sPHENIX discussion of software

[Rosi Reed <rosijreed AT lehigh.edu>]

Hello JS and Software Lists,

I realized today that our poor resolution could be the result of the landau fluctuations within the response of the detector.  If you look at figures 7 and 8 of https://arxiv.org/pdf/2009.01483.pdf, you can see the effect this has on centrality, but the same aspect is true for the event plane.  Essentially what can happen is that a single particle can leave multiple mips of energy - and thus get an unfair weight since we usually use the energy lost within the detector as the weight. 

So what we did in STAR was we excluded any tile where the energy within the tile was less than 0.2 MIPs.  And for any tile where the energy was greater than 3 MIPs, we set the energy to 3 MIPs.  This was based on the expected average number of particles to hit the tile - one can do this with more finesse - but it improved things greatly.

So I think that if Ran were to include this in his calculations of the tile-by-tile weight, that would be helpful.  My suggestion would be for the gen-matched plots would be to not weight them at all, but to have each particle come in with a weight of 1.

I'm eager to see if this causes things to make more sense.

Cheers,

Rosi

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Rosi Reed
RHIC/AGS UEC member
Associate Professor, Physics Department
Lehigh University
(610)758-3907
16 Memorial Drive East Office 406
Bethlehem, PA 18015
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