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Future Circular Collider (FCC)


Tina Potter

Future Linear Colliders


Val Gibson

After the discovery of the Higgs boson in 2012 at the Large Hadron Collider (LHC) the particle physics community is already looking to the future to make the next major breakthrough. While results are still being produced by the LHC, the scientific community is considering future projects that will be able to complement those results.

Two outstanding candidates for future projects are the Compact Linear Collider (CLIC) and the International Liner Collider (ILC). Both of these colliders would offer unparalleled precision in comparison to any other particle collider currently in existence. This precision is achievable via the application of particle flow calorimetry using the PandoraPFA software kit. This is the main area of research that the Cambridge linear collider group is involved with.

Both the ILC and CLIC are at different stages of development. The ILC community published a technical design report (TDR) in June 2013, which covers in great detail the design of the collider. This means that the ILC is ready to be built and a decision on where it will be constructed is ongoing. One of the most promising locations for the ILC is Kitakami in northern Japan. The CLIC community published a conceptual design report (CDR) in October 2012. The CLIC collaboration is currently in the process of developing new hardware and software tools so that they can extend work contained in the CRD and produce a TDR in the coming years. As CLIC is based at CERN the location for the CLIC collider would be Geneva, Switzerland.

The Interational Linear Collider (ILC)

Artist's impression of the International Linear Collider. (Courtesy of SLAC)

The ILC would enable physicists to explore in unprecedented depth energy regimes in the range 0.5-1 TeV. This is a particularly interesting energy range to consider as it allows access to the study of both the Higgs boson and the top quark. While both the discovery of the Higgs boson and the top quark have been confirmed the details of how they interact with the rest of the standard model particles requires further development, which a linear collider would offer. Also, thanks to the outstanding precision of the linear collider, any deviations from the standard model predictions will become clearer allowing a more thorough search for beyond standard model physics.

The Compact Linear Collider (CLIC)

Proposed Compact Linear Collider, superimposed on landscape, with LHC in view as a comparison.

The CLIC collider aims to go beyond the ILC in terms of the energy range being considered. CLIC aims to probe the multi TeV scale. Current designs for CLIC have it as a staged machine, where it will run for a given period of time at three energy stages, 360 GeV, 1.4 TeV and 3 TeV. At the lower energy step CLIC will also have access to the Higgs boson and top quark physics that the ILC has. At higher energies CLIC will have better power to probe beyond standard model physics such as SUSY. The final energy of CLIC would be dependant upon any beyond standard model physics discoveries at the LHC over the coming years.

The high energy beam at CLIC, coupled with very large electric fields from the accelerator giving the electrons and positrons the collision energy, produce a number of unwanted background interactions. The rates of background e+e- pairs and hadronic interactions at CLIC is one of the biggest challenges the CLIC collaboration is working to overcome. Attempting to limit the effect of these background particles imposes strong requirements on both the detector design and the reconstruction software. The application of particle flow calorimetry within the PandoraPFA software kit allows CLIC to remove the bulk do these unwanted particles. This makes CLIC a very strong contender for the next big particle collider.