t E1-DVCS : Asymmetry as a function of x B and Q 2 = 0.18 GeV 2 = 0.30 GeV 2 = 0.49 GeV 2 = 0.76 GeV 2 Accurate data in a large kinematical domain

E1-DVCS : A LU (90°) as a function of -t + models JML VGG twist-2 VGG twist-2+3 PRL , 2008

New developments in GPD modeling : minimal dual model Central quantities are t-dependent parton distributions q and e(x,t), obtained as  → 0 limits of the nucleon GPDs: q and e are estimated using a dual representation (parton distributions as an infinite series of t-channel exchanges). Only the leading function is kept for simplicity. Only the GPD H is kept, supposedly dominant in DVCS. It is a simple one-parameter model with strong predictive content. If part of the data cannot be fit, it will mean higher twists/genuine non- forward effects need to be included: first step to understand DVCS data. arXiv: v2 Polyakov, Vanderhaeghen

Minimal dual model (i.e. forward model) of DVCS data DD model (VGG) Minimal dual model Data: Hall A polarized cross section data at Q 2 =2.3 GeV 2 Difference of cross sections (imaginary part of interference term) Data are perfectly described by minimal dual model M. Polyakov, M. Vanderhaeghen arXiv:

Minimal dual model (2) Beam Spin Asymmetries (Hall B data) Total cross sections (Hall A data) DD model (VGG) Minimal dual model

K. Kumericki, D. Mueller ArXiv: Dispersion relation fits of DVCS data Fit of H1/ZEUS+CLAS+Hermes with only H +Hall A and H + H ˜ JLab Hall A data CLAS BSA Hermes BCA JLab Hall A data

H. Moutarde ArXiv: v1 To be published in Phys. Rev. D Compton Form Factor (i.e. local) or dual model fits of H only Hall A cross section data

M. Guidal Eur. Phys. J. A37 319, 2008 Compton Form Factor fits only (i.e. local fits) Includes H, H and E ˜ Hall A cross section data

0.09<-t< <-t<0.40.4<-t< <-t<11<-t<1.51.5<-t<2 PRELIMINARY, Analysis in Progress PhD Thesis H.S. Jo E1-DVCS : Cross-sections over a wide kinematical range

e’ e 00  leptonic plane hadronic plane p’ Q 2 = - (k-k’) 2 x B = Q 2 /2M  =E e -E e’ t = (p-p’) 2  ( angle between leptonic and hadronic plane ) =  (Q 2,x B ) d4d4 dQ  dx B d  dt d2d2 d  dt reduced cross section for  *p→p  0 d  TT dt +  d2d2 d  dt = 1 22 ( dTdT dt dLdL +  d  LT dt +√ 2  +1) cos  cos2  +h√ 2  -1) d  L’T dt sin   0 electroproduction cross section

VGG Laget -Low-t cross-section largely overshoots GPD & JML models !!! -TT term is large, suggesting a large transverse component. -But  0 cross-section ratio for proton and deuteron targets is found ~ 1 More data needed ! Submitted soon  0 cross sections in Hall A – a puzzle !

 0 cross sections in Hall B Arbitrary units Statistical errors only  T +  L vs. –t (GeV 2 /c 2 ) S. Niccolai PRELIMINARY, Analysis in Progress

Use of base CLAS12 equipment, including Inner Calorimeter (IC) Detection of the full (e,p,  ) final state Perform 2 experiments for the extraction of the BSA and the TSA Experimental Setup and proposed experiments at 11 GeV IC tungsten shielding Distance, target-IC: ~1.75m currently (note: this is NOT optimized for DVCS!)

Beam Spin Asymmetry From 1% statistical error on extracted Twist-2 coefficient to 10% statistical error at high x B IC in standard position – 80 days – 10^35 Lum – VGG model

The cross-section difference accesses the imaginary part of DVCS and therefore GPDs at x =  The total cross-section accesses the real part of DVCS and therefore an integral of GPDs over x Observables and their relationship to GPDs

CLAS 6 GeV DVCS BSA Proton ep→epπ o /η Hall A 6 GeV DVCS proton neutron ep→epπ o CLAS 5.75 GeV DVCS DDVCS ΔDVCS D2VCS Polarized DVCS ep→epρ L ep→epω L ep→epπ 0 /η ep→enπ + ep→epΦ HERMES 27 GeV DVCS – BSA + BCA + nuclei BSA d-BCA + Polarized target DVCS ep→epρ σ L + DSA CLAS 4-5 GeV DVCS BSA HERMES DVCS BSA+BCA With recoil detector COMPASS DVCS  +BCA With recoil detector Published or Finalized Published or Analysis in 2009 – 2001 close to be progress ? 12GeV (low/medium energy) Deep Exclusive experiments EVERYTHING, with more statistics than ever before JLab Hall A DVCS² CLAS BSA+TSA In red: selected topics for JLab