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MEIC Detector

MEIC Detector. Rolf Ent MEIC Accelerator Design Review September 15-16, 2010. The Science of an (M)EIC. Nuclear Science Goal: How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? Overarching EIC Goal: Explore and Understand QCD.

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MEIC Detector

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  1. MEIC Detector Rolf Ent MEIC Accelerator Design Review September 15-16, 2010

  2. The Science of an (M)EIC Nuclear Science Goal: How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? Overarching EIC Goal: Explore and Understand QCD • Three Major Science Questions for an EIC (from NSAC LRP07): • What is the internal landscape of the nucleons? • What is the role of gluons and gluon self-interactions in nucleons and nuclei? • What governs the transition of quarks and gluons into pions and nucleons? Or, Elevator-Talk EIC science goals: Map the spin and 3D quark-gluon structure of protons (show the nucleon structure picture of the day…) Discover the role of gluons in atomic nuclei (without gluons there are no protons, no neutrons, no atomic nuclei) Understand the creation of the quark-gluon matter around us (how does E = Mc2 work to create pions and nucleons?) + Hunting for the unseen forces of the universe

  3. EIC@JLabassumptions (x,Q2) phase space directly correlated with s (=4EeEp) : @ Q2 = 1 lowest x scales like s-1 @ Q2 = 10 lowest x scales as 10s-1 x = Q2/ys General science assumptions: (“Medium-Energy”) EIC@JLab option driven by: access to sea quarks (x > 0.01 (0.001?)or so) deep exclusive scattering at Q2 > 10 (?) any QCD machine needs range in Q2  s = few 100 - 1000 seems right ballpark  s = few 1000 allows access to gluons, shadowing Requirements for deep exclusive and high-Q2 semi-inclusive reactions also drives request for (lower &) more symmetric beam energies. Requirements for very-forward angle detection folded in IR design

  4. Where do particles go - general e p or A Token example: 1H(e,e’π+)n • Several processes in e-p: • “DIS” (electron-quark scattering) e + p  e’ + X • “Semi-Inclusive DIS (SIDIS)” e + p  e’ + meson + X • “Deep Exclusive Scattering (DES)”e + p  e’ + photon/meson + baryon • Diffractive Scattering e + p  e’ + p + X • Target fragmentation e + p  e’ + many mesons + baryons • Even more processes in e-A: • “DIS” e + A  e’ + X • “SIDIS” e + A  e’ + meson + X • “Coherent DES” e + A  e’ + photon/meson + nucleus • Diffractive Scattering e + A  e’ + A + X • Target fragmentation e + A  e’ + many mesons + baryons • Evaporation processes e + A  e’ + A’ + neutrons In general, e-p and even more e-A colliders have a large fraction of their science related to the detection of what happens to the ion beams. The struck quark remnants can be guided to go to the central detector region with Q2 cuts, but the spectator quark or struck nucleus remnants will go in the forward (ion) direction.

  5. Where do particles go - electrons 1H(e,e’π+)n 11 on 60 4 on 60 Momentum (GeV/c) Momentum (GeV/c) • Modest (up to ~6 GeV) electron energies in central & forward-ion direction. • Electrons create showers  electron detectors are typically compact. • Larger energies (up to Ee) in the forward-electron direction: low-Q2 events. • Requirements on the electron side are dominated by near-photon physics: electrons need to be peeled away from beam by tagger magnet(s).

  6. Where do particles go - mesons SIDIS p 1H(e,e’π+)n 4 on 60 11 on 60 { { Need Particle ID for p > 4 GeVin central region  DIRC won’t work, RICH or add threshold Cherenkov Need Particle ID for well above 4 GeV in forward region (< 30o?)  needs RICH, determines bore of solenoid In general: Region of interest up to ~10 GeV/c mesons Momentum ~ space needed for detection

  7. Where do particles go - baryons 1H(e,e’π+)n t ~ Ep2Q2 Angle recoil baryons = t½/Ep Ep = 12 GeV Ep = 30 GeV Ep = 60 GeV DQ = 1.3 DQ = 5 • Nuclear Science: Map t between tmin and 1 (2?) GeV • Must cover between 1 and 5 degrees • Should cover between 0.5 and 5 degrees • Like to cover between 0.2 and 7 degrees t resolution ~ dQ ~ 1 mr

  8. Detector/IR cartoon(primary “full-acceptance” detector) Make use of the (50 mr) crossing angle for ions! (approximately to scale) detectors solenoid ion FFQs ion dipole w/ detectors ions IP 0 mrad electrons electron FFQs 50 mrad 2+3 m 2 m 2 m Central detector, more detection space in ion direction as particles have higher momenta. Detect particles with angles below 0.5obeyond ion FFQs and in arcs. Detect particles with angles down to 0.5o before ion FFQs. Need up to 2 Tm dipole in addition to central solenoid. Distance IP – electron FFQs = 3.5 m Distance IP – ion FFQs = 7.0 m (Driven by push to 0.5 degrees detection before ion FFQs)

  9. Overview of Central Detector Layout IP is shown shifted left by 0.5 meter here, can be shifted Solenoid Yoke, Hadron Calorimeter, Muons TOF • 3-4 T solenoid with about 4 m diameter • Hadronic calorimeter and muon detector integrated with the return yoke (~ CMS) Solenoid yoke + Muon Detector Solenoid yoke + Hadronic Calorimeter RICH or DIRC/LTCC Particle Identification (in Central Detector) Muon Detector Tracking RICH • TOF for low momenta • π/K separation options • DIRC up to 4 GeV • DIRC + LTCC up to 9 GeV • dual radiator RICH up to 8 GeV • p/K separation options • DIRC up to 7 GeV • e/π separation • LTCC (C4F8O) up to 3 (5) GeV HTCC EM Calorimeter EM Calorimeter 4-5m Hadron Calorimeter 2m 3m 2m Central Tracker Particle Identification (in Forward Region) • Vertex Detector • Small (GEM-based?) TPC • Coarser-resolution tracking chambers • Higher momentum particles of interest, up to 10-20 GeV • More space required for ALICE-style RICH, electromagnetic (e.g., po) and hadroniccalorimetry

  10. Detector/IR – Magnetic Fields Pion momentum = 5 GeV/c, 4T ideal solenoid field, 1.25 m tracking region • Goal: resolution dp/p (for pions) better than 1% for p < 10 GeV/c • obtain effective 0.5 Tm field by having 50 mr crossing angle (for 5 m long central solenoid) • probably suffices to add 1-2 Tm dipole field for small-angles (<10o?) only to get dp/p < 1% for pions of up to 10 GeV/c. Here we added dipole for angles smaller than 25o Add <2 Tm transverse field component in forward-ion direction to get dp/p roughly constant vs. angle

  11. Detector/IR in pocket formulas • Luminosity ~ 1/b* • bmax~ 2 km = l2/b*(l = distance IP to 1st quad) Example: l = 7 m, b* = 20 mm  bmax = 2.5 km • IP divergence angle ~ 1/sqrt(b*) Example: l = 7 m, b* = 20 mm  angle ~ 0.3 mr Example: 12 s beam-stay-clear area  12 x 0.3 mr = 3.6 mr ~ 0.2o • FFQ gradient ~ Ep,max/sqrt(b*)(for fixed bmax, magnet length) Example: 6.8 kG/cm for Q3 @ 12 m @ 60 GeV  7 T field for 10 cm (~0.5o) aperture Making b* too small complicates small-angle (~0.5o) detection before ion Final Focusing Quads, and would require too high a peak field for these quads given the large apertures (up to ~0.5o).b* = 1-2 cm and Ep = 20-60+ GeV ballpark right!

  12. Use Crab Crossing for Very-Forward Detection too! (Reminder: MEIC/ELIC scheme uses 50 mr crab crossing) Present thinking: ion beam has 50 mr horizontal crossing angle Renders good advantages for very-forward particle detection 100 mr bend would need 20 Tm dipole @ ~20 m from IP

  13. Detector/IR – Forward & Very Forward • Ion Final Focusing Quads (FFQs) at 7 meter, allowing ion detection down to 0.5obefore the FFQs (BSC area only 0.2o) • Use large-aperture (10 cm radius) FFQs to detect particles between 0.3 and 0.5o (or so) in few meters after ion FFQ triplet • sx-y @ 12 meters from IP = 2 mm • 12 s beam-stay-clear  2.5 cm • 0.3o (0.5o) after 12 meter is 6 (10) cm •  enough space for Roman Pots & • “Zero”-Degree Calorimeters • Large dipole bend @ 20 meter from IP (to correct the 50 mr ion horizontal crossing angle) allows for very-small angle detection (< 0.3o) • sx-y @ 20 meters from IP = 0.2 mm • 10 s beam-stay-clear  2 mm • 2 mm at 20 meter is only 0.1 mr… • D(bend) of 29.9 and 30 GeV spectators is 0.7 mr = 2.7 mm @ 4 m • Situation for zero-angle neutron detection very similar as at RHIC!

  14. MEIC Detector Design Efforts • e-p/e-A colliders have a large fraction of their science related to the detection of what happens to the ion beams. The struck quark remnants can be guided to go to the central detector region with Q2 cuts, but the spectator quark or struck nucleus remnants will go in the forward (ion) direction. • The detector/IR design has concentrated on maximizing acceptancefor deep exclusive processes and processes associated with very-forward going particles •  detect remnants of both struck & spectator quarks • Many parameters related to the MEIC detector/IR design seem well matched now (lattices, ion crossing angle, magnet apertures, gradients & peak fields, range of proton energies, detector requirements), such that we do not end up with large “blind spots”.

  15. Backup

  16. Very-Forward Neutron/Ion Detection Context: The RHIC ZDC’s are hadron calorimeters aimed to measure evaporation neutrons which diverge by less than 2 mr from the beam axis. The RHIC Zero Degree Calorimeters arXiv:nucl-ex/0008005v1 • Timing resolution ~ 200 ps • Very radiation hard (as measured at nuclear reactor) • Angle resolution? • Position resolution ~ 1 cm, assume distance of 5(10+) m • Angle resolution 2 (<1) mr • at 30 GeV proton • energy: dt ~ 0.04 • Roman pots (photo: LHC) ~ 1 mm from beam, proton detection with < 100m resolution • Need to use this for coherent processes like DVCS(p,4He) where recoil nucleus energy = beam energy minus a small t correction. Work in progress. • Dp/p ~ 3 x 10-4 now  in ballpark

  17. Solenoid Fields - Overview Conclusion: ~4 Tesla fields, with length scale ~ inner diameter scale o.k. (for 30 (40) degree bore angle  radius = 0.58 (0.84) x length solenoid/2  3 (4) meter diameter for 5 meter length). Alternative: 5 meter ID, more tracking space  2-3 T only.

  18. dp/p dependence on tracking radius 10 GeV pions, ideal field resolutions • The momentum resolution depends both on (solenoid) field strength and tracking radius • Balance the solenoid field strength vs. the tracking radius • Here plotted for pions of 10 GeV at 90 degree angles • Can get resolutions of ~1% for 10 GeV/c pions for say • 4 T & 1.1 m track length • 2 T & 1.6 m track length • Are we better off with lower field but larger-diameter solenoid?

  19. 2nd IR Considerations

  20. Detector/IR in pocket formulas bmax ~ 2.5 km = l2/b*(l = distance IP to 1st quad) Luminosity ~ 1/b* For electroweakstudies, and if it is not important to have full acceptance at forward or backward angles, one can have a (2nd) interaction region with the Final-Focusing Quads more moved in. E.g., for high-Q2 electron scattering acceptance in the forward-ion region does not matter.  Move from l = 7 m to say l = 4.5 m  b* ~ 8 mm  luminosity * 2.4 Use aseparate & dedicated IR rather than sacrificing small-angle acceptance for the general purpose “full-acceptance” detector.

  21. Zeus @ HERA I First HERA magnets (off –axis quads) at +/- 5.8 m from the IP Calorimeter covers >99.8% of the full solid angle Very small hole in the FCAL (6.3 cm diameter), and small vertical opening of RCAL

  22. Zeus @ HERA II Focusing Quads close to IP Problem for forward acceptance

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