Minutes and Summary

Main purpose of the meeting: Data taking during the summer and HI/ppRef plans

LPC minutes 5th August

Introduction (Chris Young)

(Catrin Bernius) For the cryo re-configuration is this confirmed and is there a possibility of the pp reference run being extended if more data needs to be taken? The cryo re-configuration decision needs to be discussed with management and if it is not done then either that day will be additional pp reference data if it is needed or additional PbPb data. The exact date for the first PbPb injections is therefore not known exactly which is an important warning for the injectors.

(Catrin Bernius) It would be good to get the MD schedule soon such that detector commisioning plans can be made. This will be followed up with the MD coordinators and hopefully it can be distributed by the end of the week.

(Catrin Bernius) From the ATLAS side everything presented on the crossing angles for pp ref and PbPb shown last LPC meeting are good.

(Catrin Bernius, Federico Alessio) Are you intending on updating the Run 2 document for the backgrounds or just using the LPC webpages. The hope is to make a new Run 3 version of the document in EDMS.

ALICE (Andrea Ferrero)

(Chris Young) We can arrange the magnet polarity change to be after one of the MDs which is at top energy such that you are in the shadow of the RAMP DOWN. We can arrange this with the MD coordinators.

(Chris Young) It was clarified that the water level sensor has been confirmed to be working again.

LHCb (Elena Dall'Occo)

(Chris Young, Michi Hostettler) Do we know if non-optimized crossing planes could cause the variations through the fills of the vertex position. This is done at the beginning of the fill and then sometimes at the middle and the end and put this in as a feedforward. This feedforward can be improved by re-evaluating it in the next fills which will be done by Michi. Michi and LHCb will look for a fill when it was re-optimized during the fill to see if there is a significant shift/step in that fill. LHCb will also see if the drifts are correlated with the beta* steps at IP1/5.

(Chris Young) Are the peaks in the cooling plot during the daytime when the temperatures are higher. Yes, it is the hotest and most humid days when this is a problem. There is not much that can be done but it will be monitored.

CMS (Andrea Massironi)

No questions

ATLAS (Catrin Bernius)

(Chris Young) For the filling scheme for PbPb running this will be discussed next time. The other experiments are assumed to all prefer to have more bunches and their PbPb physics program is widely known which is why it is only LHCb that is presenting.

(Andrea Massironi, Andrea Ferrero, Elena Dall'Occo) For the CERN Phone issue while CMS does have some back-up solutions we are also thinking of requesting this to be a critical service. Similarly for ALICE there have been issues observed and backup options are being explored. For LHCb there is a backup mobile phone that the shifters can use when the other phones have issues.

(Chris Young) For the tile cooling ppv cycle is this for the whole Tile or a specific region? This is the one for the whole Tile but there is a breakdown by region. ATLAS will keep the LPC informed of how the situation evolves.

(Catrin Bernius, Federico Alessio, Chris Young, Andrea Ferrero) When will the decision be made for the pp reference run for 2025? For the CMS request for 2025 this should be discussed in advance of the run in September. The other issue is taking enough pp reference luminosity which would be dependent on how well the run goes this year and also how much PbPb data is taken. Additionally if there is an extension to Run 3 then again some more additional data might be necessary. The technical request for a noise measurement can be largely decoupled from the other considerations and both will be discussed during September.

(Andrea Ferrero) How does the number of colliding bunches translate to a reduction in luminosity. There are some subtleties in translating the reduction in the number of bunches to the reduction in luminosity due to burn-off etc. However, using the IonSharer it is seen that it does translate into almost exactly the same 5% reduction (or a tiny bit less) and the optimal fill length is very similar.

(Chris Young, Federico Alessio) The request from the research directors is that LHCb presents how they now have a different, better, HI program than has been previously published in the Yellow paper and therefore can justify the request to take more PbPb data at the expense of slightly less for the other experiments. The other experiments are largely carrying out their planned programs from the Yellow paper. The LPC will present a summary of the physics discussion to the research directors and it will also be discussed at the spokesperson meeting. Ultimately the decision will lie with the research directors.