STAR HardProbes PWG

[Helen Caines <helen.caines AT yale.edu>]

HI Priyanka, All,

I’m quickly following up on the merging discussion we just had. You should certainly also check with your local HT experts.  However, I went and looked at the analysis note of one of our recent HBT papers #273 "Flow and interferometry results from Au+Au collisions at sqrt(sNN) = 4.5 GeV"    (https://drupal.star.bnl.gov/STAR/system/files/Analysis_Note_for_FXT_Au_Au_collisions.pdf)

It says on page 72:

"2. Pair Cuts

This analysis uses pion pairs with an average momentum kT = (p1 + p2)/2 in the range 0.15 < kT < 0.60 GeV.
HBT analyses have two standard anti-merging and anti-splitting cuts. Single-track effects are common to both same-event and mixed-event pairs, and largely cancel from the correlation function, which is the ratio of these two. However, two-track artifacts can affect the numerator and denominator differently, and thus distort the shape of the correlation function, particularly at low relative momentum q = (p1 −p2).16
Track splitting (where hits from one charged particle are reconstructed as two distinct tracks) artificially enhances same-event pairs at low q. A topological cut was applied to all pairs that required each track in the pair to register distinct TPC hits on a minimum fraction of padrows. This splitting level, as it is known, is constrained to be in the range -0.5 ≤ SL ≤ 0.6. Track merging (where hits from two charged particles are reconstructed as one track) suppresses same-event low q pairs. These pairs can not be recovered, but similar pairs can be removed from the mixed-event distribution to compensate. An anti-merging cut analyses cases where both tracks in a pair have hits on the same TPC padrows, and determines the likelihood that these hits would have been merged by the track reconstruction algorithm. We require all pairs to have a fraction of merged hits FM H < 10%“

this is method that I was proposing you should be using. Can you point us to the analysis/method note that you are looking at? Maybe there is a different technique used when D0/V0s are involved in the correlation analysis?

Helen

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