Tracker Misalignment Study David Forrest CM23 HIT, Harbin January 14 th

Misalignment Study Misaligning the downstream tracker only (so trying to maximise the relative displacement) Translational and rotational misalignments: 10mm, 3mrad and 10mm+3mrad all in X and Y separately Previously presented this study for independent Monte Carlo simulations Study repeated here for same Monte Carlo seeds to separate out statistical error (next presentation) 10,000 events; Step VI; G4MICE on Grid with Ganga job submission software

Beams I used 1.5, 2.5, 4.0, 6.0 and 8.0 pi mm beams and will present results from those here I still have a few problems understanding behaviour of 10pi beam. Initially, I had too much cooling (~20%, suggesting scraping). After checking particle cuts I know observe too little cooling (~8%). Need to check conditions in simulating a realistic well behaved 10pi beam using the Matcher + Simulation Can also generate beam from Analysis code using input covariance matrix to compare to beam from matcher (ongoing)

10mm x

10mm y

3mrad x

3mrad y

10mm + 3mrad X

10mm + 3mrad Y

As a function of beam

Results Table Shorthand for misalignments x10 – 10mm in X, y10 – 10 mm in Y, x0r3 – 3mrad in X, y0r3 – 3mrad in Y, x10r3 – 10mm in Y and 3 mrad in Y, y10r3 – 10mm in Y and 3mrad in Y

Tracker Alignment Requirements for Fractional Emittance We want to quote fractional drop in emittance with 1% error. We would like for misalignment to make a negligible contribution to this error. Hence requirement is that misalignment contribute < 0.1% to error (could relax this requirement to 0.3% if we add misalignment error in quadrature with statistical error)

Tracker Alignment Requirements for Fractional Emittance Translation: 10 mm displacements cause ~1% errors. To achieve <0.1% error due to alignment then requirement is ~1 mm alignment tolerance* Rotation: 3 mrad rotations cause <1% errors (max error 0.928% in 2.5pi beam). To achieve <0.1% error due to alignment then requirement is 0.3 mrad error* * 10mm in y for 6pi beam caused 1.44% change, which suggests a stricter 0.7 mm tolerance*

Conclusions Repeated misalignment study using simulations with same Monte Carlo seeds to separate statistical effects Tentative alignment requirements for relative misalignment of the trackers: Translation: ~ mm Rotation: ~ 0.3 mrad

Future Work Will go to RAL, finish this study with live input from Chris R to sort out remaining problems with 10 pi beams: understanding beam from matcher and beam from covariance matrix and other odd behaviors, etc. Final results can feed into a MICE note