NLC - The Next Linear Collider Project
Detector Design Issues:
Interaction Region
David Asner/LLNL
Linear Collider Retreat,
Santa Cruz, June 27-29, 2002
This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
NLC - The Next Linear Collider Project
Overview
Is this assumption valid?
Is the required detector design for the same as e+e-?
What is different about the IR?
What is different about interactions?
Historically physics studies assumed an ideal detector
Recently, comparable performance to e+e- is assumed
NLC - The Next Linear Collider Project
Some Analyses in Progress
• s-channel higgs production– Mass measurement
– Cross section x BR
• bb, WW*, ZZ*, Z– MSSM deviation from SM
– CP properties
• Heavy MSSM H0,A0 – Discovery
– Tan,
– H0,A0 mass splitting
• H+H- production– Charged higgs mass
– Width, BR to extract tan
• h* hh– Higgs self coupling
• HcsH+
– Use polarization to measure L,R chiral couplings
• squarks,sleptons
• – Measure 1,2 mass
– Mixing angles
– BR to sleptons,sneutrinos
• W+W-
– 10x e+e- cross section
• tt
and e+e- Physics: Similar detector performance
• QCD
• Extra-dimensions
•b tagging is at
least as important
at
•Reflected in the
number of studies
of h bb
NLC - The Next Linear Collider Project
Integrating Laser Optics in IR
• Essentially identical to e+e- IR
• 30 mRad x-angle
• Extraction line ± 10 mRadian
• Large final mirror 6cm (0.2X0) thick Lucite, with central hole 7 cm radius.– Remove all
material from the flight path of the backgrounds
Mirror placement for LCD-Large
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2D Interaction Region: Snowmass 2001
•Cylindrical carbon fiber outer tube•Vacuum boundary with transition from thick cylinder to thin beampipe.
•Sections of “strongback” for optical support•Thermal Management
NLC - The Next Linear Collider Project
Neutron Backgrounds (e+e- IR)The closer to the IP a particle is lost, the worse
Off-energy e+/e- pairs hit the Pair-LumMon, beam-pipe and Ext.-
line magnetsRadiative Bhabhas & Lost beam
<x10
Solutions:• Move L* away from IP• Open extraction line aperture• Low Z (Carbon, etc.) absorber
where space permits
Neutrons from Beam Dump(s)
Solutions: Geometry & Shielding
• Shield dump, move it as far away as possible, and use smallest window– Constrained by angular
distribution of beamstrahlung photons
• Minimize extraction line aperture
• Keep sensitive stuff beyond limiting aperture– If VXD Rmin down x2 Fluence
UP x40
Interaction RegionExtraction line aperture is 10mRad
L1 and L2 of Silicon have direct line of site to the beam dump
Greatly increased neutron flux
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Neutrons from the Beam Dump
Geometric fall off of neutron flux passing 1 mrad aperture
Limiting Aperture
Radius (cm)z(m)
# Neutrons per Year for e+e-
1.00.5
Integral
Limiting aperture for is 10mRad
NLC - The Next Linear Collider Project
Neutron hit density in VXD
NLC-LD-500 GeV e+e- NLC-LD-500 GeV Beam-Beam pairs 1.8 x 109 hits/cm2/yr expect similar
Radiative Bhabhas 1.5 x 107 hits/cm2/yr expect similar
Beam loss in extraction line 0.1 x 108 hits/cm2/year expect similar
Backshine from dump 1.0 x 108 hits/cm2/yr 1.0 x 1011 hits/cm2/yr
TOTAL 1.9 x 109 hits/cm2/yr 1.0 x 1011 hits/cm2/yr
Neutron BackgroundsSummary
Figure of merit is 3 x 109 for CCD VXD
Takashi Maruyama & Jeff Gronberg
L1 & L2 cannot use CCD – Active Pixels?
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Summary: LD @ 500 GeV (e+e- IR)
NLC - The Next Linear Collider Project
LD Detector Occupancies (e+e- IR) from e+e- Pairs @ 500 GeV
Detector Per bunch R. O. Eff.#B
Occupancy Comment
VXD-L1 36E-3/mm2 50 s 148 5.3/ mm2 1.5cm, 4T
VXD-L2 3.1E-3/mm2 250 s 742 2.3/ mm2 2.6cm, 4T
TPC 1336, 5trks 55 s 160 Few per mil
Barrel ECAL 1176, 0.63GeV 150 ns 1 0.63 GeV 101>3MeV
Endcap ECAL 1176, 1.92GeV 150 ns 1 1.92 GeV 91>3MeV
VXD-L1 38E-3/mm2 8 ms 190 7.2/ mm2 1.2cm, 3T
VXD-L2 3.1E-3/mm2 8 ms 190 0.6/ mm2 1.4cm, 3T
TPC 1377, ?trks 8 ms 190 “Few per mil” Needs Study
Barrel ECAL 547 , 0.73 GeV 8 ms 190 139 GeV Needs Study
Endcap ECAL 597, 0.9 GeV 8 ms 190 171 GeV Needs Study
TESLA
NLC
requires single bunch resolution – relies on few ns TPC timing
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Time Resolution and Bunch Structure
3 Tesla TPC time res 1.4 ns = 2 bunches 95x120 Hz with 1.5x1010 e/bunch
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Photons have Structure
• Three types of collisions
– Direct
– Once resolved
– Twice resolved
Electroweak
Electroweak(DIS)
Strong( collider)
“”=0.99 + .01
NLC - The Next Linear Collider Project
Resolved Photon Backgrounds:#1 Concern
collisions are NOT like e+e- 1.5x1010 e- and 1x1010
• About 98% of interactions are
• About 80% ** and 18% *
Cross section to hadronic final states is about 400nb (pt>2 MeV)
Total luminosity ~100 nb-1 s-1
• Expect 3 - 4 underlying hadronic events per “interesting” event
• |cos |<0.9 about 50 GeV, |cos |<0.8 about 25 GeV
NLC - The Next Linear Collider Project
Resolved Photon Background
Cos vs Energy (GeV) 85 tracks/crossing (|cos | < 0.9)pavg = 0.6 GeV (p > 0.2 GeV)
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Conclusion
• IR design requires larger aperture extraction line 10mRad – VXD L1 & L2 have direct line of site to beam dump– CCD’s cannot handle neutron flux 1011n/cm/y– Need to study the impact on detector performance (b-tagging) if
• Only have a 3 layer CCD-VXD, L3, L4 & L5• Replace L1 & L2 with active pixels• All layers active pixels
– Need detector design for these scenarios
• Radiation Summary Table for LD–500 GeV: Redo for IR• Detector Occupancy Table: Include resolved photons• Simulation to assess if occupancy is low enough for pattern
recognition + TPC time stamp to resolve single crossing