Minutes for LArSoft coordination meeting on May 22, 2018

Present	Jim Amundson, Vito Di Benedetto, Giuseppe Cerati, Lynn Garren, Chris Green \| Herbert Greenlee, Tom Junk, Kyle Knoepfer, Erica Snider, Hans Wenzel
Remote	Katherine Lato, Paul Russo, Saba Sehrish

Project status report [Erica Snider]

Need experiment signoff before proceeding with v06_76_00_01, test release for art 2.11.02

Please see slides for detailed update
- Replace UPS with an off-the-shelf build/packaging/deployment system based on Spack.
Produce an â€œMVPâ€ â€“ Minimum Viable Product: The purpose is to let experiments experiment with the software stack.
- Currently external packages and art suite are built and all tests passing
- No guarantee that everything will eventually work out
[Herbert Greenlee] Is ups going away entirely? Originally said that it would remain for user environment configuration
- [Jim Amundson] Yes. There is no value added. But he took responsibility for those earlier comments.
[Tom Junk] : Equivalent to ups list, ups active, etc.
- Acknowledged, and will plan on providing these tools.
More discussion
- Spack was put together from the perspective of HPC admin and we have brought in a lot of new perspectives and provided feedback that have been received positively.
- There was interest in Spack by multiple groups during early HSF packaging group discussions

optical Pyhsics very important in Geant4
Want to see photon propagation / visibility calculation moved into Geant4
N2 concentration in LAr is a strong determinant of absorption length. Published values are too short for our detectors. But those are for welding grade LAr. Our detectors have lower N2 spec, so have 30+ m absorption lengths
Rayleigh scattering is important. Changes arrival times and locations by a lot
[Tom Junk]: Spectrum of LAr scintillation line is 3 nm. This is significant given steepness of index of refraction at scintillation wavelength.
[Hans]: agree. The line is simulated as a Gaussian shape, he believes.