MEIC Interaction Region & Tagging V.S. Morozov1, P. Brindza1, A. Camsonne1, Ya.S. Derbenev1, R. Ent1, D. Gaskell1, F. Lin1, P. Nadel-Turonski1, M. Ungaro1, Y. Zhang1, Z.W. Zhao1,2, C.E. Hyde2, K. Park2, M. Sullivan3 1JLab, 2ODU, 3SLAC High Energy Nuclear Physics with Spectator Tagging Old Dominion University, March 10, 2014 F. Lin

Outline Detector concept Detector integration Forward ion tagging Forward electron tagging Backgrounds Summary

MEIC Layout & Detector Location Cold Ion Collider Ring (8 to 100 GeV) Two IP locations: One has a new detector, fully instrumented Second is a straight-through, minor additional magnets needed to turn into IP Ion Source Booster Linac Warm Electron Collider Ring (3 to 10 GeV) Considerations: Minimize synchrotron radiation IP far from arc where electrons exit Electron beam bending minimized in the straight before the IP Minimize hadronic background IP close to arc where protons/ions exit

Full-Acceptance Detector 50 mrad crossing angle Improved detection, no parasitic collisions, fast beam separation Forward hadron detection in three stages Endcap Small dipole covering angles up to a few degrees Far forward, up to one degree, for particles passing through accelerator quads Low-Q2 tagger Small-angle electron detection R. Ent, C.E. Hyde, P. Nadel-Turonski

Detector Modeling & Machine Integration Fully-integrated detector and interaction region satisfying Detector requirements: full acceptance and high resolution Beam dynamics requirements: consistent with non-linear dynamics requirements Geometric constraints: matched collider ring footprints far forward hadron detection low-Q2 electron detection large-aperture electron quads small-diameter central detector with endcaps ion quads 50 mrad beam (crab) crossing angle n, g e p small angle ~60 mrad bend (from GEANT4) 2 Tm dipole Endcap Ion quadrupoles Electron quadrupoles 1 m IP FP Roman pots Thin exit windows Fixed trackers Trackers and “donut” calorimeter RICH + TORCH? dual-solenoid in common cryostat 4 m coil barrel DIRC + TOF EM calorimeter Tracking e/π threshold Cherenkov 5

Compton polarimetry region Electron IR Optics IP region Final focusing quads with maximum field gradient ~63 T/m Four 3m-long dipoles (chicane) with 0.44 T @ 10 GeV for low-Q2 tagging with small momentum resolution, suppression of dispersion and Compton polarimeter IP e- forward e- detection region FFQs Compton polarimetry region

Ion IR Optics IR design features Modular design Based on triplet Final Focusing Blocks (FFB) Asymmetric design to satisfy detector requirements and reduce chromaticity Spectrometer dipoles before and after downstream FFB, second focus downstream of IP No dispersion at IP, achromatic optics downstream of IP detector elements match/ beam compression IP match/ beam expansion geom. match/ disp. suppression FFB FFB ions

Integrated Interaction Region & Detector (top view) Accelerator view of IR Layout crab cavities ions FFQs FFQs IP e- crab cavities Design emphasis on polarization (figure-8) and on integrated detector/interaction region Nuclear Physics view of IR Layout (top view) central detector with endcaps small angle hadron detection ultra forward hadron detection low-Q2 electron detection and Compton polarimeter n, large aperture electron quads ion quads 60 mrad bend p e small diameter electron quads e p Thin exit windows Fixed trackers Roman pots 50 mrad beam (crab) crossing angle

EIC Central Detector MEIC-IP1 detector ePHENIX Focus on exclusive processes and semi-inclusive DIS With forward dipole/detector constitutes “full-acceptance detector” with ion FFQ at 7 m Could be based on dual solenoid or CLEO magnet 5 m 3 m dual-solenoid in common cryostat 4 m inner coil outer+inner EM cal π/K Cherenkov e/π HBD TOF (top view) RICH aerogel + CF4 Coil wall EM calorimeter barrel DIRC + TOF Si-pixel vertex + Si disks GEM/micromegas central and forward Forward dipole ePHENIX More focus on jet-physics Ion FFQ at 4.5 meter consistent with MEIC-IP2 “high-luminosity detector” assumption Based on BABAR magnet (approximately to scale) ePHENIX detector (side view of top half)

Forward Hadron Detection Large crossing angle (50 mrad) Moves spot of poor resolution along solenoid axis into the periphery Minimizes shadow from electron FFQs Dipole before quadrupoles Further improves resolution in the few-degree range Low-gradient quadrupoles Allow large apertures for detection of all ion fragments Crossing angle 89 T/m, 9.0 T, 1.2 m 51 T/m, 9.0 T, 2.4 m 36 T/m, 7.0 T, 1.2 m Permanent magnets 34 T/m 46 T/m 38 T/m 2 x 15 T/m e 5 T, 4 m dipole Ion quadrupoles: gradient, peak field, length 2 T dipole Endcap detectors Electron quadrupoles Tracking Calorimetry 1 m 7 m from IP to first ion quad 10

Far-Forward Hadron Detection Good acceptance for ion fragments Large downstream magnet apertures/ small downstream magnet gradients Good acceptance for low-pT recoil baryons Small beam size at second focus Large dispersion Good momentum and angular resolution No contribution from D to angular spread at IP Long instrumented magnet-free drift space Sufficient separation between the beam lines Asymmetric IR (minimizes chromaticity) Ions x βx* = 10-20 cm βFP < 1 m DFP ~ 1 m βy* = 2 cm D* = D'* = 0 FP IP e p (n, ) 20 Tm dipole (in) 2 Tm dipole (out) solenoid Roman pots at focal point Thin exit windows Aperture-free drift space ZDC S-shaped dipole configuration optimizes acceptance for neutrals 50 mrad crossing angle 11

Far-Forward Acceptance for Charged Fragments Δp/p = -0.5 Δp/p = 0.0 Δp/p = 0.5 (protons rich fragments) (exclusive / diffractive recoil protons) (tritons from N=Z nuclei) (spectator protons from deuterium) (neutron rich fragments) 12

Far-Forward Ion Acceptance Transmission of particles with initial angular and p/p spread vs peak field Quad apertures = B max / (fixed field gradient @ 100 GeV/c) Uniform particle distribution of 0.7 in p/p and 1 in horizontal angle originating at IP Transmitted particles are indicated in blue (the box outlines acceptance of interest) 6 T max 9 T max 12 T max  electron beam 13

Far-Forward Angular Ion Acceptance Quad apertures = 9, 9, 7 T / (By /x @ 100 GeV/c), dipole aperture = -30/+50 40 cm Uniform distribution of 1 in x and y angles around proton beam at IP for a set of p/p The circle indicates neutrals’ cone  electron beam p/p = -0.5 p/p = 0 p/p = 0.5 neutrons 14

Far-Forward Ion Acceptance for Neutrals Transmission of neutrals with initial x and y angular spread vs peak field Quad apertures = B max / (fixed field gradient @ 100 GeV/c) Uniform neutral particle distribution of 1 in x and y angles around proton beam at IP Transmitted particles are indicated in blue (the circle outlines 0.5 cone) 6 T max 9 T max 12 T max  electron beam 15

Ion Momentum & Angular Resolution Protons with p/p spread are launched at different angles to nominal trajectory Resulting deflection is observed at the second focal point Particles with large deflections can be detected closer to the dipole  electron beam ±10 @ 60 GeV/c |p/p| > 0.005 @ x,y = 0 16

Ion Momentum & Angular Resolution Protons with different p/p launched with x spread around nominal trajectory Resulting deflection is observed 12 m downstream of the dipole Particles with large deflections can be detected closer to the dipole |x| > 3 mrad @ p/p = 0  electron beam  electron beam ±10 @ 60 GeV/c 17

Example: DVCS Recoil Proton Acceptance Kinematics: 5 GeV e- on 100 GeV p at a crossing angle of 50 mrad. Cuts: Q2 > 1 GeV2, x < 0.1, E’e > 1 GeV, recoil proton 10σ outside of beam DVCS generator: MILOU (from HERA, courtesy of BNL) GEANT4 simulation: tracking through all magnets done using the JLab GEMC package low-t acceptance high-t acceptance p beam at 50 mrad High-t acceptance limited by magnet apertures 10σ beam size cut: p < 99.5% of beam for all angles θ > 2 mrad for all momenta -t = 1.9 GeV2 ±14 mrad Proton angle at IP e- beam at 0 mrad Recoil proton angle is independent of electron beam energy: θp ≈ pT/Ep ≈ √(-t)/Ep A wider angular distribution at lower energies makes precise tracking easier Z.W. Zhao

Far-Forward Ion Detection Summary Neutrals detected in a 25 mrad (total) cone down to zero degrees Space for large (> 1 m diameter) Hcal + Emcal Excellent acceptance for all ion fragments Recoil baryon acceptance: up to 99.5% of beam energy for all angles down to at least 2-3 mrad for all momenta full acceptance for x > 0.005 Resolution limited only by beam longitudinal p/p ~ 310-4 angular  ~ 0.2 mrad n, γ 20 Tm dipole 2 Tm dipole p solenoid e 15 MeV/c resolution for 50GeV/u tagged deuteron beam 19

Forward e- Detection & Pol. Measurement Dipole chicane for high-resolution detection of low-Q2 electrons e- ions IP forward ion detection forward e- detection Compton polarimetry local crab cavities Compton polarimetry has been integrated to the interaction region design same polarization at laser as at IP due to zero net bend c Laser + Fabry Perot cavity e- beam from IP Low-Q2 tagger for low-energy electrons Low-Q2 tagger for high-energy electrons Compton electron tracking detector Compton photon calorimeter Compton- and low-Q2 electrons are kinematically separated! Photons from IP e- beam to spin rotator Luminosity monitor A. Camsonne, D. Gaskell

Downstream Electron Acceptance 5 GeV/c e-, uniform spreads: -0.5/0 in p/p and 25 mrad in horizontal/vertical angle Apertures: Quads = 6, 6, 3 T / (By /x @ 11 GeV/c), Dipoles = 20 20 cm ion beam  21

Downstream Angular Electron Acceptance Uniform e- distribution horizontally & vertically within 25 mrad around 5 GeV/c beam Apertures: Quads = 6, 6, 3 T / (By /x @ 11 GeV/c), Dipoles = 20 20 cm ion beam  ion beam  p/p = -0.5 p/p = -0.1 p/p = 0 p/p = -0.25 22

Electron Momentum & Angular Resolution Electrons with p/p spread launched at different angles to nominal 5 GeV/c trajectory |p/p| > 0.01 @ x,y = 0 ion beam 

Electron Momentum & Angular Resolution e- with different p/p launched with x spread around nominal 5 GeV/c trajectory |x| > 0.4-4 mrad @ p/p = 0 ion beam 

IR Quad: permanent magnet and superconducting Requirements: 39 T/m 3 cm bore radius @ inner surface of quad 7 cm max radius of quad structure to clear i-beam tube P. McIntyre et al., Texas A&M University

Synchrotron Radiation Background Initial electron beam pipe design for evaluating SR Conclusion: diameter at the vertex tracker could be reduced to 25-30 mm Surface: 1 2 3 4 5 6 Power (W) @ 5 GeV 3.0 5.7 0.2 0.8 - 0.03 g >10 keV @ 5GeV 5.6x105 3.4x105 1.4x104 5.8x104 167 3,538 Power (W) @ 11 GeV 4.2 8.0 0.3 1.1 0.04 g >10 keV @ 11 GeV 2.8x105 9.0x104 3.8x105 271 13,323 Photon numbers are per bunch Modest synchrotron background M. Sullivan, SLAC

Hadronic Backgrounds HERA: Strong correlation between detector background rates and beam line vacuum.  Random background assumed to be dominated by scattering of beam ions on residual gas (mainly H2) in the beam pipe between the ion exit arc and the detector The conditions at the MEIC compare favorably with HERA Typical values of s are 4,000 GeV2 at the MEIC and 100,000 GeV2 at HERA Distance from arc to detector: 65 m / 120 m = 0.54 p-p cross section ratio σ(100 GeV) / σ(920 GeV) < 0.8 Average hadron multiplicity per collision (4000 / 100000)1/4 = 0.45 Proton beam current ratio: 0.5 A / 0.1 A = 5 At the same vacuum the MEIC background is 0.54 * 0.8 * 0.45 * 5 = 0.97 of HERA But MEIC vacuum should be closer to PEP-II (10-9 torr) than HERA (10-7 torr)

Summary & Outlook Conceptual design of the interaction region completed Interaction region integrated into collider rings Forward detection requirements fully satisfied Ongoing and future work Detector modeling Polarimetry development Design optimization Engineering design of interaction region magnets Systematic investigation of non-linear dynamics Development of beam diagnostics and orbit correction scheme