CERN’s LHC begins its final acceleration today: what can we expect from its work until 2026

The European Center for Nuclear Research, CERN, hits today the acceleration of its Large Hadron Collider (LHC) after almost four years of hiatus and a few months of partial activation. Stop in the experiments that does not mean inactivity, since during this time the largest particle accelerator in the world has been fine-tuned. Now it returns more powerful and luminous. CERN has taken the opportunity to announce a triple find.

10 years since the discovery of the Higgs boson.
And all this one day after the tenth anniversary of the discovery that most marked the work of the LHC, the discovery of the Higgs boson. Finding this elementary particle was the first major project of the European accelerator, a discovery that earned Peter Higgs the Nobel Prize in Physics in 2013.

After its successful first round, the collider faced its second period of activity after a hiatus. Period this second that served to delve deeper into the structures of protons and better understand the decay of the Higgs boson. At the end of 2018, the collider was stopped again for a second stage of maintenance and improvements, which lasted longer than it should due, among other things, to the pandemic caused by the coronavirus.

Stop and set up.
Now the LHC returns to its functions, but with improved capabilities. According to CERN, the accelerator will reach 13.6 TeV of energy, with 6.8 TeV per proton beam (in its previous configuration, each proton beam was accelerated with an energy of 6.5 TeV).

One sign of how the LHC’s capabilities have changed since its opening is the increase in inverse femtobarns. This is a measure that gives us the number of collisions produced (and therefore the information collected). Each inverse femtobarn represents 100 trillion collisions between protons. If the LHC originally generated 12 reverse femtobarns, it now produces 280, or 28 trillion collisions.

The key instruments (ATLAS, CMS, LHCb and ALICE) have been revamped and will be able to collect never-before-seen amounts of information. ALICE in particular will be able, as CERN explains, to multiply the number of collisions to be analyzed by 50.

The new phase, run3.
The new stage of the LHC begins today and we will be able to see this start-up live. The Higgs boson will continue to play an important role in the third phase of the LHC’s work, also called run 3. The collider will study the nature of this particle with greater precision. They also hope to obtain information about the origin of the asymmetry between matter and antimatter in our Universe.

“We are waiting for the measurements of the decay of the Higgs boson towards second-generation particles such as muons. This will be an entirely new result in the Higgs boson saga, confirming for the first time that second-generation particles also gain mass via the Higgs mechanism,” explains CERN theoretical physicist Michelangelo Mangano.

Leptons, muons and primordial plasma.
Muons play an important role in this third stage. They represent one of the great unknowns of the standard model. Belonging to the family of fundamental particles known as leptons, they have behaviors that differ notably from what the model predicts and from what their membership in this lepton family implies.

Heavy ion collisions will also make it possible to study the quark-gluon plasma (QGP), the state of matter that dominated the universe in the 10 microseconds after the Big Bang. Again the renewed capabilities of the LHC should serve to achieve more precise measurements of this state.

Dark matter and beyond.
Dark matter will be the last major research subject of the European accelerator. “There has to be more out there because we can’t explain so many things around us,” comments Sarah Demers, a professor at Yale University involved in the new LHC experiments. “There’s something really big missing, and it’s really big, we’re talking really big 96% of the universe.”

If you want answers you have to formulate the questions well.
When run 3 is completed, expected in about four years, the LHC will be shut down again for another round of maintenance and upgrades. Incremental improvements are not just a question of budget efficiency, they respond to the need to adapt to the incessant changes in physics.

Each successful experiment gives an answer but also raises the following questions, and the instruments must be adapted to answer these. In this sense, the four years of activity that the LHC has ahead are an eternity, who knows what the answers will be today or the questions of tomorrow.

Image | ALICE instrument, CERN