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eRHIC: Physics, Design & Status

eRHIC: Physics, Design & Status. A. Abhay Deshpande RIKEN BNL Research Center at BNL. RIKEN High pT Workshop December 5th , 2003. Some spin & Low x-high Q 2 surprises…. Stern & Gehrlach (1921) Space: quantization associated with direction Goudschmidt & Ulhenbeck (1926):

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eRHIC: Physics, Design & Status

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  1. eRHIC: Physics, Design & Status A Abhay Deshpande RIKEN BNL Research Center at BNL RIKEN High pT Workshop December 5th , 2003

  2. Some spin & Low x-high Q2 surprises… • Stern & Gehrlach (1921) Space: quantization associated with direction • Goudschmidt & Ulhenbeck (1926): Atomic fine structure & electron spin magnetic moment • Stern (1933) Proton anomalous magnetic moment 2.79 mN • Kusch(1947) Electron anomalous • magnetic moment 1.00119m0 • Prescott & Yale-SLAC Collaboration (1978) EW interference in polarized e-d DIS, parity non-conservation • European Muon Collaboration (1988/9) Spin Crisis/Puzzle Transverse single spin asymmetries: E704, AGS pp scattering, HERMES (1990s) RHIC Spin (2001) >> single spin neutron production(PHENIX) >> pion production (STAR) at 200 GeV Sqrt(S) • Elastic e-p scattering at SLAC (1950s)  Q2 ~ 1 GeV2  Finite size of the proton • Inelastic e-p scattering at SLAC (1960s) Q2 > 1 GeV2  Parton structure of the proton • Inelastic mu-p scattering off p/d/N at CERN (1980s) Q2 > 1 GeV2  Unpolarized EMC effect, nuclear shadowing? • Inelastic e-p scattering at HERA/DESY (1990s) Q2 > 1 GeV2 •  Unexpected rise of F2 at low x •  Diffraction in e-p •  Saturation(??) Further, we now are wiser in planning a detector design to observe these new/surprising physics! A facility that does both would be ideal…. Abhay Deshpande

  3. Deep Inelastic Scattering [1] [2] [3] • Observe scattered electron/muon & hadrons in current jets • Observe spectator or remnant jet • >> suitably designed detector… Lumi [1]+[2]+[3]  [3] exclusive [1]+[2]  [2] semi-inclusive [1]  [1] inclusive Abhay Deshpande

  4. Why Collider in the Future? • Past polarized DIS experiments: in fixed target mode • Collider has distinct advantages --- Confirmed at HERA • Better angular separation between scattered lepton & nuclear fragments  Better resolution of electromagnetic probe  Recognition of rapidity gap events (recent diffractive physics) • Better measurement of nuclear fragments • Higher center of mass (CoM) energies reachable • Tricky integration of beam pipe – interaction region -- detector Abhay Deshpande

  5. 5-10 GeV static e-ring up to 10 GeV injector RHIC e-cooling EBIS BOOSTER AGS LINAC Proposal under consideration eRHIC at BNL A high energy, high intensity polarized electron/positron beam facility at BNL to collide with the existing RHIC heavy ion and polarized proton beam would significantly enhance RHIC’s ability to probe fundamental and universal aspects of QCD • Linac+e-ring+RHIC • Linac+Ring Design (backup) • Linac+e-ring outside RHIC tunnel • Main design 10 GeV e beams, • 5 GeV possible • e-facility OUTSIDE the RHIC tunnel • Operations do NOT interfere with • RHIC operations Abhay Deshpande

  6. eRHIC vs. Other DIS Facilities (I) • New kinematic region • Ee = 5-10 GeV • Ep = 30 – 250 GeV • Sqrt(s) = ~25 – 100 GeV • Kinematic reach of eRHIC x = 10-4 ~0.7 (Q2 > 1 GeV2) Q2 = 0  104 GeV • Polarized e, p and light ion beams -- ~70% • Heavy ion beams of ALL elements! • High Luminosity L > (at least) 1033cm-2 sec-1 eRHIC DIS Abhay Deshpande

  7. eRHIC vs. Other DIS Facilities eRHIC: >> Variable beam energy >> p  U hadron beams >> Light Ion polarization >> Large Luminosity >> Huge Kinematic reach ELIC:electron-light ion collider at Jlab >> Variable beam energy >> Light Ion polarization >> Huge Luminosity ELIC-Jlab TESLA-N eRHIC Abhay Deshpande

  8. Scientific Frontiers Open to eRHIC • Nucleon Structure: polarized & unpolarized e-p/n scattering -- Role of quarks and gluons in the nucleon >> Unpolarized quark & gluon distributions, confinement in nucleons >> Spin structure: polarized quark & gluon distributions -- Correlation between partons >> hard exclusive processes leading to Generalized Parton Distributions (GPD’s) • Meson Structure: -- Mesons are goldstone bosons and play a fundamental role in QCD • Nuclear structure: unpolarized e-A scattering -- Role of quarks and gluons in nuclei, confinement in nuclei -- e-p vs. e-A physics in comparison and variability of A: from dU • Hadronization in nucleons and nuclei& effect of nuclear media -- How do partons knocked out of nucleon in DIS evolve in to colorless hadrons? • Partonic matter under extreme conditions -- e-A vs. e-p scattering; study as a function of A Abhay Deshpande

  9. Unpolarized DIS e-p at eRHIC • Large(r) kinematic region already covered at HERA but additional studies at eRHIC are possible & desirable • Uniqueness of eRHIC: high luminosity, variable Sqrt(s), He3 beam, improved detector & interaction region • Will enable precision physics: -- He3 beams  neutron structure  d/u as x0, dbar(x)-ubar(d) -- precision measurement of aS(Q2) -- precision photo-production physics -- precision gluon distribution in x=0.001 to x=0.6 -- slopes in dF2/dlnQ2 (Transition: QCD-to-pQCD & low x) -- flavor separation (charm and strangeness) -- exclusive reaction measurements -- nuclear fragmentation region measurements [1] [1] [1] [1] [1] [2] [2,3] [2,3] Luminosity Requirement Abhay Deshpande

  10. Polarized DIS at eRHIC [1] [1] [1] [1] [1,2] [1] [1,2] [3] [1] [1] [2,3] • Spin structure functions g1 (p,n) at low x, high precision -- g1(p-n): Bjorken Spin sum rule better than 1% accuracy • Polarized gluon distribution function DG(x,Q2) -- at least three different experimental methods • Precision measurement of aS(Q2) from g1 scaling violations • Polarized s.f. of the photon from photo-production • Electroweak s. f. g5 via W+/- production • Flavor separation of PDFs through semi-inclusive DIS • Deeply Virtual Compton Scattering (DVCS) >> Gerneralized Parton Distributions (GPDs) • Transversity • Drell-Hern-Gerasimov spin sum rule test at high n • Target/Current fragmentation studies • … etc…. Luminosity Requirement Abhay Deshpande

  11. Our knowledge of structure functions g1 F2 105 10 103 10 1 102 Q2 (GeV2) Q2 (GeV2) Abhay Deshpande

  12. Proton g1(x,Q2) low x eRHIC Fixed target experiments 1989 – 1999 Data eRHIC 250 x 10 GeV Luminosity = ~85 inv. pb/day 10 days of eRHIC run Assume: 70% Machine Eff. 70% Detector Eff. Studies included statistical error & detector smearing to confirm that asymmetries are measurable. No present or future approved experiment will be able to make this measurement Abhay Deshpande

  13. Low x measurement of g1 of Neutron • With polarized He3 • ~ 2 weeks of data at eRHIC • Compared with SMC(past) & possible HERA data • If combined with g1 of proton results in Bjorken sum rule test of better than 1-2% within a couple of months of running EIC 1 inv.fb Abhay Deshpande

  14. Polarized Gluon Measurement at eRHIC • This is the hottest of the experimental measurements being pursued at various experimental facilities: -- HERMES/DESY, COMPASS/CERN, RHIC-Spin/BNL & E159/E160 at SLAC -- Reliability from applicability of pQCD without doubt leaves only RHIC • Measurements at eRHIC will be complimentary with RHIC • Deep Inelastic Scattering kinematics at eRHIC -- Scaling violations (pQCD analysis at NLO) of g1 First moment of DG -- (2+1) jet production in photon-gluon-fusion process  -- 2-high pT hadron production in PGF  • Photo-production (real photon) kinematics at eRHIC -- Single and di-jet production in PGF -- Open charm production in PGF Shape of DG(x) Abhay Deshpande

  15. Photon Gluon Fusion at eRHIC • “Direct” determination of DG -- Di-Jet events: (2+1)-jet events -- High pT hadrons • High Sqrt(s) at eRHIC -- no theoretical ambiguities regarding interpretation of data • Both methods tried at HERA in un-polarized gluon determination & both are successful! -- NLO calculations exist -- H1 and ZEUS results -- Consistent with scaling violation F2 results on G Signal: PGF Background QCD Compton Abhay Deshpande

  16. Polarized PDFs of the Photons • Photo-production studies with single and di-jet • Photon Gluon Fusion or Gluon Gluon Fusion (Photon resolves in to its partonic contents) • Resolved photon asymmetries result in measurements of spin structure of the photon • Asymmetries sensitive to gluon polarization as well… but we will consider the gluon polarization “a known” quantity! Direct Photon Resolved Photon Abhay Deshpande

  17. Parity Violating Structure Function g5 • This is also a test • Experimental signature is a huge • asymmetry in detector (neutrino) • Unique measurement • Unpolarized xF3 measurements • at HERA in progress • Will access heavy quark • distribution in polarized DIS For eRHIC kinematics Abhay Deshpande

  18. Highlights of e-A Physics at eRHIC • Study of e-A physics in Collider mode for the first time • QCD in a different environment • Clarify & reinforce physics studied so far in fixed target e-A & m-A experiments including target fragmentation QCD in: x > [1/(2mNRN) ] ~ 0.1 (high x) QCD in: [1/(2mNRA)] < x < [1/(2mNRN)] ~ 0.1 (medium x) Quark/Gluon shadowing Nuclear medium dependence of hadronization • …. And extend in to a very low x region to explore: saturation effects or high density partonic matter also called the Color Glass Condensate (CGC) QCD in: x < [1/(2mNRA)] ~ 0.01 (low x) Abhay Deshpande See: www.bnl.gov/eic for further details

  19. E665, NMC, SLAC Experiments DIS in Nuclei is Different! Regions of: • Fermi smearing • EMC effect • Enhancement • Shadowing • Saturation? Regions of shadowing and saturation mostly around Q2 ~1 GeV2 An e-A collision at eRHIC can be at significantly higher Q2 F2D/F2A Low Q2! Abhay Deshpande

  20. Statistical Precision at eRHIC for e-A • High precision at eRHIC shown statistical errors for 1 pb-1 • Recall: eRHIC will ~85 pb-1 per day • NMC data F2(Sn/D) • eRHIC’s Q2 range between 1 and 10 GeV2 • Will explore saturation region! eRHIC Abhay Deshpande

  21. The Saturation Region… • As parton densities grow, standard pQCD break down. • Even though coupling is weak, physics may be non-perturbative due to high field strengths generated by large number of partons. • A new state of matter??? An e-A collider/detector experiment with high luminosity and capability to have different species of nuclei in the same detector would be ideal…  Need the eRHIC at BNL Abhay Deshpande

  22. E. Iancu, J.J-MarianL. McLerran,R. Venugopalan, et al. A Color Glass Condensate?? • At small x, partons are rapidly fluctuating gluons interacting weakly with each other, but still strongly coupled to the high x parton color charges which act as random static sources of COLOR charge  Analogous to spin GLASS systems in condensed matter: a disordered spin state coupled to random magnetic impurities • Gluon occupation number large, being bosons they can occupy the same state to form a CONDENSATE  Bose Einstein condensate leads to a huge over population of ground states • A new “state matter”(??): Color Glass Condensate (CGC) at high energy density would display dramatically different, yet simple properties of glassy condensates And now Color Quantum Liquid!!! (CQL)??? Abhay Deshpande

  23. Signatures of Saturation/CGC (I) • Structure functions F2(x,Q2), dF2/dlnQ2, dF2/dlnx - dF2/dlnQ2 at fixed x at high Q2 is the gluon distribution - CGC vs. conventional pQCD predict very different - Gluon measurements using semi-inclusive… di-jet final states - eRHIC will differentiate them easily for protons and heavy nuclei • Longitudinal structure function FL = F2 – 2xF1 - Provide independent gluon distribution measurement - Needs variable electron beam energy  Possible at eRHIC • Measurement of nuclear shadowing - Quark shadowing (F2A/A*F2N) in fixed target experiments observed - Gluon shadowing (GA/A*GN) indirect evidence only… pQCD at NLO - This is expected to be severe at low x and high Q2 - Ideal measurement for eRHIC Spin vs. un-polarized measurements in same detector Abhay Deshpande

  24. Signatures of CGC (II) • Shadowing and diffraction: Relation between nuclear shadowing and diffraction will be very different at high parton density media… eRHIC will study this systematically as a function of A of the nuclei. • Hard Diffraction Large rapidity gap between current and target fragmentation region. At HERA 7% cross section diffractive. In e-A at eRHIC, diffractive processes may contribute 30-40% to the total cross section. • Coherent & Inclusive vector meson production: For light vector mesons diff. Cross section. = 0.5 (inclusive) Heavy vector mesons this decreases…finally reaching 1/lnQ2 eRHIC will measure for different nuclei, r,w,f,J/y,U cross sections Detector: emphasis for forward physics! Abhay Deshpande

  25. 10GeV e 5-10 GeV IP12 p IP10 IP2 RHIC IP8 IP4 IP6 Present Lay Out of the Collider at BNL • Proposed by BINP & MIT/Bates + BNL with input from DESY • E-ring is 1/3 of RHIC ring; linac ~500m • Collisions in one interaction region >> Multiple detectors under consideration • Collision energies Ee=5-10 GeV • Injection linac 10 GeV • Lattice based on “superbend” magnets • Self polarization using Sokolov Ternov Effect: (14-22 min pol. Time) • IP12, IP2 and IP4 are possible candidates for collision points e-cooling R&D needed & started OTHER :Ring with 6 IPS, Linac-Ring, Linac-Re-circulating ring Abhay Deshpande

  26. A Detector for eRHIC  A 4p Detector • Scattered electrons to measure kinematics of DIS • Scattered electrons at small (~zero degrees) to tag photo production • Central hadronic final state for kinematics, jet measurements, quark flavor tagging, fragmentation studies, particle ID • Central hard photon and particle/vector detection (DVCS) • ~Zero angle photon measurement to control radiative corrections and in e-A physics to tag nuclear de-excitations • Missing ET for neutrino final states (W decays) • Forward tagging for 1) nuclear fragments, 2) diffractive physics • “At least one” second detector could be “rolled” in from time to time…. …under consideration • eRHIC will provide: 1) Variable beam energies 2) different hadronic species, some of them polarization, 3) high luminosity Abhay Deshpande

  27. Detector Design (I)… others expected Abhay Deshpande

  28. Detector Design II 5m 5m HCAL EMCAL p/A e Inner tracker Outer tracker Tool setup by B. Surrow Abhay Deshpande

  29. Moving Towards eRHIC…. • September 2001: eRHIC grew out of joining of two communities: 1) polarized eRHIC (ep and eA at RHIC) BNL, UCLA, YALE and people from DESY & CERN 2) Electron Poliarized Ion Collider (EPIC) 3-5 GeV e X 30-50 GeV polarized light ions Colorado, IUCF, MIT/Bates, HERMES collaborators • February 2002: White paper submitted to NSAC Long Range Planning Review  Received enthusiastic support as a next R&D project • Steering Committee: 8 members, one each from BNL, IUCF, LANL, LBL, MIT, UIUC, Caltech, JLAB, Kyoto U.+ Contact person (AD) • ~20 (~13 US + ~7 non-US) Institutes, ~100 physicists + ~40 accelerator physicists… Recent interest from HERA • See for more details: EIC/eRHIC Web-page at“http://www.bnl.gov/eic” • Subgroups: Accelerator WG, Physics WG + Detector WG • E-mails: BNL based self-registered email servers… list yourselves! Abhay Deshpande

  30. Present Activities • Accelerator & IR Design WG: • BNL-MIT/Bates collaboration on e-ring design • BNL-JLAB collaboration on linac design • Weekly meetings, monthly video meetings • Constant communication with Detector/Physics WG • ZDR Ready by January 2004: Outside BNL Review March04 • Physics & MC WG: (Theorists/Experimentalists: Welcome to Join!) • BNL, Colorado U., Jlab, LBL, MIT, UIUC (researchers+students) • Meet every three months • Setup MC generators start studies of physics processes including available detector acceptances • Will iterate with the detector/IR design and provide input guidance on the final detector design • Detector Design: Will be taken up in detail in the coming year • 2004 Meetings: January(BNL), April(Jlab), August(??), Nov/Dec(BNL) Abhay Deshpande

  31. QCD & Hadronic Physics Experiments around the world • HERA: H1, ZEUS, HERMES • End data taking ~2006 • End analysis ~2008/9 • Groups looking for construction & physics projects, of course there is LHC… but… • CERN: COMPASS • Future beyond 2007/8 uncertain for polarized DIS program • Results ready by 2007/8 • SLAC: EXXX • Spin & parity violation programs nothing beyond 2003 • RHIC II: RHIC Spin • Up to 2012/13(?) • RHIC II heavy ion program how much beyond this date? eRHIC construction 2017???!! Abhay Deshpande

  32. A possible time line for eRHIC… • “Absolutely Central to the field…” NSAC 2001-2 Long Range Planning document summary; high on R&D recommendation projects. • Highest possible scientific recommendation from NSAC Subcommittee February/March 2003, Readiness Index 2 • One of the 28 “must-do” projects in the DOE’s list • eRHIC: Zero-th Design Report (Physics + Accelerator Lattice)  Requested by BNL Management: January 2004  e-cooling R&D money started (with RHIC II) some DOE+some BNL internal FOLLOWING THIS TIME LINE FOR GETTING READY: • Expected “formal” approval 2005-6 Long Range Review (Ready CD0) • Detector R&D money could start for hardware 2008 (CD1) • Ring, IR, Detector design(s) 2009(CD2) • Final Design Ready 2010 (CD3)  begin construction • ~3/5 years for staged detector and IR construction without interfering with the RHIC running • First collisions with partial detector: 2012/13(???) Abhay Deshpande

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