Physics Prospects with the JLab 12 GeV Upgrade Gluonic Excitations 3-dim view of the Nucleon Elton S.
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Physics Prospects with the JLab 12 GeV Upgrade Gluonic Excitations 3-dim view of the Nucleon Elton S. Smith Jefferson Lab PANIC02 Osaka Valence Structure of the Nucleon Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 1 CEBAF @ JLab Today Main physics programs ─ ─ ─ ─ nucleon electromagnetic form factors (including strange form factors) N → N* electromagnetic transition form factors spin structure functions of the nucleon form factors and structure of light nuclei Superconducting recirculating electron accelerator ─ max. energy ─ max current ─ e polarization 5.7 GeV 200 mA 80% Simultaneous operation in 3 halls L[cm-2s-1] ─ 2 High Resolution Spectrometers (pmax=4 GeV/c) 1039 ─ 2 spectrometers (pmax=7 and 1.8 GeV/c) + special equipment 1039 ─ Large Acceptance Spectrometer for e and g induced reactions 1034 Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 2 add Hall D (and beam line) 126 GeV CEBAF Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 3 Gluonic Excitations Dynamical role of Glue Confinement Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 4 Lattice QCD Flux tubes realized Flux tube forms between qq → Flux Tube Model Confinement arises from flux tubes and their excitation leads to a new spectrum of mesons From G. Bali Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 5 Understanding Confinement The Ideal Experiment The Real Experiment Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 6 Hybrid Mesons Hybrid mesons 1 GeV mass difference (p/r) Normal mesons Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 7 Normal Mesons – qq color singlet bound states Spin/angular momentum configurations & radial excitations generate our known spectrum of light quark mesons. Starting with u - d - s we expect to find mesons grouped in nonets - each characterized by a given J, P and C. JPC = 0– + 0++ 1– – 1+ – 2++ … JPC = 0– – 0+ – 1– + 2+ – … Allowed combinations Not-allowed: exotic Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 8 Quantum Numbers of Hybrid Mesons Quarks S0 L 0 Excited Flux Tube 1 PC J 1 J PC J PC 0 like Hybrid Meson 1 1 p, K Exotic S 1 L 0 J P C 1 like 1 PC J 1 0 1 2 PC J 0 1 2 g, Flux tube excitation (and parallel quark spins) lead to exotic JPC Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 9 Radial excitations Mass (GeV) Meson Map Each box corresponds to 4 nonets (2 for L=0) qq Mesons 2.5 Glueballs 2.0 1.5 2 +– 2 –+ 1 –– 1– + 1 +– 1 ++ 0 +– 0 –+ 0 ++ 1.0 L=0 1 2 3 4 Hybrids 2 –+ 0 –+ 2 ++ exotic nonets Lattice 1-+ 1.9 GeV 2+- 2.1 GeV 0+- 2.3 GeV (L = qq angular momentum) Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 10 Exotic Signal JPC=1─ + E852 p1(1600) → h p ↳ hpp ↳ gg M =1.60 0.05 G = 0.34 0.06 PRL 86, 3977 (2001) Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 11 Families of Exotics p1 1-+ nonet IG(JPC)=1-(1-+) K1 IG(JPC)= h1 IG(JPC)=0+(1-+) g N X e ½ (1-) h’1 IG(JPC)=0+(1-+) Couple to V.M + e p1 p N h1 b1 , g ,, h’1 Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 12 Strategy for Exotic Meson Search Use photons to produce meson final states ─ tagged photon beam with 8 – 9 GeV ─ linear polarization to constrain production mechanism Use large acceptance detector ─ hermetic coverage for charged and neutral particles f1hKKhKKppp b1pppppp ─ typical hadronic final states: pppp ─ high data acquisition rate Perform partial-wave analysis ─ identify quantum numbers as a function of mass ─ check consistency of results in different decay modes Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 13 Coherent Bremsstrahlung This technique provides requisite energy, flux and polarization flux 12 GeV electrons Incoherent & coherent spectrum 40% polarization in peak photons out collimated electrons in spectrometer diamond crystal tagged with 0.1% resolution Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 Eg (GeV) 14 GlueX / Hall D Detector Barrel Lead Glass Calorimeter Detector Solenoid herent Bremsstrahlung Photon Beam Time of Tracking Flight Cerenkov Counter Target Note that tagger is 80 m upstream of detector Electron Beam from CEBAF Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 15 Finding an Exotic Wave An exotic wave (JPC = 1-+) was generated at level of 2.5 % with 7 other waves. Events were smeared, accepted, passed to PWA fitter. X(exotic ) p 3p Mass 5 00 500 events/20 MeV generated 4 00 400 Input: 1600 MeV Output: 1598 +/- 3 MeV PWA fit 3 00 300 Width 2 00 200 Input: 170 MeV Output: 173 +/- 11 MeV 1 00 100 Statistics shown here correspond to a few days of running. Double-blind M. C. exercise Elton S. Smith 00 1 .2 1.2 1 .4 1.4 11.6 .6 11.8 .8 Mass (3 pions) (GeV) PaNic02, Sep 30 – Oct 4, 2002 16 3-dimensional view of the Nucleon Deep Exclusive Scattering Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 18 Generalized Parton Distributions • GPD’s provide access to fundamental quantities such as the quark orbital angular momentum that have not been accessible Jquark 1 q L 2 1 2 1 dx x H q ( x,,t 0) E q( x,,t 0) 1 • and the GPD’s unify the description of inclusive and exclusive processes, connecting directly to the “normal” parton distributions: 1 GE (t ) dx 1 q H q(x,,t ) Elton S. Smith t E q( x,,t ) (for example), 4M 2 PaNic02, Sep 30 – Oct 4, 2002 19 GPDs Contain Much More Information than DIS DIS only measures a cut at =0 Quark distribution q(x) Antiquark distribution q(x) qq distribution Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 21 Measuring the GPD’s Key experimental capabilities include: ─CW (100% duty factor) electron beams (permits fully exclusive reactions) ─modern detectors (permit exclusive reactions at high luminosity) ─adequate energy (~10 GeV to access the valence quark regime) Measurements of the GPD’s are now feasible Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 22 Interpretation of the GPD’s Analogy with form factors r 3 iqrrr r F (q ) d re (r ) Charge ↔ Form Factor r mi ri r r measured relative to Rcm M iq 2 H ( x, q^ ) d b^ e b^ measured where ^ b^ f ( x, b^ ) Parton Distribution ↔ GPD’s @ 0 relative to R^CM xi ri ^ f ( x, b^ ) is a parton density of quarks with momentum fraction x at a ^ distance b^ from R^CM Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 Ref. Burkardt 23 3-dim picture from Belitsky and Mueller Elastic Scattering Deep Inelastic Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 Deep Exclusive 24 Meson Production as a Filter Use quantum numbers of meson to select appropriate combinations of parton distributions in nucleon. g* Pseudo-scalars (polarized) p0: uv - ½ dv h: uv - ½ dv + 2sv p Y(z)GiY(y) p Elton S. Smith Vector Mesons (unpolarized) L0: u + u + ½ (d + d); g L0: u + u - ½ (d + d); g L0: s + s; g PaNic02, Sep 30 – Oct 4, 2002 25 Program to determine GPD’s 0 2 2 ep ep H ,E ↳ p p en p e pg r ep ep g r ep en p ~ 2 ~2 H , E ~ 2 ~2 H , E , H , E ~ ~ H , E , H , E ~ ~ H * E 2 2 Other Channels r e p eN (h,p) Elton S. Smith e p PaNic02, Sep 30 – Oct 4, 2002 e N e (L,) K 26 Deep Virtual Compton Scattering: A Window on Quark Correlations DIS is limited by the fact that it can only measure longitudinal distributions averaged over all quarks in the nucleon DIS corresponds exactly to the imaginary part of the Deep Compton Scattering amplitude Add determination of the final state (by exclusive reactions such as DVCS) and we can (finally!) probe nucleon quark structure and correlations at the amplitude level Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 27 DVCS Single-Spin Asymmetry CLAS Q2 = 5.4 Collaboration GeV2 PRL x = 0.35 87, 182002 (2001) -t = 0.3 GeV2 Measure interference between DVCS-BH CLAS experiment e’ E0 = 11 GeV g P = 80% e e L = 1035 cm-2s-1 Run time: 2000 hrs p GPD’s p Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 28 Hard Meson Electroproduction (o) Physics issue: map out GPD’s (need to isolate s L) e’ e p GPD’s sL ~ Q -6 p Technique: determine sL from →pp decay angle distribution CLAS at 11 GeV sT ~ Q -8 400 hrs at L = 1035 cm-2s-1 Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 29 Valence Quark Structure of the Nucleon Parton Distributions at large x Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 30 Enhanced Access to the DIS Regime 12 GeV will access the valence quark regime for x > 0.3 where constituent quark properties are not masked by the sea quarks Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 31 Predictions for large xBj Proton Wavefunction (Spin and Flavor Symmetric) p 1 u 2 1 d 3 (ud ) S 0 (uu ) S 1 1 u 18 (ud ) S 1 1 u (ud ) S 1 3 2 d (uu ) S 1 3 F2n/F2p d/u A1n A1p SU(6) 2/3 1/2 0 5/9 Valence Quark 1/4 0 1 1 pQCD 3/7 1/5 1 1 Nucleon Model Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 32 Valence Quark Distribution Physics issue: ─ compare behavior of u and d quarks as xBj → 1 SU(6) Experimental problem: ─ extract information from Valence Quark comparison of hydrogen and deuterium data ─ need to correct for nuclear effects in D pQCD Solution for CEBAF upgrade: ─ compare DIS off 3He and 3H (nuclear effects ~ same) Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 33 The Neutron Spin Asymmetry A1n Study of spin structure functions has been limited to the low-x region JLab at 12 GeV with its high luminosity is a prime facility for measurements at large x Elton S. Smith Jlab E99-117 (3He) preliminary PaNic02, Sep 30 – Oct 4, 2002 34 Flavor Decomposition: (e,e’p+)/(e,e’p-) Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 35 12 GeV Upgrade Project Status Developed by CEBAF User Community in collaboration with JLab Nuclear Science Advisory Committee, NSAC ─ plan presented during last 5-year Long Range Plan ─ recommended by NSAC for new construction Plan presented to Department of Energy ─ presently waiting for CD-0 (determination of ‘mission need’) Detailed report is being prepared to be reviewed by Jlab PAC in January Construction ─ construction start expected in FY2007 (October 2006) ─ 3 year construction project Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 36 Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 37 CLAS++ Detector Forward Cerenkov Forward EC Forward DC Inner Cerenkov Central Detector Preshower EC Forward TOF Torus Cold Ring Inner Calorimeter Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 38 SHMS - HMS Spectrometers After Upgrade Max. Central Momentum 11 GeV/c Min. Scattering Angle 5.5 deg Momentum Resolution .15% -.2% Solid Angle 2.1 msr Momentum Acceptance 20% Target Length Acceptance Opening Angle with HMS 25 deg Configuration QQ(DQ) Bend Angle 18.4 deg 9 GeV/c 10 deg 4.4 msr 40% 50 cm 16 deg Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 39 Physics Program at 12 GeV Gluonic Excitations Exciting Compelling Valence Structure of the Nucleon In view of recent progress in lattice calculations 3-dim view of the Nucleon Timely Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 40 Electron-Light Ion Collider Layout Ion Source Snake IR Snake Solenoids IR 5 GeV electrons 100 GeV light ions Injector 5 GeV CEBAF with Energy Recovery Beam Dump 100 MV cryomodules Luminosity = 1035cm-2s-1 Elton S. Smith PaNic02, Sep 30 – Oct 4, 2002 Lia Merminga 41