Meeting with detectors

Wednesday 18 Jan 2023, 13:00 → 14:00 Europe/Zurich

6/R-012 - conference room (CERN)

Present: Ilias Efthymiopoulos, Riccardo De Maria, Hannes Bartosik, Frank Hatmann, Benedetto Gorini, Rogelio Tomas

 

Questions posed to the experiments:

 

- From which pile-up can we start in Run 4? How fast, and how frequently, can we increase the pile-up?

 

CMS (Frank): The detector hardware is ready for PU of 200 from day one without loss of performance wrt 140. However software is planned for PU=140 in Run 4 (140 has flexibility, 160 would be equally good). PU=200 was planned for Run 5. This is a soft limit and only implies buying more CPU in advance. The detector needs about few months with the low PU of 140 before moving to higher PU.

 

ATLAS (Benedetto): Having to buy the full CPU farm earlier is more expensive, in the scale of millions. 

 

Concerning timeline, detectors would need to start discussion with funding agencies towards LS3 times.

 

- Can we level above 5e34cm-2/s-1 as soon as the machine allows? Do we have to approach the large possible instanstanues luminosity, or the experiments needs time to adapt?

 

No issues with luminosity

 

- How frequently can we update the filling scheme during a year, knowing that very likely it will have a large fraction of 8b+4e trains? Does the fraction of 8b+4e need to be stable or can change freely?
 

CMS (Frank): No real constraints on filling schemes, only known in advance. No issue for 8b4e / mixed/ etc.

 

ATLAS (Benedetto): Clarifying that this flexibility is counting in a return on luminosity. 8b4e is less welcome in ATLAS but they are ready to accept it.