Testbeam comparisons arXiv:1704.01461

Jet measurements: Electromagnetic and Hadronic calorimetry Upsilon Spectroscopy: Excellent momentum resolution tracking in high occupancy heavy ion events b-jets: Secondary vertices

Testbeam Setup @ Fermilab sPHENIX side view Midrapidity Configuration (emcal modules + hcal tiles) Readout Si PMs Yes – sampling fraction changes with depth which makes the analysis somewhat tricky

EMCal 8 GeV electron shower, only particles with E>7.8MeV shown Tungsten epoxy with embedded scintillating fiber (Spacal) Projective in phi (+eta for forward/backward eta, next test beam) Two Towers in one block

HCals 32 GeV p- Midrapidity tiles (steel is identical for high eta) Babar cryostat mocked up by 3 aluminum plates with X0=1.4 4 Scintillating tiles/row Measurements with and without EMCal in front

In the real world and everything needs to be light tight and supported Sadly no particle gun available at FTBF

GEANT steps GEANT propagates particles one step at a time. The step size is determined by the physics processes associated with the current particle or when a boundary between volumes is crossed After each step the user stepping method is called with a pointer to the current volume which has access to the full information (energy loss, particle momentum at beginning and end of step, …)

Our G4Hits In our stepping method we add the energy loss in each volume and store the entry and exit coordinates (and for tracking detectors the momentum at the entry and exit) G4Hit We also keep the ancestry for G4Hits so any hit can be traced back to a primary particle. To reduce size we do not store particles which do not leave G4Hits and are not in the ancestry of a particle which created a G4Hit

No difference when it comes to em showers (okay - no big surprise all lists use the same em physics processes)

Major differences when it comes to hadronic showers

Simulation setup G4 version 10.02 P01 QGSP_BERT_HP Default Birks constant (0.0794 mm/MeV) Timing window 0-60ns (our electronics) Light attenuation in scintillator SiPM pixels added to simulate ADC Pedestal (measured from cosmics)

EMCal Energy resolution well reproduced (beam momentum spread folded in)

EMCal Hadron Rejection Hadron (mostly p-, < 1%K-) rejection as function on energy cut in 5x5 towers. Should be sensitive to shower sizes

HCal Energy deposition well described (inner+outer hcal), peak at low energy in data due to muons which were not simulated 4 GeV muon mip peak overlaps with hadron peak

Hcal e/h 4 GeV contaminated by muons, best description by 0.2mm/MeV Birks constant

Summary The resolution seems to be very well reproduced by G4 No real sensitivity on physics lists here Probably mainly geometry driven Hadron rejection in emcal shows sensitivity to physics lists (shower size?) Hcal e/h sensitive to Birks constant