Minutes and Summary

Main purpose of the meeting: Discuss update to the schedule after the vacuum leak repair and latest (special) run configurations

LPC 23 February 2026

Present (P = in person): Martijn Mulders (P), Chiara Zampolli (P), Eric Torrence (P),  Roderik Bruce (P), Krystian Roslon (P), Silvia Pisano (P), Flavio Pisani (P), Paula Collins (P), Matteo Solfaroli (P), Jorg Wenninger (P), Joanna Wanczyk (P), Archie Sharma (P), Julia Negro (P), David Stickland (P), Michi Hostettler (P), Matthew Nguyen, Maciej Trzebinski, Witold Kozanecki, Tomasz Bold, Stephane Willocq, Klaus Monig,  Ivan Amos Cali, Brian Petersen, Gerardo Vasquez, Riccardo Longo, Richard Hawkings, Peter Steinberg, Andres Delannoy, Reyes Alemany

LPC intro (Chiara Zampolli)

Regarding the external crossing angle to be used for the 1.2 TeV run (slide 12), Jorg Wenninger comments that they had overlooked the infamous IP offset which is in the crossing plane, meaning that we cannot go to 170 murad, but 140 murad is better and should be Ok, to be checked. (Roderik Bruce): I think that is a good working assumption. And Bjorn is checking. 

Slide 18: (Giulia Negro) discussions are ongoing regarding the possibility to test the CMS solenoid OFF (with small magnet current ON) during the MD1. It does not seem likely that it is possible but we will let you know. 

Slide 19: Paula Collins asks whether the question about minimum crossing angle in heavy ion running is about avoiding satellite collisions or something else. Roderik clarifies that this is taken into account anyway – he is asking for any additional limitations from the experiments (cfg. Acceptance of the ZDC in the cas of ATLAS). A lower crossing angle could provide longer leveling times for everyone, hopefully. Paula does not see any limitations from LHCb side, but will have to ask around to double-check with the physics analysis groups. 

A brief update from Jorg Wenninger: we are trying to close the machine. At the moment we have a vacuum valve problem in point 4 that blocks us. But we have closed all accesses. We are ready to move as soon as we get the valve open.  

CMS (Giulia Negro)

CMS reports that the new 50/15 optics will reduce the PPS acceptance by 10% because the pots have to stay further away from the beam (for the whole fill) to accommodate the conditions at 50/15. Jorg wonders whether AFP would experience a similar effect, although things could be different as it depends on the dispersion. ATLAS will check. Martijn suggests that if there is a physics case not to go to 50/15, we may want to revisit this point in the light of new information (even after the approval from the LMC). 
There is a short discussion about the alignment of the PPS roman pots that will be needed at 3 TeV during the High-Intensity test in June. This alignment for 2 pots will be quick (~1h) and is needed just to know how far the pots can be inserted. They will not be taking data (there will not be collisions at 3 TeV). 

ATLAS (Eric Torrence)

To correct for the vertical position of the beamline, it would have to be done earlier during commissioning (Roderik, Jorg, Michi), before stable beams so we could move the beam up by a 100 micron but it  would not be possible to know precisely how large the shift is. Eric will check with the physics groups and come back to this point. The preferred position would be the same as 2025, but a little bit above would also be Ok.

(David Stickland:) is it possible to do short emittance scans during the low-mu period? We don’t expect many changes, but having a couple of markers would be useful. Would ATLAS want to do them as well? Would ATLAS have to be head-on when CMS is doing an emittance scan, or can they be separated? (Michi Hostettler:) I would try it. In the past there have been situations like this and for a limited duration of time it was Ok. (Chiara:) so we assume that one experiment can do an emmitance scan and the other can just take low-mu data. And we assume we can do this at the beginning of a fill? (Unknown but confident voice:) yes. (David and Eric): traditionally we have tried to avoid this, because of stability considerations. We could also try to do it at the end of fills. But normally the conditions at the beginning of fills are more consistent, so scans can be more easily compared.

ALICE (Silvia Pisano)

(Martijn Mulders:) do you already know if the cleaning operation of your TPC during the YETS had a positive effect? (Silvia:) no, we can tell something once we get the first 800b fill. Then we will do the first test. 

LHCb (Paula Collins)

(Flavio:) LHCb will ask for about 1h during FT to time align PLUME.. whenever this would fit in the commissioning. 

(Paula:) it would be good to present the final configuration for the 1.2 TeV Run, with apertures etc, to the VELO group for their endorsement. (Roderik:) calculations taking into account the bumps and offset are ongoing, as well as the loss map simulation of possible losses in or near the VELO. Let’s follow up on that in the coming week. (Paula:) we have the ‘cheap’ backup option of slightly opening the VELO, except if this perturbs the calculations (Roderik:) no the aperture will always be better if you open the VELO. (Paula:) yes. well , this backup option is very high in our minds.