Inside the tunnel of the Large Hadron Collider (LHC), the apparatus for accelerating collimated beams of particles was switched out in the early 2000s to transition from colliding electrons and positrons (as part of LEP) to be optimized for colliding hadrons (such as protons) at the LHC. After the HL-LHC is done, will it be time to switch back? (Credit: CERN)
A next-generation collider is required for studying particle physics at the frontiers. Here’s the fastest, cheapest way to get it done.
CERN’s Large Hadron Collider (LHC) is history’s most powerful particle physics machine.
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Deep underground, this tunnel is part of interior workings of the Large Hadron Collider (LHC), where protons pass each other at 299,792,455 m/s while circulating in opposite directions: just 3 m/s shy of the speed of light. Particle accelerators like the LHC consist of sections of accelerating cavities, where electric fields are applied to speed up the particles inside, as well as ring-bending portions, where magnetic fields are applied to direct the fast-moving particles toward either the next accelerating cavity or a collision point. (Credit: Maximilien Brice and Julien Marius Ordan, CERN)
It collides protons at 14 TeV of energy: the highest ever achieved.
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This reconstruction of particle tracks shows a candidate Higgs event in the ATLAS detector at the Large Hadron Collider at CERN. Note how even with the clear signatures and transverse tracks, there is a shower of other particles; this is due to the fact that protons are composite particles, and due to the fact that dozens of proton-proton collisions occur with every bunch crossing. At higher energies, discoveries that don’t appear at lower energies become possible. Modern particle detectors are like a layer-cake, with the ability to track the particle debris in order to reconstruct what happened as close to the collision point as possible. (Credit: CERN/ATLAS Collaboration)
It discovered the Higgs, measuring many of its important properties.
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The first robust, 5-sigma detection of the Higgs boson was announced a few years ago by both the CMS and ATLAS collaborations. But the Higgs boson doesn’t make a single ‘spike’ in the data, but rather a spread-out bump, due to its inherent uncertainty in mass. Its mass of 125 GeV/c² is a puzzle for theoretical physics, but experimentalists need not worry: it exists, we can create it, and now we can measure and study its properties as well. Direct detection was absolutely necessary in order for us to be able to definitively say that. (Credit: CMS Collaboration/CERN)
Have we found the “Standard Model” Higgs, or are additional couplings/decays present?
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The observed Higgs decay channels vs. the Standard Model agreement, with the full suite of Run 1 data from ATLAS and CMS included. The agreement is astounding, and yet frustrating at the same time, as no evidence for either a second Higgs boson or for a non-Standard Model Higgs boson has yet arisen. (Credit: CERN/ATLAS & CMS collaborations)
