# FeaturedI LHC starts 2017 data-taking

1. Nov 10, 2017

### dukwon

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

2. Nov 10, 2017

### Staff: Mentor

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.

3. Nov 11, 2017

### dukwon

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

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4. Nov 11, 2017

### Staff: Mentor

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.

5. Nov 16, 2017

### dukwon

The high $\beta^*$ run is cancelled 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.