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EIC recommendation from joint QCD Town Meetings

EIC recommendation from joint QCD Town Meetings. A high luminosity Electron-Ion Collider (EIC) is the highest priority of the QCD community for new construction after

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EIC recommendation from joint QCD Town Meetings

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  1. EIC recommendation from joint QCD Town Meetings A high luminosity Electron-Ion Collider (EIC) is the highest priority of the QCD community for new construction after the JLab 12 GeV and RHIC II luminosity upgrades. EIC will address compelling physics questions essential for understanding the fundamental structure of matter: - Precision imaging of sea-quarks and gluons to determine the spin, flavor and spatial structure of nucleons; - Definitive study of the universal nature of strong gluon fields manifest in nuclei. This goal requires that R&D resources be allocated for expeditious development of collider and detector design.

  2. EIC Evolution • Substantial international interest in high luminosity (>1033cm-2s-1) polarized lepton-ion collider over decade • Workshops • Seeheim, Germany 1997 MIT, USA 2000 • IUCF, USA 1999 BNL, USA 2002 • BNL, USA 1999 JLab, USA 2004 • Yale, USA 2000 BNL,USA 2006 • EIC received favorable review of science case in US 2001 Nuclear Physics Long Range Plan, with strong endorsement for R&D • At BNL Workshop in March 2002, a plan was formulated to produce a conceptual design for EIC within three years • NSAC in March 2003, declared EIC science `absolutely central’ to future of Nuclear Physics • EIC identified in November 2003 as future priority in DOE Office of Science 20 year planning • EIC recommended as highest new construction priority beyond Jlab 12 GeV and RHIC II luminosity upgrades by joint QCD Town Meetings

  3. Accelerator Specifications for “turn-on” These specifications reflect what is required to realize the physics potential outlined by the various Monte Carlo simulations in the EIC White Paper, and motivate the R&D plan we will propose. The R&D will focus on how to achieve the highest possible luminosity and polarization, and refine the tools for achieving and utilizing these beams. Note that the sample of research highlights at “turn-on” shown earlier can already be achieved with luminosities of >few times 1032 electron-atoms/cm2/sec.

  4. = x/xIP Sample of Research Highlights of EIC at turn-on Diffractive studies in eA: • Distinguish between linear evolution and saturation models • Insight into the nature of the pomeron Syst. studies of F2(A,x,Q2): • precision measurement of G(x,Q2) • distinguish between models of shadowing Initial studies of g1(x,Q2): • Constrain unknown low-x behavior • Superb sensitivity to Dg at small x

  5. The First 5 Years (e+A only) • First measurement from scaling violations of nuclear gluon distributions (for Q2 > 2 GeV2 and x < 10-2 down to 5·10-4 in 20+100 configuration). Comparison to (i) DGLAP based shadowing and (ii) saturation models. (20 weeks-year 1 measurement) • Study of centrality/A dependence of nuclear quark and gluon distributions. Comparison to model predictions. Extract A dependence of Qs in saturation framework (would require more than 1 species in year 1) • First measurement of charm distributions in cold nuclear matter- energy loss (from Au over proton, or better deuteron). Consistency check of extracted gluon distributions to that from scaling violations. • First measurement of FL in nuclei at small x (will complement e+p PRL on wide extension of measured range). Extraction of gluon distribution, test of higher twist effects, saturation,... (will require energy scan) • First measurement of diffractive structure function in nuclei F2D - study of scaling violations of F2D with Q2. (year 1-low luminosity measurement) • Precision measurements of elastic J/y production - detailed tests of color transparency/opacity

  6. The luminosity drivers • The correlation between spin and momentum of quarks • Deep exclusive physics with non-diffractive channels Goal: spin/flavor structure of quark GPDs Requires: - Q2 ~ 10-20 GeV2 and L/T to facilitate interpretation - Significantly smaller cross sections than diffractive channels (1/100) but less statistics needed than for imaging L = 1035 assumed Perturbatively Calculable at Large pT Vanish like 1/pT

  7. LHeC 70 GeV e beam in LHC tunnel Take place of LHCb eA  New physics beyond the standard model e+A Operation at EIC allows to reach region competitive with LHeC (ep) Interferes with LHC upgrades (> 2015), CLIC (2025/2030?)  Realistic ?

  8. The EIC and the LHeC EIC: L > 1x1033 cm-2s-1 Ecm = 20-100+ GeV LHeC: L = 1.1x1033 cm-2s-1 Ecm = 1.4 TeV • Variable energy range • Polarized and heavy ion beams • High luminosity in energy region of interest for nuclear science • Add 70-100 GeV electron ring to interact with LHC ion beam • Use LHC-B interaction region • High luminosity mainly due to large g’s (= E/m) of beams Nuclear science goals: • Explore the new QCD frontier: strong color fields in nuclei • Precisely image the sea-quarks and gluons to determine the spin, flavor and spatial structure of the nucleon. High-Energy physics goals: • Parton dynamics at the TeV scale - physics beyond the Standard Model - physics of high parton densities (low x) Important cross fertilization of ideas: • Significant European interest in an EIC • EIC collaborators on LHeC Science Advisory Committee (with Research Directors of CERN, FNAL, DESY)

  9. Geometrical Scaling from DGLAP ?

  10. Systematic in FL Measurements • Estimated Systematic errors are for the self-generated set of measurements at EIC • Ldt = 5/A fb-1 (10+100) GeV • = 5/A fb-1 (10+50) GeV • = 2/A fb-1 (5+50) GeV • Errors blow up where NMC + JLAB upgrade data will kick in • Also: possibility to run EIC at lower energies to easily overcome large sys. errors

  11. Experimental Aspects

  12. Centrality & Nuclear Fragments – How ? • Many reason to study nuclear effects such as shadowing as a function of centrality. • In e+A this was never attempted • Studying diffractive events also implies measuring the nuclear fragments (or better their absence) • Both require the measurement of “wounded” nucleons and fragments •  studies and R&D • Need reliable generators that include good descripton of nuclear breakup dynamics Study (using VENUS): Chwastowski,hep-ex/0206043

  13. color opacity color transparency Survival Probability Vector Meson Production “color dipole” picture HERA: Survival prob. of qq pair of d=0.32 fm scattering off a proton from elastic vector meson production (here r). Strong gluon fields in center of p at HERA (Q2s ~ 0.5 GeV2)? b profile of nuclei more uniform and Q2s ~ 2 GeV2

  14. Further Research Highlights of EIC LHC RHIC Unique access to sea quarks and gluons! Dg/g

  15. World Data on F2p Structure Function F2 = Sq eq2 xfq(x,Q2) Next-to-Leading-Order (NLO) perturbative QCD (DGLAP) fits do a good job of reproducing the data over the full measurement range. xf(x) • 50% of momentum carried by gluons Gluons rule at small-x!

  16. The Gluon Contribution to the Proton Spin Open Charm Production Dijet Production Dg Dg/g RHIC-Spin x

  17. Total Photon Cross Sections Two-gluon (Pomeron) exchange dominant for J/y, f, rproduction at large energies At large Ecm: total cross sections rise as Wd. Associated with two-gluon or Pomeron exchange mechanism LO factorization ~ dipole picture  sensitive to gluon distribution squared!

  18. Spin-Orbit Effects and Transverse Spin  L R Now confirmed at much higher energies at STAR (and Brahms) Fermilab E704: p p  pX at 400 GeV Must be due to spin-orbit effects in the proton itself and/or in the fragmentation process Observed Large “Single-Spin Asymmetry”

  19. x = 0.01 x = 0.40 x = 0.70 m m d3r d2kT p p x GPD B TMD GPDu(x,x,t) Hu, Eu, Hu, Eu Wigner function: Probability to find a u(x) quark with a certain polarization at position r and with momentum k ~ ~ TMDu(x,kT) f1,g1,f1T ,g1T h1, h1T ,h1L ,h1 Fourier transform in momentum transfer dx x = 0, t = 0 d2kT u(x) Du, du F1u(t) F2u,GAu,GPu f1(x) g1, h1 Parton Distributions Form Factors gives transverse size of quark (parton) with longitud. momentum fraction x Towards a 3D spin-flavor landscape Wu(x,k,r) Link to Orbital Momentum Link to Orbital Momentum Want PT > L but not too large!

  20. The Origin of Mass in the Universe Most of the mass of ordinary matter is concentrated in protons and neutrons. It arises from …[a]… profound, and beautiful, source. Numerical simulation of QCD shows that if we built protons and neutrons in an imaginary world with no Higgs mechanism - purely out of quarks and gluons with zero mass - their masses would not be very different from what they actually are. Their mass arises from pure energy, associated with the dynamics of confinement in QCD, according to the relation m=E/c2. This profound account of the origin of mass is a crown jewel in our Theory of Matter.’’ Frank Wilczek CERN October 11, 2000

  21. Most of the mass in the world around us arises from QCD, predominantly from the gluons. • QCD tells us that the proton consists of spin-½ quarks that interact via exchange of spin-1 gluons. • This is a highly relativistic system described by a non-Abelian gauge theory, completely unlike an atom or nucleus. • The quark model has had great success in predicting the spins of baryons: this is a direct consequence of symmetry. • We have learned that the quark model breaks down in understanding proton structure from scattering experiments. • The gluons have been shown to play a far more dominant role than previously assumed. Proton = u + u + d Mproton >> 2Mu + Md ~ 0.02 x Mproton

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