Mohamad-Ziad Charif - Antares

6.4.1.1 Data Monte Carlo comparisonJust as in the 2007-2008 data analysis we need to test the agreement between ourdata set and our Monte Carlo, and for that we use a set preliminary cuts (basicquality cuts), we list them here 1 :• Nhit ≥ 5. BBFit χ 2 Cherenkov fit requires exactly 5 hits to fit the track.• nlines > 1. A cut on the number of lines used in the fit. These events arecalled Multi-line events, where the BBFit algorithm converge into a solutionon φ.• tchi2 < bchi2. A cut that selects events that are better reconstructed as amuon generating a Cherenkov light cone than a shower bright point.• tcosth > 0. A cut that selects up-going events.In figure 6.6 we can see the comparison of the χ 2 distribution of data, backgroundMC for atm µ and atm ν , and two dark matter spectra (1000 GeV τ + τ −and 50 GeV b + b − ). We can notice immediately that the data-MC agreement atlarge values of χ 2 is bad, background estimation coming from atmospheric muonsis twice as much data. However this will not be an issue as we are more interestedin the low χ 2 region where we have good data-MC (where atm ν dominates), alsoscrambled data is going to be used again to estimate the background in the directionof the Sun. In addition we can conclude as we did earlier in section 5.5 thatthe dark matter spectra (from the two extremes, low mass soft channel to highmass hard channel) behaves similarly in χ 2 as to atm ν . Figure 6.7 presents anothercomparison between data and MC as a function of Cos[θ] with a tight cut ofχ 2 < 1.6 . With such cut on the χ 2 , the agreement between data and MC is muchbetter.1 They are basically the same as the previous analysis115