Tracker Alignment Gammaray Large Area Space Telescope Michael

Tracker Alignment Gamma-ray Large Area Space Telescope Michael Kuss INFN Pisa Analysis Group Meeting 20 June 2005

selecting tracks 2 Analysis Group Meeting, 20 June 2005 Michael Kuss

Residual r->Draw. Residual(”X 5”, ”abs(h_abs-h_abs_ext)<1”) horizontal displacement: 59 m 3 Analysis Group Meeting, 20 June 2005 Michael Kuss

Residuals vs. slope (horizontal and vertical alignment) r->Draw. Res. Slope(”Y 9”, ”abs(h_abs-h_abs_ext)<1&&abs(inv. Slope)<1”) real position X 3 X 2 X 1 ideal position res = x + z · cot( ) Aligns: • horizontal ( to strips) • vertical 4 Analysis Group Meeting, 20 June 2005 Michael Kuss

Residuals vs. slope of track (all planes) r->Draw. Res. Slope. All() 5 Analysis Group Meeting, 20 June 2005 Michael Kuss

How To Alignment is an iterative (and before RA v 8 r 4 time consuming) process. • run with 10 k events till convergence (how do I know it converged? ) • run with 20 k events till convergence • run with 50 k events till convergence • run with 100 k events till convergence. Usually, about 5 iterations are needed, each 6 min CPU (before: 1 h). 6 Analysis Group Meeting, 20 June 2005 Michael Kuss

Alignment Blindness Attention Alignment is blind versus: • translation • shearing • vertical scaling (horizontal is fixed by strip dimensions) • rotation • twist (? ) • translation of one view vs. the other • rotation of one view vs. the other After every iteration, separately in each view, I “correct” for: • ∑posh = 0 (horizontal translation) • ∑posh 2 min. (shearing) • ∑(posv-posv, ref) = 0 (vertical translation) • ∑(posv-posv, ref)2 min. (vertical scaling) • ∑rotz = 0 (rotation around z) 7 Analysis Group Meeting, 20 June 2005 Michael Kuss

Alignment results 8 Analysis Group Meeting, 20 June 2005 Michael Kuss