Minutes and Summary

Main purpose of the meeting: General updates; p-O and O-O data-taking, Ne-Ne plans

LPC minutes 07 July 2025

Present (P = in person): Chris Young (P), Chiara Zampolli (P), Robert Münzer (P),  Giulia Negro (P), Andrej Gorisek (P), Eric Torrence (P), Paula Collins (P), Flavio Pisani (P), Brian Cole (P), Roderik Bruce (P), Peter Steinberg (P), Rosen Matev (P), Andrea Massironi, Andres Delannoy, Archie, Hiroaki Menjo, Ivan Calì, Klaus Monig, Lorenzo Bonechi, Lorenzo Rossini, Mirko Pojer, Qipeng Hu, Stanislav, Witold Kozanecki, Joanna Wanczyk (P), Jorg Wenninger (P), Michi Hostletter (P), Filip Moortgat (P), Maciej Trzebinski, David Stickland, Dragoslav, Anna Sfyrla, John Jowett, Richard Hawkings, Stephane Willocq, F. Romeo, Vladislav Balagura

Introduction (Chris Young)

Roderik Bruce: the difference in the ATLAS and CMS lumi could some from the different crossing planes. The emittance is larger in one plane than the other, and they have different crossing planes and that could induce a different geometric factor. 

Chris Young: But the emittance growth has varied in different fills and this seems quite consistently in one way in every fill. 

Brian Cole: it could be due to calibration. We took some VdM data but we don’t have the results yet.

Chris Young: so it is assumed that there are large uncertainties.

Witold Kozanecki: LLCMWG will follow up on the contact between the experiments and the BSRL team.

Roderik Bruce: if we are very optimistic, we could have the first Ne physics beam in the night. We could have beam in the LHC around 4 pm; then the validation fill, and we would start the collimation MD at ~7-8 pm. Then in the optimistic scenario the collimation MD could be over at ~2 am around 2 am then we ramp down and inject, so towards 4am we could have SB. But things can shift, and you might have it only tomorrow morning.

Andrej Gorisek: anything that you could do if we are ahead of schedule?

Chris Young: the idea is 2x6 hours of Ne, and we have other activities for pp which would advance the program.

Roderik Bruce: I don’t think it is a good idea to put other things before we have done the Neon. We have a very short time before we have to switch off the source. So I would first secure the Ne data.

Chris Young: yes, after we have secured 2 6h fills, of Ne, which complete the program, we can advance something from the pp program to get back to it as quickly as possible.

Roderik Bruce: a second point I wanted to mention is that in the validation fill, all experiments want the emittance scan, right?

Chris Young: yes.

Roderik Bruce: this will then be in the early evening in the optimistic scenario.

Brian Cole: what is the expected max lumi? I am assuming in the loss maps you will do something in collision and the ZDC is in, and we don’t want to have high lumi pp with it in.

Chris Young: at least in the VdM loss maps which are the first activities, it should not be very high. They should have low collision rate due to the high b*. 

Roderik Bruce: and there are only two nominal proton bunches, with one collision per experiment, so this should be fine.

Maciej Trzebinski: for NeNe loss maps, do you need the override key from AFP?

Chris Young: yes for both PPS and AFP.

Roderik Bruce: PPS won’t be inserted, so for that we don’t need, but since AFP (for which the plan is to insert it in the same position as for O), we need override keys for the loss maps. And then also for physics with Ne.

Maciej Trzebinski: so Ne data taking is not in stable beams, but in adjust?

Chris Young: no, the data taking will be in stable beams, but we need the override keys for the loss maps.

Jorg Wenninger: the 75b fill is replaced by the calibration transfer fill? I assume this since I think it is what was done in the past.

Chris Young: it is not what Christoph said, since there are no trains in the calibration transfer fill, just single bunches. I think it is 4 bunches per injection. Maybe they are 8 bunches, but they are not in trains of many bunches with 25ns spacing.

Jorg Wenninger: I need to check with Christoph.

Paula Collins: the schedule for the intensity ramp up is not clear, since there is a bit of mismatch between the spreadsheet and this slide [s9]. Can you explain how much time is needed for the last two bullet points? 

Chris Young: in the bottom section we have the calibration transfer fill with individual bunches which I think is a 10h program. Then we have 2h at 75b, 5h at 400b, and then 5h at 1200b. The calibration transfer fill with individual bunches comes first. Then the three intensity ramp up fills, then the calibration transfer fill with trains, which for you is physics, since you’ll be head on. The last one is a 12+ hours, but it is a physics fill, it is a full machine even though it has 3 individual bunches, and ATLAS will be doing some new scans. For ALICE and LHCb this is a physics fill. 

Paula Collins: so the first is 10h. And then the three fills.

Chris Young: yes, it is 7h plus overhead. Then three fills, intensity ramp up and the next one is 1200 bunches with trains, and lHCb is head on the whole time for physics.

Paula Collins: in the last LPC meeting the VdM was scheduled on Sat, but now it is on Sun? I am mainly interested in when the intensity ramp up is happening.

Chris Young: maybe the loss maps were not considered in the planning from the start of the year. I don’t think it was there.

Jorg Wenninger: the loss maps may be 16h. There will be many many cycles. Even if you count the hours here for the VdM, it almost fills, without any interfill, the planning. You probably should add another 4 to 8 hours. So Sunday seems ok. 

Chris Young: so Saturday for LM, then Sunday the afterglow, and then the intensity ramp up. 

Jorg Wenninger: nominal machine should be on Tuesday. Note that the spreadsheet is changing. It more or less has all the fills already. There is the 75b that I would like to get rid of.

Paula Collins: for the BB MD: if there are issues with it and the brightness drops such that we won’t be sensitive, then everything will be brought forward by 9h?

Chris Young: yes. It will not be the full 9h since you will have collisions before the brightness drops. But things will come forward of the time that would be left when it is cut.

Paula Collins: going back to the BB MD: I understand that there were some discussions among the experts. The main question from us is what is required from us. I looked at what has been added to the LPC page, and I see that something is required from LHCb, and we need to know what the conditions are, and it is already quite late. 

Chris Young: the main requirement is luminosity. Vladic indicated that it was unclear whether the BGI would be sensitive in the changes in shape, but that it would be interesting to take the data. But that is an internal LHCb decision, whether you would like to take BGI data.

Paula Collins: we need to know what is requested, and the conditions. Obviously the VELO aperture is the most important thing, but apart from that there might be other conditions that may affect the experiment. Regardless Vladic’s opinion on what the sensitivity of the measurement is, I am talking about what is requested and the conditions, since it is late.

Chris Young: Joanna, do you need something more than lumi? If there is no interest in taking BGI measurements from LHCb, we don’t need them.

Joanna Wanczyk: [confirms that they only need lumi, but she was far from the mic]

Paula Collins: we need to know what are the beam conditions to see what aperture is safe for the VELO. We need more feedback in some formal way. Without I cannot say if it is fine.

Chris Young: the optics are the same as in the ATLAS/CMS scan. The conditions are similar, but the beams are brighter. 

Paula Collins: I have to ask again. I know there were a lot of discussions, but have you gone again through the cycle of seeking the opinions of the experiments?

Chris Young: yes, we asked the opinion of the experiments and the lumi group, and the experts from all experiments. We have some that are pushing very hard and it is a request from these experiments, and this is enough.

Paula Collins: I would like to understand what is the situation. 

Chiara Zampolli: there was also a discussion at the LLCMWG meeting last week.

Paula Collins: yes, that was about the technicalities. 

Chris Young: it was about whether the experiments consider the test worthwhile doing, whether there were questions, and whether the questions had been answered. In the end there was general consensus about the positivity of the test although there were some concerns about the precision of the measurement. 

Paula Collins: I think that everybody is positive about the test but that is very different from having an opinion about what is the experiments’ position, what are the costs and benefits of doing the test. 

Chris Young: we have at least one experiment that strongly supports the test which is CMS. We have a strong request by CMS for the afterglow measurement and we do not argue about that. Whenever an experiment requests time…

Filip Moortgat: the main reason why CMS is positive on this is that it was the conclusion of the Lumi days from all experiments, and this sounded like a good idea. In the end it seems a good thing to do for everybody. It is not that CMS will particularly benefit from it, or that our lumi will get better, but the understanding of this effect for the totality of everybody is positive. That is why we are positive on it, but it is not that we will benefit more than the others. 

Chris Young: it is written in the mandate of the LPC that the LPC job is to decide if things make the threshold and can change the program with the advice and consultation of the experiments. 

Witold Kozanecki: about the BPM calibration: is Marek aware that he will have to do something manually presumably in the night from Wed to Thu and then again a few hours later? I haven’t been in contact with him. Is he fully in the loop and does he have the tools he needs?

Chris Young: we can follow up with him on the thread to make sure that he is aware when these fills are expected.

 

ALICE (Robert Münzer)

Paula Collins: can satellites interfere with the ZDC measurement of the asymmetry?

Robert Muenzer: probably not. The satellites should be out of the time acceptance window, but I am not sure where the cut exactly is. 

Paula Collins: may it depend on the side? 

Robert Muenzer: this should be a general offset that you have at the beginning of the fill. They will not change significantly during the fill.

Chiara Zampolli: which we still don’t know if they change during the fill, do we?

Robert Muenzer: we don’t know.

Chris Young: they drop less quickly than the other bunches.

Roderik Bruce: I guess they don’t change very much.

Chris Young: the nominal bunches might get burned off, while the satellites don’t, so the relative contribution may change increasing.

Robert Muenzer: to have a quantitative measurement of this effect is difficult, also because different bunches behave differently. So more can come from offline. 

Paula Collins: can we split the measurement by the bunch crossing ID?

Robert Muenzer: yes, it can be done offline.

Chiara Zampolli: there were other measurements shown internally in ALICE today, we should combine. These others don’t show much.

Robert Muenzer: we need to see what offline these observables will give. The trend you see in this plot [s6] might not be all contamination, there are surely other effects there too.

Jorg: [for the tests for the lumi excursions] we need to see because the last test was more aggressive than what we do in the ramp. We’d need to understand what you mean by “other settings found by Michi”. 

Robert Muenzer: he said there might be other optimized parameters to suppress these lumi spikes further.

Jorg Wenninger: but they were never tuned.

Robert Muenzer: if there are other settings with which we could run for a few hours, not constantly, this could give a further improvement. 

Chiara Zampolli: I thought you did not see the lumi excursions with the orbit feedback.

Robert Muenzer: they were reduced to 30%.

Jorg Wenninger: it depends on which settings it was. The problem of the most aggressive one is that it is really very very aggressive. All the noise of the BPM is put on the beam and on the orbit corrector.  We can use them if we are at the end of the fill. 

Robert Muenzer: yes. 

Jorg Wenninger: we need to discuss which conditions you refer to. In one of the fills when the test was done, the gain was increased progressively, and I am not sure which point on the curve you are referring to. 

Robert Muenzer: I also need to see what Michi exactly wrote, and maybe re-iterate. Maybe we can do something during the intensity ramp up, without risking to lose the beam.  

Jorg Wenninger: VdM is +/+ and physics is?

Robert Muenzer: physics will be -/-.

 

LHCf (Lorenzo Bonechi)

No comments. 

 

LHCb (Paula Collins)

Paula Collins: the 5 ns satellites are more important than the others: here the crossing angle effect is less visible, and it is closer to our timing window and the experiment acceptance. We are more concerned by these satellites than the others, not in terms of lumi, but for experiment considerations.

Chiara Zampolli: why is there a satellite at 2.5 ns?

Paula Collins: we don’t know.

Chiara Zampolli: could it be that it is only in some bunches?

Chris Young: one of the issues we had is that when we chose the beams we use the SPS, and there we cannot see satellites that are smaller than 1%. The BSRL is much more precise. 

Jorg Wenninger: for the magnet polarity: can you confirm that you go to positive?

Paula Collins: yes, and we’ll stay there. We’ll be available for discussion and feedback during the intensity ramp up and we are hoping to get a good experience for the magnet flip. 

Roderik Bruce: do you have any first hint of contamination?

Paula Collins: it should be measured comparing colliding to non-colliding. Of course the non colliding ones don’t have the satellites. So when we have the SMOG signal it is independent of that. I was wondering what is the effect of the satellites when it is on top of the signal as a background. Somehow it got more complex, at the same time we’re expecting a smaller effect. For the time being we’re focusing on the satellites, and we’re counting on an offline analysis for any kind of study on contamination. 

Flavio Pisani: if it agrees with the latest simulation of being an effect of 10e-3, it will be difficult to see.

Chris Young: the simulations had a very large uncertainty.

 

CMS (Filip Moortgat)

Filip Moorgat: would it be possible to go faster through b* leveling to scan a bit higher pileup? If this is a problem for MPP we will hold off, but if nobody sees an objection, we may ask for it. 

Jorg Wenninger/Chris Young: it should be fine.

Filip Moortgat: then maybe we go a bit faster to go a bit higher.

Giulia Negro: what is the highest pileup we could reach?

Jorg Wenninger: it depends what the bunches will look like.

Chris Young: so we have only 5h of VdM validation, so maybe we can go to that fill for the rest of the night. We want to do the VdM validation so that we can do the validation during the access and then go straight to the VdM program. 

Roderik Bruce: the other experiments will also appreciate a bit more Ne.

Chris Young: you’ll then get less pp.

Roderik Bruce: probably if you count the number of hours and compare to pp, in this time you can add much more in Ne compared to pp.

Chris Young: yes, but people want to start the VdM as soon as possible.

 

ATLAS (Andrej Gorisek)

Chris Young: Chiara went back to the minutes, and there was no request for SMOG during the VdM in pO. 

Flavio Pisani: in the VdM it is easy for us since we don’t do physics. We need a special trigger configuration. It was not ready, apart from something that we would have used in OO, but it was never tested. 

Andrej Gorisek: since the filling scheme was changed to have the separate individual bunches in to be able to measure with SMOG, we all assumed it would have been added automatically. 

Chris Young: but it is not the same SMOG. Since we always referred to this as an emittance scan and in emittance scans you don’t ask for ghost measurements, we assumed that you were not asking for it. Fortunately LHCb was able to react quickly for OO. 

Andej Gorisek: we really appreciated it, thank you.

Jorg Wenninger: in the end you take the number of hours you need. 2h is difficult considering the b* leveling unless you drive the pileup to crazy values. You almost naturally get 6h. 

Andrej Gorisek: we don’t want to push the duration of this fill with so few bunches, but we’d like to know for the duration of our scan. We would like to know where we could start the scan. We’d like to know a full program, so that we can decide where to put our scan.