1. FD Crosstalk or A disappointing lack of pretty colours Philip Rodrigues Oxford MINOS Meeting 20 May 2008

2. 2 Why care? Something wrong with detector modelling in FD: FD ND Affects CC variable: Nominal xtalk +10%

3. 3 Why care? 2 Given low priority by CC group… …but nue particularly sensitive to detector modelling: –Eg docdb 4578: 10-20% change in selected events with 35% xtalk change

4. 4 Method Want prob. that “true” hit on pixel j creates xtalk hit on pixel i: Ideally, identify xtalk hits and true hits. Only possible on test stand Best idea so far: –hits <3pe are used as xtalk –track hits >3pe as “true” hits In principle, mismodelling P(true) cancels(?), but err on the side of conservatism

5. 5 More method Use cosmics for high stats Restrict to few hits in plane by requiring dcosz > 0.6 Require 10 strips in event, no shower Daikon 03 MC, MC and data reco’d with cedar_phy_bhcurv Loop over all strips in detector Try using muxing pattern to separate out xtalk and physics

6. 6 (De)Muxing Tubes 0,2: Crosstalk + Physics Tube 1: Crosstalk only

7. 7 Sanity Check – no-xtalk MC Reco some MC cosmics without crosstalk Should get zeros everywhere: Don’t get zeros. Significant physics contribution Only small differences between tubes

8. 8 Vetoing Physics Assume physics modelling entirely correct, then: and xtalk scale factor is:

9. 9 Result Generally NN high, diag low in data, but not entirely Some differences between 1 and 0,2 Errors are still a bit big (~0.02 in NN, 0.1 in diag) Working on more stats

10. 10 Result 2 Histogram values in NN and diagonal pixel pairs NN about 1, diag about 1.3

11. 11 Provisional Conclusions and TODO NN crosstalk about right, diag too low –~Same conclusion as nue group Further checks: –Alter cuts, check numbers come out the same TODO: –Rerun with increased stats –Use scale factors in DetSim crosstalk model