Jet Vertex Resolution Study What is the ZVertex Algorithm used to - - PowerPoint PPT Presentation

Jet Vertex Resolution Study

• What is the ZVertex Algorithm used to pick the Jet Vertex ?
• Pros and Cons with respect to Double Parton Analysis.
• Resolution of the COT Only,SVX Only and COT+SVX Tracks

in the Jets

• Calculating the Jet Vertex only for the Jet constituent Track Z
• Inverse Sum Error or Sum Error ??

ZVertex Algorithm Used to pick the Jet Vertex

• This is a seed driven algorithm,to reduce

fake rate it uses vertices created upstream as input and assocaites to them Tracks reconstructed in the event.

• Two Lists of Primary Vertex candidates are

considered for the “Seed Vertices”

• One is th elist of Primary Vertices Created by

PVFinder which is a pre-tracking finder

• The second one is COT Standalone vertices
• The above two types of “seed vertices” are

merged to form a Single list.

Zvertex Algortihm (contd)

• An important cut applied to this list of “Seed

vertices “ is that Vertex Seeds separated by less than 3 cm are merged into one.

• DefTracks with certain quality criteria are

selected to reconstruct the Primary vertex using the Zvertex Finder algorithm

• Tracks need to have Impact parameter <

1cm

• Tracks are also classified and selected

based on the Number of Axial and Stereo Hits they have (Table on next slide)

ZVertex Finder (contd)

Type of Track Number of Axial Hits umber of Stereo Hi Chi2Dof COT Only 3 3 4 SVX only 5 3 8 COT+SVX 2-COT/4 SVX 2-COT/3-SVX Same as above