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

Slide 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): 1)What is the internal landscape of the nucleons? 2)What is the role of gluons and gluon self-interactions in nucleons and nuclei? 3)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 = Mc 2 work to create pions and nucleons?) + Hunting for the unseen forces of the universe

Slide 3 assumptions (x,Q 2 ) phase space directly correlated with s (=4E e E p ) Q 2 = 1 lowest x scales like s Q 2 = 10 lowest x scales as 10s -1 General science assumptions: (“Medium-Energy”) option driven by: access to sea quarks (x > 0.01 (0.001?) or so) deep exclusive scattering at Q 2 > 10 (?) any QCD machine needs range in Q 2  s = few seems right ballpark  s = few 1000 allows access to gluons, shadowing Requirements for deep exclusive and high-Q 2 semi-inclusive reactions also drives request for (lower &) more symmetric beam energies. Requirements for very-forward angle detection folded in IR design x = Q 2 /ys

Slide 4 Where do particles go - general p or A e Several processes in e-p: 1)“DIS” (electron-quark scattering)e + p  e’ + X 2)“Semi-Inclusive DIS (SIDIS)”e + p  e’ + meson + X 3)“Deep Exclusive Scattering (DES)”e + p  e’ + photon/meson + baryon 4)Diffractive Scatteringe + p  e’ + p + X 5)Target fragmentatione + p  e’ + many mesons + baryons Even more processes in e-A: 1)“DIS”e + A  e’ + X 2)“SIDIS”e + A  e’ + meson + X 3)“Coherent DES”e + A  e’ + photon/meson + nucleus 4)Diffractive Scatteringe + A  e’ + A + X 5)Target fragmentatione + A  e’ + many mesons + baryons 6)Evaporation processese + 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 Q 2 cuts, but the spectator quark or struck nucleus remnants will go in the forward (ion) direction. Token example: 1 H(e,e’π + )n

Slide 5 Where do particles go - electrons 4 on on 60 1 H(e,e’π + )n Modest (up to ~6 GeV) electron energies in central & forward-ion direction. Electrons create showers  electron detectors are typically compact. Larger energies (up to E e ) in the forward-electron direction: low-Q 2 events. Requirements on the electron side are dominated by near-photon physics: electrons need to be peeled away from beam by tagger magnet(s). Momentum (GeV/c)

Slide 6 Where do particles go - mesons 4 on 6011 on 60 1 H(e,e’π + )n SIDIS  Need Particle ID for p > 4 GeV in central region  DIRC won’t work, RICH or add threshold Cherenkov Need Particle ID for well above 4 GeV in forward region (< 30 o ?)  needs RICH, determines bore of solenoid In general:Region of interest up to ~10 GeV/c mesons Momentum ~ space needed for detection { {

Slide 7 Nuclear Science: Map t between t min 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  = 5  = 1.3 E p = 12 GeVE p = 30 GeVE p = 60 GeV t ~ E p 2  2  Angle recoil baryons = t ½ /E p Where do particles go - baryons 1 H(e,e’π + )n t resolution ~  ~ 1 mr

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

Slide 9 Overview of Central Detector Layout EM Calorimeter Hadron Calorimeter Muon Detector EM Calorimeter Solenoid yoke + Hadronic Calorimeter Solenoid yoke + Muon Detector TOF HTCC RICH RICH or DIRC/LTCC Tracking 2m 3m 2m IP is shown shifted left by 0.5 meter here, can be shifted 4-5m 3-4 T solenoid with about 4 m diameter Hadronic calorimeter and muon detector integrated with the return yoke (~ CMS) 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 (C 4 F 8 O) up to 3 (5) GeV Solenoid Yoke, Hadron Calorimeter, Muons Particle Identification (in Central Detector) Vertex Detector Small (GEM-based?) TPC Coarser-resolution tracking chambers Central Tracker Particle Identification (in Forward Region) Higher momentum particles of interest, up to GeV More space required for ALICE-style RICH, electromagnetic (e.g.,  o ) and hadronic calorimetry

Slide 10 Pion momentum = 5 GeV/c, 4T ideal solenoid field, 1.25 m tracking region Detector/IR – Magnetic Fields Add <2 Tm transverse field component in forward- ion direction to get dp/p roughly constant vs. angle 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 (<10 o ?) only to get dp/p < 1% for pions of up to 10 GeV/c. Here we added dipole for angles smaller than 25 o

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

Slide 12 Use Crab Crossing for Very-Forward Detection too! 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 ~20 m from IP (Reminder: MEIC/ELIC scheme uses 50 mr crab crossing)

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

Slide 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 Q 2 cuts, but the spectator quark or struck nucleus remnants will go in the forward (ion) direction. The detector/IR design has concentrated on maximizing acceptance for 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”.

Slide 15 Backup

Slide 16 Context: The RHIC ZDC’s are hadron calorimeters aimed to measure evaporation neutrons which diverge by less than 2 mr from the beam axis. Very-Forward Neutron/Ion Detection Roman pots (photo: LHC) ~ 1 mm from beam, proton detection with < 100  resolution  Need to use this for coherent processes like DVCS(p, 4 He) where recoil nucleus energy = beam energy minus a small t correction. Work in progress.  p/p ~ 3 x now  in ballpark The RHIC Zero Degree CalorimetersarXiv:nucl-ex/ v1 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:  t ~ 0.04

Slide 17 Solenoid Fields - Overview ExperimentCentral FieldLengthInner Diameter ZEUS1.8 T2.8 m0.86 m H11.2T5.0 m5.8 m BABAR1.5T3.46 m2.8 m BELLE1.5T3.0 m1.7 m GlueX2.0T3.5 m1.85 m ATLAS2.0T5.3 m2.44 m CMS4.0T13.0 m5.9 m PANDA (*design) 2.0T2.75m1.62 m CLAS12 (*design) 5.0T1.19 m0.96 m 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.

Slide 18 dp/p dependence on tracking radius 18 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? 10 GeV pions, ideal field resolutions

Slide 19 2 nd IR Considerations

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

Slide 21 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

Slide 22 Focusing Quads close to IP Problem for forward acceptance HERA II