August 2005 Snowmass Workshop

Instrumentation of the Very Forward Region of a Linear Collider Detector

Wolfgang Lohmann, DESY

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QD0

Inst. Mask

HCAL

ECAL YOK

E

WW

46mrad

113mrad

Support Tube

Pair-LuMon

BeamPipe

LowZMask Exit

radius 2cm @ 3.5m

WW

5 Tesla

SiD Forward Masking, Calorimetry & Tracking,20 mrad crossing angle

Simulation studieson several

designs

Used by H. Yamamoto

IP

VTX

FTD

300 cm

LumiCal

BeamCal

L* = 4m

Design for 0-2 mradcrossing angle (FCAL design)

Functions of the very Forward Detectors

•Fast Beam Diagnostics

•Detection of electrons and photons at small polar angles-important for searches(see talk by Philip&Vladimir

•Measurement of the Luminosity with precision O(<10-3) usingBhabha scattering(see talk by Halina)

LumiCal: 26 < θ < 82 mradBeamCal: 4 < θ < 28 mradPhotoCal: 100 < θ < 400 µrad

IP

VTX

FTD

300 cm

LumiCal

BeamCal

L* = 4m

PhotoCal downstram

•Shielding of the inner Detectors

•Measurement of the Luminosity (LumiCal)

Gauge Process:

Goal: <10-3 Precision

• Technology: Si-W Sandwich Calorimeter

• MC Simulations

e+e- e+e- (γ )

Optimisation of Shape and Segmentation,Key Requirements on the

Design

Physics Case: Giga-Z ,Two Fermion Cross Sections at High Energy, e+e- W+W-

Inner Radius of Cal.: < 1-4 µm

Distance between Cals.: < 60 µm

Radial beam position: < 0.7 mm

Requirements on Alignment

and mechanical Precision(rough Estimate)

LumiCal

LumiCalIP< 4 µm

< 0.7 mm

Requirements on the Mechanical Design

Decouple sensor framefrom absorber frame

Sensor carriers

Absorber carriers

Concept for the Mechanical Frame

)]}ln()([,0max{T

ibeami E

EEconstW +=∑

∑>=<i

ii

WWX

X

Constant value))(_( radmean genrec θθ −

))(( radθσ

value of the constant

0.11e-3 rad0.13e-3 rad

30 layers 15 rings

20rings

10rings

4 layers

15 layers

11 layers

10rings

Performance Simulations for e+e- e+e-(γ )

Event selection: acceptance, energy balance, azimuthal and angular symmetry.

Simulation: Bhwide(Bhabha)+CIRCE(Beamstrahlung)+beamspread

•More in the talks by Halina Abramowicz

X- angle background

Christian Grah, DESY-Zuethen

Beamstrahlung pair background

using serpentine field

0.E+00

1.E+09

2.E+09

3.E+09

4.E+09

5.E+09

6.E+09

8 9 10 11 12 13 14 15 16

R min (cm)

Nmbe

r of B

habh

a ev

ets

per y

ear

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500

1000

1500

2000

2500

3000

3500

Back

grou

nd (G

eV)

Events per yearBackground (GeV)

250 GeV

Number of Bhabha events as a function of the innerRadius of LumiCal

Background from beamstrahlung

•Fast Beam Diagnostics (BeamCaland PhotoCal)

e-e+

• 15000 e+e- per BX 10 – 20 TeV(10 MGy per year)

• e+e- Pairs from Beamstrahlung are deflected into the BeamCal

GeV

• direct Photons for θ < 200 µrad

Zero crossing angle

20 mradCrossing angle

total energyfirst radial momentthrust valueangular spreadL/R, U/D F/B asymmetries

Observables

Quantity Nominal Value Precision

σx 553 nm 1.2 nmσy 5.0 nm 0.1 nm

σz 300 µm 4.3 µm

∆y 0 0.4 nm

Beam Parameter Determination with BeamCal

Head-on or 2 mrad

√s = 500 GeV

Quantity Nominal Value Precision

σx 553 nm 4.8nmσy 5.0 nm 0.1 nm

σz 300 µm 11.5 µm

∆y 0 2.0nm

Beam Parameter Determination with BeamCal

PRELIMINARY!

20 mrad crossing angle

total energyfirst radial momentthrust valueangular spreadL/R, U/D F/B asymmetries

Also simultaneous determination of several beam parameter is feasible, but: Correlations!Analysis in preparation

Observables

nominal setting(550 nm x 5 nm)

>100mIP

L/R, U/D F/B asymmetriesof energy in the angulartails

Quantity Nominal Value Precision

σx 553 nm 4.2 nmσz 300 µm 7.5 µm

∆y 0 0.2 nm

Heavy gas ionisationCalorimeter

and with PhotoCal

Photons from Beamstrahlung

Heavy crystalsW-Diamond sandwich

sensorSpace forelectronics

Technologies for the BeamCal: •Radiation Hard•Fast•Compact

•Detection of High Energy Electrons and Photons

√s = 500 GeVSingle Electrons of 50, 100 and 250 GeV, detection efficiency as a function of R (‘high background region’)(talk by V. Drugakov and P. Bambade)

Detection efficiency as a function of the pad-size (Talk by A. Elagin)

Message:Electrons can be

detected!

Red – high BGblue – low BG

bunch #0 100 200 300 400 500

Em

ean

, GeV

0100200300400500600700800900

1000

mean energy in particular cell (high BG near BP)

real beams

ideal beams

mean energy in particular cell (high BG near BP)

bunch #0 100 200 300 400 500

Erm

s, G

eV

050

100150200250300350400

energy RMS in particular cell (high BG near BP)

real beamsideal beams

energy RMS in particular cell (high BG near BP)

Includes seismicmotions, Delay of BeamFeedback System, Lumi

Optimisation etc.(G. White)

Efficiency to identify energetic electrons and photons(E > 200 GeV)

Fake rate

√s = 500 GeVRealistic beam simulation

•Detection of High Energy Electrons and Photons

Sensor prototyping, Crystals

Light Yield from direct coupling

Similar results for lead glassCrystals (Cerenkov light !)

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Eve

nts

0

10

20

30

40

50

Number of Photoelectrons0 200 400

0

10

20

30

40

and using a fibre

~ 15 %

Compared with GEANT4Simulation, good agreement

Sensor prototyping,Diamonds

ADC

Diamond (+ PA) Scint.+PMT&

signal gate

May,August/2004 test beams CERN PS Hadron beam – 3,5 GeV2 operation modes:

Slow extraction ~105-106 / sfast extraction ~105-107 / ~10ns (Wide range intensities)

Diamond samples (CVD):- Freiburg- GPI (Moscow) - Element6

Pm1&2

Pads

Linearity Studies with High Intensities

(PS fast beam extraction)105 particles/10 ns

Response to mip

Diamond Sensor Performance

Relative Intensity [a.u.]0 50 100

Dia

mo

nd

res

po

nse

[A

DC

ch

]

0

10000

20000

Univ. of Colorado, Boulder, AGH Univ., INP & Jagiell.

Univ. Cracow,JINR, Dubna,

NCPHEP, Minsk,FZU, Prague,

IHEP, Protvino,TAU, Tel Aviv,DESY, Zeuthen

Workshop on the Instrumentation of the Very Forward Region of the ILC DetectorTel Aviv, Sept. 15.-20. 2005.http//alzt.tau.ac.il/~fcal/

Summary• Many (and promising) results in simulations/design studies • Concept for a Luminometer for small crossing angle isadvanced, 20 mrad needs a different design

• Mechanics design work ongoing

• Studies with sensors started- needs more effort

• High energy electron detection down to small polarangles is feasible with compact and fine segmentedcalorimeters; easier for small crossing angle

• calorimeters in the very forward region deliververy valuable information about beam parameters

• Prototype tests mandatory

Remarks

• The instrumentation of the forward region is relativelyindependent of the detector concept,

Backup Slides

Vertexdetector

FTD

297

mm55.5 mrad

83.1 mrad

27.5 mrad

3000 mm

LAT

Tungsten shield

Quadrupole

Graphite

IP

LCALInner Mask

Shower in LAT (TDR design)

Shower LEAKAGE in old (TDR) and new LumiCal design

Shower in LumiCal(new design)

Diamond performance as function of the absorbed dose

Linearity of a heavy gas calorimeter (IHEP testbeam)

Beam Energy [GeV]0 10 20 30 40 50

]- e6N

um

ber

of

Ion

izat

ion

Ele

ctro

ns

[10

0

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1

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atm)⋅E/P = 2000 V/(cm

Dose, Gy0 5 10 15

Me

an

, A

DC

ch

0

50

100

FAP21FAP22FAP23

Radius [cm]1 2 3 4 5 6

Eff

icie

ncy

[%

]

0

20

40

60

80

100

-100 GeV e

Sampling

Crystal

Comparison SamplingHeavy Crystal

Radius [cm]1 2 3 4 5 6

Eff

icie

ncy

[%

]

0

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100

= 500 GeVs, -200 GeV e

= 1 TeVs, -400 GeV e

Comparison 500 GeV - 1TeVComparison Sampling

Heavy Crystal

Z

X

in-e

out-e

in+e

out+e

B = 4TB = 4T

Depositions on the calorimter frontface

Headon 20mradBeamPar MPI

resolution

26.789

11.201

0.893

1.648

13.018

18.780

5.918

0.536

327.312

0.109

0.043

MPI resolution

σx σx’ σy σy’ σz σz’ offx

offy

wy

N

1

1

0.887

0.168

0.017

0.039

0.149

0.720

1

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0.144

-0.016

0.056

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1

-0.748

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0.290

1

0.018 0.030

0.395

-0.032

0.004

0.414

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1

0.275

-0.496

0.581

0.481

1

-0.271

-0.369

0.101

-0.527

-0.488

0.237

0.434

0.316

0.631

1

0.700

0.852

0.080

0.127

-0.803

0.901

0.619

-0.048

1

0.441

-0.143

-0.125

-0.927

0.713

0.016

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1

-0.101

-0.036

-0.577

0.623

0.869

0.066

σy (diff) 1.839

σz (ave) 17.781

σz (diff) 14.747

Beam offset x 6.652

N per Bunch (ave)

0.080

Beam offset y 6.767

Vertical waist shift

σx (ave) 20.471

σx (diff) 16.615

σy (ave) 2.196

N per Bunch (diff)

159.172

0.054