1

Silicon Detector Design Study Tracking Analysis Program for the International Linear Collider

Pelham Keahey

Richard PartridgeSULI 2008

2

International Linear Collider (ILC)

Graphic courtesy of ILC / form one visual communication

3

SiD Detector Concept Design

Graphic courtesy of Norman Graf, SLAC/Sandbox Studio

4

Analysis Program Objectives

• Develop a program(s) to:• Display and analyze pull distributions of five

helix parameters• Track purity and the fake track rate• Track finding Efficiency

5

Helix Parameters

• ω - curvature of the track• δ -distance of closest approach (dca)• Ф0 -azimuthmal angle of the momentum at

the dca• tan λ -dz/ds, slope in the sz plane• z0 -z position at the dca

6

Helix Parameter Calculations• ω

• δxc = x + R sin fyc = y - R cos f

δ = R - (xc2 + yc

2)1/2

• Ф0

• tan λ tan λ = pz / (px

2 + py2)1/2

• z0z = z0 + s tanl

)arctan(0c

c

yx

-=f

)sin(0003.1

==p

qBR

z

7

Pull Distributions

rFittedErroValueSimulationeFittedValu )( -

•Error is different per fitted helix (track)• Tracks will go through different part of the detector• Multiple scattering• How many hits

8

Z0 Pull Distribution

9

Purity—FakeTrack Rate

• Purity is taking the hits used to create a track and determining how many of those hits are actually from the MCParticle’s path being fitted

• For the Z0 events the tracking program produced no fake tracks. Fake Tracks are defined as having a purity less than 0.5

10

(1-Purity) vs Hits

11

Efficiency

• Efficiency is calculated by taking the number of found tracks divided by the number of tracks that could have been found

• The simulation is currently setup to ignore certain particles

• Pt<1.1 GeV (particle that doesn’t enter the calorimeter)

• Also if z0 > 9 mm and a δ > 9 mm• 7 hits minimum

12

Efficiency vs Theta

13

Efficiency vs Pt

14

Wire View One (Rho-z) event # 130

15

Wire View Two (xy) event # 130

16

Results

• Purity: Tracks can be expected to be pure around 96.4+-0.2% of the time, depending on event.

• In the Z0 we found no tracks below the 0.5 purity margin.

• Efficiency: During the same event 98.6±0.1% of the findable tracks were found.

17

Future Work

• As the detector evolves, different designs can be tested

• Different and more complicated events can be run

18

Acknowledgements

• Advisor: Richard Partridge• life saving help: Cosmin Deaconu• Everyone at SLAC• DOE

19

ReferencesJ. Alcaraz, Helicoidal tracks. L3 Internal Note 1666, February 18, 1995.

Internation Linear Collider website. http://www.linearcollider.org/cms/