Minutes and Summary

Main purpose of the meeting: 2025 planning, pO/OO/NeNe, LHCC input

LPC minutes 24th February

In room: Paula Collins, Silvia Pisano, Catrin Bernius, Riccardo Longo, Dragoslav Lazic, Jorg Wenninger, Giulia Negro, Michi Hostettler, Georges Trad, Delphine Jacquet, David Stickland, Rosen Matev, Flavio Pisani, Joanna Wanczyk.
On zoom: Roderik Bruce, Andrea Massironi, Andrej Gorisek, Andres Delannoy, Clara Leitgeb, Gabriella Pasztor, Ivan Cali, Klaus Monig, Lorenzo Bonechi, Natalia Triantafyllou, Robert Munzer, Stephane Willocq.

Introduction I (Chris Young)

Jorg Wenninger: Reminded us that OP would like to go up to 1.65e11 ppb over the summer slowly.

Jorg Wenninger: If we stay with 4x36b then it would be known how much of the intensity steps at the end of the year can also be done with this setup. This is another advantage of sticking with 4x36b over the summer rather than moving to 5x36b.

Jorg Wenninger: Who will describe the details of the HL-LHC High Intensity test to the LHCC. This will be in the LPC presentation in the closed session.

Scenarios for the 2025 Oxygen Run (Roderik Bruce)

Catrin Bernius, Chris Young: It was CMS who previously said 0.8 nb-1 for OO. All the experiments will come back to this later in the round-table with any updates on their targets.

Chris Young: Do you optimize the filling scheme when you consider scenarios where you can’t inject high intensity bunches? Yes, it is changed to 12b etc. as we drop in possible bunch intensity.

Robert Munzer: In the scenarios with 9 bunches do you assume that ALICE is leveled as the peak luminosity would be higher than 0.2. Yes, you can see this on the lumi vs time plots and it is also included in the time projections.

Introduction II (Chris Young)

Robert Munzer: For ALICE 3 nb-1 of integrated luminosity for pO is acceptable.

Roderik Bruce: The main reason that the pO run is a bit shorter is that LHCf now accepts a pile-up of 0.03 which is higher than what was previously assumed.

Jorg Wenninger: It is “setup beam limit” rather than “safe beam limit” (or the typo on the slide of “same beam limit”)

Roderik Bruce: Before definitely sacrificing another day of heavy ions perhaps we can try to run the numbers for the possible mitigations on the slides.

Jorg Wenninger: I spent some time thinking about this limit. Below the setup beam limit we can mask all interlocks which was thought to be advantageous. But we might not want them masked in all cases as otherwise collimators can move etc. But some eg. BPMs in point 6, we might want masked. Having discussed with Daniel there isn’t anything fundamental regarding the threshold for requiring validation. There were no immediate reactions at the MPP last Friday when this was raised but it certainly isn’t yet approved.

New beta* DIP publications (Michi Hostettler)

Chris Young, Jorg Wenninger, Michi Hostettler: What will the old flags publish? The minimum value of b* in x,y? Yes, and in the old format. At least this is what is hoped/planned.

Catrin Bernius: So there are two things that are different in the numbers? Units of m rather than cm, and now sent in double precision? Yes.

LHC Start-up 2025 (Jorg Wenninger)

Chris Young: All experiment run coordinators please distribute this to your technical coordinators (although they should be aware anyway). I’ll distribute to the FASER & SND (LHCf are present in the meeting). Experiments with tunnel activities, ZDCs etc. take note.

Jorg Wenninger: There also is currently an issue with water in the cryo system at point 6 which is not understood. It is currently on the critical path but if cooling starts soon then it won’t affect the timeline. The experiments will be kept informed of any news.

Jorg Wenninger: I am still waiting for volunteers for Easter. I’m hoping it is not as bad as last year.

CMS (Giulia Negro)

David Stickland, Catrin Bernius, Chris Young, Michi Hostettler: We are actually happy with 9-point scans. For ATLAS it would be good to discuss with Eric and Klaus. This will be discussed at lumi-days. Could the two experiments do it differently? This is strongly disfavoured by OP both for remembering to do it correctly and also for systematics in the crossing plane we want to be able to compare the experiments fairly. So for OP they want them the same and in the same fill. From lumi it is better not to mix it through the year. It will be decided at lumi-days.

Jorg Wenninger: PPS the weekend after Easter is the plan. Or maybe some other time after Easter. AFP will be at the same time.

Michi Hostettler, Chris Young: The high pile-up MD is foreseen to be requested by ABP but it is unclear when. It would also likely be with INDIVs. For trains we will need to be careful. There should anyhow be some synergy between the two and it could be possible to declare stable beams during this. LPC will follow the MD planning to keep the experiments informed so hopefully there can be some synergy.

Jorg Wenninger, Chris Young: The 50ns beams are not commissioned in the injectors. Could this be done with INDIVs? We could even add some extra INDIVs if it is more statistics that is needed. For 50ns this needs to be done by having one less splitting so there would be quite a lot of setup required. This will be followed up with the HCal group.

Catrin Bernius: For low-PU will this be at start of the year or after TS1? It is probably better to do it at the beginning of the year. ATLAS have one that they would likely prefer to be after TS1. There are usually 2 400b fills so it shouldn’t in principle be a problem.

Catrin Bernius, Chris Young: For the single bunches fill would this be 3 or more. More than that but not many. Would it be a dedicated fill? Yes. It is an activity that can be eg. during a checklist, but that means we are not advancing optics commissioning during that time.

Chris Young: For INDIVs during the ramp-up we will prepare schemes with these.

ATLAS (Catrin Bernius)

Chris Young: I will send some more filling scheme with 1us spacing between bunches where there are 3 bunches per injection rather than in the table here where they are very far apart.

Roderik Bruce, Chris Young: For the 9 bunches here you have 26kHz. Is this acceptable? 26kHz would be good, and we can tailor which events are taken. The hadronic cross-section is a little higher than this, and having a limit close to the total hadronic cross-section would be good. If there is a big difference when the bunches are only 1us apart we can do 9 injections per beam.

Roderik Bruce: Why do you not want to take it from 2026? It is to make sure we have every single pp day in 2025 that was envisioned.

Chris Young: For the case where there is a delay and oxygen takes longer this is extremely difficult. This is making a change at the beginning of July to the technical stop by an arbitrary amount after contracts are signed etc. This is a total non-starter. For taking a planned day from 2025 heavy ions rather than 2026 could be done. It would probably be easier to move a MD day into the PbPb period, as they can still do pp MDs, is probably easier than moving the TS, although this is also not ideal for the LHC experts. It is also the opposite of what all the other experiments want.

Roderik Bruce: Are you really concerned that moving 1 day of pp data-taking from 2025 to 2026 makes a difference? Yes, this is the view of people in ATLAS management.

ALICE (Robert Munzer)

Chris Young, Jorg Wenninger: For the dipole off this has a larger effect on the machine side but we have done it before. As long as it is early when there is less electron cloud this should be fine so during the 75b fill would be good.

LHCb (Paula Collins)

Chris Young: Has the residual leak in the VELO mentioned 2 weeks ago been fixed? There is a small residual leak but it isn’t a problem.

Michi Hostettler: Normally during powering tests, particularly phase 2, the tunnel needs to be empty due to the risk of a He leak while powering the magnets to nominal or near nominal currents. Normally the experiments are shielded from this. If you are still going through it affects both people traveling through but also it could pass into the experimental cavern. It also breaks the patrol. Let’s see what the experts come up with as procedures.

Chris Young, Michi Hostettler: If we lose the fill then we won’t have done the full number of hours which is why there are often three fills per step. We can adjust slightly the length of the two fills making the 1st longer and the 2nd shorter, but we can’t make the 2nd one very short. It is a requirement to go through the full leveling procedure so we can never make anything very short. Is it better to have a shorter fill earlier or later in the ramp-up. For e-cloud it is better to do this test without the dipole earlier with less bunches. The beam lifetime is sometimes less at the start too which makes the leveling steps procedure easier.

Michi Hostettler: The 1 TeV running helps a lot with the dipole issue as well as the beam is more rigid.

Roderik Bruce: So you only need about 20mins of emittance scans for OO while it was assumed 4h so this saves us some time as IP8 is limiting? Yes, that is correct.

Silvia Pisano, Chris Young: How long does closing the VELO take? In protons it is usually less than 5mins but sometimes up to 9mins. Ok, so this is not something that we need to consider in the luminosity vs time calculations.

Chris Young: Your Neon statement is unchanged? Our Neon statement remains that we want 2nb-1 of PbPb for Run 3, and this is followed by the oxygen targets. As the Neon plan is very short and constrained it is likely that there would not be strong objections and possible support.

Chris Young: Will you be able to provide space charge measurements with SMOG2 for the other experiments? Definitely for OO. For pO we need to confirm but we think so. The only reason would be if there was a physics reason not to inject the gas.

LHCf (Lorenzo Bonechi)

Chris Young: When you are coming back will you need tunnel access? Please make sure this is arranged early. Tunnel access will not be required, everything remaining will be done on the surface until TS1.