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e RHIC THE future QCD machine

e RHIC THE future QCD machine. E.C. Aschenauer BNL. The Pillars of the eRHIC Physics program. spin Physics. Hadronisation. Electro Weak. physics of strong color fields. 3D Imiging. Wide physics program with high requirements on detector and machine performance.

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e RHIC THE future QCD machine

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  1. eRHIC THE future QCD machine E.C. Aschenauer BNL

  2. The Pillars of the eRHIC Physics program spin Physics Hadronisation Electro Weak physics of strong color fields 3D Imiging Wide physics program with high requirements on detector and machine performance eRHIC Design Review, August 2011

  3. Most Compelling Physics Questions spin physics imaging what is the polarization of gluons at small x where they are most abundant what is the spatial distribution of quarks and gluons in nucleons/nuclei what is the flavor decomposition of the polarized sea depending on x understand deep aspects of gauge theories revealed by kTdep. distr’n determine quark and gluon contributions to the proton spin at last possible window to orbital angular momentum quantitatively probe the universality of strong color fields in AA, pA, and eA physics of strong color fields understand in detail the transition to the non-linear regime of strong gluon fields and the physics of saturation how do hard probes in eA interact with the medium eRHIC Design Review, August 2011

  4. The Probe: Deep Inelastic Scattering Kinematics: Measure of resolution power Measure of inelasticity Measure of momentum fraction of struck quark Quark splits into gluon splits into quarks … Gluon splits into quarks 10-16m 10-19m higher √s increases resolution eRHIC Design Review, August 2011

  5. What do we know x=10-5 small x valence quarks quark density gluon density Observation of large scaling violations Gluon density dominates • Strong increase of sea quarks towards • low x • Density increases with Q2 • more partons by magnified view Dynamic creation of partons at low x large x x=1 eA-coverage eRHIC Design Review, August 2011

  6. How many gluons have space in A proton? • current theory (DGLAP) has a • built in energy catastrophe •  G rapid raise violates unitary bound small x / higher energy x = Pparton/Pnucleon • BK/JIMWLK non-linear evolution includes • recombination effects  saturation • Dynamically generated scale Saturation Scale: Q2s(x) • Increases with energy or decreasing x • Scale with Q2/Q2s(x) instead of x and Q2 as~1 as << 1 Terra Incognita Bremsstrahlung ~ asln(1/x) Recombination ~ asr Saturation must set in at low x high occupancy space becomes crowded gluons start to overlap recombination eRHIC Design Review, August 2011

  7. eRHIC - Reaching the Saturation Regime Hera Kowalski, Lappi and Venugopalan, PRL 100, 022303 (2008)); Armesto et al., PRL 94:022002; Kowalski, Teaney, PRD 68:114005) • Saturation: • dAu: Strong hints from RHIC at x ~ 10-3 • p:Weakhints at Hera up to x=6.32⋅10-5, Q2 = 1-5 GeV2 Nuclear Enhancement: • Coverage: • Need lever arm in Q2 at fixed x to constrain models • Need Q > Qs to study onset of saturation • ep: even 1 TeV is on the low side • eA: √s = 50 GeV is marginal, around √s = 100 GeVdesirable •  20 GeVx 100 GeV eRHIC Design Review, August 2011

  8. saturation in eADIS – what to expect estimate relevance of non-linear effects from average strength of dipole scattering in DIS recall: DIS in the proton rest frame: photon splits into a quark-antiquark pair (“color dipole”) which scatters off the target proton (= “slow” gluon field) dipole amplitude dipole size r eRHIC Design Review, August 2011

  9. saturation in eADIS quantitative estimates find: most sensitive to gluons M. Diehl, T. Lappi as expected (HERA): no chance in ep eA much more favorable to study saturation than ep <NL> in eAu DIS EIC 30 x 130 <NL> in ep DIS 0.2 HERA saturation effects in eA benefit from nuclear oompf Q2[GeV2] EIC 5 x 130 EIC 30 x 325 0.3 0.4 0.2 0.5 0.3 0.6 0.4 x eRHIC Design Review, August 2011

  10. Deep Inelastic Scattering - Vacuum htf tp • production time tp - propagating quark • formation time htf - dipole grows to hadron What happens if we add a nuclear medium Observables: Broadening: Attenuation: link Dpt2 directly with saturation scale (B. Kopeliovich) modifications of nPDF cancel out eRHIC Design Review, August 2011

  11. What do we know and what can EIC do EIC: Hermes: light hadrons Charm Eq=  = Ee-Ee’13 GeV Eh= z 2-15 GeV z Unprecedented precision to distinguish between Different processes eRHIC Design Review, August 2011

  12. Important to understand hadron structure: Spin DG SqLq Lg SqDq SqDq Lg SqLq dq DG dq Is the proton spinning like this? N. Bohr W. Pauli gluon spin “Helicity sum rule” Where do we go with solving the “spin puzzle” ? angular momentum total u+d+s quark spin eRHIC Design Review, August 2011

  13. NLO FIT to World Data Polarisedopposite to proton spin Polarisedparallel to proton spin DSSVPRD 80 (2009) 034030 • includes all world data from • DIS, SIDIS and pp Dd(x) < 0 • Du(x) > 0 LDRD: 08-004 Knowledge today Quarks: 30% Gluons: close to nothing ??? Where is the spin of the proton ??? eRHIC Design Review, August 2011

  14. EIC: What is the spin of the gluons Δg? x cross section: parameterized through F2, FL, g1, g2 • low x behavior unconstrained • no reliable error estimate • for 1st moment • (entering spin sum rule) • find DIS & pp RHIC pp pQCD scaling violations positiveDg eRHIC Design Review, August 2011

  15. The answer on Dg will be revealed use precise EIC data for different beam energies in theoretical extraction ..wow-cool, will finally know the contribution of the gluons to the spin of the proton eRHIC Design Review, August 2011

  16. The Spin of the Proton in 3D Nobel Prize, 1943: "for his contribution to the development of the molecular ray method and his discovery of the magnetic moment of the proton" mp = 2.5 nuclear magnetons, ± 10% (1933) Proton spins are used to image the structure and function of the human body using the technique of magnetic resonance imaging. Otto Stern Sir Peter Mansfield Paul C. Lauterbur Nobel Prize, 2003: "for their discoveries concerning magnetic resonance imaging" eRHIC Design Review, August 2011

  17. Quantum phase-space tomography of the nucleon Wigner Distribution W(x,r,kt) Join the real 3D experience !! TMDs GPDs u-quark Polarized p Polarized p d-quark 3D picture in momentum space 3D picture in coordinate space transverse momentum generalized parton distributions dependent distributions  exclusive reaction like DVCS eRHIC Design Review, August 2011

  18. The Sivers Function HERMES: EIC: 1 month @ 20 GeV x250 GeV Sivers eRHIC Design Review, August 2011

  19. GPDs and The Hunt for Lq exclusive: all reaction products are detected missing energy (DE) and missing Mass (Mx) = 0 Study of hard exclusive processes allows toaccess a new class of PDFs Generalized Parton Distributions possible way to access orbital angular momentum From DIS Spin Sum Rule in PRF: eRHIC Design Review, August 2011

  20. DVCS at eRHIC ~ e g H, H, E, E (x,ξ,t) gL* (Q2) x+ξ x-ξ ~ e’ Study by S. Fazio and M. Diehl t p’ p Goal: Cover wide range in t impact parameter space b eRHIC Design Review, August 2011

  21. Diffractive Physics: p’ kinematics t=(p4-p2)2 = 2[(mpin.mpout)-(EinEout - pzinpzout)] “ Roman Pots” acceptance studies see later Diffraction: 5x50 ? p’ 5x100 5x250 eRHIC Design Review, August 2011

  22. Golden Measurements: Physics of strong color fields eRHIC Design Review, August 2011

  23. Golden Measurements: Spin Physics eRHIC Design Review, August 2011

  24. Golden Measurements: 3D-Imaging in bT / kT eRHIC Design Review, August 2011

  25. Emerging Detector Concept Forward / Backward Spectrometers: high acceptance -5 < h < 5 central detector good PID (p,K,p and lepton) and vertex resolution (< 5mm) tracking and calorimeter coverage the same  good momentum resolution, lepton PID low material density  minimal multiple scattering and brems-strahlung very forward electron and proton/neutron detection  maybe dipole spectrometers eRHIC Design Review, August 2011

  26. Integration into Machine: IR-Design eRHIC - Geometry high-lumi IR with β*=5 cm, l*=4.5 mand 10 mrad crossing angle this is required for 1034 cm-2 s-1 Outgoing Proton direction already far advanced D5 Q5 Q4 325 GeV p 125 GeV/u ions q=10.3255 mrad 10.26m 3 m q=0.0036745 mrad q=4 mrad 0.44843 m 0.2582 m 0.315726 m 10 mrad 5.3 m 30 GeV e- 20 10 30 4.5 39.98 m 60.0559 m 90.08703 m eRHIC Design Review, August 2011

  27. proton distribution in yvsx at s=20m without quadrupole aperture limit 25x250 5x50 with quadrupole aperture limit 5x50 25x250 eRHIC Design Review, August 2011

  28. Accepted in “Roman Pot” (example) at s=20m 25x250 5x50 25x250 5x50 Generated Quad aperture limited RP (at 20m) accepted eRHIC Design Review, August 2011

  29. Kinematics of Breakup Neutrons Results from GEMINI++ for 50 GeV Au • Results: • With an aperture of ±3 mrad we are in relative good shape • • enough “detection” power for t > 0.025 GeV2 • • below t ~ 0.02 GeV2 we have to look into photon detection • ‣ Is it needed? • Question: • For some physics rejection power for incoherent is needed ~104 • How efficient can the ZDCs be made? by Thomas Ullrich +/-5mrad acceptance seems sufficient eRHIC Design Review, August 2011

  30. and Summary • Machine and Detector Requirements determined from golden measurements • Variable beam energies and hadron beam species • Need √s ~ 100 GeVto reach saturation regime • High Polarisation for light hadrons and lepton beams • High luminosity (~100 x Hera) • Exclusive reactions • Multidimensional binning for semi-inclusive observables • Electroweak physics • Detector integration in IR design is critical • Dedicated detector critical to realize the physics program Current eRHIC machine design addresses all requirements from the physics program eRHIC Design Review, August 2011

  31. BACKUP eRHIC Design Review, August 2011

  32. Do gluons create the visible mass? That is us !!! protons, neutrons electrons Atom 10-10m Nucleus 10-14m Protons Quarks & Gluons 10-16m Binding-energy: ~eV Binding-energy: ~109eV Quark-Masses: 106-107eV mass completely dominated by gluon Binding-energy: 8.5 106eV eRHIC Design Review, August 2011

  33. How are the gluons distributed in space • Basic Idea: • Exclusive diffractive VM production • eAe’A’V • dsA/dtfouriertransformFg(b) • Promising method to measure gluon form • factor in nuclei •  long wavelength gluons (small t) Th. Ullrich, T. Toll LDRD 10-042 • Experimental Requirement: • Photo-production c.s. large & |t| ~ pt2(VM) • J/Y easy to detect for |h| < 2 well • separated from background • Crucial: detecting breakup of nuclei • started to be included in simulation • Need e’ to measure t for Q2>10-3 GeV2 based on saturated gluon distribution Kowalski, Caldwell ‘09 eRHIC Design Review, August 2011

  34. polarized DIS and impact on Δg(x,Q2) strategy to quantify impact: global QCD fit with realistic toy data W2 > 10GeV2 W2 > 10GeV2 ECA+M. Stratmann • DIS data sets produced for stage-1 [5x50, 5x100, 5x250, 5x325] and 20x250, 30x325 eRHIC Design Review, August 2011

  35. Acceptance for forward scattered protons ~ e g H, H, E, E (x,ξ,t) gL* (Q2) x+ξ x-ξ ~ t 25x250 e’ p’ p 25x250 Exclusive events: e+p/A e’+p’/A’+g/ J/ψ / r/ f detect all event products in the detector Generated Quad aperture limited RP (at 20m) accepted eRHIC Design Review, August 2011

  36. Processes used to study the Physics exclusive /diffractive reactions ep/Ae’p’/A’VM electro-weak reactions semi-inclusive reactions ep/A e’pX inclusive reactions ep/Ae’X Excellent electron identification Background suppression Close to 4p acceptance good jet identification PID: to identify Hadrons Detect outgoing scattered proton excellent absolute and/or relative luminosity Detect very low Q2 electron very precise polarization measurement high demands on momentum and/or energy resolution good vertex resolution eRHIC Design Review, August 2011

  37. CMOS-Pixel Vertex Detector for eRHIC Useful for any application, which needs high resolution and low material budget • Silicon Detectors at Atlas (61 m2) and CMS (198 m2) • CMS: huge radiation length  impossible to use for eRHIC electrons do bremsstrahlung • Pixel Detector for eRHIC (LDRD: 11-036) • Radiation length 0.05% • Pixel-layer-thickness: 50mm not 300 -500 • readout electronics integrated in Pixel • current “chip” sizes 1x2cm2 • to small for forward / backward disks • Plan: extend to 5x5cm2 with 10M pixels with 16 mm pitch • Vertex resolution ~5mm eRHIC Design Review, August 2011

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