After 17 weeks inactive, the Large Hadron Collider has started up again – and it’ll soon be performing better than ever.
While the LHC typically takes an annual ‘winter break’ so technicians can perform repairs and upgrades, this year’s stop was longer than usual.
Now, a superconducting magnet has been replaced, and a new ‘beam dump’ installed, and the particle accelerator is once again circulating proton beams.
Maintenance work began in December 2016, marking the beginning of the LHC’s extended ‘technical stop.’
Since completed, each of the machines in the chain have been turned back on and checked, one by one, ahead of the switching on of the final component – the LHC.
‘It’s like an orchestra, everything has to be timed and working very nicely together,’ said Rende Steerenberg, who leads the operations group responsible for the whole accelerator complex, including the LHC.
‘Once each of the parts is working properly, that’s when the beam goes in, in phases from one machine to the next all the way up to the LHC.’
Along with replacing a superconducting magnet at the LHC, and installing a new beam dump in the Super Proton Synchrotron, the CERN team also conducted a massive cable removal campaign.
These upgrade will push the collider to a higher luminosity, allowing researchers to gather more data.
‘Our aim for 2017 is to reach an integrated luminosity of 45-fb-1 [they reached 40 fb-1 last year] and preferably go beyond,’ said Steerenberg.
‘The big challenge is that, while you can increase luminosity in different ways – you can increase the intensity per bunch and you can also increase the density of the beam – the main factor is actually the amount of time you stay in stable beams.’
Last year, the LHC was able to run with stable beams for roughly 49 percent of the time, a big jump from just 35 percent the year before.
This year, they’re hoping to bring the numbers up even higher.
In the first few weeks, only a few bunches of particles will be circulating to test and validate the machine.
But, in the weeks to follow, this will increase until there are enough to begin collisions.
‘We’re changing how we squeeze the beam to its small size in the experiments, initially to the same value as last year, but with the possibility to go to even smaller sizes later, which means we can push the limits of the machine further,’ Steerenberg said.
‘With the new SPS beam dump and the improvements to the LHC injector kickers, we can inject more particles per bunch and bunches, hence more collisions.’
Last month, researchers at CERN’s LHCb experiment revealed the discovery of ‘intriguing anomalies’ that hint at explanations beyond the Standard Model.
The experiment found that some particles decay less often than expected under a particular set of circumstances, and researchers are now working to determine if this is sign of new physics phenomena, or simply a statistical error.
While the findings are so far considered to be only of limited statistical significance, the observation supports similar phenomena seen in earlier studies, suggesting something new could be at play.
The experiments, presented in a seminar at CERN, involved the decay of B0 mesons to an excited kaon and a pair of electrons or muons.
Despite being 200 times heavier, the muon is thought to have identical interactions to those of the electron based on a property known as lepton universality.
In the Standard Model, this property predicts that ‘up to a small and calculable effect due to the mass difference, electron and muons should be produced with the same probability in this specific B0 decay.’
But, in the LHCb experiment, the researchers found that decays involving muons were less frequent.
As the Standard Model predicts electrons and muons have a high degree of symmetry, which has been supported in many studies, the discrepancies seen in the data could ‘signal new physics,’ according to CERN.
Still, the researchers note, it is too early for a firm conclusion, and future tests will be necessary to confirm what they’ve seen, or determine if it was a statistical fluctuation.
The anomaly was detected in the entire data sample from the Run 1 of the Large Hadron Collider, and if seen in the data from Run 2, it could suggest physics beyond the Standard Model.