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Km3-realted issues

Km3-realted issues. MC WG meeting 26-10-2012. Angular Efficiency. How is angular efficiency calculated in km3? PMT effective are in km3: 0.9 x A_0 x Q.E.(lambda) x ang_eff (theta) x abs(lambda) A_0: raw effective area: pi r^2 = 438.2513 cm^ 2 0.9: ‘front-on’ efficiency factor

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Km3-realted issues

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  1. Km3-realted issues MC WG meeting 26-10-2012

  2. Angular Efficiency • How is angular efficiency calculated in km3? • PMT effective are in km3: • 0.9 x A_0 x Q.E.(\lambda) x ang_eff(\theta) x abs(\lambda) • A_0: raw effective area: pi r^2 = 438.2513 cm^2 • 0.9: ‘front-on’ efficiency factor • Q.E.(\lambda): quantum efficiency • Ang_eff(\theta): angular efficiency • Abs(\lambda): absorption of gel and glass

  3. Comparison w GEANT • 410 nm simulations: • In km3, transmittivity at 410 nm is 96.3%! • Normalisation: 400 cm^2 vs 438.25 cm. • Is Q.E. the same? • Which is correct? GEANT sim Trasmissivity (gel+glass) Coll. efficiency Aeff= 438.25 cm2 * 0.9 * 0.9653* QE (=0.2314 ) KM3 Aeff= Effective area in KM3 MC = 400 cm2 * 0.9 * 0.95 * QE

  4. Absorption of Benthos glass The absoprtion spectra used for glass are different! Where do the NIMA values come from? NIMA paper P.Amram et al., Nucl. Instrum. Meth. A484 (2002) 369-383 ANTARES-OPMO-1998-001.pdf

  5. Effective Area: Comparison KM3 – GEANT4 Angular acceptance=1 Trasmissivity (gel+glass) Coll. efficiency Aeff= Effective area in KM3 MC = 400 cm2 * 0.9 * 0.95 * QE •  = Flux of impinging photons [N/cm2] • In KM3 MC: N - detected(KM3) = *Aeff • In GEANT4: generated flux  N- detected(GEANT4-final)= N- detected(GEANT4)*0.9 • N - detected (GEANT4-final)=1.03 * N - detected(KM3) Collection efficiency of photoelectrons (not considered in GEANT4) Good agreement between GEANT4 and km3 NOW 1.03*400/438*0.965/0.95 ~ 0.955 According to NIM paper one should consider also ~ 4% less efficiency due to  metal wires . metal wires is not considered either In GEANT4 either in km3

  6. Outstanding questions • What is the correct glass absorption parameterisation? • What is the correct effective area in the forward direction? • Why does GEASIM calculate a too-low forward acceptance? • Does any of this matter?

  7. Km3 v4r5 • Very short update to v4r4 • Default Aug 2012 angular acceptance (was nov 2011) • Default x4 track merging distance (was x2) • Release once above problems get sorted • Compare with rbr v2 (v4r2, nov11 acceptance) • What do we get?

  8. All muon track events

  9. Interesting region (cumulative plot)

  10. Ratio (more interesting) v4r5/rbr v2

  11. Conclusions • V4r4/v4r5 predicts less lambda < -6 events than rbr v2 (v4r2) • This is for both up- and down-going muons (have not cut on misreconstructedmuons yet, but Vlad has enabled this) • Effects on analysis? • Shift lambda cuts 0.1 downwards • Perhaps not very much

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