Status of simulations using Direction Sensitive OMs

M.Taiuti

WP2 meeting Catania 30/10/2007

Outlook

• Why a direction sensitive optical module?

– The simulation and related results

– A possible configuration

– How to proceed

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

!

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

Implementing the Directional OMs• Check of overall response:

• Same collected light of a 10” standard PMT

• Same background noise

Implementing the Directional OMs

• Same number of active optical modules

• Same number of optical modules activated by the background noise

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

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

NEMO-KM3 Effective Area

• Median of the distribution of for all reconstructed trajectories

• Quality of reconstruction generally improves at neutrino energies below 10 TeV

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

NEMO-KM3 Effective Area

• The angular reconstruction at low energy is comparable with that of the standard 9x9 detector

8x8 Directional8x8 Standard9x9 Standard

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...

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

Water-Cube Effective Area

• Median of the distribution of for all reconstructed trajectories

• Quality of reconstruction generally improves at neutrino energies below 10 TeV

2000

3000

3600

NEMO2000

ANTARES

1000

The direction-sensitive OMThe direction-sensitive OM

► A direction-sensitive optical module A direction-sensitive optical module requires:requires:

A.A. A position sensitive photo-detectorA position sensitive photo-detector

B.B. A light collimation systemA light collimation system

R

x

R

x

Œ Ž

2000

3000

3600

NEMO2000

ANTARES

1000

Full illumination – single ph.e. chargeFull illumination – single ph.e. charge

A1

A2

A4

A3

2000

3000

3600

NEMO2000

ANTARES

1000

The Hamamatsu 10” 4-anods PMT: single The Hamamatsu 10” 4-anods PMT: single anodeanode

A1

A2

A4

A3

2000

3000

3600

NEMO2000

ANTARES

1000

The Hamamatsu 10” 4-anods PMTThe Hamamatsu 10” 4-anods PMT

► Photocathode area larger than Photocathode area larger than the standard 10” the standard 10”

► Larger (Larger (~~20%) collected light at 20%) collected light at all anglesall angles

’’

Rr

2000

3000

3600

NEMO2000

ANTARES

1000

Status of the Optical ModuleStatus of the Optical Module

► Light guides have been Light guides have been manufacturedmanufactured

► Standard electronics Standard electronics read-out has been read-out has been modified to provide the modified to provide the mask of active anods mask of active anods

DAC

DAC

DAC

DAC

S

TO FEM

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