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Reconstruction of the SC with rime

Reconstruction of the SC with rime. Dmitry Chirkin, LBNL. SC event sample cuts. distance from COG: poorly reconstructed cascades (e.g., muon events) are pushed far away log likelihood difference of cascade and track reconstructions energy part or llh (Phit-Pnohit).

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Reconstruction of the SC with rime

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  1. Reconstruction of the SC with rime Dmitry Chirkin, LBNL

  2. SC event sample cuts • distance from COG: poorly reconstructed cascades (e.g., muon events) are pushed far away • log likelihood difference of cascade and track reconstructions • energy part or llh (Phit-Pnohit)

  3. Cuts and reconstructed energy • 100% laser intensity run • cascade peak is well selected as seen from both energy and Nch distributions • reconstructed energy is log(8.76)/81 cm^2/137000 = 0.52 PeV

  4. Why Nch distribution is so wide

  5. Positional resolution

  6. Positional reconstruction accuracy

  7. All runs: summary

  8. Linearity at high Q

  9. Systematic errors, or charge reweighting • Too much emphasis is given the saturated DOMs • Remove DOMs above saturation charge from energy llh • assign them systematic errors instead of sqrt(N) Poisson • still correct charge below and close to saturation • Apply the systematic error “belt” to the probability function • for 1 d(ln f) error distribution and small systematic errors analytic approximation is possible • for 1 df distribution solution is terms of a difference of incomplete gamma functions (still computationally difficult) • may need to compute integrals numerically • a hybrid approach is possible with systematic errors larger in the intermediate distance region or for charges close to saturation

  10. Laser prepulsing • a signal component correlated with the main pulse, some 300 ns before • this is larger than the PMT transient time – due to fast decay states or circuit LED light leaking out? • While the prepulse is cleaned away by the FeatureExtractor (it’s under 5% of the main pulse), the charge estimate is incorrect

  11. 100%, 50%, 76%, 50%, 25%, 5%, 0.5% Corrected energy estimate 50%, 5%, 0.5%

  12. Laser energy linearity

  13. Laser energy estimate • Cascade: 1.37 105 photons/GeV  • PMT efficiency / glass transparency at 337 nm at 40% of max • at 0.5%: 10^7.3 m^2 / (81 cm^2 * 40%) = 6.16 10^9 photons • corresponds to energy of N/137000 = 45 TeV • scaling up 200 times: at 100% N = 1.23 10^12; E=9 PeV • while N agrees with expectation, E is somewhat smaller •  different conversion factor?

  14. Summary • Charge is underestimated due to a large emphasis on saturated PMT signal  somewhat correctable by removing oversaturated DOMs from energy llh, still needs better Ellh • deficiency in the flux function is somewhat repaired by adding systematic error consideration to the calculation • At 5 DOMs away from the laser the charge is proportional to the power percentage setting • At 0.5% the laser output is equivalent to a 45 TeV cascade • Therefore, at 100% the laser output is equivalent to a cascade of energy 9 PeV, still much less than 100 PeV • this is still much better than direct estimate: 1.5 PeV

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