Advanced Method for Pixel Stand-Alone Alignment

1. Project meeting Helsinki 31.03.2009 Pixel stand alone alignment statusV. Karimäki, T. Lampén

2. Outline • Recall the problem • Simultaneous vertex and track fit • vertex contraint (unknown position) • beam spot constraint (average position known)

3. Basics - recall • Problem inPixel stand alone alignment: short tracks, curvature purely measured • Evoke the idea presented earlier by us: • take curvature from full tracker reconstruction • use then only Pixel hits for alignment • Feasibility of the idea was studied: Curvature precision requirements for Pixel alignment • So fixing curvatures for Pixel alignment ok

4. Relevant formulas

5. Outline of the algorithm • Full tracker reconstruction • Choose tracks for Pixel alignment • Fix curvatures obtained by full tracker fit • Use pure helix: • B (almost) uniform in Pixel region • material budget smallest in Pixel region • Vertex constraint (tracks from one point) • Seed the new residuals to the HIP algo

6. Status of the work • “Toy” Monte Carlo ready to prove the concept: • Helix: circle in xy (VK), straight line in sz (TL) • Helix + VX constraint: (2+N)*(2+N) matrix Inversion (N = number of tracks) • Pull distributions fine • Start then implementation to the HIP alignment framework

7. Pull distributions