Minutes and Summary

Main purpose of the meeting: Start of 2024 data taking, experiment feedback and plans for upcoming data-taking.

LPC minutes 15th April

Introduction (Chris Young)

(Catrin Bernius, Witold Kozanecki, Georges Trad) Do we know when within MD1 the luminosity related MDs will occur? This is not yet decided. There are two MDs; one at injection and one in collision. Only the 2nd requires the experiments. It was expressed that the preference would be to have the 2nd one on Tuesday during the day as from Thursday the same experts will be very busy and some respite is needed inbetween. It was pointed out that the experts are not available during MD2 so these need to be done in MD1. The results from the data taken during the 2nd MD takes too long to analyse to impact the immediately following VdM scans, but there could be some feedback from the 1st of the two MDs.

(Witold Kozanecki) It was requested that after the factorization MD LHCb could take beam gas measurements and this can be accomodated by LHCb.

(Jorg Wenninger) It should be recalled that the preparation/validation for the VdM needs to be completed before the MD1 block. Ideally this will happen in week 19.

(Federico Alessio, Andrea Ferrero) All the MASSI files have been arriving although ALICE only provide luminosity and not the luminous region file. This has not been provided in the past either.

(Catrin Bernius) Is the filling scheme without "with pilot" the same as what was done in 2018? It was clarified that they are identical.

(Michi Hostettler) For the 120cm to 60cm we can do the fast leveling so this step will be quicker but for the 2nd step this is not possible.

(Georges Trad) It should be noted that one of the bunches will have a higher intensity but it will still have pile-up within the range that is expected from the experiments.

FASER (Jamie Boyd)

(Jorg Wenninger) The suggestion of May 8th is reasonable. There will not be needs for access during the MD and Wednesdays are usually when there are accesses, and Thursday that week is a holiday.

(Chris Young) When would the 2nd emulsion box go in? This would hopefully be in TS1 such that it is completely in the shadow.

SND (Gerardo Vasquez)

(Chris Young) Can you clarify which numbers show the background increasing by a factor of two? It is the numbers on the right, but we only have good statistics for some of the runs which is why it varies quite a lot between rows.

(Jorg Wenninger) Note that the 1st May is a CERN holiday when planning which Wednesdays to exchange.

(Daniele Mirarchi, Roderik Bruce) I can provide instructions to extract accurately the collimator setting for each run as some of the numbers in the table are not accurate. There were some fills when the collimator positions were altered and these fill numbers can be provided.

LHCb (Elena Dall'Occo)

(Chris Young) Is the movement within the Velo box the same every time? Yes, things are not shaking around but we think cables are being pushed in a repeatable way. For this reason the luminous region has not been being provided so far but will be soon.

ALICE (Andrea Ferrero)

(Chris Young) I checked that the geometry definition in the MASSI files is opposite to you for z so the shift you see is also what is seen by ATLAS and it makes sense.

(Chris Young) When I looked at the ATLAS and CMS values I also saw a larger offset in the 400b fills which seems to be improving.

(Georges Trad) What are the limits that you can handle? The mean value should not exceed +/-10 mm. Note that the distribution is ~40mm wide.

(Jorg Wenninger) It is not usually necessary to do a mini-ramp-up after you change your polarity. Last year it was probably a coincidence with the technical stop which does require a mini-ramp-up.

(Michi Hostettler) Note for magnet off in the experiments there can be electron cloud issues, but flipping the polarity should not result in this effect.

CMS (Gianni Masetti)

(Chris Young) For the 800b fills I presume you won't have beamspot information due to the pixel problems. Yes, other than the first few hours of one fill these will not be provided.

(Michi Hostettler) For the luminosity change should the apply to all configurations with lower numbers of bunches and not with trains. This has not been calculated and it could be different.

ATLAS (Catrin Bernius)

(Jorg Wenninger,  Andrej Gorisek) The y-axis, does this mean that it is a tiny amount of particles that you are seeing? We only have 8 channels, so only 8 hits can occur per crossing, so most bunches have to be giving signals to get 100s of hits in 5 us. The fear comes from horizontal sprays of particles that would pass through all the front-end electronics and could destroy them which would be disasterous for physics.

(Georges Trad) It doesn't matter for the BSRT run if AFP are in our out. They are not required for the data taking in any case.

(Gianni Masetti) The message relating to having a more efficient commissioning over Easter in 2025 is also supported by CMS.