The Physics Program at an Upgraded Jefferson Lab

The Physics Program at an Upgraded Jefferson Lab Cynthia Keppel Hampton University / Jefferson Lab DIS 2005 Madison, WI • Highlights of the 12 Ge. V Program • determination of spin and flavour structure in the valence region • exploration of the 3 dimensional picture of the nucleon • physics of nuclei • search for gluonic exitations

CEBAF @ JLab Today • Main physics programs – – – nucleon electromagnetic form factors strange form factors N → N* electromagnetic transition form factors (spin) structure functions of the nucleon physics of nuclei and hypernuclei • Superconducting recirculating electron accelerator – max. energy – max current – e polarization 5. 7 Ge. V 200 m. A 80% • Simultaneous operation in 3 halls – 2 high luminosity halls (L=1039) – large Acceptance Spectrometer for e and g induced reaction (L=1034)

add Hall D (and beam line) 126 Ge. V CEBAF Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls

Major Components to Achieve 12 Ge. V • upgrade of injector energy from 70 Me. V to 130 Me. V by adding recirculation • upgrade of linac energy from 0. 6 Ge. V/linac to 1. 1 Ge. V/linac by adding 5 new 100 Me. V cryomodules to each linac – cryomodule technology advancements allow for doubling the acceleration in onefourth the space via higher gradient and increased effective accelerating length • • • Original CEBAF: 20 MV Present CEBAF average: SL 21 70 MV FEL 3 80 MV Spec for Renascence 98 MV Required for 12 Ge. V 98 MV achieved 28 MV (max=34 MV) achieved under construction designed • build new cryogenics plant to double present capacity to 9 k. W • convert existing dipole magnets from C-magnets to H-magnets • result: – – Continuous wave (CW) operation preserved Minimize disruption to research program (~1 year) Lower pass numbers also available with 12 Ge. V delivery (2. 2/4. 4/6. 6/8. 8 Ge. V) Maximum beam current to Halls A and C (~80 m. A), and Halls B and D (~5 m. A)

Enhanced Equipment in Halls A, B, & C and a New Hall D D 9 Ge. V tagged polarized photons and a 4 hermetic detector B CLAS upgraded to higher (1035) luminosity and coverage C Super High Momentum Spectrometer (SHMS) at high luminosity and forward angles A High Resolution Spectrometer (HRS) Pair, and specialized large installation experiments

Charged Pion Electromagnetic Form Factor Where does the dynamics of the q-q interaction make a transition from the strong (confinement) to the perturbative QCD regime? • It will occur earliest in the simplest systems the pion form factor F (Q 2) provides our best chance to determine the relevant distance scale experimentally There are dozens of predictions… Hall C E 93 -021 results, and E 01 -004 and 12 Ge. V projections

Proton & Neutron Electromagnetic Form Factors (Polarization Experiments only) Here shown as ratio of Pauli & Dirac Form Factors F 2 and F 1. Taking orbital angular momentum into account ln 2(Q 2/L 2)Q 2 F 2/F 1 constant (Ji)

Extending DIS to High x The Neutron to Proton Structure Function Ratio, d(x)/u(x) pdf Ratio u(x) current uncertainties quite large! d(x) F 2 n / F 2 p x 12 Ge. V will access the valence quark regime (x > 0. 3)

An Effective Free Neutron Target e n p • Can also use 3 H/3 He mirror nuclei

Extending DIS to High x, continued. . The Neutron Asymmetry A 1 The Proton Asymmetry A 1 SU(6) breaking p. QC D valence quark models SU(6) symmetric x

Flavor Decomposition using SIDIS Valence quarks Ee =11 Ge. V NH 3+He 3 quark polarization asymmetries Sea quarks ? Ee =11 Ge. V NH 3+ND 3 Unprecedented precision for valence quarks, discriminating power for sea quarks test models for quark polarization

k. T-dependent parton distributions Semi-Inclusive Deep Inelastic Scattering (SIDIS): • Probes orbital motion of quarks through quark transverse momentum distribution • Access to new PDFs not accessible in inclusive DIS. Off-diagonal PDFs vanish if quarks only in s-state! In addition T-odd PDFs require FSI (Brodsky Mulders et al. , Collins, Ji et al. 2002) Sivers transversity ØFactorization of k. T-dependent PDFs proven at low PT of hadrons (Ji et al) ØUniversality of k. T-dependent distribution and fragmentation functions proven (Collins, Mets…)

Azimuthal Asymmetry – Sivers Effect Originates in the quark distribution. Probes orbital angular momentum of quarks by measuring the imaginary part of s-p-wave interference in the amplitude. sin(f-fs) T AUT ~ k f 1 T D 1

3 D Images of the Proton’s Quark Content M. Burkardt PRD 66, 114005 (2002) u. X(x, b ) d. X(x, b ) T T T u(x, b ) transverse polarized target d(x, b ) T b - Impact parameter T quark flavor polarization Needs: Hu Eu Accessed in Single Spin Asymmetries. Ed Hd

Beyond form factors and quark distributions – Generalized Parton Distributions (GPDs) X. Ji, D. Mueller, A. Radyushkin (1994 -1997) Proton form factors, transverse charge & current densities Correlated quark momentum and helicity distributions in transverse space - GPDs Structure functions, quark longitudinal momentum & helicity distributions

Limiting Casesfor for. GPDs Ordinary Parton Distributions (D, t, x → 0) ~ H 0(x, 0) = q(x) unpolarized H 0(x, 0) = Dq(x) polarized Nucleon Form Factors (Sum Rules) x. P (x-x) P ~ ~ H , E, H , E P P D t=D 2 difference in momentum fraction between initial and final state parton Dirac Axial vector Pauli Pseudoscalar momentum transfer to the nucleon

Measurement: Beam Spin Asymmetry DVCS e’ e p GPD’s a 3 x. B y ds = dx. B dydtd f 8 p e 3 Q 2 1 + e 2 Bethe-Heitler g e + p (T BH Beam Spin Asymmetry ~ g + TDVCS e p p 2 e’ gg p p * * +TBH TDVCS +TDVCS TBH )

DVCS: Single-Spin Single Spin Asymmetry DVCS Asymmetry CLAS Collaboration Q 2 = 5. 4 Ge. V 2 PRL 87, 182002 (2001) x = 0. 35 -t = 0. 3 Ge. V 2 Measure interference between DVCS-BH CLAS experiment e’ E 0 = 11 Ge. V g e. Pe = 80% L = 1035 cm-2 s-1 Run time: 2000 hrs p GPD’s p Many x, Q 2 and t values measured simultanously !

Transverse Momentum Dependent GPDs (TMDs) Wpu(x, k, r) “Parent” Wigner distributions k. T d 3 r 2 d T) (F TMD PDFs: fpu(x, k. T), g 1, f┴ 1 T, h┴ 1 L Measure momentum transfer to nucleon. dx d 2 k T Measures momentum transfer to quark. GPDs: Hpu(x, x, t), Epu(x, x, t), … x=0, t=0 TMD Probability to find a quark u in a nucleon P with a certain polarization in a position r and momentum k PDFs fpu(x), g 1, h 1 FFs F 1 pu(t), F 2 pu(t). . …an unprecedented level of depth to nucleon structure studies….

Quark Structure of Nuclei: Origin of the EMC Effect • Observation that structure functions are altered in nuclei stunned much of the HEP community 23 years ago • ~1000 papers on the topic; BUT more data are needed to uniquely identify the origin: What alters the quark momentum in the nucleus? Jlab at 12 Ge. V • Precision study of A- JLab 12 x dependence • Measurements at x>1 • “Polarized EMC effect” • Flavor-tagged (polarized) structure functions • valence vs. sea contributions

Nuclear effects in Hadronisation h = p, K, h, w, f, p, . … In general, Significant dependence of R on Must measure multi-variable dependence for stringent model tests! <z>=0. 3 -0. 42, <Q 2>=2. 2 -3. 5 n (Ge. V) <n>=11. 5 -13. 4, <Q 2>=2. 6 -3. 1 z

Gluonic Excitations Gluonic • predicted by QCD • crucial for understanding confinement • quantum numbers of the excited gluonic fields couple to those of the quarks to produce mesons with exotic quantum numbers • mass spectra calculated by lattice QCD possibility for experimental search From G. Bali

Quantum Numbers of Hybrid Mesons Excited Quarks Flux Tube Hybrid Meson like Exotic like Flux tube excitation (and parallel quark spins) lead to exotic J PC

Radial excitations Mass (Ge. V) Meson Map Each box corresponds to 4 nonets (2 for L=0) qq Mesons 2 –+ 0 –+ 2 ++ Glueballs 2. 0 1. 5 2 +– 2 –+ 1 –– 1– + 1 +– 1 ++ 0 +– 0 –+ 0 ++ 1. 0 L=0 1 2 3 4 (L = qq angular momentum) Hybrids 2. 5 exotic nonets Lattice 1 -+ 1. 9 Ge. V 2+- 2. 1 Ge. V 0+- 2. 3 Ge. V

Strategy for Exotic Meson Search • Use photons to produce meson final states – tagged photon beam with 8 – 9 Ge. V – linear polarization to constrain production mechanism • Use large acceptance detector – hermetic coverage for charged and neutral particles – typical hadronic final states: f 1 h KK b 1 w r • Perform partial-wave analysis – identify quantum numbers as a function of mass – check consistency of results in different decay modes

Glue. X / Hall D Detector 12 Ge. V electrons Barrel Calorimeter Lead Glass Detector Solenoid collimated Coherent Bremsstrahlung Photon Beam Note that tagger is 80 m upstream of detector Electron Beam from CEBAF Time of Tracking Flight Cerenkov Counter Target

Milestones and Timelines for 12 Ge. V • • 1994 -2002 April 2004 -2005 Oct 2004 Jan 2005 April 2005 • • Sept 2005 2007 -2008 -2011 2012 Development of Science Case and Exp. Equiment Recommendation by NSAC Long Range Planning DOE Approval of Mission Need (CD-0) Development of Conceptual Design Report Glue. X Detector Review of Spectrometer Options DOE Science Review of the 12 Ge. V Upgrade (very positive response ! ) Critical Decision on Prel. Baseline Range (CD-1) Engineering and Design Construction Beam on Target

Summary CEBAF operation @ 6 Ge. V has provided results with unprecedented precision on structure functions and form factors (including strangeness) Upcoming years will highlight precision hypernuclear studies, standard model tests and. . . The Upgrade to 12 Ge. V is essential to provide access to new kinematic regions and will: • determine with extreme precision the spin and flavour structure of the nucleon in the valence region • provide a totally new and complete view of the nucleon structure access to quark angular momentum • finally (after > 30 years) determine the origin of the EMC effect • test our understanding of quark confinement • and much more. . .

ELIC Layout (Derbenev, Chattopadhyay, Merminga et al. ) One accelerating & one decelerating pass through CEBAF (A=1 -40) Ion L inac and preboos t Electron Cooling er IR IR Solenoid IR 3 -7 3 -7 Ge. V electrons 30 --1150 30 50 Ge. V(light) light ions Electron Injector CEBAF with Energy Recovery Beam Dump Snake

Luminosity Potential with e. RHIC/ELIC e. RHIC: 10 Ge. V Electrons on 250 Ge. V Protons (up to Pb) @SPIN 2004 mention of 20 Ge. V Electrons in Linac-Ring Option ELIC : 7 Ge. V Electrons on 150 Ge. V Protons (up to Ca) 25 Ge. V TESLA-N ELIC Luminosity LINAC-RING? 8 x 1034 cm-2 sec-1 e. RHIC x 100 EIC x 8, 000 (per interaction point, one day lifetime) Precision Frontier