Minutes and Summary

Main purpose of the meeting: Meeting dedicated to near term schedule and ion run preparations

Filip (Introduction)

• Slides were prepared before the RQX.L8 incident of last Sunday night. More news will happen today Monday 17 July at 5pm after a meeting with the technician and management. 

  • Plan may change, but nevertheless we discuss it here.

• Slide 7:

  • Gianni asked what the plan is for next year regarding the intensity per bunch. Filip commented that studies are ongoing and before taking a decision these studies should mature

  • A proposal would be to start at 60, instead of 120. But studies would be needed to prepare and revalidate new optics. The solution is a trick to avoid a in-year validation.

• Slide 9: 

  • Mario commented that for TOTEM to have more than 3 colliding bunches is difficult. 

  • Sune for ALFA commented that for the background test, the 3 colliding bunches is ok. For the final run, another discussion will happen.

  • Roderik commented on the simulation studies: B1 is very positive and B2 is a bit more difficult and there is more to understand there. 

• Slide 11: 

  • Witold commented that for VdM a beta* 3.1m is already difficult to manage. 

  • Gianni commented that it is ok to not be separated at the beginning if the PU is < 10.

    • Filip commented that in principle the limit is around PU 6-7. That would also cut short the leveling length in ALICE. That also imply that there isn’t a need for a smaller beta* and remaining at 3.1m would be the best compromise. 

    • Roderik also commented that going lower than 3.1m implies adding a commissioning activity and that would be more time needed for commissioning. 

 

Roderik (Ion run)

• Slide 5: in principle the proposal for a bigger crossing angle or lower crossing angle should be ok for the ZDCs. Feedback is welcome from all other experiments with ZDCs.

  • Roderik commented that in fact no beam-beam studies were ever done in PbPb and therefore a dedicated MD should be anticipated (intensity ramp-up) to maybe profit from it for the rest of the run. 

• Slide 6: ALICE and CMS expressed the interest to have pp reference runs every year, close to the PbPb reference run. 

  • In the current schedule, the reference run is included in the ion run block

  • Details for the schedule for 2024 and 2025 are still to be discussed. Currently only place holders but we should plan for two pp reference runs.

• Slide 3: Martin Rybar asked what the meaning of “potentially higher for Ip1/5 mean”.  Roderik said that we can’t go a little higher for Ip1/5 in disfavor of ALICE. 

 

Elena (LHCb)

• The vacuum spikes are physical (see multiple slides in the LHCb presentation). 

  • No major effects, in particular on the temperature observed around the VELO

  • Also observed a big spike from last night, source unclear. 

 

Silvia (ATLAS)

• Slide 4: Matteo commented that the LHC can easily reduce the intensity as low as 0.5x10^11 ppb. Difficult to make sure the emittance is as required. 

• Klaus Monig (ATLAS on pp reference run)

  • To keep the same precision for luminosity estimation to 1% as in 2017, ATLAS asks to add 2 hours to the 2017 program (from 4h to 6h total). 

  • Filip commented that a balance between precision and data taking will need to be found.

 

Sarah (ALICE)

• Slide 8: it seems that the anti-leveling proposed by Roderik should work wrt ZDC operations. Also with an intermediate value if found.

• Slide 11: a rotation of the crossing angle implies more commissioning time. So the solution for a single larger external crossing angle with both polarities would be preferred.

  • ALICE clarified that they are discussing the possibility to do a single polarity data taking this year and flip the polarity next year.

  • However Roderik commented that there is no overhead in implementing a big crossing angle, even with the polarity swap. 

    • Roderik specified that this is subject to make sure aperture is ok.

    • This was decided to be the baseline, allowing ALICE to have both polarities already this year. 

    • To be followed-up.

 

Gianni (CMS)

• Slide 4: Filip and Roderik commented that the length of the VdM calibration goes at the expense of data taking time.