MEIC Detector

Rolf Ent

MEIC Accelerator Design Review

September 15-16, 2010

Slide 2

The Science of an (M)EICNuclear 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 = Mc2 work to create pions and nucleons?)

+ Hunting for the unseen forces of the universe

Slide 3

EIC@JLab assumptions(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

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

x = Q2/ys

Slide 4

Where do particles go - generalp or A e

Several processes in e-p:1) “DIS” (electron-quark scattering) e + p e’ + X2) “Semi-Inclusive DIS (SIDIS)” e + p e’ + meson + X3) “Deep Exclusive Scattering (DES)” e + p e’ + photon/meson + baryon4) Diffractive Scattering e + p e’ + p + X5) Target fragmentation e + p e’ + many mesons + baryons

Even more processes in e-A:6) “DIS” e + A e’ + X7) “SIDIS” e + A e’ + meson + X8) “Coherent DES” e + A e’ + photon/meson + nucleus9) Diffractive Scattering e + A e’ + A + X10)Target fragmentation e + A e’ + many mesons + baryons11)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.

Token example: 1H(e,e’π+)n

Slide 5

Where do particles go - electrons

4 on 60 11 on 601H(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 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).

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Slide 6

Where do particles go - mesons

4 on 60 11 on 60

1H(e,e’π+)nSIDIS p

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 (< 30o?) needs RICH, determines bore of solenoid

In general: Region of interest up to ~10 GeV/c mesonsMomentum ~ space needed for detection

{{

Slide 7

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

DQ = 5 DQ = 1.3

Ep = 12 GeV Ep = 30 GeV Ep = 60 GeV

t ~ Ep2Q2 Angle recoil baryons = t½/Ep

Where do particles go - baryons1H(e,e’π+)n

t resolution ~ dQ ~ 1 mr

Slide 8

solenoid

electron FFQs50 mrad

0 mrad

ion dipole w/ detectors

(approximately to scale)

ions

electrons

IP

ion FFQs

2+3 m 2 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 0.5o 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 0.5o before ion FFQs.Need up to 2 Tm dipole in addition to central solenoid.

Slide 9

Overview of Central Detector Layout

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Solenoid yoke + Hadronic Calorimeter

Solenoid yoke + Muon DetectorTOF

HT

CC

RIC

H

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 (C4F

8O) 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 TrackerParticle Identification (in Forward Region)

• Higher momentum particles of interest, up to 10-20 GeV

• More space required for ALICE-style RICH, electromagnetic (e.g., po) 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 (<10o?) only to get dp/p < 1% for pions of up to 10 GeV/c.

Here we added dipole for angles smaller than 25o

Slide 11

Detector/IR in pocket formulas

• bmax ~ 2 km = l2/b* (l = distance IP to 1st quad)

• IP divergence angle ~ 1/sqrt(b*)

• Luminosity ~ 1/b*

Example: l = 7 m, b* = 20 mm bmax = 2.5 km

Example: l = 7 m, b* = 20 mm angle ~ 0.3 mrExample: 12 s beam-stay-clear area

12 x 0.3 mr = 3.6 mr ~ 0.2o

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!

• 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

Slide 12

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Figure-8 Collider Ring - Footprint

Use Crab Crossing for Very-Forward Detection too!

Present thinking: ion beam has 50 mr horizontal crossing angleRenders good advantages for very-forward particle detection

100 mr bend would need 20 Tm dipole @ ~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 0.5o before 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 mm12 s beam-stay-clear 2.5 cm0.3o (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 mm10 s beam-stay-clear 2 mm2 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!

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 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 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 < 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

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

Slide 17

Solenoid Fields - OverviewExperiment Central Field Length Inner

Diameter

ZEUS 1.8 T 2.8 m 0.86 m

H1 1.2T 5.0 m 5.8 m

BABAR 1.5T 3.46 m 2.8 m

BELLE 1.5T 3.0 m 1.7 m

GlueX 2.0T 3.5 m 1.85 m

ATLAS 2.0T 5.3 m 2.44 m

CMS 4.0T 13.0 m 5.9 m

PANDA(*design) 2.0T 2.75m 1.62 m

CLAS12(*design) 5.0T 1.19 m 0.96 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

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• 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

2nd IR Considerations

Slide 20

Detector/IR in pocket formulas

bmax ~ 2.5 km = l2/b* (l = distance IP to 1st quad)

Luminosity ~ 1/b*For electroweak studies, 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 a separate & dedicated IR rather than sacrificing small-angle acceptance for the general purpose “full-acceptance” detector.

Slide 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 angleVery small hole in the FCAL (6.3 cm diameter), and small vertical opening of RCAL

Slide 22

Focusing Quads close to IPProblem for forward acceptance

Zeus @ HERA II