Minutes and Summary

Main purpose of the meeting: Chamonix summary, intensity ramp up and tests in 2025, OO, NeNe

LPC minutes 3rd February

Present: Chris, Chiara, Catrin, Paula, Rosen, Andrej, Giulia, Silvia, Andrea Missironi, Andrej Gorisek, Andreas Guillermo Delannoy Sotomayor, David Stickland, Filip Moortag, Gerardo Vasquez, Robert Muenzer, Klaus Monig, Lorenzo Bonechi, Manuella, Martin Rybar, Matteo Solfaroli Camillocci, Peter Steinberg, Reyes Alemany Fernandez, Riccardo Longo, Stephane Willocq, Witold Kozanecki, Ivan Amos Cali, Dragoslav Lazic, Joanna Wanczyk, Stephane Fartouk.

Chamonix feedback, intensity plans, pO, OO, NeNe (Chris Young)

S7: 

Consensus: ask for the plan for the 2.3x10^11 test to the machine.

Filip: if they want to let things commission for a bit, I was suggesting to Jorg that we may do the low ppileup run during this run. So instead of non colliding, let it collide a little bit. 

Catrin: this was discussed in Chamonix and I think that the concern would be with possible instabilities with the beams the beam offsets that you'd need to apply to get the pile-up low enough.

Filip: Jorg said it is possible.

Chris: I think it depends on what they are doing. If they have 8b4e pure, they run at top energy, then maybe they have another one they run at 2 TeV, with standard or BCMS beam, so they might be doing quite many different things.

Filip: yes, but I am not considering such cases, only the possibility that they might want some stability, which we then could combine with low mu.

Catrin: what would be the effect on the cool-down requirement?

Filip: that’d be ok, if it is low mu. Note that it is not enough on its own: it has to come after HI.

Chris: is this what the CMS RP agrees with? After HI you can do low mu for 2 weeks?

Filip: they still have to study it. But as far as I have understood from previous studies with low pileup, it is not too bad, but it is not enough, you need something else in addition, next to it. 

Catrin: so you are willing to sacrifice the low mu running in case something is wrong, and the machine breaks.

Filip: yes.

Chris: we need to know how much time they are at top energy, basically.

Filip: yes. We need to understand if they are interested, or if they say “no we don’t want to do it, we don’t want to look at stability when running at 2.3x10^11”. But if they do, rather than have non-colliding beams for the whole duration, while don’t we do the low pileup?

Chris: but this only works if we’re at top energy.

Filip: yes, only at top energy and if they are interested in seeing how it behaves for a time of the order of two weeks.

Chiara: then it should be 8b4e.

Filip: yes, 8b4e at top energy.

Chris: this is also why it’d be interesting to see their plan, to see how long they intend to spend in each configuration. There are are least three that they want to try. 

Catrin: other input on the test: for ATLAS, it is unacceptable to do anything with 2.3x10^11 in 2025 with 2000 bunches.

Matteo: we’ll show the day by day plan, but Jorg’s presentation was mainly to kick off the discussion since till ~1 month ago, the 2.3 test was considered a taboo. For the time being, we don’t have the day-by-day plan. The 2-weeks plan is debatable, we still don’t know, it depends on how much we want to do and at what level we want to take risks. So this is for the moment extremely vague. One clarification: the 8b4e choice is only to bring beams to top energy since we cannot bring BCMS to top energy full machine for heat load reasons. The option for the 2 TeV was to use standard beam, and to reduce the risk, because even if we could bring beam to top energy, we have limitation to too high intensity due to some limitation of some equipment with respect to intensity. For the statement that Catrin said, do you mean that 2.3x10^11 is not ok also at injection?

Chris: yes, even if only at injection, if with more than 2000 bunches (which is more than we did before. So if you get 2 weeks in 2026, then we don’t do anything in 2025.

Matteo: what if you split the two weeks?

Chris: you don’t know what you are going to break.

Filip: CMS agrees that all the risk should be in 2026.

Catrin: the main concern is the risk, and wanting to take as much lumi as possible. 

Matteo: The risk is for the experiments or the LHC?

Chris: for the luminosity collection program, not for having the test not done.

Catrin: LHC. We don’t know indeed what happens to the detectors, but it should technically not hurt us.

Chris: the logic is that if the experiments are sacrificing physics time for the test, then they prefer to do it after they’ve taken the data.

 

S9:

Reyes: the discussion to align the end of OO run with the North Area (NA) physics with O. Rende is preparing the schedule, such that LHC and NA physics with O will finish at the same time. This means that if we finish O data taking earlier than foreseen, we might not be able to switch to Ne, we might need to wait until NA finishes the O data taking. 

Chris: it would actually be the other way around: maybe it might take longer for Oxygen, so it might mean that we don’t get Ne. Roderick will also present at LBOC on 18.02.

 

Catrin: switching the source and setting up the beam for Ne, is it transparent?

Reyes: on week 15 (6-7 weeks before the O-run) we switch the ion source with the O beam for 2-3 days; when this comes out stable from the source, we will switch to Ne, to quantify what is the contamination of O as a function of time, to see how much time it takes to get the contamination below a certain value, and if after 5-6 h we can deliver a Ne beam with sufficient stability. If we pass the test, then we have all green light to go on. Otherwise, if we cannot stabilize the beam in 6 hours, we come back to you, and probably cancel the Ne test in the LHC.

Chris: this is an action item for LMC and IEFC (Injectors and Experimental Facilities Committee) to look at this in detail, from Chamonix.

Catrin: so the strategy is to take O data if the test was good and if everything works well, and the decision is to take Ne, then when we’re close to the target, we switch to Ne.

Chris: we spend this 5 hours doing O run, but we might lose the fill, so we want to be at target before we do this. This is like a bonus fill. Then you inject Ne and if during this bonus O fill you lose it, you have to sit and wait. But in principle we should know more or less if O will work, because by then we’ll have already a few fills with OO.  

Catrin: is there a projection about how much we can take with the lower energy in OO?

Chris: it will be on LBOC on 18.02

 

 

CMS (Giulia Negro)

 

No comments.

 

 

ATLAS (Catrin Bernius)

 

Catrin: how much extra time would it take to have a lower (than 0.6) mu in OO? This could be another question to ask for a projection with a lower mu.

Chris: we need to iterate with Roderik. But not everyone wants to take 0.6 and we’re trying to get to the same lumi target for everyone. So the run length is not dictated by ATLAS being able to take 0.6, because ALICE will be levelled to 0.2 and 0.3. So it almost makes sense that everyone is levelled at 0.3.

Catrin: this would be even better for us. It is not our request to take 0.6, but it is an answer to your question whether we could be levelled at 0.6.

Chris: maybe the GPD (General Purpose Detectors - ATLAS + CMS) will level slightly higher than ALICE, but they’ll be slightly worse in the tail-off region and people will hit the target more or less at the same time. The fills then gets longer, which is beneficial to everyone.

Catrin: this would be beneficial for our reconstruction.

 

Chiara (to CMS): how much would you need at low-mu?

Catrin/Filip: 1 fb-1 for the low-mu.

Filip: this is of the order of 2-3 weeks, but then we can play a bit with the mu. 

Chris: what mu are you playing with?

Filip: 3-ish, 4, 5.

Chris: and this gives 2 weeks? with 7 days of perfect running, we got 500 pb-1 when you were running at 7 (the pp ref run). 

Filip: but this was lower energy.

Chris: what difference does it make? It is very little as difference. 

Chris: it will take up to three weeks.

Filip: we don’t really exactly 1 fb-1. And we can let them fight among each other if we want a little bit higher mu :-) 

 

 

LHCb (Paula Collins)

 

S1:

Paula: Shims removed → beam closer to the detectors, data rate increases to a few TB/s. 

Chiara: do you do magnet field campaign every year?

Paula: no, it is a special campaign to measure at the very fringe of the field.

Chris: can you clarify the issue with the shims?

Paula: they are related to an internal movement of the silicon inside the box. So when the shims are removed we will gain 500 um, the silicon will come closer to the beam pipe by 500 um on both sides than it was before. The data rate will go up to O(TB/s) from the VELO. 

Chris: but it is mechanical?

Paula: yes, it is the same approach but the silicon is closer, and will improve the impact parameter resolution and reach design performance.

Witold: which precision LHCb needs for luminosity in both pO and OO? How much VdM time do you want to spend, if any?

Paula: for OO we do not request anything specifically. For pO, for the VdM, we are targeting at 2 hours, if we need more, it will come from our budget, in terms of lumi target. The target is 5% on lumi determination. 

Chris: We are assuming that all experiments can remain in collision during everybody’s scan since this is very low intensity, so that the time is not taken from lumi time, but on the individual experiments lumi. 

Chris: will you run SMOG in both pO and OO? 

Paula: yes, in both pO and OO.

Chris: does this mean that will there be ghost charge measurements available by default? Or this can happen at the same time as the data taking?

Paula: Witold, will you need the ghost charge measurements?

Witold: yes.

Rosen: we can do them at the same time with the SMOG program.

Paula: was there a question for LHCb about the pileup? I understood that the max pileup expected for LHCb is 0.2. If it’s higher than that, then it is good.

Chris: the question was indeed also for you since it looks you might get more than 1 collision per crossing. But if you need to level, we can discuss on the 18.02, when Roderik will show the peak pileup, and we’ll have a better idea of how high it could be. It might be that it will stay below 0.2 and then it its not an issue. 

Paula: I anticipate that we have no problem whatsoever.

 

 

ALICE (Silvia Pisano)

 

S2:

Witold: do you include long scale calibration and something to measure non-factorization?

Robert: yes, the minimum program that we require includes XY scan and long scale calibration.

David: seems aggressive, and optimistic for 1.5 hours…