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The first results of MSU groups in ANTARES project
M.Anghinolfi3, A.Afanas'ev2, V.Kulikovskiy1, E.Shirokov1
1-Skobeltsyn Nuclear Physics Institute of MSU 2-MSU Faculty of Physics 3-INFN, Genova Section


Limits of High Energy Astronomy
I. Active Galactic Nuclei (AGN) and Gamma Ray Bursts are extremely powerful sources of radiation and particles II. Low energy protons are deflected by galactic magnetic fields . High energy protons interacts with CMBR

Astrophysical source

High energy protons 50 Mpc

IV. Only neutrinos may come from the deepest region of the Universe

neutrinos
High energy gammas 10 Mpc Low energy protons deflected
III. Electromagnetic radiation interacts with C M BR

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Neutrino Detection Principle
atmospheric muon

~5000 PMT

Cherenkov light

neutrino
I. Neutrinos coming from d e ep s p a c e c r o s s t h e E a r t h interacting with the matter

muon

Connection to the shore
II. Interacting by the weak charged current, neutrinos disappear originating the charged leptonic partner I I I . M u on s f r om propagate following straight trajectories

depth >3000m
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Neutrino Detection Principle
I. Cherenkov light is e m i t t ed b y q u a n t a a t f i x ed a n g l e III. To improve the detection efficiency the Cherenkov light is collected by sensors arranged in very large volumes ( 1 km3)

II. Muon trajectory is reconstructed from PMT timing signals

IV. Number of required sensors is 10000

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The part of ANTARES collaboration (http://antares.in2p3.fr/Collaboration/index.html)

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The some direction of MSU group activity in the project
· Bioluminescence cut · Quality cuts · SN search

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Bioluminescence cut


We have collected distributions of hit counts for each PMT during one K40 run (~45min) Usually these distributions consist of 2 parts ­ Poissonian (due to K40 and plankton bioluminescence) and long tail (due to bioluminescence bursts)



PMT

C

PMT

PMT

=


PMT

PMT

Fit with Poisson distribution. Free parameters: PMT (mean value) C PMT (fit only until this hit count) PMT (scaling factor)



This cut Poisson distribution we'll call PDF (probability density function) of hit counts in PMT.
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Quality cuts
·Some of the PMTs have the following problems ­ extremely low number of hits (problems with HV) ­ extremely high bioluminescence bursts ­ Floating mean number of hitcounts (not stable HV, or change in activity of plankton) Quality cuts are needed to exclude them. To exclude for I one could use cut based on for II and III one could use cut based on (chi of the Poissonian fit)


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Fitting examples ­ Qcut passed



Total amount of this PMTs ­ 553 (only on K40 run in 17th May 2009 analyzed ­ number of working PMTs is about 570 according to e-log)

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Application of the cut



SN search Slow control of PMTs

Special offer for marine biologists!


Bioluminescence analysis (bio ratio parameter ­ ratio of area between experimental hitcount distribution and Poissonian fit to experimental hitcount distribution)
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SN search scheme




Make Poissonian fits analyzing one run. After for each PMT we'll have: i, Ci, mean value PDF (mi), standard deviation (i) Time slice by time slice: use hit counts of PMT (hi) if only hi < Ci Calculate: total hits in detector (Hdet=hi) 2 Mdet=mi S det = i

no SN

SN
cut





Approximate Hdet PDF by Gaus function with Mdet, Sdet choose H have 1 fake event in 1 hour (or another) If Hdet - Hcut > 0 we have SN in time slice

to

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SN search results
Simulations for 267 PMTs. Hcut for 1ev/hour shown





One K40 run treated Required number of fake SN events was 1/hour. Probability to detect SN was calculated using approximation, that signal from SN has Poisson distribution with = 12 11.6.


Conclusion






Bioluminescence cut was done. It could be applied for different studies. With current detector configuration probability to detect SN is incredibly low (~0.1%). With 900 PMTs situation is better, but still not enough to produce trigger. To make lower number of fake PMTs and increase probability to detect SN, we can try to use 2 subsequent time slices.

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Our website is here http://antares.sinp.msu.ru

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