Top Momentum Reconstruction

Another interesting example is the top momentum reconstruction. We compare in what follows the reconstructed top momentum distribution with calorimetric information only and that with the new combined track information for $e^+e^- \rightarrow t\bar{t} \rightarrow \mbox{ lepton + 4 jets}$with $m_t = 150 {\rm GeV}$ and $\sqrt{s}=300 {\rm GeV}$.

Fig.3.5 compares the residual distributions of top momentum reconstruction with only calorimetric (left) and combined track information (right).

 

Figure 3.5:  Difference of reconstructed and generated top momenta plotted against generated top momentum: (left) calorimeter only and (right) combined track information.

When projected to the vertical axis, the difference becomes clear (see Fig.3.6).

 

Figure 3.6:  Projections to the vertical axis of Fig.3.5: (left) calorimeter only and (right) combined track information.

We can see a significant improvement of momentum resolution. It should also be noted that the systematic shift of the center value also gets smaller when the combined track information is used as seen in Fig.3.7

 

Figure 3.7:  Average and standard deviation of Fig.3.5 for each momentum bin plotted as a function of top momentum: (left) calorimeter only and (right) combined track information.