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FD Crosstalk or A disappointing lack of pretty colours

FD Crosstalk or A disappointing lack of pretty colours. Philip Rodrigues Oxford MINOS Meeting 20 May 2008. Why care?. Something wrong with detector modelling in FD:. ND. FD. Affects CC variable:. xtalk +10%. Nominal. Why care? 2. Given low priority by CC group…

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FD Crosstalk or A disappointing lack of pretty colours

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

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

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

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

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

  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

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