S earch for neutrino emission from the Fermi Bubbles with the ANTARES telescope
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Transcript of S earch for neutrino emission from the Fermi Bubbles with the ANTARES telescope
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Search for neutrino emission from the Fermi Bubbles with the ANTARES telescope
Vladimir Kulikovskiy
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Overview
• Last updates of the analysis– sparking events cut– energy shift of the MC– limits calculation
• Short overview of analysis
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Sparking events cut
• Two possibilities were studied– EventDisplay-like cut “tχ2 < bχ2”– Cut on the distance to the OMs
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• 3/10 events with the highest EANN (5.3, 4.6, 4.6) are identified as Bright Point events on event display
• EventDisplay has a selection tχ2 < bχ2 to decide which fit to show
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• Additional tχ2 < bχ2 reduces the data, while MC stays on the same level -> the data/MC comparison improves.
• This means that cut is efficient against events which are not present in the MC.
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• sparking run 38347• Bbbfit bright point (standalone)
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• Seatray production• Distance to the closest OM• Black – events in the sparking spot• Blue – outside.
• density of the events from the distance to the closest OM for the events inside the spot.
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Conclusion 1
• tχ2 < bχ2 is efficient against sparking events• distance to the OM cut is interesting, but
more study is needed.
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• reconstructed energy of the MC events seems to be lower than of the data events• in log scale it may be interpreted as a shift• The reason may be overestimated water properties. An absorption length increase from 55 to
63 m produces a shift of logE=0.2The proper tests was done by Dimitris in his thesis work. • MC1: ang. acc. dic08 and a maximum
absorption length of 55 m at 470 nm. • MC2: ang. acc. jun09 and scaled
absorption length with a maximum of 63m at 470nm.
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• MC was scaled by 23% (obtained by λ distribution fit)• shift was fitted with a chi2 and Kolmogorov-Smirnov test by
shifting on a bin size (logE=0.03)• The best shift obtained was logE=0.1 by both fits• Kolmogorov-Smirnov probability is 0.3 after the scale and shift
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MRF optimization
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Limits calculation
• Black - Bayesian approach (Nbg = 33)
• Red - Feldman & Cousins approach with b = 11
• Blue - Conrad's approach with b = 11±2
Limits calculatedas a flux for 100 TeV cut • without 30% systematics (black) • including it (red).
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Short overview of the analysis• 12 line data 2008-2011• prod 2012-04 and MC v2+v2.2• runs
– QB≥1– no SCAN no sparking runs– good data/MC ratio
• precut– λ>-6– β<1o
– nhits>10– up-going– tχ2 < bχ2
• Difference between number of events in the zones study – 1% syst. error.• Data/MC comparison:
– Scale of MC (atmospheric nu,mu)– Energy shift of MC (atmospheric nu,mu,signal)
• Limits calculations using the Bayesian approach (check with F&C, Conrad)
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Summary
• Study of the weak points of the first analysis was done.
• Questions from referees were answered (some of them are reported on the wiki).
• An analysis note is written and distributed 5 days before today.
• Wiki page with a lot of supporting information is written.