Where no-one has gone before

Guest post by Alexander Grohsjean

Born at the end of the ’70s, I was still in school when the heaviest of all quarks was discovered at the Tevatron: the top quark. Back then I had no idea what it was about. But reading an article in the newspaper I felt the excitement surrounding such a discovery. My interest for the smallest and most basic building blocks of the universe had been awakened. When I joined the CMS Collaboration in 2014, I had no doubt that the first measurement I would like to do was that of the production rates of top-quark pairs at the new energy regime of 13 TeV. Shortly after the restart of the LHC in summer this year, we began a journey where no-one has gone before.

A top-quark candidate in the CMS detector. Credit - CMS Collaboration

The short story of Long Shutdown 1

Long Shutdown 1 (LS1) — the two-year period of maintenance, consolidation and upgrades to prepare the LHC and its particle detectors for collisions at an energy of 13 TeV — recently came to an end as the LHC was successfully restarted earlier this year. Although the term “shutdown” seems to imply a quiet period, this interpretation couldn’t be farther from the truth. Below we present in no particular order some highlights from what was a very productive two years at the CMS experimental site, as we take the final steps towards analysis data at the new energy frontier.

Night-shift live stream: #RestartLHC splash events

Yesterday, the LHC circulated the first beams in the accelerator after Long Shutdown 1 and CMS recorded some splash events.

This evening, we'll get a second batch of splash events and shifters are eagerly awaiting beam in the CMS Control Room.

We'll provide you with short updates from our shifters for the next few hours.

CMS sees first beams of LHC Run 2

Yesterday was an exciting day! While many people were hunting for eggs in their gardens and enjoying a nice Easter-Sunday lunch, physicists and engineers from CMS congregated in their control room near Cessy in France to partake in their own hunt: for the first signs of particles from the LHC in the CMS detector for two and a half years. In the morning the LHC operators started to thread the protons beams around the 27km ring, sector by sector. They first tried with "beam 2", the anti-clockwise beam.

Preparing for the first beam "splashes"

After a two-year hiatus, proton beams will soon start to circulate in the LHC and, in a couple of months from now, we will have the first collisions at 13 TeV, nearly twice as much as in the first run of the LHC back in 2010-2012. Many things have improved in the LHC, to allow this higher energy, but many things have also happened in the CMS detector too. Some changes and repairs of hardware have been made, along with many improvements to "firmware" - the computer programs embedded in the custom-made electronics that control the detector - and software.


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