astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 1 Point Source Searches with ANTARES Outline: reconstruction news event selection likelihood ratio method results full sky search Fixed point search comparison

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 2 old functional form Distribution of residuals of signal hits must be parameterised new functional form simple functions for peak and tail connected by a polynomial (spline) (unrelated) bug fixed in bg normalisation works, but complicated Reconstruction

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 3 Reconstruction bin 1 bin2bin 3bin 4bin 5

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 4 Reconstruction II more understandable likelihood functions ~10% increase in pointing accuracy standard AartStrategy with improved likelihood functions

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 5 Signal & background samples (94% efficient for E -2 signal events with an error < 1 o ) Neutrinos: GENHEN (using MUSIC + QTEQ6 GEASIM+KM3 Atmospheric Muons: 2 existing productions: HEMAS: 8 hours of minimum bias events HEMAS: 7.4 days of high E primary multi-muons pre-selection: reconstructed muon should be upward-going energy must be reconstructed (using Alain Romeyer's algorithm, without the quality cuts) estimated angular error must be < 1 o

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 6 Event selection Final selection based on single variable likelihood from reconstruction N hits -5 number tracks compatible with the preferred one.

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 7 Event selection Select events with  >5.3: ~1 atmospheric muon/day (neglected in the analysis) 10.0 atmospheric neutrinos /day (Bartol+RPQM) 74% efficient for E -2 signal events with an error < 1 o Contribution of mis- reconstructed atm. muons must be estimated from extrapolation :-(

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer events/ day with good resolution Well reconstructed Atmospheric muons same criteria as before, but now reconstructed as upward-going

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 9 Point source searching 3650 atmospheric neutrino events per year oscillations: 3% effect after selection neglected.

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 10 flux magnitude point spread functionknowledge of energy reconstructiondetector acceptance source positionflux spectral index knowledge of detector (unknown) parameters of the source likelihood if there is signal+bg likelihood for bg-only likelihood is expressed as a sum over the events As discriminating variable, we use the likelihood ratio: Likelihood ratio method

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 11 Likelihood ratio method background like signal like algorithm: find clusters of events (large cluster size ensures we find al candidate clusters) fit source parameters for each cluster calculate likelihood ratio  for each cluster test statistic  is the likelihood ratio of the 'best candidate' For a 1-year sample, ~70 clusters are found. Each cluster takes ~3sGHz. to fit source parameters and calculate likelihood ratio. 5x year bg-only samples have been analysed.

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 12 Discovery: finding a cluster that is so signal-like that the probability for the background to produce it is very small (i.e. 2.7´10 -3 / 5.7´10 -7, for 3/5  ) Examples Three rare examples of 'best candiate' clusters: signal event background event true source position fitted source position

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 13 Full sky discovery potential 1 year of data-taking 2-years of data taking Numbers have changed since previous presentations, due to increased background. Conclusion still valid: improvement over binned method

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 14 Full sky discovery potential Same quantity, now converted to the neutrino flux needed for a 50% discovery prob.

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 15 Fitted source position As an extra, we get a ML estimate of the source position 6 events seen from source single-evt resolution/  N s For pinpointing a source, ANTARES has a resolution < 0.1 o ! E -2 spectrum

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 16 Fixed point searches Suppose we have a number of candidate sources can reduce the 'trial factor' by not looking at the full sky can put exact source coordinates in likelihood, in stead of the ML estimates new sig. evts sources chosen uniform in the sky

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 17 Fixed point: discovery potential 1 candidate 10 candidates 100 candidates Improvement over binned method smaller than in case of full-sky search: due to larger binning efficiency roughly: one extra signal event needed for every factor 10 in the number of candidates

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 18 Fixed point: Upper limit This is the kind of limit that is usually presented by other experiments! If we look at only a single candidate source, we can derive an upper limit for the flux from that particular source.

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 19 Comparison now: data from ' % CL average exclusion limit discoverable at 5  CL

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 20 End Reconstruction PDF updated new selection, low contamination from atm. muon Full sky & fixed point discovery potentials and limits Software will be public... before thesis defence: June 8

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 21 Standard stuff

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 22 energy reconstruction strongly biased! Standard stuff

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 23 Error estimates 2 2

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 24 semi-analytical Binned method calculation

astrophysics working group - CERN March, 2004 Point source searches, Aart Heijboer 25