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Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

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Page 1: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

Testbeam Studies of the LHCb Vertex Locator Modules

Lisa Dwyer

Page 2: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

2

Overview

Vertex Locator

Testbeam overview

Cluster analysis

Page 3: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

3

LHCb VeLo

Page 4: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

4

Testbeam overview Data taken with 10 production

modules Capability to read out 6 Cooling and electronics used in final

experiment Check response of modules My analyses:

Signal to Noise ratio Clusters

Page 5: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

5

Cluster analysis Fraction of two strip clusters Ratio of charge Crosstalk

Zero suppressed data Zero degree tracks Clusters on tracks Look at R and Phi

sensors separately

Page 6: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

6

Phi sensor

Inner strip pitch35.5μm – 78.3μm

Outer strip pitch39.3μm – 96.6μm

Page 7: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

7

Fraction of two strip clusters

Fraction of two strip clusters as a function of pitch

Expect similar fractions of two strip clusters in each sensor

Page 8: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

8

Possible causes for distribution

Noisy strips X All noisy strips removed

Operational settings X

Crosstalk ? Charge sharing between strips Alters the actual number of two strip

clusters

Page 9: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

9

Readout trace

Oscilloscope trace of chip readout Output in voltage and time

Header information

Data from chip

Page 10: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

10

Phi sensor readout – software strip

Inner regionStrip 0

Inner regionStrip 682

Outer regionStrip 683

Outer regionStrip 2047

Page 11: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

11

Phi sensor readout - Hardware channel

0 (682)1 (2046)2 (2047)3 (2045)

4 (681)5 (680)6 (2044)

7 (2043)8 (2042)

9 (679)10 (2041)11 (2040)

12 (678)13 (2038)14 (2039)15 (2037) 16 (677)

17 (676)

Outer strips Inner stripsHW

HWSW

SW

Crosstalk in hardware channel

adjacent

4 apart

3 apart

Page 12: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

12

Measuring crosstalk Look at two strip clusters Look at ratio of charge Check if crosstalk is asymmetric

Ratios > 1 Earlier >Later Later > Earlier

Comparison between testbeam data and simulation

Crosstalk found to be asymmetric

Page 13: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

13

Data shows asymmetry No asymmetry in simulation

Simulation accounts for crosstalk on sensor but not in cables

Page 14: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

14

Crosstalk simulation

Simulate testbeam events in MC Add noise and smear data (hardware

channel order) Re-cluster (software strip order) Compare results to data

Page 15: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

15

Smearing data To model crosstalk Smearing formula:

Negative f & g values → charge sucked in from neighbouring strips

Positive f & g values → charge dispersed to neighbouring strips

jjijjiinew gadcfadcgf

adcadc1

1

Page 16: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

16

Effects of f & g

f

f

g

g

Page 17: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

17

Effect of f Negative f f=-0.2

Positive f f=0.2

Smeared

Not smeared

Page 18: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

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Phi sensor data

Before smearing With best fit

f=-0.2+0.05-0.02

g=-0.22+0.04-0.08

Page 19: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

19

Conclusion and outlook Adjacent channels

f=-0.2 +0.05-0.02

g=-0.22 +0.04-0.08

Channels separated by 3 f = -0.12 +0.02 -0.06

g = -0.1 +0.06 -0.01

Obtain smearing factors (f & g) for all modules Use smearing factors to remove crosstalk from data Re-calculate signal to noise Prepare J/ψ analysis for first physics at LHC

Page 20: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

Back up

Page 21: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

21

Signal to Noise ratio Theoretical value for 300μm

Silicon sensor is 28 S/N for R sensors 21.7 – 29.4 S/N for Phi sensor 22.8 – 27.7

NoiseSignal

Page 22: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

22

Crosstalk simulation

SW

SWHW

HW

Page 23: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

23

Noisy Strips

Page 24: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

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Clustering process Use standard algorithm Looks for strip with ADC value > 10 Then looks at adjacent strips ADC value >5

Produces 1, 2 and 3 strip clusters If two strip cluster consider its neighbouring

strips Produces 2, 3 and 4 strip clusters

Page 25: Testbeam Studies of the LHCb Vertex Locator Modules Lisa Dwyer

17/12/2007 Lisa Dwyer - Liverpool HEP Christmas meeting 2007

25

Results

Module f g

M30p adjacent -0.2 +0.05 -0.02

-0.22 +0.04 -0.08

M30p 3 apart -0.12 +0.02 -0.06

-0.1 +0.06 -0.01

M31p adjacent +0.12 +0.005 -0.01

-0.28 +0.01 -0.02

M31p 3 apart -0.16 +0.04 -0.05

-0.18 +0.04 -0.02

M30p –least affected by crosstalkM31p –most affected by crosstalk