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Sensor planarity study(pogress report)

V. Karimäki

Project meeting

Helsinki 03.03.2009

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Recall the basic idea

Q: track impact point at planar sensorP: true impact point at curved sensor near the true hit positionQ': point where our flat detector model assumes the hit lies

Departure from planarity causes a systematic offset:

u = (du/dw)*wP

du/dw=t1/t3 from track direction t = (t1,t2,t3)

Our CMSSW detector model: planar sensors (w=0)

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Hit correction for non-planarity

Corrected u-coordinate: uc = uh - u = uh - (t1/t3)*w [1]

So preserve the detector model, but

do correction

From [1]:

w=(t3/t1)* u

For fixed position (u,v):

w=<(t3/t1)*u> [2]

So systematics (u) in residuals give an estimate of w

i.e. the surface coordinates, computing [2] in bins

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Sensor curvature can be studied

1. Parametrizing shape: w=au2+buv+cv2 and fitting a,b,c

2. Model independent sensor shape by plotting mean residuals weighted with

(t3/t1) as a function of u,v

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Verification with Monte Carlo

Parameterized surface Fitted surface

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Model independent surface shape

By plotting weighted uncorrected mean residuals

Here MC

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Sensor shape study in cosmics

CRAFT data CMSSW TOB and TIB so far Begin with non-aligned data Pick up a few sample modules

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Residuals profile, uncorrected

v [cm]

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Residuals profile, corrected

v [cm]

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1

Residuals, uncorrected, a TOB mod

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1

Residual correction for non-planarity

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1

Corrected residual

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1

Sensor shape, example

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1

Summary

By simple Monte Carlo:Demonstrated method to fit sensor shapeMethod to correct hit positionsDemonstrated model independent way to

look for possible sensor curvatureCosmics: First studies using TOBNo significant effects so far Further studies with many more modules