Pass8 Workshop - Day 1 - Discussion notes

We had excellent talks in the morning that people could look at to get an update.
You can find a complete overview from Bill and specific updates on some topics (more in the following days).
AI are identified action items.

Here are some more discussion items we went through in the working sessions:

Moving to Geant4

• worth trying but not at the expense of slowing down other development areas
• besides benefit from all areas, particularyl interesting are high energy routines (from LHC and future ones), hadronic physics lists (see slides 15,22,46 from this talk at LLR to learn about gray areas between existing hadronic physics lists we use and slide 50 for the consequences on energy measurement)
• BUT it's a lot of work, here is the detailed list of things to check from Francesco:
  1. Decide which are the current implementations we need to mantain (at least to test the new G4 version)
  2. Compile new G4 source at SLAC (opt and no-opt).
  3. Revise the current code of G4Generator, G4HadronSim and GlastMS (maybe also G4Propagator?)
  4. Create new BTR and new GR with the new G4 code
  5. Define the new data sets for crucial tests before switching to the new G4.
  (at least from BeamTest and Flight Data (eg. Vela, the earth albedo, 1 week of full sim (eg. ~ DC2?)
• AI: Tracy will start with the mechanics and evaluate if worth cotinuing; possibly Francesco could help starting from July on

Validation datasets

• start gathering dataset from Eric's list and his Paris CM talk for possibe uses of them- specifically discussed
  • Vela: need a more detailed Vela-like Gleam source wrt tweaking AG; AI: will ask Tyrel to provide good spectral model and comment on required frequency for ephemeris updates; limited to both high energy (cutoff) and low energy (~200MeV) for bkg issues
  • Crab/Geminga: not much gain wrt Vela
  • AI request Earth limb pointed observation (1-2 orbits max): need to support request with existing analysis of Earth limb data; Earth limb is optimal as it is short, quick to reprocess, and has no dependence on external choices (like phase cut, annulus cut for "aperture photometry"); other "cusomters" for new Earth limb data would be Walrit, Rolf and Stefan for science studies
  • Alignment dataset: AI: move existing AGN separate datasets (~260 in Toby's set) into a single file containing photons within a given threshold from the actual position
  • priorities: Vela and Earth limb should come first in reprocessing, then Mkn421
  • prescaling events with energy: consider something more realistic beyond the existing scheme of smaller prescales for different energy ranges, like an energy-dependent function (prescales are there to keep file sizes reasonable)
  • processing time would be ~1day for ~1M evts (as per current table); disk space would not be an issue; AI: need to sort out a mechanism to trace back eventIDs that are skimmed at the merit level back into digis and recon (critical to save space); probably need to keep full MC info for a bunch of files