Status of simulations using Direction Sensitive OMs

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