Abstract
Multiple scattering effects of 12 and 20 GeV electrons on 8 and 20 mm thickness carbon targets have been studied with high-resolution silicon microstrip detectors of the UA9 apparatus at the H8 line at CERN . Comparison of the scattering angle between data and GEANT4 simulation shows excellent agreement in the core of the distributions leaving some residual disagreement in the tails.
Highlights
AlignmentThe alignment procedure is based on a recursive algorithm minimizing track residuals
: Multiple scattering effects of 12 and 20 GeV electrons on 8 and 20 mm thickness carbon targets have been studied with high-resolution silicon microstrip detectors of the UA9 apparatus at the H8 line at CERN
In order to compare the multiple scattering on the target with the one expected from the GEANT4 simulation, we describe the x and y projection of the reconstructed scattering angle by a convolution of the detector and target effects: f (θ) = ftelescope(θ) ⊗ ftarget(θ)
Summary
The alignment procedure is based on a recursive algorithm minimizing track residuals. Tracks that have generated a single hit in each sensor are selected and straight line tracks have been defined through the selected planes (1 and 2) in the upstream region. Straight lines are extrapolated to the downstream region (planes 3, 4, 5) to get the expected coordinates and measure hit residuals (defined as differences between measured and estimated positions). Hit residuals are minimized in both views and rotational misalignments (which appear as a correlation between the hit positions in one view and residuals in the other) corrected by an iterative procedure [8]. Residual misalignment in the longitudinal direction, which is more difficult to correct with data, is estimated to be of the order of 1 mm
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