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NIKHEF point source search: final update. Claudio Bogazzi AWG Videoconference 28/07/2011. Outline. Runs selection and final sample Data / MC comparison The algorithm for the search Ingredients Q distribution: - fixed search

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## NIKHEF point source search: final update

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**NIKHEF point source search:final update**Claudio Bogazzi AWG Videoconference 28/07/2011**Outline**• Runs selection and final sample • Data / MC comparison • The algorithm for the search • Ingredients • Q distribution: - fixed search - full sky search - candidate search • Sensitivity and discovery potentials: - fixed search - full sky search - candidate search**Documentation**• July 13th , first version of the internal note submitted. • July 21st, second version of the internal note submitted. • July 28th, third version! • What has been changed from the 2nd version to the last one? 1) All plots made with the SeaTray and run-by-run production. 2) Candidate search results included (see later). • What else? • http://www.nikhef.nl/~claudiob/pnt2/index.shtml All the old talks of this analysis are here. Q & A answer continuously updated.**Final runs selection**• Adopted Veronique’s criteria for the basic classification of runs with one exception: included also runs with livetime < 1000s. • DataQuality database table not up to date for Nov and Dec 2010 -> ran our own script to select basic runs for this period (same criteria) • Not all the basic runs reconstructed within SeaTray (21 days) -> Thomas recovered so far 124 runs -> not yet available in the DST format (both analyses uses it). • Not all the basic runs for the run-by-run MC (see http://antares.in2p3.fr/internal/dokuwiki/doku.php?id=list_of_problematic_runs ) Total basic runs = 7735 DST basic runs = 7322 DST & RBR basic runs = 7162 25 sparking runs: 36600, 33610, 38352, 41668, 38347, 34663, 38482, 42511, 33608, 38355, 38351, 36689, 44035, 42507, 38357, 38349, 38348, 44030, 43215, 36670, 43196, 38353, 36666, 43684, 44070.**Data / MC comparison**Λ > -5.2 & β < 1° Left: cos(zenith) distribution (black = data, red = up/down nu/anu, purple = mupage. Right: cumulative lambda distribution More plots here: http://antares.in2p3.fr/users/heijboer/PNT/plots_v2/ALL.html**Data / MC comparison: lambda**Not from L5 data weird peak at -7! Only for a limited period of runs**High baseline runs**High baseline => lot of background events not modeled in the Monte Carlo. Kept these runs since the discrepancy is only in the lambda region we don’t consider in the final sample.**Optimization of the cut**• Previous analysis (2007 – 2008 data): lambda chosen in order to optimize the sensitivity. • Final choice was Λ > -5.4 => high muon contribution (40%). • For the current analysis we decide to choose the lambda value by optimizing the discovery potential. • Final choice: Λ > -5.2 => 14% muon contribution.**Final sample**• Cuts: β < 1°, Λ > -5.2 and θ < 90°. • The final sample consists of 3007 events. Error estimate, β, distribution 2007 – 2008 analysis: 2190 events with Λ > -5.4 (1314 neutrinos) 2007 – 2010 analysis: 3007 events with Λ > -5.2 (2586 neutrinos) Factor 2 more neutrinos.**Search method**• Unbinned likelihood method. • Included information on the number of hits. Point spread function Background rate Number of hits**Ingredients**• Let’s make a distinction between the PE generation level and the likelihood computation. • PE generation: - background: sin(decl) distribution & Nhits distribution (both from data) - signal: PSF & Nhits extracted from 3D distribution sin(decl) vs log(β) vs Nhits 2) Likelihood computation: - background: sin(decl) parameterization from data and Nhits from MC (mu + nu) - signal: spline parameterization for the PSF and E-2 nu for Nhits**Ingredients in plots**Lik + PE PE PE - bkg lik - bkg Lik**Gain with Nhits**Fixed search: 3σ -> 34% better 5σ -> 25% better Full sky search: 3σ -> 29% better 5σ -> 22% better Full sky search, δ = -70°, Λ > -5.2**Systematic on Nhits**• It will be treated as for the angular resolution systematic (random number from a Gaussian with width equal to our uncertainty). • Value not yet decided. • Tested the algorithm with neutrino files with reduced OM acceptance (85%) (only for the aafit production) • Less than 10% effect on the sensitivity • 5% for the 3σ discovery pot. • Negligible for the 5σ discovery pot.**Systematic on Nhits**• Computed the sensitivity with a 10% systematic on Nhits (even if we think is a conservative value) • A challenge for everybody: find the difference! • 10% systematic has a negligible effect on the sensitivity! no sys sys**Systematic (same as before)**• Absolute pointing: 0.13° for φ, 0.06° for θ . To take into account these values, we smear the θ and ϕ angles by two random variables from a Gaussian distribution with the above sigmas as weidth. • Angular resolution: 15% . We take into account this number by generating a resolution-scale factor drawn from a Gaussian distribution with mean 1 and width equal to the uncertainty. • Background model: vary the background rate used for PE generation according to 2 different spline parameterizations to the data. • Acceptance: 15%. Not done in the PE but in the limit setting code**Q - distributions**Full sky search, δ = -70° Q3σ = 15.46 Q5σ = 22.02 Candidate search Q3σ = 7.55 Q5σ = 15.67 HESS-J1837-067 = [-6.95, 279.41] Fixed search, δ = 0° Q3σ = 3.77 Q5σ = 12.00**Discovery potentials – full sky**Solid = 5σ Dashed = 3σ Solid = 5σ Dashed = 3σ δ = -70°**Sensitivity - fixed search**Λ > -5.2 x 2.75 gain**Candidate list**• 50 sources: 24 “old” + 26 “new” (old = in the previous analysis). • 26 “new” sources: 18 TeV GALACTIC sources + 8 GeV EXTRA GALACTIC ones. • Selection done considering ONLY the convolution between the visibility and the gamma ray flux for the source.**Candidate search**• Algorithm tested for one source of the list: HESS J1837 – 067 (same one as in the previous analysis). δ = -6.95 α = 279.41. • For each PE we define 50 clusters (one for every source) • Signal events (up to 20) added only for HESS J1837 – 067. • Results from the fit: . δfit = -6.96 αfit = 279.38. • 10.64 fitted signal events with 11 injected. 3σ = 3.29 5σ = 5.44 A source with a signal that is 3σ significative in the full sky search, will be almost 5σ in the candidate search.**Crosschecks**• Spent last week crosschecking every step of the analysis with Valencia. • Acceptance: very small difference probably due to different binnings ✓ • Selected events: 3007 SAME events for both analysis ✓ • Currently the last crosscheck is on going: Aart generated some PE for the full sky search -> goal is to see the s / b separation by the two methods. • Results expected before the end of the week.**Conclusion**• The analysis has been finalized. • Finally adopted the official SeaTray production and run-by-run MC. • Factor 2.5 gain in the sensitivity, compared with the previous analysis. • Big improvement in the discovery potential using the Nhits information: for the full sky search 7.68 -> 5.94 for 3σ (29% better) and 9.64 -> 7.9 for the 5σ (22% better), declination -70°. • We official ask to un-blind the data. • If it’s ok, the actual unblinding will be done AFTER last crosscheck with Valencia (see next slide for proposal).**We now formally request to unblind the 2007-2010 data**• so let us know now if you agree/object • However: we also propose the following • Even if unblinding is approved now, we will not unblind until next week • We will have another public meeting before we unblind with 2 purposes • Another opportunity for people to raise questions / concerns(if they expose problems, we will halt the unblinding) • Discuss some technical issues (who runs which jobs, etc) • if cross-checks*, further internal checks, or any questions we receive • by email or in a meeting yield serious problems/concerns, then we will: have at least another meeting to discuss the issue and • re-request unblinding • So we are in fact asking for “ provisional permission to unblind, provided • no new issues arise in the next week”). And there will be more opportunities to raise questions in the mean time. * many cross-checks already done, only detailed'data-challenge'.

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