Minutes and Summary

Main purpose of the meeting: Plan for 2026; updated schedule; progress with commissioning

LPC 9 March 2026

Present (P = in person): Martijn Mulders (P), Chiara and Nicolas Zampolli (P), Eric Torrence (P),  Jörg Stelzer (P), Andrzej Filip Moortgat (P), Krystian Roslon (P), Silvia Pisano (P), Flavio Pisani (P), Paula Collins (P), Roderik Bruce (P), Jorg Wenninger (P), Joanna Wanczyk (P), Michi Hostettler (P), Archie Sharma, Julia Negro, Maciej Trzebinski, Witold Kozanecki, Brian Petersen, Gerardo Vasquez, Riccardo Longo, Richard Hawkings, Peter Steinberg, Andres Delannoy, Matthew Nguyen, Tomasz Bold, Stephane Willocq, Ivan Amos Cali, Dragoslav Lazic, Anna Sfyrla, Benoit Salvant

LPC intro (Chiara Zampolli)

Paula Collins [concerning the updated 2026 schedule]: what happens if the van der Meer scan takes longer than planned, e.g. by one day? Chiara Zampolli: then the MD1 and 1.2 TeV run get shifted; they will have to be a bit flexible. Filip Moortgat: so in the end it will be absorbed by pp. Chiara Zampolli: yes, exactly. Which is unfortunate. So, ideally, the van der Meer scan should stay on time.

Eric Torrence: I guess I had one quick question on your comment about the intermediate 400 bunch fill coming back from the MD1 period. That's really triggered by the MD period, not by whether we're running low-mu or high-mu before? 
Chiara Zampoli: Yes, it is triggered by the fact that there's a long stop of normal operation, so this is the standard MPP request. If both experiments decide to go back to high mu directly [without stop in between], then it is just one intermediate fill with a bit lower intensity that is required. If it is only Atlas, then no requirement. [we would anyway be using a bit lower intensity 1.4-1.6 in that case]. Jorg Wenninger: so the message is: you go back to high-mu in one fill, and the next fill CMS...  

CMS (Filip Moortgat)

Chiara Zampolli [about Filip’s concern that the request of 1h at PU==1 during the 3rd 800b fill is propagated properly]: I have added it to the table of requests. Filip Moortgat: Yes, so you are all good for now. I will probably still send an email to Xavier. Martijn Mulders: Does the 1h have to be at the beginning of the fill? Filip Moortgat: no any time during the fill is fine. 

Jorg Wenninger: [regarding the offer from CMS to use 1 magnet cycle to test the effect of switching the CMS solenoid off] we will request CMS to switch off the magnet during the 2 days High Intensity test after MD1. From there we can extrapolate. If the effect is catastrophic we will ask you to switch back on and then we don’t know what to do in the summer but that is another story. 

Chiara Zampolli [about Filip’s recommendation to publish the new schedule officially in EDMS now that it is approved by the LMC]: yes I think they also wanted to check with the other committees.

Chiara Zampolli: one question about the first fill with full machine. Did you discuss whether you need the INDIVs? Filip Moortgat: no, we did not. Chiara Zampolli: Ok, we can iterate offline. 

Witold Kozanecki: beta star measurements were taken during the van der Meer cycle this weekend. How steady do you expect those values to be between now and when we get there by late April? Jorg Wenninger: you can only say something about the comparison to last year. It is surely better than 10 percent. To know how much better you have to compare the beta-beating value of this weekend with the one taken last year, and the k modulation by the way. Witold: Ok, I am happy with 10 percent or better. 

ATLAS (Eric Torrence)

Chiara Zampolli [about the opportunistic request for horizontal muons ]: can you remind me which subdetectors are using these horizontal muons? Eric Torrence: it is mainly the tile calorimeter end-caps, that we can’t get from cosmics data. Martijn Mulders: and you want to have this before the high-luminosity data? Eric Torrence: no, it doesn’t matter. We will take it whenever we can get it. We have done this for several years. For several reasons every year but last year the Toroid was off. We got data last year for the first time with the Toroid on, and would like another data set to compare. 

Chiara Zampolli [about the question what are the consequences for Run4 if the Oxygen source test is delayed or cancelled]: I did not ask, but they can move it to Run4 and Reyes did not sound concerned at all. I will check.

Chiara Zampolli: so for ATLAS is not a problem to switch back on the Toroid in case of physics data taking? Eric Torrence: yes, for us switching off the Toroid helps with the LS3 schedule but it is not a critical path item. 

Chiara Zampolli: also for you.. If you need the INDIVs. Eric Torrence: I will ask. Yes. 

Martijn Mulders: for the 1.2 TeV Run, were any emittance scans planned? Michi Hostettler: presently not, but we have to see with aperture how this fits. We are anyway tight, and to get the same separation in sigma the displacement in mm would be larger. In the non-squeezed IPs it is probably not a big deal but we have to see how far we can separate. Close to 3 sigma we can probably get. Eric Torrence: yes, we will take whatever we can get. Chiara Zampolli: and LHCb also does not need scans? Flavio Pisani: no, we do. Michi Hostettler: so we also have to see how far we can scan. 

Witold Kozanecki: I remind you that we did scan that 900GV center of mass in November of 2018. And I don't recall of any tight limits there, but maybe Michi can look back at the history and see whether he's comfortable with this. I presume that at high energy it should be slightly more comfortable, right? Michi Hostettler: I think 3 sigma is fine, but anything more we will have to check. 

ALICE (Silvia Pisano)

Chiara Zampolli: Same question for the INDIVs. Silvia Pisano: We will let you know. 

LHCb (Flavio Pisani)

Michi Hostettler [regarding the request to do 1D x, y, and LS calibration scans during the 800b fill] Okay, for the length scale calibration, we have to see for the range, because normally, in physics, we limit to 3 sigma or 2.5 sigma displacement per beam, and your length scale calibration uses more than that. But I remember from last year, we have probably a length calibration sequence that is a bit more tame. They have to run in the mode that they don’t block other activities but the problem is that they do block the beta star leveling. So, do you need them all in the same fill? Flavio Pisano: I will check with the experts. Michi Hostettler: the only place to reasonably do it would be at the end of the fill. Jorg Wenninger: or to use the low-mu 800b fill, when the progression is slower, but maybe that is stretching a bit that fill. Michi Hostettler: we could of course try to do it at the beginning and play a bit with separation and skip ahead a few steps in beta star but then it would no longer be a standard fill. We have to check with MPP what they would be fine to do. Flavio Pisano: of course we don’t want to slow down the commissioning. Michi Hostettler: if it takes only 10-15 minutes for x and y, and 10-15 minutes for the LS calibration we can just do it at the end of the fill. Then we don’t have to play any tricks. 

Michi Hostettler [regarding the request for the emittance scan to 3.1 sigma during the 1.2 TeV run ]: 3.1 separation, or per beam? It has to be separation, otherwise 6.2 is more than we normally do with lumi scans.

Chiara and Filip discuss the settings for the potential Oxygen run, and conclude that with the same settings as last year, it would mean just an increase in the number of days, to about 7 days (maximum) which would be an increase of a factor 4 compared to last year.  

Chiara Zampolli: Also check the INDIVs. Flavio Pisani: I don’t think we need them but I will double-check Chiara Zampolli: it anyone needs them it is no problem to do it. Filip Moortgat: maybe having it for the first fill is not a bad idea. 

AOB

Eric Torrence: I forgot to put it on my slides, but we also have a change in Run coordination. Joerg Stelzer is here now until the end of Run 3. Some of you may recognize him because he was run coordinator already in the past, at the start of Run 3. And so, Andrzej is now released from his obligations. But he is still here today. Thanks a lot, Andrzej.

Chiara Zampolli: It was very, very nice, a lot of fun working together. So, I really liked it. So, thanks a lot, Andrzej !