10 - H1 - Desy

76 Photon signal extraction
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Transverse Radius [cm]
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Kurtosis
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Hottest Cell Fraction
Figure 6.2: Shower shape variables used to discriminate between signal and background
clusters. Data is compared to the sum of MC predictions (shadowed gray) as well as
signal (solid red) and background (dashed blue) distributions.
that variable has the scale comparable to the granularity itself 1 . Taking into account both
effects, all variables have been studied in bins of transverse energy E T and pseudorapidity
η, where pseudorapidity bins correspond to wheels of LAr calorimeter. In figures 6.3 and
6.4 this study is presented for two of the shower shapes: R T and FLF. The binning
used for these plots is consistently used in the following multivariate analysis (MVA)
throughout all this chapter and is summarised in appendix table A-1.
Studying the transverse radius distributions, presented in the figure 6.3 one can note the
influence of the wheel granulity. Particularly, the R T distribution is wider in the CB1
and CB2 wheels, where LAr calorimeter granularity is the poorest. One can observe the
weaking of the discriminating power with the rise of energy of studied particles. Similar
effect can be noted for FLF distributions (figure 6.4), which variations in η is reflected
in its sensitivity to the technical details of the LAr calorimeter geometry. Particularly
FB2 wheel, with different absorber material in the first layer produces lower FLF values
in comparison to other wheels. Since the photon conversion probability has only a weak
energy dependence, the shapes of FLF do not vary between transverse energy bins.
1 As indeed is the case in presented analysis.