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Future Directions in studying QCD aspects of Nuclear Physics

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blair-barlow
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Future Directions in studying QCD aspects of Nuclear Physics.  + (1540). Gerard van der Steenhoven (NIKHEF/KVI). International Nuclear Physics Conference, Götenburg, Sweden, July 2 nd , 2004. What remains to be discovered ? (*). WMAP satellite: 70% dark energy 25% dark matter

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  1. Future Directions in studying QCD aspectsof Nuclear Physics +(1540) Gerard van der Steenhoven (NIKHEF/KVI) International Nuclear Physics Conference, Götenburg, Sweden, July 2nd, 2004

  2. What remains to be discovered ?(*) • WMAP satellite: • 70% dark energy • 25% dark matter • 5% visible matter • The task of LHC: • Unravel the Higgs Mechanism ~ 2% of the visible universe • The task of QCD nuclear physics: → Unravel the origin of 98% of the mass of the visible universe (*) After: J. Maddox, What Remains to be Discovered?, XXXX Press, 2000

  3. The QCD structure of the nucleon • Lattice QCD calculations: • Deep-Inelastic Scattering: (From: G. Bali, Glasgow) The nucleon contains a large amount of quark-antiquark pairs and gluons. gluon Quark-antiquark pair

  4. The challenges of QCD • Extrapolate s to the size • of the proton, 10-15 m: • For s > 1 perturbative expansions fail……… •  Non-perturbative QCD: • Proton structure & spin • Confinement • Nucleon-Nucleon forces • Hadron spectroscopy….. Lattice QCD simulations…

  5. Future directions • Hadronic form factors • Transition to pQCD, strangeness • Hadron spectroscopy • Pentaquarks, hybrids, glueballs,... • Spin structure • Gluons, transversity • Generalized parton distributions • Partonic correlations, orbital motion • Future facilities MAMI-C

  6. 1. Hadronic Form Factors • Physics issues: • Proton: new data onGEp(Q2)/GMp(Q2) • Pion: transition to pQCD? • Axial form factors: role strangeness in proton • Kaon and hyperon form factors: hadron size • Relevant new facilities: • MAMI-C…………………… 2005 • 12 GeV @ JLab …………. 2010 • PAX @ GSI ……………… 2012 (Letter of Intend)

  7. Proton Form Factors

  8. Time-Like Form Factors • Measure single-spin asymmetry in : → Relative phase ofGMandGE • Entirely new concept: (F. Rathmann et al., LOI – 2004) Polarized anti-protons in the HESR ring @ FAIR: - The PAX project -

  9. MAMI facility • MAMI-C: • Emax→1500 MeV • Starting in 2005

  10. 2. Hadron spectroscopy Harvest in 2003: • Allowed multi-q states in QCD: • states  mesons • states  baryons • states pentaquarks? Discovery Discovery CLAS Discovery

  11. New Narrow DsJ-states • BaBar studied decay • Two new mesons ? • The K+K-+-spectrum: 1+ @ 2.46 GeV 0+ @ 2.32 GeV

  12. New charmed baryons • SELEX experiment at FermiLab (E781) • 600 GeV/c π/Σ beam • Decay schematic: • Discoveries:

  13. New narrow S=+1 states Chiral-Soliton mod. prediction in 1997 by Diakonov, Petrov and Polyakov (97): Spring-8 H1 NA49

  14. Accumulating experimental evidence • Results of three more experiments: • In all cases: a narrow peak near 1535 MeV/c2 HERMES CLAS SAPHIR

  15. Overview of +(1535) data • Averaged mass value: • 1536.2 ± 2.6 MeV • /dof = 12.4/6 • Conf. level = 0.053 • Measured FHWMs: • in most cases consistent with exp. resolution • HERMES data: HERMES paper:A. Airapetian et al, Physics Letters B 585 (2004) 213

  16. Glueballs and Hybrids • Partonic systems predicted in QCD: • “What remains to be discovered”: • Tetraquarks • Glueballs • Hybrids • ……….?

  17. Glueball searches • Lattice QCD: flux tubes • Normal mesons: • JPC = 0-+1+-2-+ • Flux tubes (J=1, S=1): • JPC = 0-+0+- 1+-1-+2-+2+- exotic (mass ~ 1.7 – 2.3 GeV) • Real photons couple to exotics via -VM transition

  18. CHL-2 Hall D: the GlueX detector • At JLab 12 GeV beam: • coherent  beam • new exp. Hall (D) • GlueX detector Photon Flux 108g/s Charged Particles coverage 1° - 170° momentum reso 1 - 2% position reso 150 µm vertex reso 500 µm Photons energy measured 1° - 120° Pb glass reso 2 + 5%/√E barrel reso 4.4%/√E Trigger level 1 rate 20 kHz

  19. Hybrid searches • Antiproton annihiliation: gluon rich • Production mechanism: • Charmonium production • Clear signature/tag • Not so many states

  20. What is to be expected? • First glimpse ??

  21. PANDA @ FAIR* : pellet target, particle ID, ~4 (*) Facility for Anti-proton and Ion Research

  22. 3. Search the carriers of proton spin • Three possible sources: • quarks: • valence quarks • sea quarks • gluons • orbital momentum • Mathematically: ½ = ½ Sq + DG + Lq EMC: q ~ 10% ~ 20  10 % ? ?

  23. How to probe the quark polarization? Polarized deep inelastic electron scattering Measure yield asymmetry: Parallel electron & proton spins Anti-parallel electron & proton spins In the Quark-Parton Model: Spin-dependent Structure Function

  24. QCD analysis of world data (’03) • Next-to-Leading-Orderanalysis of -data Excellent data forx > 0.01

  25. Polarized Parton Densities • First moments: • input scale • pol. singlet density: • pol. gluon density: There must be other sources of angular momentum in the proton

  26. Future data on and • Assume 400 pb-1 collected at e-RHIC: Domains of existing precision data

  27. Flavour decomposition of spin • Semi-inclusive deep inelastic lepton scattering • Hadron tags flavour of struck quark • Derive purity of tag from unpolarized data Key issue: role of sea quarks in nucleon spin

  28. Sea quark polarization • Up and down quarks haveopposite spins • Sea is unpolarized... • First dataon : [HERMES, hep-ex/0307064] Chiral Quark Soliton Model

  29. Future data on s and qvalence

  30. Gluon polarization • High-pTpion pair production: ’99: First direct evidence for non-zero gluon polarization Curves consistent with

  31.  or  photon  or  New experiments • Photon-gluon fusion: • COMPASS: • Open charm production: • HighpT–pairs (> 1 GeV) • Prompt photons (RHIC):

  32. Beam:160 GeV µ+ 2 . 108 µ/spill (4.8s/16.2s) Muon filter 2 MWPCs ECal2 & Hcal2 ~50m SM2 Muon filter 1 ECal1 & Hcal1 RICH GEM & MWPCs SciFi SM1 GEM & MWPCs Silicon SciFi Scintillating fibers • Polarization: • Beam: ~80% • Target:<50%> GEM & Straws Micromegas &Drift chambers Polarized target The COMPASS experiment

  33. First COMPASS data • Tagging of D*→D0: • y-axis: MK - MK - m  • x-axis: MK - mD0 80% 2002 data 317 D0 MKp -mD0 [MeV/c2]

  34.  or  photon  or   or  (heavy flavor)  or  Gluon Polarization at RHIC • Longitudinal double spin asymmetry in : • Dominant processes: Direct photon production Di-jet production

  35. Absolute Polarimeter (H jet) RHIC pC CNI Polarimeters BRAHMS PHOBOS RHIC s = 50 - 500 GeV PHENIX STAR Siberian Snakes Spin Rotators Partial Solenoid Snake LINAC BOOSTER Partial Helical Snake Pol. Source 500 mA, 300 ms AGS AGS pC CNI Polarimeter AGS Quasi-Elastic Polarimeter 200 MeV Polarimeter Rf Dipoles Polarized Protons at RHIC

  36. Anticipated improvement in xG(x) • Present QCD analysis • Expected STAR data M. Hirai, H.Kobayashi, M. Miyama et al.- preliminary

  37. What is transversity? transverse quark spin, dS • Three leading order quark distributions: momentum carried by quarks longitudinal quark spin,DS • Gluons don’t contribute toh1(x) - dominant in g1(x): •  Study nucleon spin while switching off the gluons • New QCD tests: Q2evolution h1(x); dS > DS(lattice)

  38. Measuring transversity - + quark flip target flip - + • The relevant diagram: • helicity flip of quark & target • chirally odd process • Consequences: • no gluon contributions…. … & measure single-spin asymmetries:

  39. Single – Spin Asymmetries • Sivers effect: AUT driven by orbital motion struck quark: measure L • Collins effect: AUT driven by fragmentation process: measure transversity

  40. First data on transversity ‘Collins’: ‘Sivers’: First evidence for non-zero Collins and Sivers effects

  41. Future options - COMPASS • First results based on 2002 data • Future: • Particle ID, more statistics, data on AUT for Collins/Sivers • Comparison HERMES data: measure Q2 evolution

  42. l+ q2=M2 l- q qT p p qL Future options - PAX FAIR@GSI • Polarized antiproton beam x polarized target: • Double transverse spin asymmetry: • Key issue: amount of -polar.: • Concept proven in FILTEX exp. • Separate -ring being studied Panda anti-P

  43. 4. Generalized Parton Distributions • Consider exclusive processes: • Deeply virtual Compton scatt. • Exclusive vector meson prod. • Collins et al. proved factorization theorem (1997): GPD Distribution amplitude (meson) final state Hard scattering coefficient (QCD) Generalized Parton Distribution (GPD) (Nasty: x = xBj for quarks and x = -xBj for antiquarks → x  [-1,1])

  44. GPDs give access toOrbital Angular Momentum of Quarks The remarkable properties of GPDs • Integration over x gives Proton Form Factors: Dirac Axial vector Pauli Pseudoscalar • The forward limit: • Second moment (X. Ji, PRL 1997):

  45. Applying the GPD framework • GPDs enter description of different processes: • Take Fourier transform of leading GPD: As Jq = ½q + Lqinformation on Jqgives data on Lq. GPDs Spatial distribution of quarks in the perpendicular direction

  46. A 3D-view of partons in the proton Form Factor Parton Density Gen. Parton Distribution A.V. Belitsky, D. Muller, NP A711 (2002) 118c

  47. Key differences Experimental access to GPDs • Exclusive meson electroproduction: • Vector mesons (0): • Pseudoscalar mesons (): • Deeply virtual Compton scattering: • Beam charge asymmetry: • Beam spin asymmetry: • Longitudinal target spin asymmetry:

  48. Selected DVCS results • Azimuthal dependence beam-spin asymmetry: • Beam-charge and target spin asymmetries……..

  49. Future data on DVCS at JLab • 2000 hr data taking in upgraded CLAS detector

  50. Prospects: short-term future ’04-’09 • The spin structure of the proton: • Gluon polarization DG: COMPASS (& HERMES & RHIC) • Exploring transversity h1(x): HERMES, COMPASS (& RHIC) • GPDs: HERMES & JLab • Hadron spectroscopy • Pentaquarks: JLab • Heavier hadrons: COMPASS • RHIC spin: • Optimizing polarization • First double-spin asymm. • Mainz: • starting MAMI-C