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Explore the new QCD frontier: strong color fields in nuclei

How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD?. Explore the new QCD frontier: strong color fields in nuclei - How do the gluons contribute to the structure of the nucleus? - What are the properties of high density gluon matter?

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Explore the new QCD frontier: strong color fields in nuclei

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  1. How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? Explore the new QCD frontier: strong color fields in nuclei - How do the gluons contribute to the structure of the nucleus? - What are the properties of high density gluon matter? - How do fast quarks or gluons interact as they traverse nuclear matter? - How do the gluons contribute to the structure of the nucleon? Precisely image the sea-quarks and gluons in the nucleon - How do the gluons and sea-quarks contribute to the spin structure of the nucleon? - What is the spatial distribution of the gluons and sea quarks in the nucleon? - How do hadronic final-states form in QCD?

  2. 50% of momentum carried by gluons … but still unknowns in our knowledge S g xS > xg ??? S A low Q2 puzzle …

  3. 50% of momentum carried by gluons … but still unknowns in our knowledge Hadron-hadron scattering energy dependence Observe transition from partons to hadrons (gluon clumps?) in data at a distance scale  0.3 fm ?? Parameterize as l = -dlnF2/dlnx

  4. 50% of momentum carried by gluons … but still unknowns in our knowledge Longitudinal Structure Function FL • Experimentally can be determined • directly IF VARIABLE ENERGIES! • Highly sensitive to effects of gluon + EIC alone + 12-GeV data (includes systematic uncertainties)

  5. The Spin Structure of the Nucleon Proton helicity sum rule: ½ = ½ DS + DG + Lq + Lg • We know from lepton scattering experiments over the last three decades that: • quark contribution ΔΣ ≈ 0.3 • gluon contribution ΔG ≈ 1 ± 1 • Du > 0, Dd < 0, Ds ~ 0 • measured anti-quark polarizations are consistent with zero G: a “quotable” property of the proton (like mass, momentum contrib., …)

  6. The Quest for DG First approach: use scaling violations of world g1 spin structure function measurements g1 = Sq eq2Dfq(x,Q2) Not enough range in x and Q2

  7. The Quest for DG     HERMES, COMPASS PHENIX, STAR

  8. World Data on F2p World Data on g1p The dream is to produce a similar plot for xg(x) vs x • 50% of momentum carried by gluons • 20% of proton spin carried by quark spin

  9. Region of existing g1p data World Data on F2p World Data on g1p The dream is to produce a similar EIC plot for g1(x,Q2) over similar x and Q2 range An EIC makes it possible!

  10. The Gluon Contribution to the Proton Spin at small x Superb sensitivity to Dg at small x!

  11. The Gluon Contribution to the Proton Spin Dg/g Projected data on Dg/g with an EIC, via g + p  D0 + X K- + p+ Advantage: measurements directly at fixed Q2 ~ 10 GeV2 scale! RHIC-Spin • Uncertainties in xDg smaller than 0.01 • Measure 90% of DG (@ Q2 = 10 GeV2) Access to Dg/g is also possible from the g1p measurements through the QCD evolution, and from di-jet measurements.

  12. Precisely image the sea quarks Spin-Flavor Decomposition of the Light Quark Sea u u u > u d Many models predict Du > 0, Dd < 0 | p = + + + … u u u u d d d d RHIC-Spin region No competition foreseen!

  13. GPDs and Transverse Gluon Imaging Deep exclusive measurements in ep/eA with an EIC: diffractive: transverse gluon imaging J/y, ro, g (DVCS) non-diffractive: quark spin/flavor structure p, K, r+, … [ or J/y, f, r0 p, K, r+, … ] Are gluons uniformly distributed in nuclear matter or are there small clumps of glue? Describe correlation of longitudinal momentum and transverse position of quarks/gluons  Transverse quark/gluon imaging of nucleon (“tomography”)

  14. GPDs and Transverse Gluon Imaging ,g Fourier transform in momentum transfer x < 0.1 x ~ 0.3 x ~ 0.8 x ~ 0.001 gives transverse size of quark (parton) with longitud. momentum fraction x EIC: 1) x < 0.1: gluons! d x - x x + x 2) x ~ 0  the “take out” and “put back” gluons act coherently. 2) x ~ 0

  15. GPDs and Transverse Gluon Imaging ,g Two-gluon exchange dominant for J/y, f, rproduction at large energies  sensitive to gluon distribution squared! LO factorization ~ color dipole picture  access to gluon spatial distribution in nuclei: see eA! Fit with ds/dt = e-Bt • Measurements at DESY of diffractive channels (J/y, f, r, g) confirmed the applicability of QCD factorization: • t-slopes universal at high Q2 • flavor relations f:r Unique access to transverse gluon imaging at EIC!

  16. GPDs and Transverse Gluon Imaging k'  e k q q' * p p' A Major new direction in Nuclear Science aimed at the 3-D mapping of the quark structure of the nucleon. Simplest process: Deep-Virtual Compton Scattering At small x (large W): s ~ G(x,Q2)2 Simultaneous measurements over large range in x, Q2, t at EIC!

  17. GPDs and Transverse Gluon Imaging Goal: Transverse gluon imaging of nucleon over wide range of x: 0.001 < x < 0.1 Requires: - Q2 ~ 10-20 GeV2 to facilitate interpretation - Wide Q2, W2 (x) range - Sufficient luminosity to do differential measurements in Q2, W2, t EIC enables gluon imaging! Q2 = 10 GeV2 projected data EIC (16 weeks) Scaled from 2 to 16 wks. Simultaneous data at other Q2-values

  18. The Future of Fragmentation h h D s p x TMD q s p h M Target Fragmentation Current Fragmentation Can we understand the physical mechanism of fragmentation and how do we calculate it quantitatively? dsh ~ Sq fq(x) s Dfh(z) dsh ~ Sqs Mh/pq(x,z) QCD Evolution Correlate at EIC

  19. Proposed EIC recommendation for the Galveston meeting 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: - 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. This goal requires that R&D resources be allocated for expeditious development of collider and detector design.

  20. eRHIC: (ERL-based) linac-ring design e-cooling (RHIC II) PHENIX Main ERL (2 GeV per pass) STAR Four e-beam passes • Electron energy range from 3 to 10 (20) GeV • Peak luminosity of 2.6  1033 cm-2s-1 in electron-hadron collisions; • high electron beam polarization (~80%); • full polarization transparency at all energies for the electron beam; • multiple electron-hadron interaction points (IPs) and detectors; •  5 meter “element-free” straight section(s) for detector(s); • ability to take full advantage of electron cooling of the hadron beams; • easy variation of the electron bunch frequency to match it with the ion bunch frequency at different ion energies.

  21. 2 – 10 GeV e-ring 2 -10GeV Injector RHIC e-cooling LINAC BOOSTER AGS TANDEMS eRHIC ring-ring design • Based on existing technology (+ electron cooling) • Collisions at 12 o’clock interaction region • 10 GeV, 0.5 A e-ring with 1/3 of RHIC circumference • (similar to PEP II HER) • Inject at full energy 5 – 10 GeV • Polarized electrons and positrons • Peak luminosity of 4.7  1032 cm-2s-1 in electron-hadron collisions

  22. ELIC ring-ring design ElectronCooling Snake 30-225 GeV protons 30-100 GeV/n ions IR IR Snake 3-9 GeV electrons 3-9 GeV positrons • Visionary green-field design: • “Figure-8” lepton and ion rings to ensure spin preservation and ease of spin manipulation. • Peak luminosity up to ~1035 cm-2s-1 through short ion bunches, low β*, and high rep rate (crab crossing) • Four interaction regions with  3m “element-free” straight sections. • SRF ion linac concept for all ions ~ FRIB • 12 GeV CEBAF accelerator, with present JLab DC polarized electron gun, serves as injector to the electron ring.

  23. Detector design Main detector: learn from ZEUS (+ H1) But: low-field region around central tracker better particle identification forward-angle detectors auxiliary detectors for exclusive events auxiliary detectors for normalization

  24. Detector design p/A Si tracking stations EM calorimeter Main detector: Top view Hadronic calorimeter e Main detector: Emphasize high-luminosity full physics program Alternate detector: Emphasize low-x, low-Q2 diffractive physics (“HERA-III design”, MPI-Munchen)

  25. Cost & Realization “This goal requires that R&D resources be allocated for expeditious development of collider and detector design.” Generic R&D to advance the ongoing EIC conceptual design efforts in order to pursue the best EIC design by next LRP: $6M per year for 5 years (see next slide) Realization of the three different EIC design options (eRHIC linac-ring, eRHIC ring-ring, ELIC ring-ring) were discussed earlier in the BNL and JLab Facility Reports. The cost scale of an EIC (here taken as the TPC of the 10 GeV x 250 GeV eRHIC linac-ring design) is estimated at ~700M$.

  26. (pre-)R&D General: all designs require Electron Cooling • $4M/year Accelerator R&D encompasses: • Design Studies to Optimize Existing EIC Approaches • High-Intensity Polarized Electron Source (eRHIC L-R) • Energy Recovery Technology for High Energy and High Current Beams (eRHIC L-R) • Development of Compact Recirculation Loop Magnets (eRHIC L-R) • Design and Prototype of Multi-Cell Crab Cavities (ELIC) [required for L~1035 cm-2s-1] • Simulations of Stacking Intense Ion Beams in Pre-Booster (ELIC) [required for L~1035 cm-2s-1] • Simulations of Electron Cooling w/circulator ring and GHz kicker prototype (ELIC) • Precision High-Energy Ion Polarimetry • Polarized 3He Production (EBIS) and Acceleration • $2M/year Detector R&D encompasses: • Low-Angle Electron Tagging System • Multi-Level Triggering System to Include Tracking and Reject Background • High-Speed Data Acquisition System to Handle Small Bunch Spacing ( ELIC) • Central Tracker Development • cost-effective and compact high-rate tracking solution • cost-effective method for hadron identification • tagging systems for recoiling neutrons and heavier nuclei

  27. Summary • The last decade or so has seen tremendous progress in our understanding of the partonic sub-structure of nucleons and nuclei based upon: • The US nuclear physics flagship facilities: RHIC and CEBAF • The surprises found at HERA (H1, ZEUS, HERMES) • The development of a theory framework allowing for a • revolution in our understanding of the inside of hadrons … • QCD Factorization, Lattice QCD, Saturation • This has led to new frontiers of nuclear science: • - the possibility to map the role of gluons • - a new QCD regime of strong color fields • The EIC presents a unique opportunity to maintain US and BNL&JLab leadership in high energy nuclear physics and precision QCD physics

  28. Proposed EIC recommendation for the Galveston meeting 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: - 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. This goal requires that R&D resources be allocated for expeditious development of collider and detector design.

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