March 3, 2009 V.Karimäki, Sensor planarity 1 1 Sensor planarity study (pogress report) V. Karimäki Project meeting Helsinki

March 3, 2009 V.Karimäki, Sensor planarity 2 1 Recall the basic idea Q: track impact point at planar sensor P: true impact point at curved sensor near the true hit position Q': point where our flat detector model assumes the hit lies Departure from planarity causes a systematic offset:  u = (du/dw)*w P du/dw=t 1 /t 3 from track direction t = (t 1,t 2,t 3 ) Our CMSSW detector model: planar sensors (w=0)

March 3, 2009 V.Karimäki, Sensor planarity 3 1 Hit correction for non-planarity  Corrected u-coordinate: u c = u h -  u = u h - (t 1 /t 3 )*w[1]  So preserve the detector model, but do correction  From [1]: w=(t 3 /t 1 )*  u  For fixed position (u,v): w= [2]  So systematics (  u) in residuals give an estimate of w i.e. the surface coordinates, computing [2] in bins

March 3, 2009 V.Karimäki, Sensor planarity 4 1 Sensor curvature can be studied 1.Parametrizing shape: w=au 2 +buv+cv 2 and fitting a,b,c 2.Model independent sensor shape by plotting mean residuals weighted with (t 3 /t 1 ) as a function of u,v

March 3, 2009 V.Karimäki, Sensor planarity 5 1 Verification with Monte Carlo Parameterized surface Fitted surface

March 3, 2009 V.Karimäki, Sensor planarity 6 1 Model independent surface shape  By plotting weighted uncorrected mean residuals Here MC

March 3, 2009 V.Karimäki, Sensor planarity 7 1 Sensor shape study in cosmics  CRAFT data  CMSSW  TOB and TIB so far  Begin with non-aligned data  Pick up a few sample modules

March 3, 2009 V.Karimäki, Sensor planarity 8 1 Residuals profile, uncorrected v [cm]

March 3, 2009 V.Karimäki, Sensor planarity 9 1 Residuals profile, corrected v [cm]

March 3, 2009 V.Karimäki, Sensor planarity 10 1 Residuals, uncorrected, a TOB mod

March 3, 2009 V.Karimäki, Sensor planarity 11 1 Residual correction for non-planarity

March 3, 2009 V.Karimäki, Sensor planarity 12 1 Corrected residual

March 3, 2009 V.Karimäki, Sensor planarity 13 1 Sensor shape, example

March 3, 2009 V.Karimäki, Sensor planarity 14 1 Summary By simple Monte Carlo:  Demonstrated method to fit sensor shape  Method to correct hit positions  Demonstrated model independent way to look for possible sensor curvature Cosmics:  First studies using TOB  No significant effects so far  Further studies with many more modules