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LPC meeting summary 25-03-2019 - final |
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Main purpose of the meeting: Discuss plans for Run-3
Recap of Run-3 plans:
- summarized Run-3 plans as presented in Evian and LMC
- optimal fill length is 14 hours (round) or 15 hours for flat
- 2021 start with round optics and same crossing planes as in 2018
- Q1: issues with mixing filling scheme
- 40% decrease in luminous region size (and pile-up density) in IP1/5
- ALICE luminous region size?
- minimum size in LHCb? vertical crossing in LHCb - feedback?
- in 2018 saw large spread in luminosity after several hours in SB
* driven mainly by intensity variations, not transverse emittances
* could give large variation at end of leveling
* more study of data for instance BCMS beams in 2017 - could be multiple source
* mechanism not understood
* Run-3 might be better since will have more burn-off
- understand effect on B-B variations on leveling strategy
? how to level IP1/5 separately? beta* is assumed to be same. Would have to use separation leveling on top - need simulation to understand if this has issues
Round table:
ATLAS:
- mixed filling scheme is possible, but prefer to go only if significant. mu should be similar
- studies needed for beta* leveling and flat optics.
- energy preference still not decided. But could use 13.5 TeV
- will come back on pile-up
LHCb:
- LHCb thanked for Run-3 WG as many of their request were taking into account
- HL Physics in Run-3
- ok, not to level at 2x10^33 for full year
- strong preference for pure BCMS,
- level to average pile-up and cut high pile-up events at HLT
- still worried about horizontal crossing angle -> don't need answer soon, willing to sacrifice time to commission this in 2021
- LHCb will have to redo simulation at end of 2021 in any case
- no conclusive result yet on lumi region size. not problem with changes in size, but concerned about size<37mm, but can be dealt with
* main concern is difference between polarities
- no strong feeling on energy, but willing to sacrifice time in 2021 and don't want to spend time in 2022/23
ALICE:
- vertex cut can be relaxed from |z|<10cm to 11-12cm due new ITS - will loose some events, but acceptable
- beta*=10m is ok for 2021. Better ITS resolution again makes less requirement of beam size, but might revise that after/during 2021 * also matters how oxygen-oxygen run is done
- filling scheme not strong preference
- for O-O run same beta* for IP1/5
- machine preference for same beta* in all three years to avoid new optics in 2022
CMS:
- no feedback on energy as up to management (prefer to move to 14 TeV soon)
- vertical crossing in IP5 would make most events miss diamond detector . also pixel loose acceptance
- CMS strong preference for round optics due to PPS
- mixed filling scheme with 23% and 45% of 8b4e trains - large increase in trigger rate 8b4e - why?
* 45% would be disfavoured as it require L1 changes
- lumi region size: looked at vertex efficiency - see a few % loss for |z|>15cm (not detector acceptance, but tracker software)