May 14, 2001 C.Rott 1

The CMS Forward Pixel Detector

Carsten Rott

Purdue University

May 14, 2001

May 14, 2001 C.Rott 2

The LHC

Technically extremely challenging

• Luminosity • Center of mass energy • pp collider• 26.67km circumference

Accelerator

Detector• Radiation damage• High occupancy• Interaction rate 25ns

scmL 2

34 1101

TeVs 14

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Physics at the LHC

Higgs searchLEP II exclusion limit mH <113.5GeVLHC will cover expected Higgs mass range completely

• Bottom physics• Top physics• Extension of standard model

will allow us to explore physics at the TeV scale

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Pixels/blade24 Blades/disk

The CMS Detector

51018.1

Barrel + Forward Pixel Disks

FPIX-Disk

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The Blade

The HDI connects the Plaquettes to the outside world

PlaquetteSensorROCVHDI

Kapton,HDI

Be Panels

PSS

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The Plaquette

Sensors

ROC

Pump Bonded to

Plaquette

VHDI2 metal layersflex on 300m Si

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How does a Pixel Detector work?

N N+ P+

-- +

+

- H.V.

• Semiconductor detectors are “diodes”• By applying a reverse bias voltage to it the depletion zone can be enlarge until it the sensor is fully depleted • If an ionizing particle passes through the bulk it creates electron-hole pairs• Charge carriers move in the E-field and are collected to give the signal

Pixels

Pixels with indium bumps

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FPIX Beam Test at CERN

DAQ

3T magnet

Si-strips Repeater cardFibers

Scintillator

The telescope

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Repeater Card with Pixel SensorPixel Data150m x m pixelthickness 270m 22x30 pixel arrayunirradiated sensor

rad. hard DMILL ROCVvdepl 160

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• 250GeV/c pion beam• Repeater card can be rotated• Can trigger on region as . small as 1mm2

The Telescope

Beam

Si-Strips vertical

Si-Strips horizontal

Scint.Counters

X/Y-Fibers1mm Dia.few mm2

Extrapolated trackx= 2.0 my= 3.6 m

Pixel Detector and Repeater Card

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CorrelationsPixel hits in coincidence with the telescope trigger

A clear correlation can be seen

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Pedestal

System shows correlated noise

Adjacent pixel Non-adjacent pixel

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Signal height:

Noise:

Signal to noiseratio of 60

S/N and Efficiency

An absolute efficiency could not bemeasured because of a time stamp problem.A strong correlation between trackedposition and pixel hit position, suggestshigh efficiency.

ADCS 550

ADC3.9

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Charge sharing between rows (rotated by 20o)

Charge sharing between rows (not rotated)

150m

150 m

LC

L

RC

R

PHPHPH

PHPHPH

• PH is 12bit ADC value• Charge sharing is increased by rotating the sensor• Charge sharing can be used to improve the resolution

Charge Sharing Comparison

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Distribution

Position correction curve RC

R

LC

L

PHPHPH

PHPHPH

is the difference of the fraction of charge deposited in the neighboring pixel

)(1)( ydyWA

P)(W

A is a normalizationfactor

vs position (20o rotation angle)

mPxx hitpixelcorr 150)(

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Resolution in micron between rows (rotated by 20o)

Resolution in micron between rows (not rotated)

Resolution

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Resolution

00 rotation

200 rotation

Highest resolution for large charge sharing and hits in between pixel

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Magnetic Field

Sensors at 20o with beamB=3T parallel to beam

No asymmetry can be seen

The Lorentz angle is defined as the angle between the drift direction and the electric field

Lorentz angle could not be measured experimentally

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Results from the Beam Test

• No surprises• Charge sharing can improve the resolution• Resolution at 200 rotation 10-20 m• Resolution at 00 rotation 10-50 m• Resolution is position dependent • S/N = 60 • High efficiency

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Importance of Pixel System

Crucial role for success of the experiment

High resolutionSeparation of particle tracks

Fast signalAble to deal with a high occupancy

Flavor taggingClose to primary vertex

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The Future of New Physics

Max. integrated Luminosity

Interaction Energy

First collisions 2006

TeVs 14

LHC

starts nowTevatron

1100 fbIntegrated Luminosity

Interaction Energy

Data taking 2001-2003

12 fb

TeVs 2

CDF RUN II is a great opportunity to do new physics

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New Physics at the Tevatron

Important for new physics

Produce it

Find it

Identification of objects that make up the signature

Understanding of the calibration and resolution of the detector

Understanding background

With a center of mass energy of 2TeV and an integrated luminosity of in RunII 2001-2003 D0 and CDF will be able to extend searches to new parameter space

12 fb

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Example:”Light Stop search”

)~)(~(~~ 01

0111 ccttpp

)~)(~(~~1111 bbttpp

R-Parity: Quantum number RP

SUSYSM

R SLBP

11

)1( 2)(3

BosonFermionQ

FermionBosonQ

SUSY

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New Physics involving Heavy Flavor Jets

Susy

Heavy Gauge Bosons

Technicolor

Higgs

4. Gen quarks

bt 1

~

1 ct 01

~

1

qqZ ` qqW `bbT 0 cbT

bbH 0

bZb '

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How do we look for it ?

Is there more ?

Signature based searches

SLEUTH

Typically:

Chose model, signature

Backgrounds, model efficiency

Optimize cuts

Data, limit xBR

Limit model param.

Model based search Problem: the number of competing candidate theories is large !

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How do we look for it ?

Typically:

Chose model, signature

Backgrounds, model efficiency

Optimize cuts

Data, limit xBR

Limit model param.

Model based search

A different way:

Chose signature

Study backgrounds

Chose cuts, vary cuts

Efficiencies

Limit xBR

Signature based search

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Signature Based SearchesUnderstanding data rather than what the data has to say about one specific model

Objects of interest

TZWtjetjetcjetb

e

,,,,,,

,,,

Some of the objects can be treated in parallel

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Tracks in a jet fall into 3 categories• decay tracks from heavy hadron• fragmentation tracks• tracks coming from other interactions in the event

Flavor Tagging

CDF has many different specialist algorithms depending on the physics you want to do

To find a jet use information fromthe tracker and calorimeter

Goal:want to identify the particle that created the jet

Understand the jet and identify parameters that can be used to distinguish between them

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Status (Understand Jets)My Event Viewer

Generator (Pythia, Isajet)

Production

Simulation

Analysis Program (modified Secvtx)

Questions• Performance of current jet tagging algorithms• How does a jet look like• What information can be used to distinguish jets

(Monte Carlo sample ) tt

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Conclusions

• The work on the CMS Forward Pixel system was a great experience and will be an enormous help for my future work with vertex detectors• Beam test at CERN was challenging and great learning experience• CDF has the potential to discover new physics• Signature based searches have greater chance of identifying an anomaly in the data• Lots of new physics is expected to produce jets • Flavor-tagging is crucial to distinguish signatures • Looking forward for the first data from CDF