A Search for Rare Decay D0 --> mu+mu - High Energy Physics UPRM

4.7 Background Study 76”Figure 4.7: Dimuonic invariant mass of D† ŒK Š Ø ˆgenerated by Monte Carlo.called Global Vertex) was used to determine the background ratio. This superstream wasselected with a minimum of requirements and contains all backgrounds to our signal. Inparticular, no particle identification was used in making SS2. Our procedure consisted insubmitting this sample to the same skimming process as the real data except that no muonrequirement was used. It was only necessary to work Û with 10% of the total SS2 data inorder to obtain sufficient statistical power for our purposes.As an example of the dimuonic invariant mass distributions obtained with thisprocedure, Figure 4.8 shows the results when one applies tight cuts to the SS2 sample.