sPHENIX discussion of physics

["Perepelitsa, Dennis" <dvp AT bnl.gov>]

Hi sPHENIX colleagues,

I thought it might be useful to circulate a few links to papers related to some recent topics of discussions in the Jet Structure group.

1. Measuring pi0 mesons at high pT given the segmentation of the sPHENIX EMCal.

As we discussed, decay photons from pi0’s will have their showers start overlapping at significantly lower pi0 pT values than those of us who were on PHENIX (for example) are used to, and also well below the full kinematic reach of the experiment. ALICE has devised a method to statistically separate such merged clusters and thus measure pi0’s out to very high pT: https://inspirehep.net/literature/1512110 . It could be interesting to explore this with a GEANT4 simulation study in sPHENIX - although I worry that it will be more difficult for us given the higher relative rates of direct photons at RHIC compared to the LHC.

2. Establishing a jet energy scale without pp data.

We discussed the possibility of using the calorimeter response to isolated hadrons (comparing this in data and MC) as a way of setting or at least checking the jet/calorimeter energy scale and its uncertainties. Here is a paper from early in Run 1 by ATLAS which describes one particular methodology: https://inspirehep.net/literature/1092978 - can we learn from this? 

3. Having an event generator which implements jet quenching to check the impact of quenching on the JES. 

A persistent problem with this kind of study is that we are very limited in the available MC codes. Many are not full event generators which result in final-state hadrons (they are an analytical calculation, or are at the parton level, or have non-physical accounting tricks like ghosts/thermal recoils) or may technically be available but are not user / computationally friendly. (For example, I think for these kinds of checks in Run 1, ATLAS used PYQUEN.)

This summer, there was a recent update by the JEWEL authors: https://inspirehep.net/literature/2128092 , which I believe would make JEWEL usable for this kind of study - i.e. it would produce physical final-state hadrons. Can we configure JEWEL to use this new subtraction method, output via HEPMC file, and thus have quenched jets available for use in our GEANT4 simulations?

Welcome to send your send your thoughts to the list, 

Dennis

Dennis V. Perepelitsa
Associate Professor, Physics Department
University of Colorado Boulder
on sabbatical at Brookhaven National Laboratory