ANTARES News

1

• ANTARES News
• G. Lambard
• Phd student - CPPM

2
Outline

• expected performance and background noises from
  MC
• Reconstruction strategy and analysis
• Neutralino research perspectives

3
Actuality
In January, three lines connected Actually, 5
lines detector
4
Monte-carlo studies
can
extension of 2.5 - 3 ?att w.r.t. the
instrumented volume
particle tracking only
detector
instrumented volume
particle tracking AND Cerenkov light generation
sea floor
5
Monte-Carlo studies

• Estimations
• Effectives areas and angulars resolutions _at_
  E(Gev) gt 10 GeV
• Background noises as
• 40K decays
• Random noise from bioluminescence
• Cerenkov light behavior in the can with
• Scattering and chromatic dispersion
• Light decrease in the cone (a inverse distance)
  (min. ionization ? dE/dx cst)
• Taking in account
• PMTs parameters (quantum efficiency, eff. area,
  amplitude resolution, tts)
• Refraction index in sea water (1.35)
• Detector geometry

6
Expected performances
Earth opacity for E gt 100 TeV
For 12 lines, likelyhood And 60 KHz Background
Increase with energy
7
Expected performances
E lt10TeV kinematic E gt10TeV the detector

• Angular resolution lt 0.3 (EgtTeV) limited by
• TTS in photomultipliers s 1.4 ns
• Time Calibration s 0.6 ns
• Line positioning s lt 10cm (s lt 0.5 ns)
• Scattering and chromatic dispersion s lt 1.0 ns

8
Expected optical background
40K ? 40Ca e- ? 1g
40K ? 40Ca e- ? 2g
number of coincidences
Dt ns
Measured 14.5 0.1 Hz Monte Carlo 13 2 Hz
Random noise to simulate the bioluminescence
rates
9
Trigger

• Before to really reconstruct a muon track, there
  are five data processing levels from the data
  taking to the discovering of potential events
• Level 0 (L0) All hits
• Level 1 (L1) local trigger search
• local coinciding hits in a time gate (20 ns) on
  2 PMTs of the same floor
• and/or all hits with charge gt threshold param.
  (2.5 p.e.)
• Level 2 (L2) global trigger search
• Space-time relation between signals due to
  unscattered light from the same muon trajectory
  or bright point
• assuming high relativitic muons, slowest
  possible speed c/n (n1.35). For two hits,
  causality implies

?t time between hits ?x diff. Between PMTs
positions
10
Trigger

• Level 2 (L2)
• if the number of correlated hits gt
  minClusterSize parameter(4) ? Cluster
• For example for a 3D Trigger
• Minimum number of hits in the cluster 5
• Minimum number of floors in the cluster 5
• Minimum charge of the largest hits in the
• cluster 0.3 p.e.
• etc
• Level 3 (L3) merging of overlapping events
• each event contains a snapshot of all hits in a
  time window around the cluster
• tmaxCausal 2.2 µs
• All hits within causality condition added
• Level 4 (L4) event building
• All raw hits collected in a snapshot and
  combined into PhysicsEvent with data of
  clusters

11
Trigger

• After, all processing levels used into different
  forms of triggers which look for
• 1D time correlated hits in a given direction
  (L0 data in input)
• 3D time correlated hits from any directions
  (L1 data in input)
• MX similar to 1D one local coincidence (1
  L1) to speed up the processing of L0 data
• And the number of L0 or L1 levels for each
  trigger can vary
• At the end, the muon track reconstruction
  strategy can apply to the selected hits

12
Reconstruction strategy

• Current track reconstruction strategy
• 4 parameters prefit on L1 hits with most
  coincidences using loop over the zenithal angle ?
  

m
Cerenkov cone
13
Reconstruction strategy

• Current track reconstruction strategy
• 5 parameters (x, y, z, ?, f) fit using loop over
  the azimuth angle f
• ?² minization (s 1.5 ns issue to the PMTs
  parameters)
• With Cerenkov cone model, we only have time
  informations

14
Reconstruction results
Case of Line 1 only
m
z m

• q 172o
• P(c2,ndf) 0.94

t ns
15
Reconstruction results
Case of Line 1 only
Time residual (hits/track)
Number of events a.u.
s 5.6 ns
Dt ns

• muon bundles
• bias to scattered light
• line shape

16
Reconstruction results
Case of Line 1 only
Zenithal angle of atm. muon
z
2qc
Number of events a.u.
Removal ghost solution
z
t
zenith angle q degrees
17
Reconstruction results
Case of Line 1 only
The BIG one (Chargegt1000 photons)
z m
t ns
18
Reconstruction results
Hits distribution over zenith and azimuth angles
On 10h
Deficit in hits

• Good cuts for the ghost events over zenith angle
• Azimuth angle ? detector topology effect on the
  hits distribution

19
Reconstruction results
Last case with five Lines
20
Reconstruction results
run 25685, frame 81559
3D reco. (A. Heijboer)
21
Dark Matter research perspectives
ANTARES
WIMP
?
Accretion into the sun Auto-annihilation
E? ? Mwimp
Sun
22
Background noise expected
Muons distribution over zenith angle
Need a high factor of discrimination!
23
Trigger efficiency
Trigger efficiency
Triggers 1D and MX are better than 3D because of
requirements of local coincidences and /or large
charge in a L1 level
24
Energy reconstruction
25
Wimps search
µ

• At low energy
• low angular resolution
• reduction of eff. Area

?
µ
?
High E
Low E
26
Conclusions

• ANTARES with 5 lines and 12 lines at the end of
  year
• many efforts about calibration and detector
  understanding
• Dark matter search is challenging
• Work in progress to update and improve ANTARES
  sensitivity
• trigger efficiency
• event selections
• reconstruction algorithm