Minutes and Summary

Main purpose of the meeting: PbPb feedback and planning 2025/2026 input to LHCC/JAPW/RB

LPC minutes 18th November

Introduction (Federico Alessio)

(Chris Young) There was an LBOC talk recently by Lotta on potential filling schemes for next year if people are interested in looking at the details.

(Catrin Bernius) Obviously our leveling targets will depend on the filling scheme. Giving a range is fine though.

(Andrea Ferrero) For beam quality and beam configuration are you also interested in opinions on ions for JAPW? Yes, both pp and PbPb.

(Catrin Bernius) Some points will need to be discussed at the ATLAS EB so it will be tight to get feedback for next week but we will try to get it to you as quickly as possible.

AOB (Federico Alessio)

We have started to think about asking to remove the MD on Wednesday if it is not necessary. This is because it is include the squeeze in the ramp which saves time, but if there is the additional squeeze in LHCb next year then this squeeze needs to be moved out of the ramp again such that the MD is not useful. This will be discussed by MD coordination.

(Catrin Bernius, Enrico Bravin) Today it was mentioned that the loss maps for the crossing angle MD might be post-poned? This is true as this can be done at any time, although it takes some time to look at them before the MD. It is not convenient to do it today due to the access meaning this would end up being later. Do you need lumi for the loss maps for the MD? Yes, this is needed to optimize collisions in the 2nd part.

(Enrico Bravin) The jump in the intensity also mentioned this morning is now explained as they found a issue in how the previous cycle was being setup. Therefore we should expect the intensity from the last fill in future fills.

CMS (Andrea Massironi)

(Federico Alessio) The colinearity knob was also tested for IP1/5 but there was little improvement.

(Chris Young) ALICE have a slightly smaller crossing angle so it is expected that they can level longer than IP1/5, which is exactly what we see in the data.

(Federico Alessio) The numbers from Chris's slides last week indicate that it will be tight/difficult in most of the scenarios (and very difficult if 2025 is shorter) to get to 7 nb-1 by the end of 2025, but not ruled out.

ATLAS (Catrin Bernius)

(Federico Alessio) The INDIVs in the 400b fill has been announced so this should definitely happen.

(Enrico Bravin) After the quench we can't inject so, assuming it isn't a very small one (quench-ino) where they might want to re-do it, nothing can happen and you can access.

(Chris Young) You want twice the 2016 lumi? Yes. We had 2x160 nb-1, without taking into account the extra setup days Roderik mentioned, in the "even day split" scenario. This projection was for the higher energy (and there is a gamma factor in the luminosity formula) so twice 2016 in the "even day split" scenario will be difficult based on the current projections.

ALICE (Andrea Ferrero)

(Federico Alessio, Chiara Zampolli) You mean consistent with last year after the mitigations were in place. Yes. The red bar is higher but it is within the uncertainties and changes/improvements in the detector. It is red only to indicate the year, not that it is bad.

(Chris Young, Federico Alessio) This is 500x lower than you usually take data at? Yes, this is the optimal for the calibration. If it is not possible we will level higher.

(Chris Young) Remember that these projections didn't include an additional vdM for the other configuration in the p-Pb/Pb-p projections. Also the setup and switch might be optimistic. To take out 2 days you can multiply the numbers 16/18.

(Federico Alessio, Chris Young) Remember that unlike PbPb this is a single run so there isn't the improvements built up over the years, although the Pb beam is better this year (higher intensity) which will also benefit p-Pb. In the past we have done well compared to projections/targets, but this won't always be the case, and the projection methodology has a strong reasoning.

LHCb (Elena Dall'Occo)

(Federico Alessio) Can you clarify if the 0.3 pb-1 minimum is just for Run 3/2026? This is just for 2026, for Run 3+4 it is 0.6 pb-1.

(Chris Young) Do you use pp reference data for p-Pb at all? Yes, but we interpolate from the pp reference data we have already taken.

(Chris Young) Just to clarify; you did reach your pp reference target so you have sufficient data? Yes, this is an old bullet from before the data-taking.

(Federico Alessio) The value of 0.3 pb-1 is clearly beyond the projections for 2026 under all the scenarios. Yes, this is why the preference is for PbPb.

(Federico Alessio) Is the statement from ATLAS that it is useless to do p-Pb data-taking without an additional pp reference run.

(Chris Young) Did CMS have a statement on the energy for p-Pb? This will need to be clarified under the scenario that ATLAS will require a pp reference run if we are at the higher energy.

Summary

(Federico Alessio, Chris Young) For the LHCC and RB we don't need to specify the exact days but we should have a baseline, which can be slightly altered eg. at Chamonix. For the PbPb or pPb decision in 2026 this doesn't need to be decided now and will obviously depend on the performance for the rest of 2024 and 2025. The bottom scenario, "Max 2025" doesn't appear to be favoured (and was explicitly vetoed by ALICE) as it doesn't give enough time to do both p-Pb and Pb-p which is the desire of 2 experiments. The split scenario allows the possibility of p-Pb/Pb-p and gives opportunities for improvements in PbPb. If we do PbPb all the time we will possibly have a lot of PbPb data such that additional pp reference data could be required which could affect the cool-down, but this would need to be discussed later as it would reduce the PbPb time a lot.

(Andrea Ferrero) For ALICE, we would be happy with a smaller pPb sample in Run 3 compared to Run 4 as in Run 4 there will be the additional forward calorimeter.