TrackJet Distributions

In Fig. 5.4 the number of tracks reconstructed within a TrackJet and the transverse momentum of the highest transverse momentum track are compared to the MC simulation and a good agreement is found. These results are relevant in view of the measurement of the -quark production cross-section as the analysis presented here is based on a precise determination of the muon momentum with respect to the TrackJet direction. A good understanding of the TrackJet reconstruction and a reliable simulation of the TrackJet distributions are thus of utmost importance. 

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Fig. 4.6 The average difference between the transverse energy of the generated and the reconstructed jet as a function of the transverse energy of the generated jet. The energy response of TrackJets (triangles) is compared to the energy response of CaloJets (circles). The three levels of jet corrections are applied to the CaloJets. The errors correspond to the width of a Gaussian distribution fitted to the core of the distribution of the residuals...

Fig. 4.8 Distribution of the number of tracks reconstructed within a TrackJet...

The relative transverse momentum of the muon with respect to the TrackJet does depend on the modeling of the fragmentation and the decay. In order to quantify the effect, the shapes of the distribution obtained from the different samples are again used in the fitting procedure. A change by 1 % is observed for the value of the fitted b fraction. 

Tracks from the underlying event can change the properties of TrackJets associated to the muon. Especially in events with low multiplicity TrackJets, the distribution of additional tracks may influence the TrackJet reconstruction efficiency and angular... 

Fig. 4.24 Muon transverse momentum (left), TrackJet transverse eneigy (center) and distribution (right) in flavor excitation (FEX), flavor creation (FCR) and gluon splitting (GS) events...

Fig. 5.4 Number of tracks per TrackJet (/ ) and transverse momentum of the highest transverse momentum track in the TrackJets (right). The data distributions are compared to simulation. The simulated distributions have been normalized to the number of TrackJets in data. The open circles and the dotted line correspond to a center-of-mass eneigy of. Js = 900GeV and represent the data and MC events, respectively. The events corresponding to a center-of-mass energy of = 2.36 TeV are shown as filled circles (data) and solid lines (MC)...

Fig. 5.5 Transverse impact parameter significance of all tracks in the TrackJet (/ ) and of the track with the highest transverse impact parameter in the TrackJet (right). The upper plots correspond to a center-of-mass energy of = 900GeV, the lower plots to = 2.36 TeV. The simulated distributions are normalized to the number of tracks in data. The black circles represent the data distribution. The MC distributions are split into the contribution of b (red), c (blue) and udsg (green) events...

The distribution of the TrackJet kinematic variables are compared to simulation and the result is displayed in Fig. 6.4. In general, the data distribution are well described by simulation. The TrackJet pseudorapidity distribution is more central since it is correlated with the pseudorapidity distribution of the muon which also shows this feature. The disagreement between data and MC in the TrackJet transverse energy distribution at low transverse energy is due to the imperfect PYTHIA D6T tune which does not describe correctly the track multiplicity and the track transverse momentum spectrum for low transverse momentum tracks [3]. 

Fig. 6.4 Transverse energy (top left), pseudorapidity (top right), azimuthal angle (lower left) and number of tracks (lower right) of selected TrackJets. The data distribution (circles) is compared to the MC simulation (solid line) normahzed to the integrated luminosity...

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