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.
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.
Having successfully performed a Magnet Test in mid-November where the CMS magnet was run at the full operating field of 3.8 tesla, the focus in the CMS underground experimental cavern has transitioned to full activity to re-open the detector.
“Welcome to the CMS Experiment. We are 100 metres underground and I will now pass by the eye scanner to take you for a virtual tour and show you our massive scientific machine,” said CMS physicist, Abdollah Mohammadi, to 200 enthralled students sitting in the hall in the Sharif University of Technology in Iran last Tuesday.