10 - H1 - Desy
10 - H1 - Desy
10 - H1 - Desy
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92 Calibration and tuning<br />
D Ej<br />
1.1<br />
1.05<br />
a. b.<br />
D Ej<br />
1.1<br />
before calibration<br />
1.05<br />
after calibration<br />
1<br />
1<br />
0.95<br />
0.95<br />
0.9<br />
6 8 <strong>10</strong> 12 14 16 18 20<br />
γ<br />
E T<br />
0.9<br />
6 8 <strong>10</strong> 12 14 16 18 20<br />
γ<br />
E T<br />
D Ej<br />
1.1<br />
1.05<br />
c. d.<br />
before calibration<br />
D Ej<br />
1.1<br />
1.05<br />
after calibration<br />
1<br />
1<br />
0.95<br />
0.95<br />
0.9<br />
-1 -0.5 0 0.5 1 1.5 2<br />
γ<br />
η<br />
0.9<br />
-1 -0.5 0 0.5 1 1.5 2<br />
γ<br />
η<br />
Figure 7.7: Double ratio plots as a function of transverse energy of photon candidate<br />
E γ T (a, b) and its pseudorapidity ηγ (c, d). Plots show situation before the calibration (a,<br />
c) and after calibration (b, d). Horizontal lines show the evaluated 2% error on the MC<br />
description of hadronic energy.<br />
criteria 0.7 < z < 0.9). In such a phase space, the prompt photon signal contributes<br />
on the negligible level and the background samples may be scaled to the measured<br />
data distribution. Figure 7.8a presents the x jet<br />
γ distribution together with the fitted<br />
direct and resolved background MCs. Significant difference between both distributions<br />
can be observed, which allows a meaningful fit. A good description of the data<br />
by the sum of scaled background MC can be noted as well. The background direct<br />
MC must be scaled by a factor 5.46, and the resolved component by 1.71. One<br />
should though keep in mind that due to preselection of the isolated neutral particle<br />
on the generator level (see section 2.1.2) those scaling factors do not have much<br />
meaning outside of the analysis presented in this particular thesis. The background<br />
scaling factors, with the assumption of the cluster shapes insensitivity to event class,<br />
is important only for the next step of the event class ratio tuning.<br />
• Tuning signal event class ratios<br />
The signal event class ratio determination is more complicated, as it is not easy to<br />
obtain pure enough signal event sample. The signal enhanced selection follows the<br />
standard inclusive prompt photon selection with an additional cut on the discriminator<br />
(D > 0.7). In this way the influence of the background is minimised, but still<br />
can not be fully neglected. The x jet<br />
γ distribution together with two fitted components<br />
(direct and resolved prompt photons) and a fixed background distribution is<br />
shown in figure 7.8b. The background in this case was fixed to the scales obtained
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