The Science Program of CLAS12 and the JLab 12 GeV Upgrade Latifa Elouadrhiri Jefferson Lab December 4, 2009

Outline Brief historical overview Generalized Parton Distributions - a unifying framework of hadron structure Experiments to access GPDs 12 GeV Upgrade project 3D Imaging of the Proton Quark Structure Summary

Some well known facts about the proton Charge: Qp = +1 It has a neutral partner, the neutron, Qn = 0 Mass: Mp ~ 940 MeV/c2 Proton + neutron make up 99.9% of the mass of the visible universe Spin: s = ½ћ Magnetic moment mp = 2.79mN Anomalous magnetic moment ma = 1.79mN 1950’s: Does the proton have internal structure? The exploration of the internal structure of the proton began in the 1950’s with Hofstadter’s experiments.

Electron Scattering as a Probe of the Proton Structure elastic inclusive exclusive p, r, g gv gv gv Q2 = -(e-e’)2 n = Ee – Ee’ xB = Q2/2Mn t = -(p-p’)2 xB = 1 (for elastic scattering) 1/Q2 is spatial sensitivity of virtual g

Does the Proton have finite size? Elastic electron-proton scattering the proton is not a point-like particle, it has finite size ds/dW = [ds/dW]n.s.|F(q)| 1955 Proton form factors, transverse charge & current densities Physics Nobel Prize 1961 R. Hofstadter

What is the internal structure of the proton? Nobel prize 1990 J. Friedman H. Kendall R. Taylor => Deep inelastic electron-proton scattering ep→e’X ds/dWdE’ = ds/dWMott[W2 (Q2,n)] 1968 = 1/xB Scaling => Quarks are point-like objects! Determine quark momentum distribution f(x). Quarks carry ~ 50% of the proton momentum.

? How is the Proton Charge Density Related to its Quark Momentum Distribution? D. Mueller, X. Ji, A. Radyushkin, A. Belitsky, … M. Burkardt, … Interpretation in impact parameter space Correlated quark momentum and helicity distributions in transverse space - GPDs ? Proton form factors, transverse charge & current densities Structure functions, quark longitudinal momentum & helicity distributions

GPDs & PDFs z z y x x x 2-D Golden Retriever 3-D Golden Retriever Deeply Virtual Exclusive Processes & GPDs 1-D Golden Retriever Water probablity Calcium Deep Inelastic Scattering & PDFs Carbon x

3 dimensional imaging of the nucleon Deeply Virtual Compton Scattering (DVCS) t x+x x-x hard vertices 2x – longitudinal momentum transfer x – longitudinal quark momentum fraction –t – Fourier conjugate to transverse impact parameter g GPDs depend on 3 variables, e.g. H(x, x, t). They describe the internal nucleon dynamics.

[ ] ò Link to DIS and Elastic Form Factors [ ] å ò ) ( , ~ q H D = ) , Form factors (sum rules) [ ) ( , ~ ) Dirac f.f. 1 t G x E dx H F1 q P A = ] ò å - ) Pauli f.f. F2 DIS at x =t=0 ) ( , ~ q H D = ) , ( ~ t x E H q [ ] ò - x + - J G = = 1 ) , q( 2 E H xdx J q X. Ji, Phy.Rev.Lett.78,610(1997) Angular Momentum Sum Rule

Deeply Virtual Meson production Universality of GPDs Elastic form factors Real Compton scattering at high t Parton momentum distributions GPDs Deeply Virtual Meson production Deeply Virtual Compton Scattering Single Spin Asymmetries

How can we determine the GPDs?

} Accessing GPDs in Exclusive Processes ep ® e ' p ' g ep e p L ® ' L Deeply virtual Compton scattering (clean probe, flavor blind) Sensitive to all GPDs. Insensitive to quark flavor ep ® e ' p ' g ep e p L ® + - ' L Hard exclusive meson production (quark flavor filter) Sensitive to H, E ~ } In a minute I’ll give an example of how GPDs show up in this processes. 4 GPDs in leading order, 2 flavors (u, d) → 8 measurements

Accessing GPDs through DVCS Eo = 11 GeV Eo = 6 GeV Eo = 4 GeV BH DVCS DVCS BH p e d4 dQ2dxBdtd ~ |TDVCS + TBH|2 TBH : given by elastic form factors F1, F2 TDVCS: determined by GPDs I ~ (TBH)Im(TDVCS) BH-DVCS interference generates beam and target polarization asymmetries that carry the proton structure information.

Measuring GPDs through polarization s+ - s- s+ + s- = Polarized beam, unpolarized target: ~ H(x,t) DsLU ~ sinfIm{F1H + x(F1+F2)H +kF2E}df x = xB/(2-xB) k = t/4M2 Kinematically suppressed Unpolarized beam, longitudinal target: ~ ~ H(x,t) DsUL ~ sinfIm{F1H+x(F1+F2)(H +x/(1+x)E) -.. }df Kinematically suppressed Unpolarized beam, transverse target: H(x,t), E(x,t) DsUT ~ sinfIm{k(F2H – F1E) + ….. }df Kinematically suppressed

Pioneering Experiments Observe Interference 2001 e+p->e+pg e-p->e-pg AUL = asinf + bsin2f First GPD analyses of HERA/CLAS/HERMES data in LO/NLO consistent with a ~ 0.20. A. Freund (2003), A. Belitsky et al. (2003) twist-2 twist-3

Jefferson Lab - a DOE Science National Laboratory JLab is a forefront facility with unique scientific and technical capabilities One of 17 DOE National Laboratories One of ten Office of Science National Laboratories Serves an international user community of 1200 Experimental program to elucidate the quark structure of matte delivers world leading experiments in nuclear science World leader and national resource in superconducting radiofrequency accelerating technology Superconducting Radio Frequency (SRF) R&D yielded the new single-crystal niobium cavity for use in future accelerators Operates a high power Free Electron Laser More than 1/3 of US Ph.Ds awarded in nuclear physics; 248 Ph.Ds, granted, 192 more in progress Excellent education program supporting local school science teaching

Jefferson Lab Today A C B Hall A Hall B Hall C Two high-resolution 4 GeV spectrometers Large acceptance spectrometer electron/photon beams Hall C Be brief A B C 7 GeV spectrometer, 1.8 GeV spectrometer, large installation experiments

Hall B – CLAS Present Day CLAS Hall B currently houses the CEBAF Large Acceptance Spectrometer (CLAS) L=1034 cm-2s-1 Present Day CLAS

Hall B - DVCS Solenoid and Calorimeter Solenoid cryostat Calorimeter

Deeply Virtual Compton Scattering & GPDs Unprecedented set of Deeply Virtual Compton Scattering data accumulated in Hall A and with CLAS Hall A Phys.Rev.Lett.97:262002,2006 CLAS t hard vertices g A = DsLU 2s s+ - s- s+ + s- = At low and medium energies DVCS is the cleanest probe of GPDs. A hard virtual photon strikes a quark in the proton, which emits a hard real photon. The prpton remains intact and gets a transverse momentum kick. DVCS is sensitive to all 4 GPDs. Hall A cross section measurements showed that DVCS is consistent with dominance of the handbag mechanism. The CLAS data cover much larger kinematics in x_B, Q2, and t. but are currently limited to polarized beam asymmetries which also depend on the real parts of the Compton amplitude in a convolution integral that are more difficult to model. GPD based description show qualitative agreement with the CLAS asymmetry measurements. Nevertheless, these sets of data have been subjected to a model-independent extraction of the GPD related Compton form factors. Polarized beam, unpolarized target: Kinematically suppressed DsLU ~ sinf{F1H + x(F1+F2)H +kF2E}df ~ Φ Phys.Rev.Lett.100:162002,2008

In the past few years, we have made a start in the quest to unravel the Structure of the Proton. What does the future hold?

JLab Upgrade to 12 GeV At 12 GeV, CEBAF will be an ideal for GPD studies. Add new hall CHL-2 Enhance equipment in existing halls

Scope of the 12 GeV Upgrade

New Capabilities in Halls A, B, & C, and a New Hall D 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 B CLAS12 high luminosity, large acceptance. A new Hall will be constructed to house the GlueX detector, that will conduct a search for excited mesons with gluonic components, and the existing Halls will be upgraded with new equipment as well. Hall C will have an additional super high momentum spectrometer. Hall A will retain the existing spectrometers and provide space for new specialized equipment to address a variety of physics topics. Hall B will house the CLAS12 detector which is the focus of this of workshop. At 12 GeV JLab will be ideal for precision studies at large Bjorken x.

Hall B 12GeV upgrade overview Hall B currently houses the CEBAF Large Acceptance Spectrometer (CLAS) L=1034 cm-2s-1 CLAS will be replaced by CLAS12 CLAS12 is designed to operate with an upgraded luminosity of L=1035 cm-2s-1 CLAS12 will be world wide the only large acceptance high luminosity spectrometer for fixed target electron scattering experiments CLAS12 Present Day CLAS

CLAS12 – Design parameters Forward Detector Forward Central Detector Detector Angular range Tracks 50 – 400 350 – 1250 Photons 30 – 400 n.a. Resolution dp/p (%) < 1 @ 5 GeV/c < 5 @ 1.5 GeV/c dq (mr) < 1 < 10 - 20 Df (mr) < 3 < 5 Photon detection Energy (MeV) >150 n.a. dq (mr) <4 @ 1 GeV n.a. Neutron detection efficiency < 0.7 (EC+PCAL) n.a. Particle ID e/p Full range n.a. p/p Full range < 1.25 GeV/c p/K Full range < 0.65 GeV/c K/p < 4 GeV/c < 1.0 GeV/c p0gg Full range n.a. hgg Full range n.a. Central Detector

Central Detector Forward Detector FTOF 2 LTCC FTOF 1a FTOF 1b PCAL DC R1, R2, R3 Central Detector Solenoid SVT EC CTOF Forward Detector TORUS HTCC

CLAS12 Central Detector Superconducting 5T Solenoid Magnet, 78cm ø warm bore. Central Time-of-Flight array (CTOF) Silicon Vertex Tracker Extension under development Tracking w/ Micromegas Neutron Detector

CLAS12 – Central Detector SVT, CTOF SVT - Charged particle tracking in 5T field Vertex reconstruction ΔT < 60psec in CTOF for particle id Moller electron shield Polarized target operation ΔB/B < 10-4 in 3x5 cm cylinder around center CTOF 6 layers 8 layers SVT

CLAS12 – Solenoid and Torus Magnets The Torus and Solenoid magnets provide bending power for tracking with sufficient momentum resolution to allow exclusive processes to be identified. At forward angles the Torus field provides large integral Bdl while the solenoid provides tracking at large angles over a limited radial distance. The B-field transverse to the particle trajectory is approximately matched to the average particle momentum.

A Program at the Forefront of Hadron Physics 3D Structure of the Nucleon Structure - the new Frontier in Hadron Physics Nucleon GPDs and TMDs – exclusive and semi-inclusive processes with high precision Precision measurements of structure functions and forward parton distributions at high xB Elastic & Transition Form Factors at high momentum transfer Hadron Spectroscopy – heavy baryons, hybrid mesons Some of the topics to be addressed are – the 3D structure of the nucleon which is a new frontier of hadron physics. This requires measurements of GPDs and TMDs in deeply exclusive and semi-inclusive processes.

Initial Science Program CLAS12 Physics Focus Approved experiments LOIs supported GPD’s & exclusive Processes 3 1 TMDs & SIDIS 4 Parton Distribution Function & DIS 2 Elastic & resonance form factors Hadronization & Color Transparency Baryon Spectroscopy Total 13 7 Approved experiments correspond to about 5 years of scheduled beam operation .

CLAS12 Institutions Institution Focus Area Argonne National Laboratory (US) Cerenkov Counter California State University (US) Cerenkov Counters Catholic University of America (US) Software College of William & Mary (US) Calorimetry, Magnet Mapping Edinburgh University (UK) Software Fairfield University (US) Polarized Target Florida International University, Miami (US) Beamline/Moller polarimeter Glasgow University (UK) Central Detector, DAQ, Forward Tagger, RICH Grenoble University/IN2P3 (France) Central Detector Idaho State University (US) Drift chambers INFN –University Bari (Italy) tbd, interest in RICH INFN –University Catania (Italy) tbd INFN – Frascati and Fermi Center (Italy) Central Neutron Detector+ interest show in RICH INFN –University Ferrara (Italy) (will join in 2010) tbd, interest in RICH INFN – University Genoa (Italy) Central Neutron Detector+ interest in Forward Tagger INFN – ISS/Rome 1 (Italy) tbd, interest in RICH INFN – University of Rome Tor Vergata (Italy) Central Neutron Detector+ HD target Institute of Theoretical and Experimental Physics (Russia) SC. Magnets, Simulations James Madison University (US) Calorimetry Kyungpook National University (Republic of Korea) CD TOF Los Alamos National Laboratory (US) Silicon Tracker Moscow State University, Skobeltsin Institute for Nuclear Physics (Russia) Software, SVT Moscow State University (High Energy Physics) (Russia) Silicon Tracker Norfolk State University (US) Preshower Calorimeter Ohio University (US) Preshower Calorimeter Orsay University/IN2P3 (France) Central Neutron Detector Old Dominion University (US) Drift Chambers Renselear Polytechnic Institute (US) Cerenkov Counters CEA Saclay (France) Central Tracker, Reconstruction software Temple University, Philadelphia (US) Cerenkov Counters Thomas Jefferson National Accelerator Facility (US) Project coordination & oversight University of Connecticut (US) Cerenkov Counters University of New Hampshire (US) Central Tracker, Offline Software University of Richmond (US) Offline Software University of South Carolina (US) Forward TOF University of Virginia (US) Beamline/Polarized Targets Yerevan Physics Institute (Armenia) Calorimetry

Deeply Virtual Exclusive Processes - Kinematics Coverage of the 12 GeV Upgrade H1, ZEUS H1, ZEUS 11 GeV 27 GeV 200 GeV 11 GeV JLab Upgrade JLab @ 12 GeV COMPASS W = 2 GeV HERMES Study of high xB domain requires high luminosity 0.7

DVCS/BH- Beam Asymmetry Ee = 11 GeV ALU With large acceptance, measure large Q2, xB, t ranges simultaneously. A(Q2,xB,t) Ds(Q2,xB,t) s (Q2,xB,t)

CLAS12 - DVCS/BH- Beam Asymmetry Ee = 11 GeV Q2=5.5GeV2 xB = 0.35 -t = 0.25 GeV2 Luminosity = 720fb-1

CLAS12 - DVCS/BH Beam Asymmetry e p epg E = 11 GeV DsLU~sinfIm{F1H+..}df Selected Kinematics L = 1x1035 T = 2000 hrs DQ2 = 1 GeV2 Dx = 0.05

CLAS12 - DVCS/BH Target Asymmetry E = 11 GeV L = 2x1035 cm-2s-1 T = 1000 hrs DQ2 = 1GeV2 Dx = 0.05 e p epg Longitudinally polarized target ~ Ds~sinfIm{F1H+x(F1+F2)H...}df

CLAS12 - DVCS/BH Target Asymmetry Sample kinematics e p epg E = 11 GeV Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2 Transverse polarized target Ds ~ sinfIm{k1(F2H – F1E) +…}df AUTx Target polarization in the scattering plane AUTy Target polarization perpendicular to the scattering plane Asymmetries highly sensitive to the u-quark contributions to the proton spin.

Exclusive r0 production on transverse target 2D (Im(AB*)) T AUT ~ A ~ 2Hu + Hd r0 Q2=5 GeV2 B ~ 2Eu + Ed A ~ Hu - Hd B ~ Eu - Ed r+ r0 Eu, Ed allow to map the orbital motion of quarks. B K. Goeke, M.V. Polyakov, M. Vanderhaeghen, 2001

∫ Tomographic Images of the Proton Ed(x,t) Eu(x,t) d2t (2p)2 Target polarization dX(x,b ) T Ed(x,t) Eu(x,t) uX(x,b ) T ∫ d2t (2p)2 e-i·t·b E(x,0,t) T q(x,b ) = flavor polarization CAT scan slice of human abdomen M. Burkardt

2007 NSAC Long Range Plan (4 recommendations) We recommend the completion of the 12 GeV Upgrade at Jefferson Lab. - It will enable three-dimensional imaging of the nucleon, revealing hidden aspects of its internal dynamics. It will complete our understanding of the transition between the hadronic and quark/gluon descriptions of nuclei. It will test definitively the existence of exotic hadrons, long-predicted by QCD as arising from quark confinement. It will provide low-energy probes of physics beyond the Standard Model complementing anticipated measurements at the highest accessible energy scales. The importance of GPDs for the future of hadronic and nuclear physics was recognized last week by the NSAC Long Range Plan meeting in Galveston. The board gave the Jlab upgrade the highest recommendation and lists the 3-D imaging of the nucleon as the #1 program for the upgrade.

DOE Generic Project Timeline We are here Almost half-way between CD1 and CD2 MAR 2004 FEB 2006 NOV 2007 SEP 2008 12 GeV Upgrade – Approval dates

DOE Project Critical Decisions – 12 GeV Schedule CD-0 Approve Mission Need (Mar 2004) CD-1 Approve Alternative Selection and Cost Range (Feb 2006) Permission to develop a Conceptual Design Report Defines a range of cost, scope, and schedule options CD-2 Approve Performance Baseline (Nov 2007) Fixes “baseline” for scope, cost, and schedule Now develop design to 100% Begin monthly Earned Value progress reporting to DOE Permission for DOE-NP to request construction funds CD-3 Approve Start of Construction DOE Office of Science CD-3 Approval: September 15, 2008 CD-4 Approve Start of Operations or Project Close-out

12 GeV Upgrade – Immediate Future 12 GeV Upgrade Project Start of Construction: October 2008

12 GeV Schedule May ’11 - Oct ‘11 6-month “down” for initial installations Nov ’11 - May ‘12 6-month run 6GeV Jun ’12 - May ‘13: 1-year “down” for major installation June ’13 - Sep ‘13: Accelerator commissioning

12 GeV Schedule Oct ‘13: Hall A commissioning start Apr ‘14: Hall D commissioning start Oct ‘14: Hall B & C commissioning start

Summary The JLab 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 hadrons by accessing GPDs and TMDs mapping the valence quark structure of nucleons with high precision understanding hadronization processes extending nucleon form factors to short distances Design of accelerator and equipment upgrades are underway Construction started October 2008

12 GeV Upgrade Science, Technology & Education Jefferson Laboratory 12 GeV Upgrade Science, Technology & Education Center Stage

This is a very exciting time for hadronic physics, and the perfect time for new collaborators to make significant contributions to the physics and equipment of CLAS12