Minutes of 29 Sep 2009 meeting of Geant4 Technical Forum

Editor: G.Cosmo, 29 Sep 2009


- Starting at 16:50.

Update on Open Requirements
===========================
  + #1503, low-energy physics-lists: lists available in release 9.3-beta. Migration
           of physics models achieved, including Livermore and Penelope models.
           Transition energy chosen to be 1 GeV.
  + #1202, RPG model under development, missing resources; priorities to be discussed
           with people who are interested.
  + #2501, choices of physics lists by region: specific use-case for EM processes
           (msc) demonstrated with existing toolkit; CMS has been able to run
           simulation utilizing this.
  + #2502, fluctuation of energy deposition in gas: fix included in 9.3-beta.
           Proposed to be closed once included in final release.
  + #2503, steering field tracking by region: implementation expected by end-October.
  + #0402, documentation on physics-lists: prototype pages in place with partial
           coverage.

Geant4 Relase 9.2.p02 - and 9.3-beta
====================================
  + Not clear if all developments planned for 2009 will go in release 9.3; certainly
    some will not make it.

Period of Support for Geant4 release 9.2
========================================
  + From last meeting, support should be provide until November 2010 for release 9.2.
    The Steering Board agreed on this, although only restricting to important fixes.

Input from Experiments, Users
=============================
  + CMS: using 9.1.p01 for mass production, several hundred million events produced.
    Needs to keep stable on that version; no significant problems found so far; will
    keep an eye on the current development. Will test in parallel release 9.3;
    testing startup performance improvement provided aside on top of 9.1.p01;
    looking to 9.2.p02 in the context of the Calorimetry Task Force.
    Concerned about the FPE reported in Bertini, G4CollisionOutput.
    Needed visualization of Boolean solids; specialized physics-lists per region
    (workaround provided, functionality anyhow useful to have); interest in using
    Glauber-Gribov cross-section above 90-100 GeV; looking forward for the efforts
    going on to resolve discontinuity in energy report in QGSP_BERT.
    Abort ratio of jobs due to Geant4 is very low; 1 event out of hundred thousand;
    not possible to quantify the impact of the FPE observed. Some evidence of cases
    of non-reproducibility, which can become problematic for the debugging of rare
    crashes.
  + LHCb: millions events produced, abort rate of 0.5%. 9.2.p02 to be used in future.
  + ATLAS: using 9.2.p02, just started production; plan to continue to end 2010.
    SLC4/gcc-3.4 32-bits, plan to move to SLC5/gcc-4.3. Focus on performance
    optimization; happy for the latest fixes introduced in 9.2.p02.
    Concerning stability, two open issues: rare crash in hadronics from a corrupt
    nucleus; stuck tracks in field, observed now, but probably old story (?)
    attempted solution by increasing the threshold for abandoning tracks; some
    guidance on how to set geometric tolerances would be useful; a rate from 0.1%
    to 1% of stuck tracks which are a concern on ATLAS GRID production.
    Other issues concern memory allocated by transportation (>2GB per event).
    New class for caching field in Geant4 introduced in ATLAS version, suggest to
    include in official Geant4.
    Few problems in the physics; constructing EM processes in a vector helped in
    saving 3.5 ins per job in initialization time; also improvements in Bertini
    memory had helped. A case of Valgrind run-time error detected.
    Thanking for help an response from the Geant4 team; would be nice to have more
    public patches to avoid divergences; back-porting fixes from 9.3 to 9.2 would be
    helpful. 400 million events in 2009; launching several 100 millions events with
    9.2 (around 2 million per day).
    GC: would be useful to know the exact place where the Valgrind errors occurs.
  + ALICE: activity on Geant4 is ramping up to get Gent4 production ready; the
    experience gained so far is rather positive; comparing with Fluka and Geant3;
    some issues on TPC may come up, as observed in the past.
    An abstract will be submitted at the next Geant4 Users Workshop in Catania.

Investigation on Energy Response
================================
  + See presentation by Alberto.
  + Observations: LEP seems to provide more energy into pions versus the other models;
    in general worst than the other models; Bertini and Binary cascade appear to
    produce too much energy in protons and neutrons above around 5 GeV; Fritiof, too
    many pi-0 below 6 GeV; QGS could be extended down to 8-9 GeV; energy non-
    conservation to be fixed in FTF/BIC.
    New experimental physics lists to try as better model mixing: FTFP_BERT_TRV and
    QGSP_FTFP_BERT; available in 9.3-beta.
    Work to do: more validations with thin-target data in 1-20 GeV; continue to
    improve/extend models; try to link model-level features to calorimeter
    observables. This requires a major effort of the whole Geant4 hadronic group.

A.O.B.
======
  + Next meeting towards the end of November.


Closing meeting at 18:25.