Speaker
Dr
Jan BALEWSKI
(Indiana University Cyclotron Facility)
Description
One of the world's largest time projection chambers (TPC) has been used at STAR for
reconstruction of collisions at luminosities yielding thousands of piled-up
background tracks resulting from few hundreds pp minBias background events or several
heavy ion background events, respectively.
The combination of TPC tracks and trigger detector data used for tagging of tracks
are sufficient to disentangle the primary vertex and primary tracks from the pileup.
In this paper we will focus on techniques for vertex reconstruction. A luminosity
driven evolution of vertex finder algorithms at STAR will be sketched. We will make
distinction between multiple primary vertices from the trigger bunch crossing (bXing)
and reconstructing vertices associated with minimum bias collisions from early/late
bXings.
The vertex finder algorithm based on likelihood measures will be presented. We will
compare it with a chi square-minima method (Minuit). Fine-tuning criteria for
weighting the matching of TPC to fast detector data, taking into account efficiency,
purity, trigger dependence, stability of calibrations, and benefits of external beam
line constraints, will be discussed.
The performance of the algorithm for real and simulated STAR pp data (including
pileup) will be assessed. Extension of the algorithm for reconstruction vertex in
CuCu and heavier ions collisions will be discussed.
Primary author
Dr
Jan BALEWSKI
(Indiana University Cyclotron Facility)
Co-authors
Dr
Dan MAGESTRO
(Ohio State University)
Dr
Jerome LAURET
(BROOKHAVEN NATIONAL LABORATORY)
Dr
Marco Van Leeuwen
(Lawrence Berkeley National Laboratory)
Mr
Pibero DJAWOTHO
(Indiana University Cyclotron Facility)
Mr
Victor Perevoztchikov
(BROOKHAVEN NATIONAL LABORATORY)
