I What are the challenges faced by LHC in the initial data-taking of 2017?

[dukwon]

It's the energy used for proton "reference" runs, with the same per-nucleon energy as the lead-ion collisions.

 

[mfb]

In numbers: Protons can be accelerated to 6.5 TeV each, lead with its 82 protons to 82*6.5 TeV per nucleus, with its 208 nucleons this leads to an energy of 6.5*82/208 = 2.56 TeV per nucleon. The difference to 2.51 TeV is probably a rounding error.

Result of the high energy high luminosity proton run: 51/fb for ATLAS and CMS, 1.75/fb for LHCb, 0.017/fb for ALICE.
And a luminosity world record, the first time a proton-proton collider achieved it.

 

[dukwon]

The Pb beams in Run 2 have been 6.37 Z TeV per ion for some reason.

 

[mfb]

Ah right. There was some reason, if I remember correctly it was chosen to match the nucleus-nucleus center of mass energy of earlier proton lead collisions or something like that. The better comparability was more important than 2% in energy.

 

[dukwon]

The high $\beta^*$ run is canceled because the background levels are too high for the Roman Pot experiments. Therefore the LHC will return to 13 TeV proton physics for 22nd–26th November. CMS will level lower to make the intervention easier.

 

[websterling]

The 2017 run has ended this morning and the machine is being shutdown.

 

[websterling]

Here's a short summary of this year's run-
LHC Report: An eventful and successful 2017

 

[mfb]

Updates and outlook:

Sector 1-2, which had the 16L2 problem, has been warmed up partially. It is expected that nearly all of the gas in it is gone now.
For 2018, 138 days of proton-proton running are planned (compared to 127 in 2017), with an expected luminosity of 60/fb for ATLAS and CMS.
It is expected that both ATLAS and CMS will want to keep pileup at about 60 interactions per bunch crossing. Without the 16L2 issue we get up to 2544 colliding bunches, or 2.15*10³⁴/(cm²*s) luminosity, 215% the design value. If that works well and the experiments are happy with more pileup, the machine operators have some ideas how they could possibly go to 250% to 280% the design value. Such a high initial luminosity makes faster re-filling more interesting for ATLAS/CMS. LHCb mainly wants long fills and is not interested in these high luminosity values, so some compromise has to be found.

 

[Greg Bernhardt]

Updates and outlook:

Will need to start a 2018 thread soon :)

 

[mfb]

With 2018 data-taking probably. I don't expect so many events in 2018, however. Unless something unexpected comes up the focus will be on doing more of the same to get as many collisions as possible before the longer shutdown.

SuperKEKB/Belle II are expected to start data-taking in 2018, that will be new.