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Status of simulations using Direction Sensitive OMs

This presentation discusses the status and results of simulations involving direction-sensitive optical modules (OMs) designed to improve track reconstruction in neutrino detection experiments. By focusing on the directionality of emitted Cherenkov light, these OMs significantly enhance angular accuracy and effective detection area at low neutrino energies (below 10 TeV). The proposed configuration involves implementing modified photomultiplier tubes (PMTs) that capture light from multiple angles, thus optimizing performance and potentially reducing infrastructure costs by 20%. Testing of prototype OMs is anticipated by year-end.

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Status of simulations using Direction Sensitive OMs

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  1. Status of simulations using Direction Sensitive OMs M.Taiuti WP2 meeting Catania 30/10/2007

  2. Outlook • Why a direction sensitive optical module? • The simulation and related results • A possible configuration • How to proceed

  3. ! Motivations • Present solutions do not take into account the directionality of emitted Cherenkov light • BUT ... • Information on direction of the detected light • improves the track reconstruction • Reduces the background contribution

  4. The Simulation and Related Results • The description of direction-sensitive OM has been implemented in the ANTARES software • For simplicity the Directional OM is described with 4 different small PMTs looking at different directions • Sensitive area equal to the 10” PMT of ANTARES • The OM recognizes 4 different directions, i.e. solid angle has been divided into 4 • Reconstruction has been optimized

  5. Implementing the Directional OMs • Check of overall response: • Same collected light of a 10” standard PMT • Same background noise

  6. Implementing the Directional OMs • Same number of active optical modules • Same number of optical modules activated by the background noise

  7. Implementing the Directional OMs • Linear prefit • Standard OM: position of the most probable emission point along the simmetry axis of the module • Directional OM: 4 most probable emission points, one for each PMT • For all step in the reconstruction procedure the compatibility between the orientation of the photomultiplier and the reconstructed track is checked, all non-corresponding signal removed and fit procedure reprocessed

  8. NEMO-KM3 Effective Area • 9x9 towers configuration • 140 m tower-tower distance • Selected trajectories reconstructed with  < 2° • Effective area increases at low neutrino energy, mainly below 10 TeV

  9. NEMO-KM3 Effective Area • Median of the distribution of  for all reconstructed trajectories • Quality of reconstruction generally improves at neutrino energies below 10 TeV

  10. NEMO-KM3 Effective Area • 8x8 towers configuration • 180 m tower-tower distance • Number of towers (and pmts) reduced by 20% • Almost the same effective area of the 9x9 equipped with standard pmts! 8x8 Directional 8x8 Standard

  11. NEMO-KM3 Effective Area • The angular reconstruction at low energy is comparable with that of the standard 9x9 detector 8x8 Directional 8x8 Standard 9x9 Standard

  12. Water-Cube Effective Area • Also in this case directionality increases the detector effetive area at low energy • Improvement less pronounced than for NEMO-KM3 • But...

  13. Comparison • NEMO-KM3 effective area larger than Water-cube • The difference increases at low energy • Possible reason: the reconstruction algorithm is less efficient NEMO-KM3 WATER-CUBE

  14. Water-Cube Effective Area • Median of the distribution of  for all reconstructed trajectories • Quality of reconstruction generally improves at neutrino energies below 10 TeV

  15.  Œ Ž x x R R The direction-sensitive OM • A direction-sensitive optical module requires: • A position sensitive photo-detector • A light collimation system

  16. Full illumination – single ph.e. charge A1 A4 A2 A3

  17. A1 A4 A2 A3 The Hamamatsu 10” 4-anods PMT: single anode

  18.  R ’’ r The Hamamatsu 10” 4-anods PMT • Photocathode area larger than the standard 10” • Larger (~20%) collected light at all angles

  19. Status of the Optical Module • Light guides have been manufactured • Standard electronics read-out has been modified to provide the mask of active anods

  20. Summary • Simulations show that information on the direction of the detected Cherenkov light improves the reconstruction at “low” energies (< 10 TeV) • Better angular reconstruction and larger effective area means improved performancies for point-source search • Alternatively it would be possibile to reduce the number of structures maintaing the same overall performances with a cost reduction of ~ 20% • By the end of this year two directional optical will be available and tested

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