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

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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

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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

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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)

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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

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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

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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