1. E.C. AschenauerEIC INT Program, Seattle 2010 - Week 81

2. Kinematics of elastic diffraction E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 82 4x250 4x100 4x50 no cuts: cuts: Q2 > 0.1 GeV && y 0.1 GeV && y < 0.9 GeV decay products of  & J/ ψ go more and more forward with increasing asymmetry in beam energies

3. Diffractive Physics: p’ kinematics E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 83 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: p’ need “roman pots” to detect the protons and a ZDC for neutrons t=(p 3 –p 1 ) 2 = m ρ 2 -Q 2 - 2(E γ* E ρ -p x γ* p x ρ -p y γ* p y ρ -p z γ* p z ρ )

4. How to detect exclusive protons  Detector concepts  Roman Pots for protons / charged particles  Zero Degree Calorimeters (ZDC) for neutrons  Preshower & ECal for photons, important for eA  e’A’   Challenges  angular emittance of the beam eRHIC: 0.1 mrad  how close to the beam can the roman pots go normally 10   1mrad  geometric acceptance of magnets  need thin exit windows for particles  need most likely more than one place to put roman pots E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 84

5. eRHIC Detector Concept E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 85 Forward / Backward Spectrometers: 2m 4m  central detector acceptance: very high coverage -5 <  < 5  Tracker and ECal coverage the same  crossing angle: 10 mrad;  y = 2cm and  x = 2/4cm (electron/proton direction)  Dipoles needed to have good forward momentum resolution and acceptance  DIRC, RICH hadron identification  , K, p  low radiation length extremely critical  low lepton energies  precise vertex reconstruction (< 10  m)  separate Beauty and Charmed Meson minimum angle for “elastic protons” to be detected in the main detector 10 mrad  p t = 1 GeV

6. IR-Design-Version-I 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 Dipole © 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 Assume 50% operations efficiency  4fb -1 / week E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 86 Spinrotator

7. A detector integrated into IR – Version 1 E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 87 ZDC FPD  for ERL solution need not to measure electron polarization bunch by bunch  need still to integrate luminosity monitor  need still to integrate hadronic polarimeters, maybe at different IP FED space for e-polarimetry and luminosity measurements

8. Can we detect DVCS-protons and Au break up p E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 88  track the protons through solenoid, quads and dipole with hector  beam angular spread 0.1mrad at IR  Quads +/- 5mrad acceptance; geometric acceptance: 1.5cm  Proton-beam: p’ z > 0.9p z  100 GeV: p t max < 0.45 GeV  suboptimal as we loose intermediate p t (0.4 – 1.2 GeV)/ t range  solution could be to do the same as for the electrons swap the dipole and quads  lumi goes down  see next slides dipole and quads  lumi goes down  see next slides proton track  p=10% proton track  p=20% Equivalent to fragmenting protons from Au in Au optics (197/79:1 ~2.5:1) proton track  p=40%

9. 2 468 10 2.5 m 3.5 m 1214 90 mm 5.75 m 16 IP Dipole: 2.5 m, 6 T  =18 mrad 4.5 m  =18 mrad  =10 mrad Estimated  * ≈ 8 cm  =44 mrad 6.3 cm ZDC p c /2.5 15.7 cm 6 mrad 11.2 cm 4.5 cm neutrons p c /2.5 IP configuration for eRHIC – Version-II E.C. Aschenauer 9EIC INT Program, Seattle 2010 - Week 8 e Quad Gradient: 200 T/m

10. 0.44843 m Q5 D5 Q4 90.08703 m 10 mrad 0.39065 m 60.0559 m 10 20 30 0.333 m IP configuration for eRHIC – Version-II E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 810 4 m 4.5  =18 mrad 5.75 m 5.75 cm 11.9 m 17.65 m  =27.194 mrad

11. Can we detect “exclusive” protons E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 811  lets see acceptance now  beam angular spread 0.1mrad at IR  Dipole +/- 10 mrad; geometric acceptance: +/- 11.5 cm  Quads +/- 3 mrad acceptance; geometric acceptance: < 1.5cm  Proton-beam: p’ z > 0.9p z  lets assume p z = p beam  maximal p t  100 GeV: p t max < 1 GeV  50 GeV: p t max < 0.8 GeV  minimal p t  assume 10  distance of roman pot to beam  100 GeV: p t min ~ 100 MeV  50 GeV: p t min ~ 50 MeV Looks much more promising than v-I, need to do full particle ray tracing

12. 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 ~ p z A tanθ min For beam energies = 100 GeV/n and θ min = 0.1 mrad θ min = 0.1 mrad  Large momentum kicks, much larger than binding energy (~8 MeV) than binding energy (~8 MeV)  Therefore, for large A, coherently diffractive nucleus cannot be separated from beamline without breaking up E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 812 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

13. How to measure coherent diffraction in e+A ? E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 813  Rely on rapidity gap 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 breakupPurityEfficiencyrapidity

14. E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 814 BACKUP

15. 6.5 T magnet, 2.5 m long 4.5 cm E.C. Aschenauer 15EIC INT Program, Seattle 2010 - Week 8

16. E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 8 Quads for β*=5 cm © B.Parker 16