1. PROGRESS ON WATER PROPERTIES ON TRACKS RECONSTRUCTION Harold Yepes-Ramirez 09/11/2011

2. Water Model   data sc0.0075 aa09 abs55 sca53 eta0.1790403125997 sc0.01 aa09 abs55 sca41 eta0.178739905997 sc0.02 aa09 abs55 sca22 eta0.178840845997 sc0.01 aa09 abs55 sca41 eta0.116020985997 sc0.02 aa09 abs55 sca22 eta0.02226635997 sc0.0075 aa09 abs63 sca53 eta0.178636655997 sc0.01 aa09 abs63 sca41 eta0.178838415997 sc0.02 aa09 abs63 sca22 eta0.178540325997 sc0.01 aa09 abs63 sca41 eta0.117130545997 sc0.02 aa09 abs63 sca22 eta0.024618445997 DATA/MonteCarlo SELECTION: Data  2008 – 2010 data from the official SeaTray production May 2011 (5997 runs). First run: 31051. Last run: 54244. Lifetime: 618.96 days. MonteCarlo  SoS prepared (C. Bogazzi) with the previous runs (5997 data runs). Mupage for muons + Geasim for neutrinos. MonteCarlo statistics (up to now): sc = scattering centers; aa = om angular acceptance; abs = absorption; sca = scattering; eta = fraction of Rayleigh scattering.

3. SANITY CHECKS WITH PREVIOUS PRODUCTIONS: Harold: It is not a run-by-run simulation. 5997 data runs (2008-2010). 312 mupage muon runs. 90 neutrino + 40 anti-neutrino Geasim files. TE May 2011. Down-going neutrinos not used in this MC. Juan Pablo: Run-by-run simulation. 5997 data runs (2008-2010). 5941 mupage muon runs. 5898 neutrino + 5900 anti-neutrino files. TE September 2010. Down-going neutrinos are used in the r-b-r MC. The  cut at -5.2 remove some muons-neutrinos close to the horizon, not enough affected by JP ones due to large statistics.  > -5.4 relax this zone (SEE NEXT PAGE).

4.  > -5.4 relaxes the zone close to the horizon for neutrinos and muons. Left  My distribution for 2008-2010 data. Right  JP distribution ONLY for 2007-2008 data (CM Amsterdam). Not directly comparable but both distributions have a nice agreement no matter the selected period.

5. UPDATED PLOTS FOR THE NUMBER OF HITS USED IN THE FIT: DISTRIBUTIONS FOR A LARGE MC SAMPLES AND OVERVIEW TO THE WATER MODELS

7. NUMBER OF HITS USED IN THE FIT: Lesson learnt since the CM in Moscow: the extreme scattering models ( sca <22) shows the worst agreement to data: Lower values (~0.02) of contribution of Rayleigh scattering (eta) over-estimates the data, and higher (~0.17) values under-estimates it. The ANTARES site seems to have a large scattering length. Values of abs higher than 55 m could not be an good approach. The ANTARES standard model, works reasonably well specially at nhit<80 where first photons are expected. The uncertainty in the labs for a set of common scattering parameters seems to be less than 20%. The best agreement to data is then expected for large scattering lengths and not enough higher absorption lengths.

8. UPDATED PLOTS FOR THE ZENITH ANGLE CONTRIBUTION: UNCERTAINITY ESTIMATION OF RECONSTRUCTED TRACKS DUE WATER OPTICAL PARAMETERS

11. INFLUENCE OF abs ON RECONSTRUCTED TRACKS: 1.Strategy  For a couple of water models with different labs but same scattering parameters, estimate the difference on the reconstructed track rate  Uncertainty on labs Vs uncertainty on the muon rate. 2.Previous systematic studies in ANTARES (J.A et al / Astroparticle Physics 34, 2010, 179-184, Pag. 182)  “The uncertainty of the light absorption length in water is assumed to be ±10% over the whole wavelength spectrum and yields a variation of ±20% on the number of expected events”. Case 1: Uncertainty on abs : ~13 % (8 m). Uncertainty on muon rate: ~25 % (0.14 Hz). Case 2: Uncertainty on abs : ~13 % (8 m). Uncertainty on muon rate: ~13 % (0.07 Hz).

12. Case 3: Uncertainty on abs : ~13 % (8 m). Uncertainty on muon rate: ~10 % (0.07 Hz). Case 4: Uncertainty on abs : ~13 % (8 m). Uncertainty on muon rate: ~13 % (0.07 Hz). Case 5: Uncertainty on abs : ~13 % (8 m). Uncertainty on muon rate: ~15 % (0.08 Hz).

13. Case 1:   _rate ~25 % UNCERTAINTY ON abs (~13%) and UNCERTAINTY ON MUON RATES: FUNCTION OF ZENITH ANGLE Case 2:   _rate ~13 % Case 3:   _rate ~14 % Case 4:   _rate ~14 % Case 5:   _rate ~14 % UNCERTAINTY ON abs ±13% MEAN UNCERTAINTY  rate ± 15%

14. INFLUENCE OF sca,eff ON RECONSTRUCTED TRACKS: 1.Strategy  Two optical parameters fixed (absorption, eta) and one free parameter (scattering length), for both absorption lengths. Case 1: Uncertainty on sca_eff : ~23 % (51.5 m). Uncertainty on muon rate: ~16 % (0.08 Hz). Uncertainty on sca_eff : ~46 % (81.5 m). Uncertainty on muon rate: ~17 % (0.1 Hz). Uncertainty on sca_eff : ~58 % (133 m). Uncertainty on muon rate: ~31 % (0.18 Hz). Case 1: Uncertainty on sca_eff : ~23 % (51.5 m). Uncertainty on muon rate: ~4 % (0.02 Hz). Uncertainty on sca_eff : ~46 % (81.5 m). Uncertainty on muon rate: ~14 % (0.09 Hz). Uncertainty on sca_eff : ~58 % (133 m). Uncertainty on muon rate: ~17 % (0.11 Hz). UNCERTAINTY ON sca_eff [23-58]% UNCERTAINTY  rate [4-17]%

15. INFLUENCE OF  ON RECONSTRUCTED TRACKS: 1.Strategy  One optical parameters fixed (absorption) and two free parameters (scattering length and eta), for both absorption lengths. Case 1: Uncertainty on  : ~35 % (0.06). Uncertainty on muon rate: ~13 % (0.06 Hz). Uncertainty on  : ~81 % (0.09). Uncertainty on muon rate: ~2 % (0.01 Hz). Uncertainty on  : ~88 % (0.15). Uncertainty on muon rate: ~15 % (0.07 Hz). Case 1: Uncertainty on  : ~35 % (0.06). Uncertainty on muon rate: ~2 % (0.01 Hz). Uncertainty on  : ~81 % (0.09). Uncertainty on muon rate: ~2 % (0.01 Hz). Uncertainty on  : ~88 % (0.15). Uncertainty on muon rate: ~4 % (0.02 Hz). UNCERTAINTY ON  [35-88]% UNCERTAINTY  rate [2-4]%

16. CONCLUSIONS/COMMENTS: 1.For the water models different to the “standard water model” a bug was founded, a factor scale of ~15 % was not applied, now the correct ones are running. So, for the preliminary comparison such water models have to be considered with a 15% less events. The preliminary “comments in boxes” as a kind of conclusions on the slides, are referred to the expected results. 2.Preliminary and raw results point that, for the current physics conditions simulated in the ANTARES KM3 code (whichever they are), the impact of water parameters could be summarized as follow (  = uncertainty): 3.The effective scattering length seems to be the most relevant parameter. These uncertainties could be more lower if we consider that scattering lengths less than 22 m are not possible in ANTARES site. Data/MC agreement could mainly come from other systematics? 4.Once the corrected data sample is going to be ready, the analysis will be done once again and it will prove the preliminary and raw conclusions. 5.A first look on effective areas and angular resolution will be performed. 6.An internal note will be prepared with a dedicated description of the analysis. Parameter  abs [%]  sca_eff [%]   [%]   rate [%] Absorption length±13±15 Effective scattering length±58±17 Rayleigh scattering±88±4

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