Background Estimation


5 jets with $p_T$ > 30 GeV /$c^2$ and $|\eta|$ < 2.4 and a minimum of 3 of these jets with a CSV b-discriminant > 0.244 (loose cut)

Of the 66,790,000 events,
273,723 events make these selection cuts.

From these selected events, we performed the $\chi$ $^2$ test on the 5 jets in the event.

The five jets are compared in such a way that one jet has its mass compared to the Higgs mass with an RMS of ~15 GeV /$c^2$, a dijet pair has its invariant mass compared to the Higgs mass with an RMS of ~14 GeV /c$^2$ (These RMS values were calculated from Monte Carlo).

The remaining two jets are paired with either the single jet (merged) Higgs or the dijet (resolved) Higgs by comparing the possible mass differences of the pairings, looking to make the difference as close to 0 as possible. (The mass difference is defined as a unitless $\frac{m_1 - m_2}{m_1 + m_2}$).

Each mass comparison has it's $\chi$ $^2$ value $\left(\frac{(Observed - Expected)^2}{(RMS)^2}\right)$ calculated, and the sum of these 3 values (the total $\chi ^2$ value) is assumed to have the correct jet configuration when it is at its lowest possible value (see $\chi ^2$ Correctness Study section of this page).

For estimating background present in the comparison of these jets to the Higgs mass, mass windows above and below the accepted Higgs mass were selected to be the comparison masses in the $\chi ^2$ calculations. We selected 55, 64, 72, 81, 90, 98, 108, 117, 134, 142, 151, 160, 169, 177, 186, and 195 GeV /$c^2$ for these mass windows. After the $\chi ^2$ and mass difference (|mass diff| < 0.2) cuts were made, we implemented separate mass cuts on the total reconstructed b' mass (> 600 GeV /$c^2$, > 800 GeV /$c^2$, > 1000 GeV /$c^2$, and > 1200 GeV /$c^2$) from each event and the number of events selected for each cut at each given mass window were recorded.

From these event acceptance numbers, we can estimate a number of expected background events in the Higgs mass window for mass comparisons. Combining the estimates from each of these mass cut plots, we can estimate how the background is effected by the rising mass of the b'.

The plots are available below, first a raw plot of the event acceptance for each mass window, followed by the same plot with a fit line overlay and finally a zoomed in view of the fit plots. 1000 and 1200 GeV /$c^2$ showed lower acceptance at the initial mass windows of 55 and 64 GeV /$c^2$, so a gaussian curve with a trailing exponential was used because it fit the data better than a standard exponential (an example from 1000 GeV /$c^2$ plot is shown below).

-- BrianAnthonyFrancisco - 2015-07-24

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng 1000GeV-fit.png r1 manage 15.4 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 1000GeV-fit_zoom.png r1 manage 14.0 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 1000GeV-gausfit_zoom.png r1 manage 15.1 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng 1000GeV.png r1 manage 13.6 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 1200GeV-fit.png r1 manage 15.5 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng 1200GeV-fit_zoom.png r1 manage 14.2 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng 1200GeV.png r1 manage 13.1 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng 600GeV-fit.png r1 manage 16.5 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 600GeV-fit_zoom.png r1 manage 15.6 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 600GeV.png r1 manage 14.8 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 800GeV-fit.png r1 manage 17.4 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 800GeV-fit_zoom.png r1 manage 15.1 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng 800GeV.png r1 manage 15.3 K 2015-07-24 - 22:08 BrianAnthonyFrancisco  
PNGpng bprime1000.png r1 manage 12.7 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng bprime1200.png r1 manage 12.7 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng bprime600.png r1 manage 17.5 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
PNGpng bprime800.png r1 manage 14.4 K 2015-07-24 - 22:09 BrianAnthonyFrancisco  
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Topic revision: r3 - 2015-08-04 - BrianAnthonyFrancisco
 
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