1. PROGRESS ON WATER PROPERTIES ON TRACKS RECONSTRUCTION H Yepes -Ramirez IFIC (CSIC – Universitat de València) ANTARES Collaboration Meeting Strasbourg, November 21 st -25 th, 2011

2. OUTLINEOUTLINE ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 2 Brief reminder of light propagation in sea water: Brief reminder of light propagation in sea water: ANTARES Monte Carlo model Simulation: Simulation: data selection, absorption and scattering length inputs and codes Selected results Conclusions and outlook Brief reminder of light propagation in sea water: Brief reminder of light propagation in sea water: ANTARES Monte Carlo model Simulation: Simulation: data selection, absorption and scattering length inputs and codes Selected results Conclusions and outlook

3. Brief reminder of light propagation in sea water 3

4. ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 4 Scattering phase function (  ) Morel and Loisel approach  Molecular scattering ( Rayleigh )  Isotropic ( =0)  = contribution of Rayleigh scattering  Particle scattering ( Mie )  Strong forward peaked ( Mie =0.924) Attenuation Length (COLIMATED BEAM) Effective Attenuation Length (ISOTROPIC SOURCE) Absorption length Scattering Length Scattering length wavelength dependence (Kopelevich parameterization) b = scattering coefficient. v s, v l = scattering centers. = Average cosine of the global distribution Petzold values for particle scattering

5. SimulationSimulation 5

6. SimulationSimulation ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 6 DATA/MonteCarlo SELECTION: Data  2008 – 2010 data from the official SeaTray production May 2011 (5997 runs). First run: 31051, Last run: 54244. Subsample from Point Sources data from Juan Pablo analysis (2007-2010). Lifetime: 618.96 days. MonteCarlo (no run-by-run)  SoS prepared (C. Bogazzi) with the previous subsample (5997 data runs). Mupage for muons + Geasim for neutrinos. Statistics hugely increased from CM Moscow (two runs per water model: 2, 2 -, 2  ), right now: Water Model   data sc0.0075 aa09 abs55 sca53 eta0.1790403125997 sc0.01 aa09 abs55 sca41 eta0.1787393125997 sc0.02 aa09 abs55 sca22 eta0.1788403125997 sc0.01 aa09 abs55 sca41 eta0.1160203125997 sc0.02 aa09 abs55 sca22 eta0.022263125997 sc0.0075 aa09 abs63 sca53 eta0.1786363125997 sc0.01 aa09 abs63 sca41 eta0.1788383125997 sc0.02 aa09 abs63 sca22 eta0.1785403125997 sc0.01 aa09 abs63 sca41 eta0.1171303125997 sc0.02 aa09 abs63 sca22 eta0.0246183125997 sc = scattering centers; aa = om angular acceptance; abs = absorption; sca = scattering; eta = fraction of Rayleigh scattering.

7. SimulationSimulation ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 7 Water models are selected based on: Three models with the same  value and different scattering spectrum for a given absorption length. Three models with different  values, but  is computed in such a way that the three models will have the same effective scattering length at 470 nm, for a given absorption length. OM Angular acceptance of June 2009 (Genova Meeting 2009).

8. SimulationSimulation ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 8 GEN WATER MODEL: Photon tables production (water tables)  Water tables (hbook files) + Description files (ASCII files). HIT OM PARAMETERS: Hit probability computation from the water tables for a given OM parameters  Hit tables (hbook files) + Description files (ASCII files). KM3 SIMULATED EVENTS: GEOMETRY + KINEMATICS Physics events reading and OM hits production based on event geometry and hit probability tables  Detector events: Signal hits (muons, not tracks from hadronic showers), physical background. GEASIM MCEW TE RECO SIMULATIONS OF ATMOSPHERIC NEUTRINO INTERACTIONS. Process (and evaluation) tracks from particles coming from the hadronic showers (also muons from KM3). TRANSLATION OF INFO ASCII FILES INTO ROOT FORMAT. FORMAT CONVERSION TO “LOOK LIKE DATA”: electronics smearing effects (calibration, ARS response) and optical background. RECONSTRUCTION: Reconstruction of track direction (AAfit) and ntuples information arrangement as number of hits, zenith distribution…(AntDST). Simulation chain:

9. SimulationSimulation ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 9 Main options and software versions in muons and neutrinos simulation: CODE/INPUTOPTIONS/VERSIONS GENv3r7 HITv3r7 KM3v3r7 DETECTORr12_c00_s01 GEASIMv4r10 MCEW2011-01-27 TriggerEfficiencyGaussian ARS threshold file: threshold_gaus_0.33_0.08_0.1.txt SoS file: noise_basic_harold_new.root (based on data subsample) -n 10000000 –t 104.858 –C3 – p 0.035 -t 104.858  Frame time in ms. To determine the number of background hits to be generated in case the summary data are used. -C3  Hit generator type: 3, Gaussian, according observed charge distribution, with time- dependent contribution of after pulses. May 2011 version Aafitv0r9 AntDSTv1r2p3

10. SimulationSimulation ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 10 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. Run-by-run simulation. 5997 data runs (2008-2010). 5941 mupage muon runs. 5898 neutrino + 5900 anti-neutrino Geasim files. TE September 2010. Down-going neutrinos are used in the run-by-run MC.  >-5.2 removes some events close to the horizon (my sample),  > -5.4 relax this zone (SEE NEXT SLIDE) Sanity check with the official production (sc0.0075 aa09 abs55 sca53 eta0.17): My productionOfficial production

11. SimulationSimulation ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 11 A restrictive cut at  > -5.2 removes neutrinos and muons near the horizon (and some muons below the horizon). This may have a large impact on this analysis due to the smaller statistics (concerning the run-by-run MC statistics). If we relax the cut to  > -5.4 the agreement to data is better within the different available samples (typical cut on point sources analysis before run-by-run MC). ±[31-43]%  [-1, -0.1] ±25% [>0.2] ±45%  [-0.1, +0.1]

12. Selected Results

13. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 13 Lesson learnt since the CM in Moscow: extreme scattering models ( sca < 22 m) gets worst agreement to data: Higher values ( ≈ 0.17) of contribution of Rayleigh scattering (  ) under-estimates the data, however it is not clearly seen for lower values ( ≈ 0.17). Values of abs > 55 m could not be an good approach. The best agreement to data is then expected for large scattering lengths and not enough higher absorption lengths. The ANTARES site seems to have a large scattering length.

14. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 14 DATA/MC rates for zenith angle distribution: Lowest effective scattering lengths can be discarded (< 100 m). Contribution of Rayleigh scattering seems to be lower. sca = 22 m &&  = 0.02 && abs = 55 m fit better to data, overall at neutrino region.

15. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 15 DATA/MC rates for zenith angle distribution: abs ≈ 63 m is not enough clear to be discarded. Lowest effective scattering lengths can be discarded (< 100 m). Contribution of Rayleigh scattering seems to be lower.

16. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 16 Influence of abs on reconstructed tracks: 1.Strategy  For a couple of water models with different abs but same scattering parameters, estimate the difference on the reconstructed track rate  Uncertainty on abs 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”. Muons uncertainty (   _rate )  abs ≈ 13% (8 m)   _rate ≈ 13% (0.06 Hz) Neutrinos uncertainty (  _rate )  abs ≈ 13% (8 m)  _rate ≈ 10% (0.0003 Hz) CASE 1

17. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 17 Muons uncertainty (   _rate )  abs ≈ 13% (8 m)   _rate ≈ 14% (0.07 Hz) Neutrinos uncertainty (  _rate )  abs ≈ 13% (8 m)  _rate ≈ 8% (0.0002 Hz) Muons uncertainty (   _rate )  abs ≈ 13% (8 m)   _rate ≈ 11% (0.06Hz) Neutrinos uncertainty (  _rate )  abs ≈ 13% (8 m)  _rate ≈ 6% (0.00015 Hz) CASE 2 CASE 3

18. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 18 Muons uncertainty (   _rate )  abs ≈ 13% (8 m)   _rate ≈ 15% (0.07Hz) Neutrinos uncertainty (  _rate )  abs ≈ 13% (8 m)  _rate ≈ 26% (0.00055 Hz) Muons uncertainty (   _rate )  abs ≈ 13% (8 m)   _rate ≈ 13% (0.06Hz) Neutrinos uncertainty (  _rate )  abs ≈ 13% (8 m)  _rate ≈ 60% (0.0008 Hz) CASE 4 CASE 5

19. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 19  THE UNKNOWLEDGE ABOUT ABSORPTION LENGTH FOR DIFFERENT WATER OPTICAL PARAMETERS HAS AN IMPACT ≈ 13% ON AVERAGE ON THE RECONSTRUCTED MUON RATE  Case 1:   _rate ≈ 13 % Case 2:   _rate ≈ 14 % Case 3:   _rate ≈ 11 % Case 4:   _rate ≈ 15 % Case 5:   _rate ≈ 13 %

20. Case 1:  _rate ≈ 10 % Case 2:  _rate ≈ 8 % Case 3:  _rate ≈ 6 % Case 4:  _rate ≈ 26 % Case 5:  _rate ≈ 60 % NEUTRINO RATES: UNCERTAINTY ON abs ≈ 13% UNCERTAINTY rate ≈ [6-60]% Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 20 RECONSTRUCTED NEUTRINO RATE IS VERY SENSITIVE TO THE RAYLEIGH SCATTERING CONTRIBUTION GIVING A UNCERTAINTY BETWEEN [26- 60]%. TAKING INTO ACCOUNT THAT EXTREME SCATTERING MODELS ARE DISCARDED, THE UNCERTAINTY ON NEUTRINO RATES DUE TO THE UNKNOWLEDGE OF ABSORPTION LENGTH COULD BE LESS THAN THE 26%.

21. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 21 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. UNCERTAINTY ON sca_eff [23-58]% UNCERTAINTY  rate [5-16]% Uncertainty on sca_eff : ≈ 23 % (51.5 m). Uncertainty on muon rate: ≈ 5 % (0.02 Hz). Uncertainty on sca_eff : ≈ 46 % (81.5 m). Uncertainty on muon rate: ≈ 12 % (0.06 Hz). Uncertainty on sca_eff : ≈ 58 % (133 m). Uncertainty on muon rate: ≈ 16 % (0.08 Hz). Uncertainty on sca_eff : ≈ 23 % (51.5 m). Uncertainty on neutrino rate: ≈ 0 % (0 Hz). Uncertainty on sca_eff : ≈ 46 % (81.5 m). Uncertainty on neutrino rate: ≈ 2% (0.00005 Hz). Uncertainty on sca_eff : ≈ 58 % (133 m). Uncertainty on neutrino rate: ≈ 2 % (0.00005 Hz). UNCERTAINTY ON sca_eff [23-58]% UNCERTAINTY rate < 2%

22. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 22 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: ≈ 11 % (0.06 Hz). Uncertainty on sca_eff : ≈ 58 % (133 m). Uncertainty on muon rate: ≈ 15 % (0.08 Hz). Uncertainty on sca_eff : ≈ 23 % (51.5 m). Uncertainty on neutrino rate: ≈ 0 % (0 Hz). Uncertainty on sca_eff : ≈ 46 % (81.5 m). Uncertainty on neutrino rate: ≈ 6 % (0.00015 Hz). Uncertainty on sca_eff : ≈ 58 % (133 m). Uncertainty on neutrino rate: ≈ 6 % (0.00015 Hz). UNCERTAINTY ON sca_eff [23-58]% UNCERTAINTY  rate [4-15]% UNCERTAINTY ON sca_eff [23-58]% UNCERTAINTY rate < 6%

23. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 23 INFLUENCE OF  ON RECONSTRUCTED TRACKS: 1.Strategy  One optical parameters fixed (absorption) and two free parameters (scattering length and eta), for both absorption lengths. Uncertainty on  : ≈ 35 % (0.06). Uncertainty on muon rate: ≈ 2 % (0.01 Hz). Uncertainty on  : ≈ 81 % (0.02). Uncertainty on muon rate: ≈ 5 % (0.01 Hz). Uncertainty on  : ≈ 88 % (0.03). Uncertainty on muon rate: ≈ 7 % (0.07 Hz). Uncertainty on  : ≈ 35 % (0.06). Uncertainty on neutrino rate: ≈ 38 % (0.00095 Hz). Uncertainty on  : ≈ 81 % (0.09). Uncertainty on neutrino rate: ≈ 67 % (0.00105 Hz). Uncertainty on  : ≈ 88 % (0.15). Uncertainty on neutrino rate: ≈ 79 % (0.0019 Hz). UNCERTAINTY ON  [35-88]% UNCERTAINTY  rate [2-7]% UNCERTAINTY ON  [35-88]% UNCERTAINTY  rate [38-79]%

24. Selected results ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 24 Uncertainty on  : ≈ 35 % (0.06). Uncertainty on muon rate: ≈ 0 % (0.00 Hz). Uncertainty on  : ≈ 81 % (0.09). Uncertainty on muon rate: ≈ 4 % (0.02 Hz). Uncertainty on  : ≈ 88 % (0.15). Uncertainty on muon rate: ≈ 4 % (0.02 Hz). Uncertainty on  : ≈ 35 % (0.06). Uncertainty on neutrino rate: ≈ 21 % (0.00055 Hz). Uncertainty on  : ≈ 81 % (0.09). Uncertainty on neutrino rate: ≈ 34 % (0.0007 Hz). Uncertainty on  : ≈ 88 % (0.15). Uncertainty on neutrino rate: ≈ 48 % (0.00125 Hz). UNCERTAINTY ON  [35-88]% UNCERTAINTY  rate < 4% UNCERTAINTY ON  [35-88]% UNCERTAINTY  rate [21-48]%

25. Conclusions and outlook

26. CONCLUSIONS AND OUTLOOK ANTARES Collaboration Meeting Strasbourg, Nov 21 st -25 th 26 1.Current study shows that, for the current physics conditions simulated in the ANTARES KM3 code the uncertainty on water parameters could be summarized as follow: 2.The effective scattering length seems to be the most relevant parameter for muons. 3.Neutrino tracks reconstruction is very sensitive to the absorption length and Rayleigh scattering. 4.An extensive study to effective areas and angular resolution will be performed. 5.An internal note will be prepared soon with a dedicated description of the analysis. Parameter (for muon tracks)  abs [%]  sca_eff [%]   [%]   _rate [%] Absorption length ≈ 13 < 13 Effective scattering length ≈ 58 < 16 Rayleigh scattering ≈ 88 < 7 Parameter (for neutrino tracks)  abs [%]  sca_eff [%]   [%]  _rate [%] Absorption length ≈ 13 < 60 Effective scattering length ≈ 58 < 6 Rayleigh scattering ≈ 88 < 79

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