2. E.C. AschenauerPheniX Summer Student Program, June 20101 The Electron Ion Collider EIC The 2010 TOUR

3. The Standard Model E.C. Aschenauer PheniX Summer Student Program, June 20102 QED: Theory of the Electromagnetic Interaction QCD: Theory of the Strong Interaction

4. A reminder of Quantum Electro-Dynamics (QED) E.C. Aschenauer PheniX Summer Student Program, June 20103  Theory of electromagnetic interactions  Exchange particles (photons) do not carry electric charge  Flux is not confined: V(r) ~ 1/r, F(r) ~ 1/r2 Coupling constant (α): Interaction Strength In QED: α em = 1/137 √α√α Feynman Diagram: e + e - annihilation

5. Quantum Chromo-Dynamics (QCD) - 1973 E.C. Aschenauer PheniX Summer Student Program, June 20104  Theory of strong (nuclear) interactions  Three colour charges: red, green and blue  Exchange particles (gluons) carry colour charge and can self- interact  Flux is confined: V(r) ~ r, F(r) ~ constant q qq qg √α√α α s = strong coupling constant ≈ 0.3 long range force ~ r gluons can self-interact - more vertices are allowed ~1/r at short range

6. Features of Quantum Chromo-Dynamics E.C. Aschenauer PheniX Summer Student Program, June 20105  Confinement  At large distances, the effective coupling between quarks is large, resulting in confinement (V(r) ~ r)  Free quarks are not observed in nature  Asymptotic freedom  At short distances, the effective coupling between quarks decreases logarithmically  Under such conditions, partons appear to be quasi-free 0.2 fm 0.02 fm 0.002 fm

7. QED vs QCD E.C. Aschenauer PheniX Summer Student Program, June 20106  Potentials:  long range aspect of V s (r) leads to quark confinement and the existence of nucelons QED QCDQCD Chargeselectric (2)colour (3) gauge bosonsγg (8) charged?noyesyes coupling strength α em = e 2 /4π ≈ 1/137 α s ≈ 0.3

8. Experimental Prerequisites E.C. Aschenauer PheniX Summer Student Program, June 20107 longitudinally un-(polarized) lepton beam longitudinally un-(polarized) lepton beam longitudinally un-(polarized) nuclear target longitudinally un-(polarized) nuclear target large geometrical acceptance large geometrical acceptance small angles small angles limited by synchrotron radiation limited by synchrotron radiation big angles big angles limited by money limited by money good particle identification good particle identification So far only “fixed target” experiments for polarized physics at :

9. The contemporary “spin” experiments 8 PheniX Summer Student Program, June 2010E.C. Asc hena uer Beam: 27.5 GeV e ± ; % polarization Target: polarized gas targets H, D, He 3 polarization unpolarised gas targets H 2 to Xenon unpolarised gas targets H 2 to Xenon Lumi: pol: 5x10 31 cm -2 /s -1 ; unpol: 3x10 32-33 cm -2 /s -1 Data taking finished June 2007 SM1 SM2 6 LiD Target 160 GeV μ RICH ECal & HCal μ Filter Trigger-hodoscopes Silicon Micromegas SciFi Gems Drift chambers Straws MWPC 50 m Beam: 160 GeV  : 80% polarization Target: 6 LiD: 50% polarization (2002-2006) NH 3 : 80% polarisation (2007) NH 3 : 80% polarisation (2007) Lumi: 5x10 32 cm -2 s -1 2010 & 2011: longitudinal and transverse NH 3 Large acceptance spect. electron/photon beams Hall B 7 GeV spectrometer, 1.8 GeV spectrometer, large installation experiments Hall C Beam: ≤6 GeV e - ; 85% polarization Target: polarized targets 3He, 6LiD, NH3 several unpolarised targets several unpolarised targets Two high-resolution 4 GeV spectrometers Hall A

10. HERA @ DESY E.C. Aschenauer PheniX Summer Student Program, June 20109 HERA: e + /e - (27GeV) - proton (920 GeV) collider The Experiments @ HERA Explore the structure of the nucleon with a lepton beam  Deep Inelastic Scattering (DIS) (DIS)  Scattering angle and energy of electron of electron  x of the quarks  x of the quarks High energy = short wave length  Scattering angle ~ Q 2 mass of the exchanged mass of the exchanged particle particle  Centre-of-mass energy  resolution;  resolution; √s = 314GeV  10 -18 m √s = 314GeV  10 -18 m

11. Deep Inelastic Scattering E.C. Aschenauer PheniX Summer Student Program, June 2010 q Important kinematic variables: cross section: DF FF Photon:Photon: Hadron:Hadron: Quark:Quark: 10

12. The structure of the proton – simple view E.C. Aschenuer PheniX Summer Student Program, June 2010 Quark splits into gluon splits into quarks … Increasing resolution (large angle scattering = large Q 2 ) Increasing resolution: we see “small” partons Increasing resolution: we see “small” partons How do the quarks behave at low-x How do the quarks behave at low-x E.C. Aschenauer

13. Main Underlying Processes E.C. Aschenauer PheniX Summer Student Program, June 201012 Q2Q2Q2Q2 q g q g qg + + + „Soft“ & Hard VMD: Elastic, diffractive, non-diffractive minimum bias Splitting of   qq hard QCD 2  2 scattered lepton in detector virtual photon know x of parton Scale: p t or m q x of parton is not known very much like pp Scale: Q 2 p t can be big +

14. E.C. Aschenauer PheniX Summer Student Program, June 2010 Deep Inelastic Scattering q Important kinematic variables: cross section: DF FF Photon:Photon: Hadron:Hadron: Quark:Quark:Collider: E.C. Aschenauer

15. “Structure Function” & quark densities E.C. Aschenauer PheniX Summer Student Program, June 2010 Strong increase of sea quarks Strong increase of sea quarks towards low x towards low x Density increases with Q 2 Density increases with Q 2 more partons by magnified more partons by magnified view view quark density Dynamic creation of quarks at low x E.C. Aschenauer

16. Measure Glue through DIS E.C. Aschenauer 15 small x large x Observation of large scaling violations Gluon density dominates PheniX Summer Student Program, June 2010

17. F L : measures glue directly 16 F L ~ α s G(x,Q 2 ) requires √s scan Q 2 /xs = y  G(x,Q 2 ) with great precision E.C. Aschenauer PheniX Summer Student Program, June 2010

18. What do we know till know E.C. Aschenauer 17 F 2 =C(Q 2 )x  Q 2 = 1GeV  0.2fm EM proton radius: 0.9fm Transition, Why, How? Does the rise of F 2 set in at the same Q 2 for nuclei? PheniX Summer Student Program, June 2010

19. Bremsstrahlung ~  s ln(1/x) x = P parton /P nucleon small x small x Recombination ~  s  Parton Saturation  at small x linear evolution gives strongly rising g(x) strongly rising g(x)  violation of Froissart unitary bound  BK/JIMWLK non-linear evolution includes recombination effects  saturation recombination effects  saturation  Dynamically generated scale Saturation Scale: Q 2 s (x) Saturation Scale: Q 2 s (x)  Increases with energy or decreasing x  Scale with Q 2 /Q 2 s (x) instead of x and Q 2 separately E.C. Aschenauer 18PheniX Summer Student Program, June 2010 Saturation must set in at forward rapidity/low x when gluons start to overlap and when recombination becomes important

20. EIC - Reaching the Saturation Regime 19 Saturation:  Au: Strong hints from RHIC at x ~ 10 -3  p: No (?) hints at Hera up to x=6.32  10 -5, Q 2 = 1-5 GeV 2 Kowalski, Lappi and Venugopalan, PRL 100, 022303 (2008) ) ; Armesto et al., PRL 94:022002; Kowalski, Teaney, PRD 68:114005) Nuclear Enhancement: Hera Coverage:  Need lever arm in Q 2 at fixed x to constrain models  Need Q > Q s to study onset of saturation  ep: even 1 TeV is on the low side  eA: √ s = 50 GeV is marginal, around √ s = 100 GeV desirable  20 GeV x 100 GeV  20 GeV x 100 GeV E.C. Aschenauer PheniX Summer Student Program, June 2010

21. F 2 : for Nuclei 20 E.C. Aschenauer PheniX Summer Student Program, June 2010 Assumptions:  10GeV x 100GeV/n  √s=63GeV  Ldt = 4/A fb -1  equiv to 3.8 10 33 cm -2 s -1  T=2weeks; DC:50%  Detector: 100% efficient  Q 2 up to kin. limit sx  Statistical errors only  Note: L~1/A antishadowing “sweet” spot R=1 shadowing LHC  =0 RHIC  =3

22. EIC - What Luminosity is Needed? 21 syst. uncertainties F L : inclusive measurements at different √ s, assume 1% energy-to-energy normalization assume 1% energy-to-energy normalization Conclusion from this study: good control on systematic uncertainties critical ∫ L dt = 4/A fb -1 (10+100) GeV & 4/A fb -1 (10+50) GeV & 4/A fb -1 (10+50) GeV & 2/A fb -1 (5+50) GeV 2/A fb -1 (5+50) GeV All together 5 weeks at L ~ 1x10 34 cm -2 s -1 & 50% duty cycle (Note: 1000x Hera L) E.C. Aschenauer PheniX Summer Student Program, June 2010

23. Diffractive Physics: E.C. Aschenauer PheniX Summer Student Program, June 201022 ? DIS: Diffraction:  J  Hit a proton at rest with a 60 TeV e and nothing happens to it ! It just spits out a VM.  Hera: Diffraction / DIS ~ 20%  dσ/dt ~ [xG(x,Q 2 )] 2  experimentally very difficult need to detect proton  a long beam line  Physics extremely interesting  3d pictures of the proton/nuclei

24. Measure the Gluon Form Factor E.C. Aschenauer 23 R A = 1.2A 1/3 fm Elastic scattering on full nucleus  long wavelength gluons (small t) PheniX Summer Student Program, June 2010 Basic Idea: Studying diffractive exclusive J/  production at Q2~0 Ideal Probe: large photo-production cross section t can be derived from e,e’ and J/  4-momentum

25. Proton Tomography M. Burkardt, M. Diehl 2002 FT (GPD) : momentum space  impact parameter space: probing partons with specified long. momentum @transverse position b T polarized nucleon: [  =0] from lattice d-quark u-quark E.C. Aschenauer 24PheniX Summer Student Program, June 2010DVCS p + 

26. Important to understand hadron structure: Spin E.C. Aschenauer 25 qqqqqqqq GGGG LgLgLgLg qLqqLqqLqqLq qqqq qqqqqqqq GGGG LgLgLgLg qLqqLqqLqqLq qqqq Is the proton spinning like this? “Helicity sum rule” total u+d+s quark spin angularmomentum gluonspin Where do we go with solving the “spin puzzle” ? N. Bohr W. Pauli PheniX Summer Student Program, June 2010

27. How to measure Quark Polarizations E.C. Aschenauer PheniX Summer Student Program, June 2010 Virtual photon  * can only couple to quarks of opposite helicity Virtual photon  * can only couple to quarks of opposite helicity Select q + (x) or q - (x) by changing the orientation of Select q + (x) or q - (x) by changing the orientation of target nucleon spin or helicity of incident lepton beam target nucleon spin or helicity of incident lepton beam Asymmetry definition: inclusive DIS: only e’ info used semi-inclusive DIS: e’+h info used 26

28.  Scaling violations of g 1 (Q 2 -dependence) give indirect access to the gluon distribution via DGLAP evolution. (Q 2 -dependence) give indirect access to the gluon distribution via DGLAP evolution. E.C. Aschenauer 27PheniX Summer Student Program, June 2010  RHIC polarized pp collisions at midrapidity directly involve gluons  Rule out large DG for 0.05 < x < 0.2 Δg from inclusive DIS and polarized pp Current knowledge on  g RHIC DIS EIC constrained x-range still limited

29. x How does it look at EIC 5fb -1 integrated luminosity EIC: Access to ΔG at small x where uncertainties are very large translates into E.C. Aschenauer 28PheniX Summer Student Program, June 2010 will constrain

30. E.C. Aschenauer PheniX Summer Student Program, June 2010 Polarised quark distributions Correlation between detected hadron and struck q f “Flavor – Separation” “Flavor – Separation” Inclusive DIS: Semi-inclusive DIS: Extract  q by solving: In LO-QCD: MC DF FF 29

31. Measured Asymmetries E.C. Aschenauer PheniX Summer Student Program, June 2010 Proton Deuterium statistics sufficient for statistics sufficient for 5 parameter fit 5 parameter fit 30

32. Polarized Quark Densities E.C. Aschenauer PheniX Summer Student Program, June 2010 good agreement with NLO-QCD Polarised opposite to proton spin  u(x) > 0 First complete separation of First complete separation of pol. PDFs without assumption on pol. PDFs without assumption on sea polarization sea polarization Polarised parallel to proton spin  d(x) < 0   u(x),  d(x) ~ 0 No indication for  s(x) < 0 No indication for  s(x) < 0 In measured range (0.023 – 0.6) In measured range (0.023 – 0.6) 31

33. E.C. Aschenauer Polarized Quark Distributions @ EIC 32 eRHIC: 10GeV@250GeV at 9 fb -1 X 0.2 -0.8 0.0.0.0. 0.8 PheniX Summer Student Program, June 2010

34. Why is  s interesting E.C. Aschenauer PheniX Summer Student Program, June 201033 e.g. elastic scattering of SUSY dark matter neutralino  gives spin-dep. cross sec. Ellis et al. arXiv: 0801.3656

35. EIC Scope - QCD Factory 34 e-e-e-e- e+e+e+e+ p Unpolarized and polarized leptons 4-20 (30) GeV Polarized light ions (He 3 ) 215 GeV/u Light ions (d,Si,Cu) Heavy ions (Au,U) 50-100 (130) GeV/u Polarized protons 50-250 (325) GeV Electron accelerator RHIC 70% e - beam polarization goal polarized positrons? Center mass energy range: √s=28-200 GeV; L~100xHera e-e-e-e- Mission: Studying the Physics of Strong Color Fields E.C. Aschenauer PheniX Summer Student Program, June 2010

36. The Relativistic Heavy-Ion Collider @ BNL E.C. Aschenauer 35 RHIC BRAHMS PHOBOS PHENIX STAR AGS TANDEMS v = 0.99995  c = 186,000 miles/sec ERL Test Facility 12 o’clock proposed RF BOOSTER LINAC EBIS PheniX Summer Student Program, June 2010

37. eSTAR ePHENIX 36 100m |--------| 6 pass 2.5 GeV ERL Coherente-cooler 22.5 GeV 17.5GeV 12.5 GeV 7.5 GeV Common vacuum chamber 27.5 GeV 2.5 GeV Beam-dump Polarized e-gun eRHIC detector 25 GeV 20 GeV 15 GeV 10 GeV Common vacuum chamber 30 GeV 5 GeV 0.1 GeV The latest design of eRHIC The most cost effective design RHIC: 325 GeV p or 130 GeV/u Au eRHIC staging all-in tunnel E.C. Aschenauer PheniX Summer Student Program, June 2010

38. IR-Design 0.44 m Q5 D5 Q4 90 m 10 mrad 0.329 m 3.67 mrad 60 m 10 20 30 0.188036 m 18.8 m 16.8 m 6.33 mrad 4 m © D.Trbojevic 30 GeV e - 325 GeV p 125 GeV/u ions eRHIC - Geometry high-lumi IR with β*=5 cm, l*=4.5 m and 10 mrad crossing angle E.C. Aschenauer PheniX Summer Student Program, June 201037 m Spinrotator

39. eRHIC – Geometry high-lumi IR 1.6 m 1 32 45 6 0.85 m 7 10 mrad 5.4 cm 8.4 cm 10.4 cm 1 m © D.Trbojevic E.C. Aschenauer PheniX Summer Student Program, June 201038  Two designs of the IR exist for both low luminosity (~ 3x10 33 ) and high luminosity (~ 2x10 34 ) depends on distance IR to focusing quads  By using a crossing angle (and crab cavities), one can have energy- independent geometries for the IRs and no synchrotron radiation in the detectors  Big advantage in detecting particles at low angle  can go as low as 0.75 o at hadron side  |  | < 5.5 Beam-p: y ~ 6.2 m eRHIC IR1 p /Ae Energy (max), GeV325/13020 Number of bunches16674 nsec Bunch intensity (u), 10 11 2.00.24 Bunch charge, nC324 Beam current, mA420 50 Normalized emittance, 1e-6 m, 95% for p / rms for e 1.225 Polarization, %7080 rms bunch length, cm4.90.2 β *, cm55 Luminosity, cm -2 s -1 1.46 x 10 34 (including hour-glass effect h=0.851) Luminosity for 30 GeV e-beam operation will be at 20% level

40. Detector Requirements from Physics  Detector must be multi-purpose  Need the same detector for inclusive (ep -> e’X), semi-inclusive (ep -> e’hadron(s)X), exclusive (ep -> e’  p) reactions and eA interactions  Able to run for different energies (and ep/A kinematics) to reduce systematic errors reduce systematic errors  Ability to tag the struck nucleus in exclusive and diffractive eA reactions  Needs to have large acceptance  Cover both mid- and forward-rapidity  particle detection to very low scattering angle; around 1 o in e and p/A direction  particle identification is crucial  e, , K, p, n over wide momentum range and scattering angle  excellent secondary vertex resolution (charm)  small systematic uncertainty for e,p-beam polarization and luminosity measurement E.C. Aschenauer PheniX Summer Student Program, June 201039

41. Processes to Study Physics E.C. Aschenauer PheniX Summer Student Program, June 201040 γ*γ*γ*γ* Diffraction γ*γ*γ*γ* u,d,s,c,b,g ,K semi-inclusive DIS u,d,s,c,b,g ? inclusive DIS exclusive DIS

42. ? Diffractive Physics: p’ kinematics PheniX Summer Student Program, June 201041 4 x 100 t=(p 4 -p 2 ) 2 = 2[(m p in.m p out )-(E in E out - p z in p z out )] 4 x 50 4 x 250 Diffraction: E.C. Aschenauer

43. A typical High Energy Detector E.C. Aschenauer PheniX Summer Student Program, June 201042 Particle types:  neutrinos (missing energy)  muons    hadrons  p  quarks, gluons  jets  electrons, photons,  0  charged particles beam pipe Rough Classification  track detectors for charged particles  “massless” detectors  gas detectors  solid state detectors  magnet coil (solenoid, field || beam axis) Calorimeter for energy measurement  electromagnetic  high Z material (Pb-glas)  absorber (mostly Fe)  flux return yoke + active material active material  hadronic  heavy medium (Fe, Cu, U) + active material + active material

44. A detector integrated into IR E.C. Aschenauer PheniX Summer Student Program, June 201043 ZDC FPD  Dipoles needed to have good forward momentum resolution  Solenoid no magnetic field @ r ~ 0  DIRC, RICH hadron identification  , K, p  high-threshold Cerenkov  fast trigger for scattered lepton  radiation length very critical  low lepton energies FED a lot of space for polarimetry and luminosity measurements

45. eRHIC Detector in Geant-3 E.C. Aschenauer PheniX Summer Student Program, June 2010  DIRC: not shown because of cut; modeled following Babar  no hadronic calorimeter in barrel yet  investigate ILC technology to combine  ID with HCAL Drift Chambers centraltracking ala BaBar Silicon Strip detector ala Zeus EM-CalorimeterLeadGlas High Threshold Cerenkov fast trigger on e’ e/h separation Dual-RadiatorRICH ala HERMES Drift Chambers ala HERMES FDC 44

46. MeRHIC Detector in Geant-3 E.C. Aschenauer PheniX Summer Student Program, June 201045

47. E.C. Aschenauer John's 60th Birthday, Yale, March 201046 and Summary EIC many avenues for further many avenues for further important measurements and important measurements and theoretical developments theoretical developments we have just explored the tip of the iceberg tip of the iceberg you are here  u tot,  d tot L q,g ssss gggg spin sum rule Knowledge about Gluons in p /A Come and join us The BNL EIC Taskforce

48. E.C. Aschenauer 47 BACKUP PheniX Summer Student Program, June 2010

49. Beyond form factors and quark distributions E.C. Aschenauer 48 Generalized Parton Distributions Proton form factors, transverse charge & current densities Structure functions, quark longitudinal momentum & helicity distributions X. Ji, D. Mueller, A. Radyushkin (1994-1997) Correlated quark momentum and helicity distributions in transverse space - GPDs PheniX Summer Student Program, June 2010

50. Diffractive physics: ep vs eA E.C. Aschenauer PheniX Summer Student Program, June 201049 x IP = mom. fraction of pomeron w.r.t. hadron  HERA/ep: ~20% of all events are hard diffractive  Diffractive cross-section σ diff /σ tot in e+A ?  Predictions: ~25-40%?  Diffractive structure functions  F L D for nuclei and p extremely sensitive  Exclusive Diffractive vector meson production: dσ/dt ~ [xG(x,Q 2 )] 2 !!  Distinguish between linear evolution and saturation models ? Curves: Kugeratski, Goncalves, Navarra, EPJ C46, 413 DIS: Diffraction:

51. How to measure coherent diffraction in e+A ?  Beam angular divergence limits smallest outgoing  min for p/A that can be measured  Can measure the nucleus if it is separated from the beam in Si (Roman Pot) “beamline” detectors  p Tmin ~ pAθ min For beam energies = 100 GeV/n and θ min = 0.08 mrad: θ min = 0.08 mrad:  These are large momentum kicks, much greater than the binding energy (~8MeV)  Therefore, for large A, coherently diffractive nucleus cannot be separated from beamline without breaking up E.C. Aschenauer PheniX Summer Student Program, June 201050 species (A) p Tmin (GeV/c) d (2)0.02 Si (28)0.22 Cu (64)0.51 In (115)0.92 Au (197)1.58 U (238)1.90  Need to rely on rapidity gap method method  simulations look good  high eff. high purity possible with gap alone possible with gap alone ~1% contamination ~1% contamination ~80% efficiency ~80% efficiency  depends critical on detector hermeticity hermeticity  improve further by veto on breakup of nuclei (DIS) breakup of nuclei (DIS)  Very critical  mandatory to detect nuclear fragments from breakup fragments from breakup  n: Zero-Degree calorimeter  p, Afrag: Forward Spectrometer  New idea: Use U instead of AU