Search for point-like source in ANTARES. Juan Antonio Aguilar Sánchez IFIC (Instituto de Física Corpuscular) CSIC-Universitat de València, Spain on behalf of the ANTARES collaboration. ANTARES: Very good angular resolution Galactic Centre visible 63 % of time. Motivation.
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Juan Antonio Aguilar Sánchez
IFIC (Instituto de Física Corpuscular) CSIC-Universitat de València, Spain
on behalf of the ANTARES collaboration
Background-likeMethods for the search of point-like sources
RAGrid and Cluster Methods
Pi is the probability for the background to produce Ni or more events if there are Ntotal events in the declination band
Pi is the probability of the background to produce the observed number of events N0 or more (up to the maximum number Ntotal). is each element of the set CnNtotal of combinations of Ntotal elements in groups of n elements.
As a discriminator observable (test statistic) the likelihood ratio is used:
likelihood if there is signal+bg
likelihood for bg-only
Knowledge of detector:
point spread function
Pdf muon energy reconstruction
Parameters to fit:
flux spectral indexLikelihood Ratio Method
Try to develop a method that uses all available information:
1.- Event distribution
3.-Energy dependence of the angular resolution
Likelihood is expressed as a sum over the events
Parameters to fit:The EM algorithm
position of event: x = (αRA, δ)
proportion of signal and background
COMPLETE data set
The vector zi is a class indicator that indicates if the event i belongs to the background or the source.
Successive maximizations of the function Q(Ψ,Ψ(m)) lead to the maximization of the log-likelihood
where Nσ = 3σ, 5σSearching procedure
-s cluster size
-pS cluster elements
As a discriminator observable we use the Bayesian Information Criterion (BIC) used in a frequentist fashion:
m = m +1
FindY* = arg max Q(Y,Y(m))
Y(m+1) = Y*
The discovery power of the test (or discovery potential) is the percentage of success in detecting a source over the background
YML = Y(m+1)
Grid/ClusterResults and Comparison
Comparison among methods
Probability to detect a source at 5σ and 3σ as a function of the observed average number of events from a source located at -80º per year.
Power @ 50%: <8 events (<6 events) with 5σ (3σ).
Discovery power as a function of the mean number of observed events (after track reconstruction and quality cuts)
Grid/ClusterDiscovery potential and sensitivity
Sensitivity to a E-2 neutrino spectrum from a δ = - 60º declination point-like source for ANTARES, and NEMO (astro-ph/0611105) and averaged over all declinations in the Northern Sky for IceCube (astro-ph/0305196v1) with a 90% C.L. as a function of the exposure of the detector