Mohamad-Ziad Charif - Antares

6.4.2 BBFit Single-line analysisThe single line events in BBFit are events that are reconstructed will all hits happeningon one line (nlines = 1). Since every hit on the different OMs in eachfloor are merged in BBFit the information on the horizontal direction of the muon(azimuth or φ) is lost. This present us with a problem, if we have no informationon the horizontal direction of the muon then its direction can not be compared tothe Sun. For this reason in chapter 5 these events were removed from our dataselection with the pre-analysis cut nlines > 1. However, if we take a look at figure6.13 we can clearly see that for low WIMP masses the ratio of the single lineevents to multi line events can be as high as 7. The reason for this is that the singleline events are dominated by low energy events for which the muon track is short,this is seen with the fact that the soft channel have a higher ratio than the hardchannels, and that the lighter the WIMP is the higher the ratio is. However, thereason why the 50 GeV b + b − has a smaller ratio than the next WIMP mass (80.3GeV) or when compared to 50 GeV τ + τ − is because that spectrum is so soft thata good part of its low energy events falls below our low energy neutrino threshold.Figure 6.13: The ratio of single line events to multi line events as a function ofthe the WIMP mass and the annihilation channel. No quality selection cuts wereapplied here.Removal of these events is clearly an issue as we are neglecting a large portion ofour signal, and if we can use these events we can greatly improve our sensitivitiesat low WIMP masses. The way to do this is to simply change the definition of∆(Ψ ◦ ) in the cone search analysis. ∆(Ψ ◦ ) is defined as the half-cone angle be-122