Minutes and Summary

Main purpose of the meeting: 2026 schedule - heating test in MD1 and risks - physics case for 2026 data taking - targets for high-mu and low-mu runs - configuration for 2026 - open points and organizational matters

LPC 12 January 2026

Zoom-only meeting: Chiara Zampolli, Martijn Mulders, Eric Torrence, Andrej Gorisek, Filip Moortgat, Flavio Pisani, Juan Esteban, Jorg Wenninger, Krystian Roslon, Paula Collins, Riccardo Longo, Roderik Bruce, Silvia Pisano, Stephane Willocq, Witold Kozanecki, Ivan Amos Cali, Joanna Wanczyk, Matteo Solfaroli, Federica Oliva, Michi Hostettler

LPC intro (Chiara Zampolli)

Jorg Wenninger: (regarding the option of splitting MD1 in two parts) next week Sofia will present our proposed plans for MD1 
Roderik Bruce: (on the possibility to start the PbPb run earlier IF high-intensity pp becomes impossible due to machine limitations).. It is not sure that the injectors would be ready. It is likely that we will not have a final beam then. For commissioning we have special slots in PS and SPS that have this particular schedule in mind. This would have to be thought about. 
Chiara Zampolli: yes, since we will only know such a thing at the time of MD1, we cannot replan the whole schedule of the injectors. You are right. 

Paula Collins: (on the importance of the 2026 run for physics) the importance of 2026 is enormous for LHCb. We expect at least 50% of what we had in 2025; we hope that it will be more, because we hope we’ll benefit from all the improvements to make both the machine and the experiments more stable, improve cryogenic shielding, etc. On top of that we want to profit from the big investment to mobilize all of the experiments to take data this year and we want to maximize the output at the beginning of a very long LS3. We will have targets but we hope we will not be limited by them, we hope we will go for as much as possible. 2026 will match 2024 in statistical significance. Our top priority is to maximize the pp dataset for 2026 and not do anything that could put this at risk. We will give you a more official reaction. It does not make sense to point to a specific physics measurement, as it is a huge advantage across the board.
Chiara Zampolli: yes, of course, for LHCb it is a bit different than for ATLAS and CMS, but it was more to trigger an official statement, which is important.
Martijn Mulders: yes it is not so much about specific physics results, but for example if there are improvements on experimental side, as you already mentioned, if you (Paula) could be a bit more specific about those it would be very useful, providing a strong argument. 
Paula Collins: Besides the large increase in statistics, there are improvements on the machine side such as improvements in the shielding of the cryogenics, which will hopefully no longer be a question mark like it was last year, causing a bit of disruption. We have a short YETS with very few changes, so we can start from the (very good efficiency) point we got to at the end of 2025. We have a list of things like that.
Chiara Zampolli: yes, also these kinds of arguments we wanted to have listed.

Filip Moortgat: I would like to fully support Paula on that. We can list physics channels if you want but we made the commitment to operate the detector, which takes hundreds of people away from other activities such as upgrades. Either we take this data and do it well, or we don’t. It is really not an option to try and take some risks. We would have been happy with doing HI tests at the end of last year, when you have the YETS to fix things. We are not happy with putting a large part of this short run at risk. 
Chiara Zampolli: nono, this is clear – we just wanted to back this up with some specific arguments. But this is clear.

Stephane Willocq: confirms that – like CMS – the ATLAS collaboration is taking the short 2026 data taking completely seriously, counting on accumulating luminosity for all different physics programs that are planned. It is concerning to hear about a possible risky high-intensity test already in MD1. It would be good to understand exactly what those risks are. Given the already short run it would really be a shame to give some of it up. We should maximize the remaining running time so we can complete the programme of Run3, and not add any risk to MD1.
Chiara Zampolli: yes, so the proposal will be presented and discussed at the LPC next week. To be on the safe side we should not add any risk to MD1. But there will be a push. In December an increase of 50% of the difference between what we have now and what we’d have at the high-intensity test was mentioned. Not sure if that is still the proposal being discussed. Jorg Wenninger: it is a little bit less, it is about 30%.

Roderik Bruce: (on the question of reducing the crossing angle for the heavy-ion run in 2026) .. From the machine side we are more or less ready. We have to converge on the value. It will not be zero. We will look at beam-beam studies and the results from the MD and I think well in advance we can come up with a set of crossing angles that will work from the machine size. But what we will need is the feedback from the experiments, for example what are the constraints on the ZDCs.
Chiara Zampoli: can we set a target (for Chamonix) before fixing the crossing angle?
Roderik Bruce: we will not fix the crossing angle before Chamonix
Chiara Zampoli: then we take the configuration from 2025 for the prediction
Roderik Bruce: yes I would say so  
Chiara, Roderik and Paula (on follow-up from 2025) agree that it is a hypothesis that beam background killed some VELO ASICs, in combination with a higher voltage. Paula: in any case we don’t want to operate with highly-energetic beam particles in the detector if that is confirmed. Roderik: at the PbPb backgrounds meeting next week this will be discussed in more detail with presentations from ALICE, LHCb and CMS.

Jorg Wenninger: points out that
1) for the low-mu run, lowering the beam current is not necessarily improving the situation, as it forces the separation to be reduced and at some point you could reach the regime where you become unstable. So from the point of view of beam stability it is actually better to have high current. We are considering 1.6 - 1.8 at the moment.
2) for the 1 TeV run, we realized that beta * of 3.1m does not give us enough aperture for the VELO to be closed. We are missing one beam sigma. This is a very fresh result. So we’ll look again to see what the options are, e.g. a slightly higher beta *, which would reduce performance a little bit. Another option might be to rotate the crossing angle, but this might also not be good for the aperture. Unless we go closer to the beam, but that might not be good Chiara Zampolli: no we should be safe. Better safe than sorry.
3) for the low beta … after discussion between ABP and OP about 50/15. Our optics colleagues still think that 50/15 is very valuable for HL-LHC (just reporting as is). We are thinking about a scheme that is easier to be decoupled. I will report next week at the LBOC. We are almost more worried about the bumps and possible side-effects.   For example the TCL6 setting, the dispersion, and interference. I think you didn’t mention the AFP displacement bump, which would interfere. We are looking at this. In the past we had problems with dispersion that was not visible at low intensity, and at high intensity with long range beam-beam suddenly you get into resonances that break the hierarchy. Those are things we are nervous about and we have to check carefully.
Chiara Zampolli: but this would be different from being at 60/18 ? 
Jorg Wenninger: it is probably the same. Well, it does not get better when you go to 50/15 with long range beam-beam, but it is also potentially a problem for 60/18.
Roderik Bruce: since the squeeze to 50/15 is not strictly telescopic we might have to rematch the bumps at every optics, and study if the effect of the bumps is not exactly the same at every optics. It is for sure a bit more work. We have to see also for the commissioning if this has an impact or not.
Chiara Zampolli: yes, so we need to see how much work it would be to have the 50/15: how much more commissioning time and how many risks. But do we have to decide this before Chamonix, or can we take more time? 
Jorg Wenninger: strictly speaking we would like to know when we make the settings. It would be good to know by the end of the Chamonix week. 
Chiara Zampolli: but we don’t have to present the final decision in Chamonix
Jorg Wenninger: it is always better if we can.
Chiara Zampolli: but if we don’t manage we can say that it is a possibility
Jorg Wenninger: yes
Chiara Zampolli: Ok
Roderik Bruce: It will be good to learn from SND what is the exact benefit of having the bump. We will have a meeting with them later this week. We have to weight the benefit against any possible inconvenience. 
Jorg Wenninger: technically, putting in the bump is pretty straightforward .. it is more the little side effects. 

Michi Hostettler: I will send an email about this, but just as a forewarning – we will do our annual handshake-and-interlock test. Preliminary date: Feb 12. A compromise between giving people time to be ready, but not too late to intervene in case of problems, as from the 18th or so we will need the interlocks to be cleared for the check-out.

Paula Collins: on slide 7 the expected luminosity is a bit higher than the numbers to be used as targets
Chiara Zampolli: yes, there is always some margin. Last year between 5 and 10%, the year before 10%. So we put 4.5 fb-1 here, with a 10% margin.
Paula Collins: I am surprised that we are not closer to the 2025 performance. When we went through the numbers we arrived at 5.3 fb-1 for the lower estimate, which roughly corresponds to what the graph shows. I think 10% is quite a large amount to take off. How do we arrive at a target? 
Chiara Zampolli: to have some margin for operational issues is always good. In 2025 it was tough to arrive at the target. So to be a bit more conservative like in 2024 is not a bad idea.
Paula Collins: we gained a lot of operational experience so I was hoping we could be a bit more optimistic in 2026
Chiara Zampolli: it is not so much about operational experience, but more about faults.
Michi Hostetter: from a pragmatic operational perspective, indeed there can be some unexpected troubles like in 2025. If you fall behind the target people always get very anxious. To have a bit of margin is good.
Paula Collins: in 2025 there was a list of things that caused doubts, but we don’t have that in 2026. It is good to be pragmatic but I’d maybe argue for 5% rather than 10%
Chiara Zampolli: ok, we will consider that
Jorg Wenninger: if I may say – this target is just a number.
Chiara Zampolli: yes let’s be clear.. If we reach the target it does not mean that we start to do other things. No.. we continue to follow the programme and take data for physics. 
Jorg Wenninger: maybe we should put a target, and then put an upper and a lower bound so that people see that we are in the band. I want to echo with Michi, that every time we get behind the curve, people get very nervous and somewhat irrational about being behind. This puts sometimes unnecessary pressure and entropy in the system. Anyway we will go to the end of the run and reach whatever value we reach, even if we have twice the value.
Chiara Zampolli: the space between the target and the prediction is a bit like that band 
Jorg Wenninger: yes
Paula Collins: but then we should also put a band on the more optimistic side.
Chiara Zampolli: of course if we have 80% or 100% availibility we can go higher, as this prediction is based on 60%. But I would not go beyond the prediction. Unless we want to take the average availability from 2025, which we could also do. 
Michi Hostettler: but to be fair, we should also consider that with such a short run, the variance of this number is significantly larger, because unavailability typically comes in chunks of days at a time, which relatively has a larger impact on such a short run.
Chiara Zampolli: OK let’s iterate a bit. It also depends on whether there will be a high-intensity test in MD1. 

ATLAS (Andrej Gorisek)

Jorg Wenninger: for AFP, the bump is probably the only option. There is a meeting end of the week. Matteo will attend. About splashes: I did not plan any this year. We may do without threading and go around directly. Also we did not plan any horizontal muons a priori in the already packed schedule. If you want splashes we can put them back.
Chiara Zampolli: how much time do splashes take? I understand horizontal muons take 4 hours
Eric Torrence: as we said in December, we take horizontal muons only if opportunistic if there is nothing else to do, even in the middle of the night. We are not going to ask for beamtime for that.
Jorg Wenninger: one thing is to do Splashes in the beginning, on Saturday morning of the first day, and we’d have to see if we can fit it in dynamically in the flow of activities.
Eric Torrence: that is Ok. It would not make sense to ask for a separate fill just to do splashes.
Andrej Gorisek: horizontal muons is a special fill that takes 4 hours with special bunches that are individually blown up. 
Jorg Wenninger: if all is set up it would take about 15 minutes to switch side, then 10 minutes. It would be best to do all of them together (the 10 splashes). We can see if we can dynamically slot it in. Ok, I wrote down that we shoot 10 times on the TCT during the first circulation. The horizontal muons we have to handle very dynamically. 
Andrej Gorisek: yes for the muons if there is an opportunity that is compatible with your commissioning  that is great, but we don’t ask for it explicitly.

Chiara Zampolli: for the Beam Based Alignment in the case of the 1 TeV run… I don’t know how much time it would add, but the time allocated is quite tight. If it add to the 2 days I don’t think we should take it.
Eric Torrence: sure we just want to know the number and what is the possibility of insertion without the BBA (even if partial).
Jorg Wenninger: to do an alignment would cost you a fill (a shift, say 8h). In fact we did not plan collisions in IP1/5 to limit the burnoff to LHCb. And then we need to know what mu you would like to run. It is possible, and should be pretty transparent. 
Chiara Zampolli: I think we should not plan for any BBA. If you can work in a position that does not require this, we can arrange collisions. 
Michi Hostettler: we had understood that there was no interest for collisions. But we can adapt the calculations. I don’t think it has a huge impact.  
Andrej Gorisek: yes there were new studies from the AFP group that show it could be useful
Chiara Zampolli: if we collide ATLAS should we also collide CMS by default? 
Jorg Wenninger: no.. not necessarily, The long range collisions are there anyway and head-on we don’t have to [inaudible].. 

Chiara Zampolli: about the 12 non-colliding bunches. It would be fine to have them for low-mu, as long as we don’t switch too often. The benefit is very small. If there is any single doubt we will keep them.
Eric Torrence: yes there are still doubts.
Jorg Wenninger: we don’t use them anymore in collisions. We use them, but only before collisions to monitor the tune. You can decide what you want to do with them. 

CMS (Filip Moortgat)

(no questions)

ALICE (Silvia Pisano)

Chiara Zampolli: was the test of switching on the magnet also done last year? 
Silvia Pisano: yes normally we do. But last year we only did the test ramping up the magnets to positive polarities for 2-3 hours. This year the plan is to do both polarities. We stop cosmics data taking the whole day and do FIT detector gain calibrations in parallel. That is why it will be so long. 
Chiara Zampolli: Paula, do you do the same for LHCb? 
Paula Collins: no. 

LHCb (Paula Collins)

(no slides today)