sPHENIX HCal discussion

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

Dear sPHENIX Jet Structure and HCal teams (and in particular John L., Aaron, 
Songkyo, Raghav),

As we agreed at the HCal meeting last week, we have begun coordinating the 
production of simulation jobs to investigate the sensitivity of the jet 
response (especially as a function of fragmentation pattern) to different 
Inner HCal scenarios.

I have run a set of 10k Pythia QCD hard scattering events with the 
requirement of a >50 GeV, R=0.4 jet in |eta|<0.6. A full G4 simulation and 
then standard (pp) jet reconstruction were performed under three scenarios: 
(1) the default IHCal description, (2) an Al-material IHCal, and (3) an 
Al-material IHCal which is not read out (this is implemented as tower reco 
jets not being given the HCALIN_TOWER container as an input to jet 
reconstruction in G4_Jets.C ).

The input Pythia8 HepMC files are here: /sphenix/user/dvp/gen/QCD35/

My G4 setup is here: 
/phenix/upgrades/decadal/dvp/production-IHCal/macros/macros/g4simulations/ 

At this point, I have not kept the resulting G4 hits files, but have rather 
“tree-ified” the results using a simple TreeMaker class you can find here: 
/direct/phenix+upgrades/decadal/dvp/production-IHCal/src/ . The trees store 
the (pt/eta/phi) for truth and tower-reco jets for R=0.2,0.3,0.4,0.5 cone 
sizes, as well as the pt/eta/phi/particle-ID of all final-state truth 
particles. A few comments here:

1. R=0.5 is a somewhat larger cone size than we normally look at, but I 
included it for completeness so analyzers can study the jet R-dependence of 
these different scenarios.
2. The final-state truth particles are included so that analyzers can also 
study the fragmentation pattern (for example, max-z) dependence. 
3. I think we have been wanting a “standard” tree-maker AKA ntuple-dumper 
like this for a while — we should flesh this out and formally add it to git 
soon.

Anyway, I have compiled the resulting output trees, which should have 10k 
events each, here: 

/sphenix/user/dvp/sims/sPHENIX-Sep17-QCD35-10k-DefaultIHCal.root
/sphenix/user/dvp/sims/sPHENIX-Sep17-QCD35-10k-AlIHCal.root           
/sphenix/user/dvp/sims/sPHENIX-Sep17-QCD35-10k-AlIHCalNoReadout.root

I would strongly and warmly encourage Aaron, Songkyo, Raghav and any other 
interested parties to please take a look at the setup and the resulting 
output trees. (I know that the Colorado group is planning to have a look at 
these outputs and try to produce some initial plots for the simulations 
meeting tomorrow, but it is highly preferable that this is not the only group 
doing so.)

Actually, I know that Raghav has taken the lead and run some initial 
simulations of his own — I attach some slides from him here which briefly 
summarize those studies. In the near future, it would be great to check that 
we are getting consistent answers in the region where our simulations overlap.

Depending on how the first studies turn out, we are happy to coordinate an 
additional production (including “tree-ification”) with HIJING embedding and 
a more extensive pT range, also in the near future.

All are welcome and encouraged to take a look,

Dennis

Dennis V. Perepelitsa
Assistant Professor, Physics Department
University of Colorado Boulder

Attachment: Raghav_INHCAL_descoping_jetperformance_JESER_raghav_v1.pdf
Description: Raghav_INHCAL_descoping_jetperformance_JESER_raghav_v1.pdf