Minutes and Summary

Main purpose of the meeting: Discuss 2026 schedule ; 1.2 TeV run ; summary of low-mu run

LPC 27 April 2026
 

Present (P = in person): Chiara Zampolli (P), Martijn Mulders (P), Eric Torrence (P), Fedrica Oliva (P), Flavio Pisani (P), Silvia Pisano (P), Julia Negro (P), Filip Moortgat (P), Helga Timko (P), Roderik Bruce (P), Dragoslav Lazic (P), Xavier Buffat, Andres Delannoy, Antonio Sbrizzi, Sune Jakobsen, Brian Petersen, Christophe Lannoy, Gerardo Vasquez, Georges Trad, Ivan Amos Cali, Juan Esteban, Joerg Stelzer, Maciej Trzebinski, Matthew Nguyen, Michi Hostettler, Mirko Pojer, Riccardo Longo, Tomasz Bold, Witold Kozanecki, Jorg Wenninger, Richard Hawkings, Juan Esteban, Ivan Amos Cali, Gerardo Vasquez

 

LPC intro (Chiara Zampolli)

Regarding the schedule for the 1.2 TeV run: discussion about the flexibility of the vacuum people to exchange the gas bottle on Thursday morning… could they wait a few hours and do it later in the day? (Flavio Pisani:) As long as it is during working hours, I can ask yes.  

In case there is a longer stoppage we may also consider resuming the 1.2 TeV later (i.e. 1 or 2 weeks later..). 

Low-mu run: performance summary (Xavier Buffat)

Filip Moortgat: thanks Xavier et al for doing the extra simulations needed to prepare the (very successful!) low-mu run. Initially ATLAS and CMS were told that it would be ‘impossible’ to have the low-mu at the same time for the two experiments, that we had to do one at the time. We didn't like this at all, and we had full confidence that the machine could do this. Thank you very much, Xavier, you and your colleagues who did the study, who then confirmed by Chamonix that in simulation, it was possible. We just did it and had an amazing performance. People are super happy with what we got: the long, fills, very stable, and we will get very nice results out of it, so thank you very much. 

Xavier Buffat:  Maybe that is the message you received from us. It was not necessarily that this would be impossible, but that this required a bit of simulation and understanding to be sure that this could be robust enough. But if it is useful, we are very happy to do it, and thanks for pointing this out. Thanks a lot.

LHCb (Flavio Pisani)

Discussion about the planning of luminosity scans during the 75 or 400 bunch fills: Eric Torrence wonders what the head-on luminosity would be at the start of the 75b fill (ideally not much more than 1 PU)... a possibility would be for ATLAS to do the scan after CMS, later in the 400b fill. It would take only half an hour. Or in the 75b fill, if it stays long enough.
Chiara Zampolli: the 75b fill is planned to last 3 hours.

Roderik Bruce: For the checklists, do you [LHCb] have some points on backgrounds or losses on the velo or something? Flavio Pisani: Yes, this is not in the official checklist, of course, yes.

Roderik Bruce: Because in the simulations that Bjorn did of the collimation cleaning performance, we see, out of the, I think, 10 million protons simulated, a few protons on the Velo itself, which could be about 2 protons out of 10 million.

Flavio Pisani: We're very careful. We still have the trigger running and are planning to do a tomography… we have a live tomography monitoring of the velo, basically. To check for background where material is. The idea is, okay, to check the rates of the other backgrounds, taking into account different crossing angles, different energy, different everything. And then to check if we see new features, let's say, appearing in hotspots.

Filip Moortgat: But his question was: should MPP look at that, or you do this yourself?

Flavio Pisani: So, part of our own MPP checklist is also to check that.

[...long discussion about the number of bunches, backgrounds and possible effect on physics data taking or damage to the Asics in the velo detector…]

CMS (Giulia Negro)

[... some discussion about the electrical fault and incident panel in CMS]

ATLAS (Eric Torrence)

Eric Torrence mentions that AFP would like a 2h access in the tunnel. Helga Timko: this Thursday we are not planning any tunnel access, to avoid needing a pre-cycle. Chiara Zampolli: it might be better to wait until next week, when we have the access for SND. 

Jorg Wenninger: we have not configured a vertical bump for AFP in the 1.2 TeV setup. Maciej Trzebinski: yes that’s ok; we know that.  

ALICE (Silvia Pisano)

Silvia Pisano: TOF experts would like to do the access (in cavern) on Thu morning in the shadow of the planned access. Chiara Zampolli: if it is not in the tunnel it should be ok.

Silvia Pisano: Regarding the big open point of the collimators and the ZDC during heavy ion running, we are already checking with our ZDC what is the tolerable aperture, depending on the possible crossing angles, so it would be good if you can send us a possible range of the crossing angles. 
Roderik Bruce: As it looks today, we'll run with the same crossing angle as last year, 150 external for ALICE, while we go down in crossing angle in CMS and ATLAS, most likely to 100 murad.

Silvia Pisano: Okay, very good, because then we will have 150 external, 78 internal, so the net is 73, that is within the 100 microrad tolerable for the ZDC acceptance.

Roderik Bruce:  Probably what we have to do is simply we have to cross our fingers and cycle the collimator anyway. There are actually two collimators, the TCDD and the TCLIA, which are both at risk of breaking the bellows, and they're both cycled. And the TCDD is simpler to study. They're studying this now, and if our, let's say, intuition is correct, we might be able to live without that one inserted at injection. This could stay open and parked during the full ion run. Also considering the lower intensity and so forth. So the TCDD, hopefully it can stay open, but we have to wait for the results. The TCLA required significantly longer studies, so it's not sure that we get those results before the ion run. I think, since your physics is killed, if the collimator is in, then I don't think we have much choice. We cycle it at every fill, or risk keeping it open.