Minutes and Summary

Main purpose of the meeting: Meeting dedicated to the restart schedule and beams activities

Filip (Introduction)

Slide 3:

current schedule approved by LMC. Likely to already shift earlier by one-two days, to be confirmed.
Unclear at the time of the meeting, when the SB at injection energy can happen. Agreed during the meeting that the 4h of SB are anticipated on Friday (about 4h)
If the plan is anticipated linearly, the high beta* run would be anticipated to Sunday (instead of Tuesday). This needs to be confirmed depending on availability of experts.
Mario for TOTEM confirmed that it should be ok to start the high beta run on Sunday, then followed by the VdM2 session on Monday.
- ATLAS instead commented that the experts are not around until Monday.
- It was agreed at the meeting that the high beta star run will be then scheduled for Monday to maximize the chances of success
It is understood that the schedule may still shift and change on short notice.

Slide 4:

Request to highlight when luminosity should be provided by the experiments.
Matteo underlined that once they go into collisions, the machine will dump. Unless otherwise requested.

Slide 5:

Filip asked if the roughly 1000 bunches of space in between fills are a requirement from ALICE and LHCb or if it can be reduced by roughly half (525ns) .
- ALICE confirmed that that is fine for them.
- LHCb will confirm later.

Slide 7:

Filip commented that a new filling scheme editor was provided by the LHC colleagues and that changes slightly the format of the .csv files. Experiments are asked to crosscheck if this is ok or not. It has been requested to also made the old files/filling scheme available in the new format.

Slide 8:

A compromise for the VdM filling must be found during the pp reference run as the fill will happen with physics optics.

Marco D’Andrea (LHC, Update on simulated background at TOTEM for the very high beta* run)

Two solutions (options) were presented at the meeting, reducing dramatically the background at TOTEM.

Mario asked if impedance is really a problem as there are tiny currents involved in the test. Andrea confirmed that it will be checked with the impedance team.
Daniele also confirmed that a more relaxed option allows one to keep the settings for a very long time.
Daniele also highlighted to TOTEM that in Option 2 rate is still quite high and it may overlap with the signal region. Valentina confirmed that this is not a problem of rate but of reconstruction/alignment. Valentina will study offline and she would prefer to test Option 1 during the background test.
Sune asked if there is no leaking background into other pots or ALFA. Andrea said that this will be studied more but at the moment nothing is seen.
Sune also asked if crystal collimators are also used in the H plane. Daniele e Andrea confirmed that this is possible and will need a few hours of extra setup.
Mario asked if it has ever been tried to insert some other collimators a little closer. Would it help? Andrea confirmed that many configurations were tried and that this is the best they could find.

ALICE (Sarah)

Alice confirmed offline that the limit of the VdM bunch spacing is at minimum 400ns.

LHCb (Elena)

The possibility of having more stable beams at injection after the startup is dependent on how fast the plan will proceed. Matteo and Filip commented that it could be added to fill up the week-end, if possible.

ATLAS (Silvia)

If luminosity values are requested during recommissioning, it needs to be known in advance in order to calibrate the luminometers based on the energy.

ATLAS luminosity in PbPb (Klaus)

Filip asked Rende if 100ns beams would be ok if the slip stacking would not be ready yet. Rende confirmed this is ok even without slip stacking.
Roderik asked for “late enough” means. Filip confirmed that means the end of the ramp-up. We could however keep the option open to do it before the end of the ramp-up as a stocking fill.

CMS (Gianni)

Next Meeting on Monday 4th September 2023.