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

‘°4.3 Data Selection 62iTable 4.2: Descriptions of Superstream 1. This Superstream was developed bythe University of Puerto Rico at Mayagüez Campus. There are five differentskims grouped according to physics topics.Sub Physics OutputStream Topics Tapes1 Semimuonic 262 Dileptonic/PPbar 453 Semielectronic with mesons 374 Semielectronic with baryons 275 Normalization 58The data in Substream 2 of Superstream 1 was used as the starting point in Skim3because it provided the highest efficiency for the detection Da b d e d g of . The mainidea of Skim3 was to require the existence of two linked muon candidate trajectorieswith opposite charge coming from a parent that was identified with a cut in the dimuonicinvariant mass around the mass of the Da (between 1.7 and 2.1 “ª”¢– ).In addition tothis, certain vertex identification conditions were required consisting of „N.POQ1 z43 andz43 . Furthermore, the production vertex was required to be separated from thea reduction in the data size from 45 tapes of 4.5 Gbytes each to one 3 Gbyte tape. The 3decay vertex by at least three times the separation error (.s¯„.0/R11 ). With this we achievedGbytes were easily kept on disk for greater convenience.At the end of Skim3, we continued to reduce the data by a process which we callSkim4. The selection criteria required for Skim4 were the following:These cuts were based on the experience acquired in previous FOCUS data analysis;these were known to have high efficiency.The output from Skim4 was a matrix of S¸ as an event file where m is the number