1. IMPACT OF WATER OPTICAL PROPERTIES ON RECONSTRUCTION: HINTS FROM THE OB DATA. A PRELIMINARY STUDY ANTARES Collaboration Meeting CERN, February 07 th -10 th, 2011 H Yepes -Ramirez IFIC (CSIC – Universitat de València)

2. OUTLINEOUTLINE ANTARES Collaboration Meeting CERN, February 07 th -10 th 2 Motivation of the study: Motivation of the study: hints from OB data Brief reminder of light propagation in sea water Simulation: Simulation: inputs and codes Preliminary results Conclusions and outlook Motivation of the study: Motivation of the study: hints from OB data Brief reminder of light propagation in sea water Simulation: Simulation: inputs and codes Preliminary results Conclusions and outlook

3. MOTIVATION OF THE STUDY ANTARES Collaboration Meeting CERN, February 07 th -10 th 3 HINTS FROM THE OPTICAL BEACON MEASUREMENTS FOR TRANSMISSION/ABSORPTION LENGTH: The transmission length procedure has given confidence to extract the absorption length using the “  R” technique based on the information of the single scattering light, when the data/MC (CALIBOB) agreement will be checked. A preliminary value for the absorption length ( abs = 63 m) was given to the collaboration under the constrains of the full data/MC (CALIBOB agreement)  J Ruiz, “Extraction of the absorption length using the  R technique”, ANTARES collaboration meeting in Paris. Several combinations (25) of optical parameters were used in order to find “the best” model which could be adapted to the real data: To resume old analysis, in particular  A Margiotta, “Study of water properties on Monte Carlo simulation of the atmospheric muon flux”, ANTARES-SOFT-2007-006.

4. LIGHT PROPAGATION IN SEA WATER ANTARES Collaboration Meeting CERN, February 07 th -10 th 4 Scattering phase function (  ) Scattering angle distribution  Molecular scattering ( Rayleigh )  Isotropic  = contribution of Rayleigh scattering.  Particle scattering ( Mie )  Strong forward peaked Attenuation Length (COLIMATED BEAM) Effective Attenuation Length (ISOTROPIC SOURCE) Absorption lengthScattering Length REMINDER OF LIGHT PROPAGATION IN SEA WATER: 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 ANTARES Collaboration Meeting CERN, February 07 th -10 th 5 SIMULATION INPUTS AND CODES: A dedicated simulation was prepared taking into account our interest to see the influence of the water parameters in the MC: 1)Production of the absorption and scattering spectrum for different water models (12 runs in total):

6. SIMULATIONSIMULATION ANTARES Collaboration Meeting CERN, February 07 th -10 th 6 2)Six MC runs for different absorption length (55 m and 60 m): Three runs with the same  value and different scattering spectrum. Three runs with different  values, but  is computed in such a way that the three runs will have the same effective scattering length at 470 nm. In total 10 runs are created: 3)Angular acceptance of June 2009 (Genova Meeting 2009). 4)MC production for neutrinos, not for atmospheric muons. abs [m] V s, v l (scattering centers) scat at 470 nm [m]  550.0075530.17 550.01410.17 550.02220.17 550.01410.11 550.02220.02 630.0075530.17 630.01410.17 630.02220.17 630.01410.11 630.02220.02

7. SIMULATIONSIMULATION ANTARES Collaboration Meeting CERN, February 07 th -10 th 7 5)Simulation chain: GEN WATER MODEL: Photon tables production (water tables)  Water tables (hbook files) + Tables description (ASCII files). HIT OM PARAMETERS: Hit probability computation from the water tables for a given OM parameters  Hit tables (hbook files) + Tables description (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).

8. SIMULATIONSIMULATION ANTARES Collaboration Meeting CERN, February 07 th -10 th 8 5)Main options and software version in neutrino simulation: 6)Only reconstructed events will be shown, a systematic study from non-reconstructed events will be established since now. The purpose is just to have a first look on the influence of optical parameters! CODE/INPUTOPTIONS/VERSIONS GENv3r7 HITv3r7 KM3v3r7 DETECTORr12_c00_s01 GEASIMv4r10 MCEW TriggerEfficiencyGaussian ARS threshold file: threshold_gaus_0.33_0.08_0.1.txt ARS noise file: noiseblendL12-basic.root (Aart) -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. Aafitv0r6 AntDSTv1r1

9. PRELIMINARY RESULTS ANTARES Collaboration Meeting CERN, February 07 th -10 th 9 RECONSTRUCTION QUALITY PARAMETER (  ): The scattering length has a big influence on the lambda distribution, as seen when  is fixed: Changing values for the contribution of Rayleigh scattering (  ), the scattering effects on  have not an appreciable effect  Combinations of  and scat gives the same effective scattering length in the three cases. scat [m] 534122 scat,eff [m] 227.4175.994.4

10. PRELIMINARY RESULTS ANTARES Collaboration Meeting CERN, February 07 th -10 th 10 RECONSTRUCTION QUALITY PARAMETER (  ): If the values for  are kept as fix, with a reduced abs = 55 m, the impact of scat on , is not evident enough for  < -5. At abs = 55 m, changing values for the contribution of Rayleigh scattering (  ), the scattering effects on  have not an appreciable effect.

11. PRELIMINARY RESULTS ANTARES Collaboration Meeting CERN, February 07 th -10 th 11 ZENITH ANGLE DISTRIBUTION: The most appreciable effects from neutrinos arriving in zenith direction are seen when the scattering length is low. If  changes and effective scattering length is fixed, gives the same result for zenith distributions.

12. PRELIMINARY RESULTS ANTARES Collaboration Meeting CERN, February 07 th -10 th 12 ZENITH ANGLE DISTRIBUTION: If the absorption length is low, there is not appreciable differences is  and the effective scattering length are fixed or not.

13. CONCLUSIONS AND OUTLOOK ANTARES Collaboration Meeting CERN, February 07 th -10 th 13 1.Several MC productions using Partic Model have been performed in order to study the influence of the scattering in the reconstruction: The scattering effects are remarkable, but if  and the scat is changed, and fixing one value for the effective scattering length at 470 nm, the differences on zenith and reconstruction quality parameter distributions are not so evident. 2.Present work is an ONGOING work, some cross- checks before and after the reconstruction will be review in detail and some priorities on physics analysis will be defined. 1.Several MC productions using Partic Model have been performed in order to study the influence of the scattering in the reconstruction: The scattering effects are remarkable, but if  and the scat is changed, and fixing one value for the effective scattering length at 470 nm, the differences on zenith and reconstruction quality parameter distributions are not so evident. 2.Present work is an ONGOING work, some cross- checks before and after the reconstruction will be review in detail and some priorities on physics analysis will be defined.

14. BACKUPBACKUP ANTARES Collaboration Meeting CERN, February 07 th -10 th 14 5 parameters fit -  2 minimization : t 0, , , x 0, y 0 Reconstruction quality factor L: Linear prefit photon hit coordinates x, y, z, t Minimization with hit-charge weights. Maximum likelihood (L) fit computed from MC PDF of time residuals.