12/7/20151 Vertex characteristics J. Bouchet 12/7/20151

2 outlines Spiros has some ‘concerns’ about the cut on primary vertex resolution. Are we loosing a lot/ good events ? I run the macro with filling only the vertex properties(position, resolution, number of vertices/per event, gRefMult) I use day122 ProductionMinBias (~30k events, which seems enough to draw some conclusions in term of statistic) The cuts we were using in the first production are : – |VZ|<10 cm – σ VZ <200μm – No cut on the index of the vertex 12/7/20152

3 Vertex position in XY (old prod) All verticesAll vertices with |Vz|<10cm All vertices with σ VZ <200μm and |V Z |<10cm The right plot represented the cuts we were using We see that even with the loop over all vertices, we were taking relatively good events by adding the cut on the primary vertex resolution 12/7/20153

4 Vertex resolution in XY(old prod) All verticesAll vertices with |Vz|<10cm All vertices with σ VZ <200μm and |V Z |<10 The right plot represented the cuts we were using We see that even with the loop over all vertices, we were taking relatively good events by adding the cut on the primary vertex resolution 12/7/20154

5 Vertex position in XY (new) We see that with the cut on the vertex Z resolution, we clean up the vertex position in XY The cut on the first vertex makes also a big cleaning (see next slide) 12/7/20155 All verticesVertices with l=0, |Vz|<10 cm Vertices with l=0, σ VZ <200μm and |V Z |<10cm

12/7/20156 Cut on the best vertex for the vertex resolution in XY (new) The second plot shows when we apply the best vertex rank cut It cleans up the primary vertex resolution in X,Y Adding cuts on Vz(position) and resolution Vz cleans to have ResVx~ResVy < 300 microns

12/7/20157 What are we gaining with the best vertex rank cut We remove vertex with Low refMultiplicities 12/7/20157

8 Primary vertex resolution with the best vertex rank only Black : no cut Red : index ==0 Black : no cut Red : index ==0 Black : no cut Red : index ==0 the cut on the best vertex makes the primary vertex resolution (in X,Y and Z) better

12/7/20159 if we add the cut on the index l =0, we have events (red curve) If then we add the cut on primary vertex resolution Z (200 microns),we cut 3k events, which represents 7% of the event 12/7/20159 Primary Z vertex resolution

12/7/ Summary/ to check We see that with our previous cuts (|Vz|<10cm,  Vz <200µm), we were selecting good events (by ‘good’ I mean a relatively tigh X,Y position and small resolution It seems that the cut on the first vertex also clean the resolution for the 3 components but that the cut on the resolution Z is needed to clean up more the X,Y primary vertex resolution (see slide 6) It would be interesting to see the implication for TCFIT: – We set the total single track resolution as the quadratic sum of the single DCA + primary vertex resolution – Caveat : we don’t use later any cuts on single track resolution