deletions | additions       diff --git a/section_Week_4_5_During__.tex b/section_Week_4_5_During__.tex  index 2b50a45..2dc6650 100644  --- a/section_Week_4_5_During__.tex  +++ b/section_Week_4_5_During__.tex 
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so I fear there is a issue somewhere in the simulation. Using the particles gun so far we haven't found any possible explanation for this because it's working perfectly.  In addition we managed to create successfully an algorithm which find the mc lepton and neutrino in the mc history, and a second one that matches the charged rec particles with the gen particles looking at the angle between the two. We are going to use this algorithm also to match mc b-jet with the reconstructed ones in the top analysis.  \subsection{b-tagging}  I started following the paper "Tagging b hadrons using impact parameters", David Brown, Markus Frank, 1992, where they implemented a b-tagging algorithm for the ALEPH detector.\\  Actually there are two ways to do b-tagging:  \begin{itemize}  \item Considering a set of tracks ask the questions: what is the probability that, if they come from the decay of a zero-lifetime hadron, I measure these set of impact paramters or larger IP?  \item Considering a set of tracks reconstruct the primary and the secondary vertex, and understand if it is significantly displaced or not.  \end{itemize}  Basically the procedure is the following:  \begin{itemize}  \item For each track, calculate the IP and its significance by dividing the IP by the resolution signif = $\frac{IP}{\sigma} $  \item For each track calculate the "track probability", that is the probability that if the track comes from a zero-lifetime hadron (that means that the IP value is entirely due to the experimental resolution) I measured an IP (hence a significance) that is equal or larger than what I actually measured. We expect this distribution to be flat between 0 and 1 for tracks coming from zero-lifetime hadrons and to be peaked at 0 for tracks containing lifetime.  \item Put some quality cuts on the tracks: requiring for instance to be good measured tracks or IP not too large to avoid long lifetime particles like K0.  \item After this selection calculate the combine probability of a set of tracks (basically a jet), that is the probability that, if the jet doesn't contain lifetime, I observed a set of track probabilities that are equal or larger than those I have actually measured. \\  It is expected that the distribution of this variable is almost flat for light quarks jets (only almost because of the presence of V0 particles, like K0, $\Lambda$ and so on which actually contain lifetime) and that is squezed at 0 for c and b jets.  \item This probability is a tag for the jet, and giving a cut purity and efficiency of the selected sample could be study.  \end{itemize}  Here is the definition of the IP: