Luminosity detector at the International Linear...

Luminosity detector at the International Linear Collider:Monte Carlo simulations and analysis of test beam data

Jonathan Aguilar

Thesis supervisor: Dr Bogdan PawlikResearch co-supervisor: Dr hab. inż. Marek Idzik

AGH University of Science and TechnologyHenryk Niewodniczanski Institute of Nuclear Physics - Polish Academy of Sciences

February 28, 2012

J. Aguilar (AGH/IFJ-PAN) LumiCal simulations and prototyping February 28, 2012 1 / 20

Forward calorimetry at the ILC

LumiCal goals

High precision in ∆L/LBhabha scattering for gaugeprocess

10−3 (√s = 500GeV)

10−4 (GIGA-Z)

BeamCal goals

Fast luminosity estimation(using beamstrahlung)

Assist beam tuning

Good hermeticity

ILD forward region

Challenges

LumiCal: Mechanical precisionand position monitoring

BeamCal: Radiation hardness

Both: Fast front-end electronics


LumiCal introduction

Parameters

Type Si-W# layers 30Absorber ∆z 1 X0Si ∆z 300 µmLayer offset 3.75o

Inner radius 80 mm32.0 mrad

Outer radius 195.2 mm77.9 mrad

Distance from IP 2.5 m

(top) Mechanical model of LumiCal(bottom) Sensor half-plane


LumiCal simulations

Simulation introduction

Stand-alone model

Dependent only on Geant4 andROOT

Identical geometry tointegrated model

Portable - moved to localcluster computing facility whichdoes not have the ILC softwarepackages available

Simulation parameters

Single e-

φ ∈ [0, 2π]

θ ∈ [0.033, 0.073]

Energies [GeV]: 5, 25, 50, 100,150, 200, 250, 500

4000 events/energy


LumiCal simulations

Tile gap effect

Energy resolution analysis

Accuracy of reconstructed energy:RMS(Erec)/< Erec >Can be parametrized as:

RMSEbeam

=

√a2

E+ b2

a → stochastic contribution

b → geometric contribution

Simulated model

Visible energy [GeV]1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

1

10

210

Visible energy [GeV]1.4 1.6 1.8 2 2.2 2.4 2.6 2.8

1

10

210

Energy deposited by 250 GeV e-

Reference design

No rotation

No gaps

RMS: 0.172

RMS: 0.274

RMS: 0.041

Energy deposition in the gapsJ. Aguilar (AGH/IFJ-PAN) LumiCal simulations and prototyping February 28, 2012 5 / 20

LumiCal simulations

Correction methods

Gap-cutting

Azimuthal angle [deg]-150 -100 -50 0 50 100 150

Vis

ible

en

erg

y fo

r 25

0 G

eV e

lect

ron

s [G

eV]

2

2.2

2.4

2.6

2.8

3

Gap cut: 4.8mm, 24.08% in gap Gap hit

Sensor hit

Remove particles in red; cut width canbe varied

Gap-fitting

Hits projected onto one tile


LumiCal simulations

Correction methods

f (x) = A− B

1 +(x−CD

)2 − E · e−F ·x2


LumiCal simulations

Correction methods

Gap-cutting


Vis

ible

en

erg

y fo

r 25

0 G

eV e

lect

ron

s [G

eV]

2

2.2

2.4

2.6

2.8

3


Sensor hit


Gap-fitting

Hits projected onto one tile


LumiCal simulations

Correction methods

Gap-cutting


Vis

ible

en

erg

y fo

r 25

0 G

eV e

lect

ron

s [G

eV]

2

2.2

2.4

2.6

2.8

3


Sensor hit


Gap-fitting

Hits projected onto one tile, with fitting


LumiCal simulations

Correction methods

Gap-cutting


Vis

ible

en

erg

y fo

r 25

0 G

eV e

lect

ron

s [G

eV]

2

2.2

2.4

2.6

2.8

3


Sensor hit


Gap-fitting

Hits projected onto one tile, flattenedand scaled


LumiCal simulations

Correction comparison

Comparison of different cut widths(width on each side of the gap) withthe gap-fitting and ideal gap-lesscalorimeter cases.

RMSEE

=

√a2

E+ b2

Stochastic Value Error

No correction 0.2147 0.00322.5mm cut 0.2094 0.002920mm cut 0.1865 0.0025gap-fitting 0.2006 0.0014

gapless 0.2027 0.0013

Geometric Value Error

No correction 0.058 0.0292.5mm cut 0.048 0.02420mm cut 0.029 0.015gap-fitting 0.010 0.005

gapless 0.006 0.003


LumiCal simulations

No rotation


LumiCal simulations

Position reconstruction


Test beams

Test beam introduction

Test beam 1 (of 3)

DESY-HamburgAugust 2010BeamCal and LumiCal groups

Goals

Characterize readout chain(sensor - fanout - FE ASICs -further readout)

Measure SNR, CCE (GaAs)

Check sensor perfomance as afunction of position

Investigate edge effects in GaAssensors

Collimator

Fiberγ

e−

Spill Counter

MagnetConverter

e−

e+e+

DESY II

e+/e−


Test beams SensorMeas

Motorized Position Control Interface


Test beams SensorMeas

Program design

t

Event-driven design conservesCPU usage.Three ways to set position:

Input manuallyStep manuallyGenerated automatically

Positions can be labeled andstored for later use.

User can set axis motion limitsto prevent crashing.

Motor speed and step sizecontrol for high precisionmotion (up to 0.31 µm).

Current maximum vertical loadshould be up to 6 kg.

User manual and programmingmanual available.


Test beams

Setup

Schematic showing telescope planes andtrigger electronics

Photograph of BeamCal sensors in placeand LumiCal sensors behind telescope


Test beams Test beam simulation

Test beam simulations

0

200

400

600

800

1000

1200

1400

0 5 10 15 20 25 30

Co

un

t

Energy [MIP]

2 X0

measurementsimulation

0

100

200

300

400

500

600

700

800

900

1000

0 5 10 15 20 25 30 35 40

Co

un

t

Energy [MIP]

4 X0


1

2

3

4

5

6

7

8

9

10

11

0 1 2 3 4 5 6 7 8 9 10 11 12

<Q

sum

>

[MIP

]

Aborber thickness [X0]



Summary

Summary

SimulationsRealistic LumiCal model implemented and simulatedTile gap effect understood and calculated“No-rotation” geometry produces good results, but must beinvestigated further

Test beamSimulation of the test beam good in general, but needs to be refinedX-Y table software implemented and improved over succesive testbeams(Backup slides) Good SNR (∼18)(Backup slides) Low crosstalk even from longest fanout channelsFirst test of readout chain - sensors with FE ASICs - was successful!

Many thanks to the Marie Curie Network on Particle Detectors forfunding this work.


Dziękuję za uwagę!


Backup

Backup slides

Backup

Lumical sensor description

Sensor design

Custom Hamamatsu sensors

1 tile (4 sectors)

64 pads/sector (1.8mm radialpitch)

300 µm high-resistivity n-typeSi bulk

p+ pads with Al metalization,DC coupled

Capacitance ∼ 30pF at 50V

Backup

Readout chain

Components

16 sensor pads bonded

Sensor and fanout glued on

FE ASICs bonded onto PCB

Output buffers

Biasing and power blocks

Backup

Electronics

FE ASIC - custom

Charge-sensitive amplifier with1st-order shaping

Tpeak ∼ 60ns2 modes of operation:

Calibration modePhysics mode

Active or passive feedback

M. Idzik. et. al., NIM-A 2009,608:169-174

ADC - commercial

CAEN VME-V1724

14 bits, 8 channels, 100 MSps

Backup

Results - Amplitude

Good amplitude response

(top) Time response toelectrons with different energies

Shape does not depend onamplitude

(bottom) Spectrum for 4.5GeVelectrons

SNR ∼ 19 for largest sensorcapacitance

Backup

Results - Crosstalk

Crosstalk ¬ 1%

Backup

BeamCal charge collection

Pad structure corresponds to∼ 5× 5 mm2 + ∼200 µm gaps

4 independent pad areas showidentical chare collection

Signals in pads exhibit Landaudistribution

Two clusters of 8 pads eachirradiated

SNR: FET > 20, Rf > 13

CCE: 33% at -60 Vbias

Luminosity detector at the International Linear...

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