Minutes and Summary

Main purpose of the meeting: Schedule. Data taking status. G7. Hybrid filling scheme. Next meetings. High intensity tests.

LPC 8 June 2026

Present (P = in person): Chiara Zampolli (P), Eric Torrence (P),  Silvia Pisano (P), Krystian Roslon(P), Filip Moortgat (P), Roderik Bruce (P), Flavio Pisani (P), Federica Oliva (P), Jorg Wenninger (P), Joanna Wańczyk (P), Juan Esteban Muller (P), Joerg Stelzer (P), Krystian Roslon (P), Sune Jakobsen (P), Dragoslav Lazic (P), Paula Collins, Witold Kozanecki, Riccardo Longo, John Jowett, Peter Steinberg, Georges Trad, Antonio Sbrizzi, Mirko Pojer,

LPC intro (Chiara Zampolli)

Roderik Bruce: for the MD with the new ion beams from the injectors, I have some news: they think that maybe they can work on the 6b scheme with 25 ns spacing this evening, and if by tomorrow morning they have a beam that looks promising, we might try to put that beam in as well. In that case we’ll change the filling scheme. But we’ll know tomorrow morning. 

Roderik Bruce: For the MD with the new IR7 collimation settings we asked 10 hours, but it is indeed ~12h in the end as on the slides.

Roderik Bruce: for the background test for LHCb, I prepared a detailed planning which sums up at exactly 5 hours, but with the cycle it will be more 6h. With some contingency it can get to 8h. 

Georges Trad: about the statement “no procedures on ASM”: they are there. [Clarified later that they do not appear yet in the calendar, but just as a list where then one should look for the MD of interest.]

Jorg Wenninger: about MD4: half of them or even ⅔ of the MDs will actually be part of the high-intensity tests.

 

High Intensity tests (Jorg Wenninger)

Roderik Bruce: about the things to revert when we go to proton, we should not forget, we need to move out the crystals and put them in the replacement chamber. And revert the AGK. 

Jorg Wenninger: Yes, good point. For the AGK, it is kind of standard, so I don’t even mention it. 

Chiara Zampolli: on day 13 we go back to single beam. Why? Because we cannot have collisions?

Jorg Wenninger: ABP asked to have it this way, and then there is also that indeed we should have no collisions. 

Silvia Pisano: whenever there are collisions, do you need lumi?

Jorg Wenninger: yes, it will be written in the spreadsheet. In the first week, only LHCb will collide. No need for precise calibration though. 

Eric Torrence: when you say 1h in collisions, will it be head-on, at mu = 150…?

Jorg Wenninger: it will be later. 

Chiara Zampolli: will the pileup for LHCb stay always at 0.2?

Jorg Wenninger: we aim at keeping that separation, maybe at 75b we’ll have to go closer. The idea is also to gain experience on stability during the ramp up. 

Flavio Pisani: I think that 0.2 is ok to close VELO. 

Chiara Zampolli: the limit is the closing of the VELO because it’d take long?

Flavio Pisani: to close you need vertices, so it might then take long to have enough. But it should be fine with 0.2.

Jorg Wenninger: we might gain a factor 2 if we go to 2.5 sigma. We can also do further tests at 6.8 TeV, even if the heating will be lower, if you are interested. Maybe it depends on what we observe at 3 TeV. If the 3 TeV is ok, and we go to nominal intensity, there might not be much interest. 

Jorg Wenninger: AFP will stay out, right Eric?

Eric Torrence: yes.

Silvia Pisano: is it ok if the ALICE polarity stays at -/-?

Jorg Wenninger: it should be ok, but I will confirm. 

Silvia Pisano: Just let us know 2-3 days in advance.

Krystian Roslon: for 3 TeV we will not have to provide lumi, correct?

Jorg Wenninger: no, you will be separated. For the solenoid support, EPC will provide the extended support → the technician can come outside working hours, also during the high-intensity tests. They have their usual piquet service, but for some specific faults they need a technician who is usually not on piquet.

Jorg Stelzer: for luminosity, do you need it relative or absolute?

Jorg Wenninger: absolute, but not needed to be super accurate, 20-25% is good enough. 

Flavio Pisani: we can also do a short emittance scan. 

 

CMS (Filip Moortgat)

Filip Moortgat: after the 1st week of high intensity tests, will the pots be inserted? 

Chiara Zampolli: since it is not clear and it might be interesting to have them in the 6.8 TeV, let’s remove the line on the slide.

Filip Moorgat: is what I present all that is needed? Something else needed?

Jorg Wenninger: no. 

Joerg Stelzer: will your luminosity be affected by the magnet off?

Filip Moortgat: no, they should be fine, maybe a bit less precise. 

 

ATLAS (Eric Torrence)

Chiara Zampolli: what rack is mis-behaving?

Eric Torrence: it is a MUON rack. If this goes goes out, it is not clear how much of the detector will go out with it. It should be one of the two fans that is broken. But hopefully we will be ok. Trying to fix it might be a lot of knock off effects.

Eric Torrence: For MD4, are there any high mu collisions planned? I see only injection or setup beams. Does it mean pilot bunches.

Jorg Wenninger: In the first phase there is only injection and there is one setup beam that is at flat top, but I have to check. But no plan for high mu.

Chiara Zampolli: we forgot to discuss the mu at which we will take data.

Eric Torrence: putting in the intensity and b*, I get ~70, which is fine. What is important is to know if we go to very high mu, for the luminosity algorithm, and to know what we can do with the detectors.

ALICE (Silvia Pisano)

No comments.

LHCb (Flavio Pisani)

Chiara Zampolli: This year in pp you also had background, and we don’t know if it is the same origin as PbPb. The location is the same as in PbPb, right?

Flavio Pisani: in pp there is a structure closer to the same location but different which does not correspond to material. The background in pp and PbPb are different. And in pp it is much lower. 2022 resembles PbPb and had the same crossing plane as PbPb. This is the only data from Run 3 with horizontal crossing. In 2026 most of the pp background comes from beam-gas interactions.

Chiara Zampolli: So you plan to change the crossing angle?

Flavio Pisani: we don’t have data in PbPb, but in 2024 we have pp data with and without the IP bump since it was added only after the TS. In pp there is no major difference, but we don’t know if it will be the same as in PbPb. The reason to have the bump is to not have the VELO in a two asymmetric position since this poses issues with the closing, but given that in PbPb we are open 0.5 mm per side, it does not matter if the bump is there or not. 

Roderik Bruce: The voltage this year is 300V?

Flavio Pisani: yes. And we will keep it the same if we do further tests, like during the commissioning. In fact, we even see something when the VELO is more open. 

Silvia Pisani: Given that the current understanding of the background are phenomena built along the machine, and not localized, how can the tests done with the current LHC help in HL with a different machine?

Roderik Bruce: typically the bkg depends on the dispersion along the ring that in HL can change due to the different optics in IR1/5. We don’t have an optics for Run 4 and when we have we’ll try to correct dispersion then. But there can always be surprises.

Chiara Zampolli: if you understand the origin, with different optics you will still have a hint of where to look. 

Roderik Bruce: last year we thought we understood most of the ALICE bkg, but suddenly you had an additional bkg in -/- which we did not expect. We have some ideas, but the studies are not conclusive. This is an example that if something is there, it needs time to study and understand, and it is difficult to predict beforehand all the additional effects that you could have.

Silvia Pisani: yes, and I can anticipate that for Run 4 we would like to have background tests in PbPb during the intensity ramp up. For ALICE it will be essential, probably also LHCb. 

Roderik Bruce: If we do, we need to define beforehand what we will do. Which knob to play with. We need to know for the loss maps. 

Silvia Pisani: for the first run in Run 4 we might just go and see. If things work good, otherwise we might have ideas of what to test then. A very important lesson from this year is that it seems that the bkg scales with intensity, which was not clear before, and we understood with the end of fill tests this year. 

Roderik Bruce: it makes sense to still do the low intensity tests in Run 4 if we trust the extrapolation to full machine. In the low intensity we can be creative online, which we cannot do at high intensity. 

Chiara Zampolli: Maybe one can allocate some time for background test in the planning. 

Roderik Bruce: I would just put a low intensity test. 

Chiara Zampolli: Was it not that last year we had some low intensity tests that showed that -/- should have worked?

Silvia Pisani: no we did tests at low intensity (400b) only with +/+.

Roderik Bruce: there was also a test with low intensity at -/- because we had forgotten a knob. Initially online it seemed fine, but then offline it was probably not that fine. We should have probably had a better reference. 

Chiara Zampolli: you have the LPC support for the LHCb test. We would like to have also the feedback from the other experiments.

Roderik Bruce: in the plan, with ramp down, it should be 6h. 

[Discussion of when to do the test]

 

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Chiara Zampolli: please provide also feedback on the possible additional MD. 

Filip Moortgat: we should not forget that the target is Run 3 + Run 4, so the more we get now, the better. 

Roderik Bruce: if you want 13 nb-1 Run 3 + Run 4, you will need two runs in Run 4. We are too far. 

Filip Moortgat: we could go to 12. There might then be time for lighter ions. 

Chiara Zampolli: the LHCb test is an important one though. For the extra MD, we can be more reluctant. We need also to see if we’d have people to do it. 

Roderik Bruce: we have to check. 

Chiara Zampolli: the idea was to push the extra activities to the end, and we’d give priority to the test for LHCb.