Minutes and Summary

Main purpose of the meeting: Planning rest of 2022: - Scheduling of LHCb insertion - Test and possible switch to mixed scheme - Plans for vdM scans - Ion test period Follow-up on beam spot length in IP1/5 and luminosity difference between IP1/5.

1) Introduction (Brian)

Today’s topic: planning rest of 2022:

- Scheduling of LHCb insertion

- Test and possible switch to mixed scheme

- Plans for vdM scans

- Ion test period

Follow-up on beam spot length in IP1/5 and luminosity difference between IP1/5.

Schedule for 2022 (slide 3):

MD blocks 1 and 2 are now fixed.

Efficient ramp-up at the end of last week. Good physics production during the weekend (1.5 fb-1)

LHCb VELO is ready for partial insertion:

Will need dedicated 12b (<1 hour) and 300b fills (~1 hour), with filling schemes:

Single_12b_8_8_8_2018.csv

25ns_315b_302_237_240_48bpi_11inj.csv

Aim to do in a day shift.

Aim for doing this tomorrow with Thu as backup.

Once LHCb is ready for full insertion (~1 week later), we will do a dedicated ramp-up as requested by MPP

12b (30min)

300b (2hours)

1200b (2hours)

25ns_1167b_1154_1022_1088_144bpi_12inj_3INDIV.csv

Mixed filling scheme (slide 6):

Currently running with trains of 36 bunches (2461 total).

Switching to mixed filling scheme would allow LHC to push to bunch intensity and gain up to 20% in luminosity.

Prepared possible filling scheme:

25ns_2365b_2352_1696_1848_200bpi_14inj_mixed_1INDIV.csv

When would experiments be ready to change? No ramp-up required from MPP unlike with a pure 8b4e scheme.

What pile-up value to target in IP1/5? mu=60 would give L=2x1034 cm-2s-1, but can also continue with 52.

Tentatively plan this on Thursday in morning.

VdM planning post MD2: see slide 9. No changes.

Short LHC test with Pb ions, see slide 10.

Longitudinal beam spot size (slide 11):

Initial bunch length at start of fill has been pushed towards 1.2ns by machine. Still drops below 1ns at the end of the fill.

No Massi files with beam spot info yet to compare ATLAS and CMS beam spot lengths, but from internal pages, difference appears to remain.

Luminosity difference in IP1/5 (slide 12):

Pre-TS1 IP1 luminosity typically 5-6% higher than IP5. Still within current luminosity precision (~10% in IP1).

First fills after TS1 has IP5 higher ... change in luminometer calibration?

Valerie: indeed, ATLAS has updated LUCID mu-dependent calibration. Still studying behaviour. One issue with paired bunches.

Have asked for Z-counting numbers for last two fills of August from ATLAS/CMS - do not want to launch large studies until evidence luminosity difference is real.

Next meetings scheduled for October 10.

2) Round Table

CMS (Gianni)

Hybrid 8b4e:

We would like to have a test: Thursday or Friday this week?

Any estimation about bunch-by-bunch difference in luminosity?

JW: ~10% difference is possible. Will have to see in test.

Problems with emittance scan (blow up of beam):

For the moment, CMS is not requesting an emittance scan at the beginning of the fill, but just at the end of the fill.

Feedback about transverse beamspot is not yet ready: we need the post-TS1 data with new Tracker alignment/calibration. More news hopefully at next LPC.

1 day of HI commissioning:

Which energy?

A: maximum energy (6.8 TeV)

We prefer to do it after the beginning of November.

A: fine

ATLAS (Joerg)

overview of last week (roller-coaster week) on slide 2.

Details of CT and muon alignment run on slide 3.

Mixed filling scheme:

ATLAS appreciates the move to the mixed scheme in order to increase the integrated luminosity for 2022 and aid the conditioning of the LHC.

The detector readout setup will be ready by Thursday this week. We can then stay with the new scheme for the remainder of 2022.

We ask for one day advanced notice and for the first fill with the mixed scheme to be during daytime (start in the morning).

For now, we would like to operate at mu=52 due to operational constraints, but might ask for mu=60 later on, if feasible.

ALICE (Federico)

special activities need to be interleaved with our high rate tests. Need some stable beam time, long fills with reasonable # of bunches.

E.g. Wednesday.

LHCb (Federico)

Concentrate now on VELO.

All other detectors have completed time alignment.

For later: at the end of November, LHCb will want to do a magnet-off test, 1 or 2 fills.

JW: No ramp up needed for this. But we will want a ramp-up in 2023 when we start rotating the crossing plane.

Brian: any problem to switch to mixed scheme?

Both Federico’s confirm they do not foresee a problem.