Minutes and Summary

Main purpose of the meeting: 2024 preparations: timeline, including pp reference run and potential delay of YETS.

26th February -- 2024 preparations: timeline, including pp reference run and potential delay of YETS

Introduction (Federico Alessio)

(Jorg Wenninger) It was pointed out that if you lower the crossing angle during leveling you have the same target so it will make little difference. If you are lowering to have lower b* after leveling then you need to re-commission the machine.

(Witold Kozanecki) It was clarified that the degredation when changing the crossing angle during leveling was affecting the lifetime of the beam which is why it is not the default in 2024.

(Federico Alessio, Jorg Wenninger, Matteo Solfaroli Camillocci) For the loss maps we will definitely do loss maps at 160um. It is suggested that we would also do it at a smaller crossing angle later in the year, particularly if we will decrease this later in the year. This will be discussed alongside the rest of the loss maps in the LBOC on 27/2/24.

(Jorg Wenninger) From the machine commissioning side this change of moving the YETS 5 weeks earlier does mean that commissioning overlaps with Easter again which is not preferred.

(Catrin Bernius, and others) It was asked if the end of 2025 is fixed, and if we can consider changing the program to re-balance, or extend 2025. The end-date of 2025 should be taken as fixed at the moment. As the Oxygen was moved to 2025 this year Magnesium is being tested in the injector complex such that moving the Oxygen run is not possible. TS1 is fixed, and one of the questions to the TCs was if a short technical stop would be needed between TS1 and TS2 which would result in a reduction in overall physics data-taking. Moving HI days to 2024 is generally not preferred as it is hoped that 2025 will be move efficient with gained knowledge and it would make the 2025 run very short and inefficient. Additionally some HI weeks are needed in 2025 ahead of LS3 work beginning after the end of the run. The decision timeline is not entirely fixed but it is hoped that by mid-March a decision is needed. The ultimate decision will come from CERN management and it doesn't necessarily require approval at a Research Board or similar meeting.

2024 Commissioning Plan (Jorg Wenninger)

(Catrin Bernius) Will horizontal muons definitely be close the splashes as it involves the same experts, however, 1 hour is needed between splashes and horizontal muons. This can be arranged.

(Niels Tuning) Are there any impacts on other IPs during the horizontal muons. There should be little effect but some residual muons may be seen.

(Jamie Boyd) Will horizontal muons be done with both beams? Yes. This is good as it gives some data for FASER too.

Jamie Boyd (FASER)

(Chris Young) For the argument on the crossing angle does this assume the same partial RP in 2025. Yes, but the situation would be even more extreme with horizontal crossing as this is better than both up and down.

Silvia Franchino (ATLAS)

(Silvia Franchino, Rende Steerenberg) Stopping on the 9th of December would not be suitable for ATLAS, but this also doesn't work for the injectors so the suggestion is the 2nd.

(Jorg Wenninger) We can go back and check what intensities were in beam 1 and beam 2 on 31st March.

(Daniela Mirarchi) The collimators can be tilted so it becomes more transparent so it may be possible to tune the strength of the splashes. However, we should be careful not to prolong the length of the splash activities.

Andrea Ferrero (ALICE)

(Niels Tuning) Why does the decommissioning need to be done in November? This is because the Russian experts need to do the de-commissioning.

(Chris Young) Will this detector be replaced by another detector for 2025? No, 2024 would be the end of the physics program for this detector.

Giulia Negro (CMS)

(Federico Alessio) It was checked that the 20 splashes per side is expected to sit within the allocated time which it is.

(Chris Young) For 2023 data you don't have a method of extrapolating the 2024 pp reference to the 2023 PbPb data? There is a method but it gives prohibatively large uncertainties.

(Chris Young) We should make sure that everyone understands that running a low-mu 13.6 TeV run would be 4 hours, compared to 4 days (2+2 commissioning + ramp-up + data-taking) of PbPb data.

(Silvia Franchino) Why do you need a VdM? This is a lower priority, but it would be to do physics. The priority is to get an accurate JES to do precision physics. It is indicated in preliminary studies this results in a 10% uncertainty on one of the measured distributions.

(Federico Alessio) What fraction of the CMS HI program is the high energy program. This is a very large fraction of the CMS HI program and a speciality of CMS.

(Federico Alessio, Chris Young) We look forward to seeing these results when they are mature. It should be noted that there are procedures to show plots which are not approved at the public level in these meetings as LHC internal meetings. We certainly need to quantify the results and see the physics impact in numbers.

Elena Dall’Occo (LHCb)

(Jorg Wenninger) We will need to be careful if the interlocks are removed such that the velo can move the LHC doesn't know if it is in a safe place. There will be no automatic test so this will need to be discussed from a safety point of view offline.

(Witold Kozanecki) Why do you need to do the cross-calibration? Do you not have another luminometer to do the calibration. As all the luminometers may be affected by the velo position it is desired to do the cross-calibration in this way.

(Witold Kozanecki) Does this mean that you need to double the scaning time? This will be followed up for the timetable.

(Witold Kozanecki) When you take ghost charge data is the velo open or closed. It is closed in the same way as for physics data-taking.

(Jorg Wenninger) Can you tell where the beamspot is before stable beams are declared? No, the velo needs to be powered and closed. It may be possible with it powered and open but this would still need a stable beams flag. It would maybe be possible at 450 GeV but this has different crossing angles. This needs further thought and discussion offline.