LPC meeting summary 20-01-2016 - final
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LPC meeting summary 20-01-2016 - final |
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Main purpose of the meeting: Review of the contents of the LPC talk for Chamonix to be held Wednesday the 27th January 2016.
Jamie thanked the Lumi Working Group to have come up with an agreement on the week for the VdM scan (week 20). At the same time he reminded experiments to stay flexible in case the schedule slips due to unforeseen difficulties.
Witold underlined that ideally the VdM scan should start directly after some running with high intensity beams (i.e. with "warm" luminometers). This was confirmed by CMS. This in mind he asked how long loss maps of the machine (in particular for the VdM scan) would be valid before they expire. Mike answered that the machine in general prefers to use a setup directly after the corresponding loss maps have been established but we could assume that the maps would stay valid for a month.
Mario remarked that the RPs of Totem would be aligned during physics data taking, whereas the new pots for CTPPS would be aligned in the early commissioning phase of the machine.
Federico repeated the requests of ALICE for the Heavy Ion period. Assuming that the request of ALICE (p-Pb at 5TeV) would be accepted he stated that most of the time ALICE would like to run at a lumi of 10e28 to take min. bias data which would result in a 20khz rate. Some time however they would request to run at a lumi of 10e29 in the "rare running-mode". The cross section assumed to calculate the requested lumi from the desired rates is 2.1 +/- 0.1 barn. Considering the desired pileup of 0.5% they request of the order of 300 colliding bunches in IP2. In the optimal scenario they would like to have one VdM scan per configuraion (i.e. one for Pb-p and one for p-Pb) and one polarity flip in the HI period.
If possible ALICE would like to parasitically participate in a high β* run also if there would be no Stable Beams declared and there would be only one colliding bunch in ALICE.
ALICE was asked to provide answers to the detailed questions sent around by the LPC via email (possible the same day).
ATLAS answered to all questions of the LPC questionaire in the slides. In case levelling will be necessary due to excessive pile-up ATLAS wants to review the optimal pile-up value chosen for levelling. It was confirmed by Mike that it is not very likely that LHC will reach average peak pileup values which will make levelling necessary in 2016 (i.e. pu 50).
CMS answered to all questions of the LPC questionaire in the slides.
During the discussion about the VdM scan CMS confirmed that the same setup as in 2015 would be suitable for them.
LHCb answered to all questions of the LPC questionaire in the slides.
LHCb remarked that β* of 24m for the LHCb VdM scan would be ok.
LHCb considers to take SMOG data during the VdM scan (since there will be no possibily to take this data during the high β* run which will not have "STABLE BEAMS" declared.
TOTEM confirmed that nothing changed in their request. In particular there is no request for a 90m run in 2016 from TOTEM. The required data taking time during the 2.5km β* run was given with 1 day. Considering the necessary re-filling, the beam cleaning phases during running and other "overhead" a realistic estimate for the duration of the physics data taking period would be 3 days.
ALFA and TOTEM would agree that the high beta star run would take place at or close to the date currently foreseen in the schedule (week 38 in schedule v1.0).
Helmut Burkhard reminded that a 2.5km &beta!* run is a completely new challenge for the machine and would need some preparation before the week foreseen for the special run. For example 1 day of preparation attached to the June MD and 1 day attached to the July MD could be a possible scenario for this.
It was also clarified by the machine experts that this run would not need a full set of loss maps due to its low intensity beam.
ALFA remarked that some time could be gained by optimising the strategy for the collimator setup for this run.
In principle the third non-colliding bunch in the three bunch beam setup could be brought to collision in ALICE but this should not have any priority and should be only done if it does not lead to any complications.
It was agreed that ALFA and TOTEM will send a slide with details for the planned setup to the LPC for inclusion in the Chamonix talk.
The date of the next LPC meeting will be announced to the lpc-contacts.