The Jefferson Lab 12 -Ge. V Upgrade JLab’s Scientific Mission • • • Understand how hadrons are constructed from the quarks and gluons of QCD Understand the QCD basis for the nucleon-nucleon force Explore the limits of our understanding of nuclear structure – The transition from the nucleon-meson to the quark-gluon description We know that QCD works, but we still need to understand how. Must address critical issues in “strong” QCD + What is the mechanism of confinement? Where is the Glue? + Where does the dynamics of the q-q interaction make a transition from the strong (confinement) to the perturbative (QED-like) QCD regime? + How does the nucleon mass, spin, shape come about from the sea of gluons & quark/anti-quarks? + Do quarks and gluons play any direct role in Nuclear Matter?
Jefferson Lab Today • Provides unique capabilities for ~2000 member international user community to explore and understand the structure of matter at its most fundamental level (quarks and gluons). • The SRF electron accelerator provides CW beams of unprecedented quality with a maximum beam energy of 6 Ge. V. • CEBAF’s innovative design allows delivery of beam with unique properties to three experimental halls simultaneously, increasing scientific output. • Each of the three halls offers complementary experimental capabilities and allows for large equipment installations to extend scientific reach. A B C
12 Ge. V Upgrade is designed to build on existing facility: all accelerator and nearly all experimental equipment have continued use Add beam transport Enhanced capabilities in existing Halls New Hall Scope of the proposed project includes doubling the accelerator beam energy, a new experimental Hall and associated beamline, and upgrades to the existing three experimental Halls.
Architect’s Rendering of Hall D Complex Hall D Counting House Cryo Plant Service Buildings North East corner of Accelerator
Overview of 12 Ge. V Physics Program Hall D – exploring origin of confinement by studying exotic mesons Hall B – understanding nucleon structure via generalized parton distributions Hall C – precision determination of valence quark properties in nucleons and nuclei Hall A – short range correlations, form factors, hyper-nuclear physics, future new experiments
50% of momentum carried by gluons 20% of proton spin carried by quark spin
But miserable knowledge of especially d-quarks at large x and spin dependence at large x (here A 1 n is shown) Resolution: e. g. , F 2 n tagging spectator proton from deuterium, and 3 He(e, e’)
Unambiguous Resolution @ 12 Ge. V F 2 n/F 2 p at 11 Ge. V A 1 n at 11 Ge. V W>1. 2
Charged Pion Electromagnetic Form Factor Where does the dynamics of the q-q interaction make a transition from the strong (confinement) to the perturbative (QED-like) 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 To measure F (Q 2) : • At low Q 2 (< 0. 3 (Ge. V/c)2): use + e scattering Rrms = 0. 66 fm • At higher Q 2: use 1 H(e, e’ +)n Scatter from a virtual pion in the proton and 1) extrapolate to the pion pole large uncertainty 2) use a realistic pion electroproduction model • In asymptotic region, F 8 s ƒ 2 Q-2
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
Link to DIS and Elastic Form Factors Form factors (sum rules) dxå H q ( x, x, t) ò ] = F 1 ( t ) Dirac f. f. E ò dxå[ ] = F 2 ( t) Pauli f. f. 1 DIS at x =t=0 H q ( x, 0, 0) = q( x), -q (-x) ~ H q ( x, 0, 0) = Dq( x), Dq (-x) q [ 1 q ( x, x, t) q 1 ~q ò dx H -1 1 ~ ( x, x, t ) = GA, q ( t ) , ò dx E q ( x, x, t) = GP, q ( t ) -1 ~ ~ H , E , H q , E q ( x, x , t ) q q t Quark angular momentum (Ji’s sum rule) 1 1 1 J q = - J G = ò xdx H q(x, x, 0) +E q ( x, x, 0) 2 2 -1 X. Ji, Phy. Rev. Lett. 78, 610(1997) [ ]
DVCS: Single-Spin Asymmetry in ep Measures phase and amplitude directly DVCS and Bethe-Heitler are coherent can measure amplitude AND phase Eo = 11 Ge. V Eo = 6 Ge. V Eo = 4 Ge. V BH DVCS/BH comparable, allows asymmetry, cross section measurements DVCS at 11 Ge. V can cleanly test correlations in nucleon structure (data shown – 2000 hours)
Exclusive r 0 production on transverse target T AUT = - 2 D (Im(AB*))/ |A|2(1 -x 2) - |B|2(x 2+t/4 m 2) - Re(AB*)2 x 2 r 0 AUT r+ A ~ 2 Hu + Hd B ~ 2 Eu + Ed A ~ Hu - Hd B ~ Eu - E d Asymmetry depends linearly on the GPD E, which enters Ji’s sum rule. r 0 K. Goeke, M. V. Polyakov, M. Vanderhaeghen, 2001 x. B
The QCD Lagrangian and Nuclear “Medium Modifications” The QCD vacuum Long-distance gluonic fluctuations Lattice calculation demonstrates reduction of chiral condensate of QCD vacuum in presence of hadronic matter Leinweber, Signal et al. Does the quark structure of a nucleon get modified by the suppressed QCD vacuum fluctuations in a nucleus?
Quark Structure of Nuclei: the EMC Effect q Observation that structure functions are altered in nuclei stunned much of the HEP community 24 years ago q ~1000 papers on the topic; the best models explain the curve by change of nucleon structure, BUT more data are needed to uniquely identify the origin What is it that alters the quark momentum in the nucleus? J. Ashman et al. , Z. Phys. C 57, 211 (1993) J. Gomez et al. , Phys. Rev. D 49, 4348 (1994) x
g 1(A) – “Polarized EMC Effect” q New calculations indicate larger effect for polarized structure function than for unpolarized: scalar field modifies lower components of Dirac wave function q Spin-dependent parton distribution functions for nuclei nearly unknown q Can take advantage of modern technology for polarized solid targets to perform systematic studies – Dynamic Nuclear Polarization
g 1(A) – “Polarized EMC Effect” q New calculations indicate larger effect for polarized structure function than for unpolarized: scalar field modifies lower components of Dirac wave function q Spin-dependent parton distribution functions for nuclei nearly unknown q Can take advantage of modern technology for polarized solid targets to perform systematic studies – Dynamic Nuclear Polarization (polarized EMC effect) Curve follows calculation by W. Bentz, I. Cloet, A. W. Thomas
QCD and confinement Small Distance High Energy Large Distance Low Energy Strong QCD Perturbative QCD Spectroscopy High Energy Scattering Gluon Jets Observed Gluonic Degrees of Freedom Missing
Gluonic Excitations and the Origin of Confinement Theoretical studies of QCD suggest that confinement is due to the formation of “Flux tubes” arising from the self-interaction of the glue, leading to a linear potential (and therefore a constant force) Color Field: Because of self interaction, confining flux tubes form between static color charges Hybrid mesons Jpc = 1 -+ 1 Ge. V mass difference Normal mesons Experimentally, we want to “pluck” the flux tube and see how it responds
Lattice QCD Heavy Quarks Only! Flux tubes realized From G. Bali Confinement arises from flux tubes and their excitation leads to a new spectrum of mesons ? From D. Leinweber Rather like a “hole in the vacuum”, as also assumed in the Bag Model, now responsible for the famous “flux tube” of QCD.
Where is the Glue? Can JLab at 12 Ge. V find 1 -+ Hybrids? What Mass? Models + Lattice QCD predict M ~ 2 Ge. V 12 Ge. V 9 Ge. V polarized photon beam good “acceptance” up to M ~ 2. 5 Ge. V How Strong? Calculations predict plenty of statistics Find plenty of glue in deep inelastic scattering, that has to end up in hadrons due to unitarity _ How Wide? No reason (yet) to believe qqg wider than qqq DM ~ 100 -200 Me. V How Brittle? Not known whether the string is brittle or not… Will there be a flux tube to excite, or will the string break? Regardless of the flux tube (here used as pedagogical example) there should be gluonic excitations with masses < 2 Ge. V
Why Photoproduction ? q after beam Quark spins anti-aligned q before q q q beam q q A pion or kaon beam, when scattering occurs, can have its flux tube excited Much data in hand but little evidence for gluonic excitations (and not expected) Quark spins aligned after before q Jpc = 1 -+ Almost no data in hand in the mass region where we expect to find exotic hybrids when flux tube is excited
Finding the Exotic Wave g V(ector Meson) S = 1 Double-blind M. C. exercise An exotic wave (JPC = 1 -+) was generated at level of 2. 5 % with 7 other waves. Events were smeared, accepted, passed to PWA fitter. Mass Input: 1600 Me. V Output: 1598 +/- 3 Me. V Width Input: 170 Me. V Output: 173 +/- 11 Me. V Statistics shown here correspond to a few days of running.
Electron-Quark Phenomenology A V V A C 1 u and C 1 d will be determined to high precision by APV and Qweak C 2 u and C 2 d are small and poorly known: can be accessed in PV DIS New physics such as compositeness, new gauge bosons: Deviations in C 2 u and C 2 d might be fractionally large Proposed JLab upgrade experiment will improve knowledge of 2 C 2 u. C 2 d by more than a factor of 20
2 H DIS Experiment at 11 Ge. V E’: 6. 8 Ge. V ± 10% lab = 12. 5 o APV = 290 ppm Ibeam = 90 µA 60 cm LD 2 target 800 hours 1 MHz DIS rate, π/e ~ 1 HMS+SHMS x. Bj ~ 0. 45 Q 2 ~ 3. 5 Ge. V 2 W 2 ~ 5. 23 Ge. V 2 (2 C 2 u-C 2 d)=0. 01 PDG: -0. 08 ± 0. 24 Theory: +0. 0986 (APV)=1. 0 ppm
Møller Parity-Violating Experiment: New Physics Reach (example of large installation experiment with 11 Ge. V beam energy) JLab Møller ee ~ 25 Te. V LHC New Contact Interactions LEP 200 ee ~ 15 Te. V Complementary; 1 -2 Te. V reach Kurylov, Ramsey-Musolf, Su Does Supersymmetry (SUSY) provide a candidate for dark matter? • Lightest SUSY particle (neutralino) is stable if baryon (B) and lepton (L) numbers are conserved • However, B and L need not be conserved in SUSY, leading to neutralino decay (RPV) 95% C. L. JLab 12 Ge. V Møller
Highlights of the 12 Ge. V Program • Revolutionize Our Knowledge of Spin and Flavor Dependence of Valence PDFs • Finalize Our Knowledge of Distribution of Charge and Current in the Nucleon • Totally New View of Hadron (and Nuclear) Structure: GPDs Towards the quark angular momentum • Exploration of QCD in the Nonperturbative Regime: Existence and properties of exotic mesons • New Paradigm for Nuclear Physics: Nuclear Structure in Terms of QCD Spin and flavor dependent EMC Effect Study quark propagation through nuclear matter • Precision Tests of the Standard Model Factor 20 improvement in (2 C 2 u-C 2 d)
12 Ge. V Upgrade: Project Schedule (Feb ’ 06 CD-1 Documents) Critical Decision (CD) CD-1 Documents CD-0 Mission Need 2 QFY 04 (Actual) CD-1 Preliminary Baseline Range CD-2 A/3 A Construction and Performance Baseline of Long Lead Items 2 QFY 06 4 QFY 06/3 QFY 07 CD-2 B Performance Baseline 4 QFY 07 CD-3 B Start of Construction 4 QFY 08 CD-4 Start of Operations 1 QFY 14 • • 2004 -2005 2004 -2008 2006 2007 -2009 2008 -2012 -2013 Conceptual Design (CDR) Research and Development (R&D) Advanced Conceptual Design (ACD) Project Engineering & Design (PED) Long Lead Procurement Construction Pre-Ops (beam commissioning)
12 Ge. V Upgrade: Status • CD-0 approval March 31, 2004 • Period CD-0 to CD-1 is referred to as project “definition phase” • DOE Review of the Science of the 12 Ge. V Upgrade (April 6 -8, 2005) – outstanding rating, several areas described as “discovery potential” • DOE Independent Project Review or IPR (July 12 -14, 2005) – outstanding endorsement for CD-1 readiness from Lehman review in July • CD-1 Approval February 14, 2006 – Announcement at JLab by DOE Secretary Samuel Bodman – 12 Ge. V Upgrade featured in DOE Office of Science Five Year Plan – Completed “definition phase” • Period CD-1 to CD-4 is referred to as project “execution phase”
12 Ge. V Upgrade: Status Near Term: • June 2006 Annual Project Review – Focus on preparations for CD-2 B Performance Baseline – CD-2 B Review anticipated for mid-2007 • August 2006 JLab PAC 30 – First review of 12 Ge. V proposals – “commissioning experiments” – Spokespersons make commitments to construction of equipment – Key first step in identifying the research interests and significant contributions of international collaborators • October 2006 – start Project Engineering & Design (PED)
12 Ge. V Upgrade: The 12 Ge. V Upgrade, with its 1038+ luminosity, is expected to allow for a complete spin and flavor dependence of the valence quark region, both in nucleons and in nuclei. Long-Term: Electron-Light Ion Collider (ELIC) ELIC is designed to provide a complete spin and flavor dependence of the nucleon and nuclear sea, to study the explicit role gluons play in the nucleon spin and in nuclei, and open the new research territory of “gluon GPDs”.
ELIC@JLab Physics Specifications § Flexible Center-of-mass energy between 20 and 65 Ge. V § Ee ~ 3 Ge. V on Ei ~ 30 Ge. V up to Ee ~ 7 Ge. V on Ei ~ 150 Ge. V worked out in detail (gives Ecm up to 65 Ge. V) § CW Luminosity up to 8 x 1034 cm-2 sec-1 per Interaction Point § Ion species of interest: protons, deuterons, 3 He, light-medium ions § Proton and neutron § Light-medium ions not necessarily polarized § Up to Calcium § Longitudinal polarization of both beams in the interaction region (+Transverse polarization of ions +Spin-flip of both beams)
ELIC@JLab Layout (Derbenev, Chattopadhyay, Merminga et al. ) One accelerating & one decelerating pass through CEBAF Ion L inac and preboo Electron Cooling ster IR Solenoid IR IR 3 -7 3 -7 Ge. V electrons 30 150 30 --150 Ge. V light ions Electron Injector CEBAF with Energy Recovery Beam Dump Snake
ELIC@JLab Realization Because ELIC is based on a completely new ring it is possible to optimize for spin preservation & handling and for high luminosity Parameters have been pushed into new territory… ß, lb, ring shape, crab crossing, … “ELIC proposes some very elegant and innovative features worth further investigation” (U. Wienands, EIC 2004 Summary) The physics needs that drove us to this design are the importance of spin, a luminosity as high as possible, and a broad and flexible energy range for Hadron Physics Data from RHIC/RHIC-Spin, COMPASS, HERMES, JHF, JLab forthcoming to guide the requirements for key physics
Science Addressed by ELIC@JLab • Luminosity of up to 8 x 1034 cm-2 sec -1 (one-day life time) • How do quarks and gluons • One day 4, 000 events/pb provide the binding and • Supports Precision Experiments spin of the nucleons? Lower value of x scales as s-1 • What is the quark-gluon • DIS Limit for Q 2 > 1 Ge. V 2 implies structure of mesons? x down to 2. 5 times 10 -4 • How do quarks and gluons • Significant results for 200 evolve into hadrons? events/pb for inclusive scattering • How does nuclear binding • If Q 2 > 10 Ge. V 2 required for Deep originate from quarks and Exclusive Processes can reach x down to 2. 5 times 10 -3 gluons? • Typical cross sections factor 100 • How do gluons behave in 1, 000 smaller than inclusive nuclei? scattering high luminosity essential
Examples: g 1 p, Transversity, Bjorken SR EIC Monte Carlo Group GRSV • Antje Bruell (JLab) • Abhay Deshpande (SBU) • Rolf Ent (JLab) ELIC projection (~10 days) • Ed Kinney (Colorado) • Naomi Makins (UIUC) • Christoph Montag (BNL) • Joe Seele (Colorado) • Ernst Sichtermann (LBL) • Bernd Surrow (MIT) + Several “one-timers”: Harut Avakian, Dave Gaskell, Andy Miller, … EIC Monte Carlo work by Naomi Makins EIC Monte Carlo work by Antje Bruell + Mindy Kohler Can determine the fundamental Bjorken Sum Rule to precision of better than 2%? (presently 10%)
ELIC@JLab – Conclusions § An excellent scientific case is developing for a high luminosity, polarized electron-light ion collider; will address fundamental issues in Hadron Physics: • The (spin-flavor) quark-gluon structure of the proton and neutron • How do quarks and gluons form hadrons? • The quark-gluon origin of nuclear binding § JLab design studies have led to an approach that promises luminosities as high as 8 x 1034 cm-2 sec-1 (one day lifetime), for electron-light ion collisions at a center-of-mass energy between 20 and 65 Ge. V • Evolutionary approach: 1 x 1033 cm-2 sec-1 1 x 1034 cm-2 sec-1 8 x 1034 cm-2 sec-1 § Multi-pronged R&D Strategy to illuminate details of the design • Conceptual development (“Circulator Ring”, Crab Crossing) • Analysis/Simulations • Experiments (ER at high I@JLab/FEL, ER at 1 Ge. V@CEBAF, High I source) § This design, using energy recovery on the JLab site, can be integrated with a 25 Ge. V fixed target program for physics
Backup Slides
N and N- Form Factors @ 12 Ge. V GM(N-D) G Ep 6 Ge. V G En GMn § 6 Ge. V Projections 12 Ge. V Projections
Separated Structure Functions @ 12 Ge. V Rosenbluth Separations up to Q 2 ~ 12 R = s. L/s. T “DIS” (W 2 > 4 Ge. V 2) Limit |
GPDs & Deeply Virtual Exclusive Processes “handbag” mechanism Deeply Virtual Compton Scattering (DVCS) hard vertices x+x x-x g x x – quark momentum fraction x– longitudinal momentum transfer –t – Fourier conjugate to transverse impact parameter t H(x, x, t), E(x, x, t), . . “Generalized Parton Distributions” Quark angular momentum (Ji’s sum rule) 1 1 - J G = 1 Jq = xdx H q(x, x, 0) +E q ( x, x, 0) ò 2 2 -1 X. Ji, Phy. Rev. Lett. 78, 610(1997) [ ]
Measuring GPDs through polarization s+ - s s A = s+ + s- = 2 s Polarized beam, unpolarized target: ~ H(x, t) s. LU ~ sinf. Im{F 1 H + x(F 1+F 2)H +k. F 2 E}df x = x. B/(2 -x. B) Kinematically suppressed k = t/4 M 2 Unpolarized beam, longitudinal target: s. UL ~ ~ sinf. Im{F H+x(F +F )(H +x/(1+x)E) -. . 1 1 2 }df ~ H(x, t), H(x, t) Kinematically suppressed Unpolarized beam, transverse target: s. UT ~ sinf. Im{k(F 2 H – F 1 E) + …. . }df Kinematically suppressed H(x, t), E(x, t)
PV Asymmetries Weak Neutral Current (WNC) Interactions at Q 2 << MZ 2 Longitudinally Polarized Electron Scattering off Unpolarized Fixed Targets (g. Aeg. VT + g. Veg. AT) • The couplings g depend on electroweak physics as well as on the weak vector and axial-vector hadronic current • With specific choice of kinematics and targets, one can probe new physics at high energy scales • With other choices, one can probe novel aspects of hadron structure
12 Ge. V Technology Evolutionary upgrade in machine and experimental equipment: – cryomodule technology advancements • allow for nearly 100% increase in acceleration using only 25% additional space via higher gradient and increased effective accelerating length – – – Original CEBAF: Present CEBAF average: SL 21 (first prototype) FEL 3 (second prototype) Renascence (final prototype) 20 MV achieved 28 MV (max=34 MV) achieved 70 MV achieved 80 MV achieved 98 MV (12 Ge. V requirement) testing underway – demonstrated detector technology for upgraded equipment • much Hall D detector technology well-developed by Glue. X collaboration • Hall C SHMS detectors are copies of existing HMS detectors • most Hall B and Hall C magnet designs close to existing designs
New Capabilities in Halls A, B & C, and 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
An Electron Ion Collider will allow us to look in detail into the sea of quarks and gluons, to create and study gluons, and to discover how energy transforms into matter From DOE 20 -year plan 150 Ge. V proton 7 Ge. V electron One-event display from EIC Monte Carlo
The same electron accelerator can also provide 25 Ge. V electrons for fixed target experiments for physics § Implement 5 -pass recirculator, at 5 Ge. V/pass, as in present CEBAF (straightforward upgrade, no accelerator R&D needed) § Luminosity of 1038+ § Complementary capabilities for broad class of experiments § Exploring whether collider and fixed target modes can run simultaneously (can in alternating mode)
Towards Higher Electron Beam Current JLab FEL program with unpolarized beam Ave. Beam Current (m. A) ELIC with circulator ring @highest luminosity Lifetime Estimate @ 25 m. A: CEBAF enjoys excellent gun lifetime: ~200 C charge lifetime (until QE reaches 1/e of initial value) ~100, 000 C/cm 2 charge density lifetime (we use a ~0. 5 mm dia. spot) If Charge-Lifetime assumption valid: With ~1 cm dia. spot size lifetime of 36 weeks at 25 m. A! Year First polarized beam from Ga. As photogun Source requirements for ELIC less demanding with circulator ring! Few m. A’s versus >> 100 m. A of highly polarized beam. First low polarization, then high polarization at CEBAF Need to test the scalability of charge lifetime with laser spot diameter Measure charge lifetime versus laser spot diameter in lab. (Poelker, Grames)
ERL Technology demonstrated at CEBAF @ 1 Ge. V Special installation of a RF/2 path length delay chicane, dump and beamline diagnostics. 500 Me. V 500 Me. V ~1 Ge. V Accelerating beam 1 Ge. V ~55 Me. V Decelerating beam
RF Response to Energy Recovery • Gradient modulator drive signals with and without energy recovery in response to 250 sec beam pulse entering the RF cavity (SL 20 Cavity 8) 250 s without ER with ER
Gluon Spin in the Nucleon Gluon contribution is likely to be substantial: Profound implications for our basic understanding of the nucleon which must be directly measured by experiment The gold standard: measure G from a variety of experiments, where the dominant theoretical input is NLO QCD and residual model dependence is negligible and non-controversial HERA The dream is to produce a similar plot for x g(x) vs x G/G from open charm: similar precision as RHIC-SPIN extended down to x = 0. 001
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