Aidan Robson (Glasgow)
The Compact Linear Collider (CLIC) is a multi-TeV electron-positron collider under development. It offers the potential for a rich precision physics programme, combined with sensitivity to a wide range of new phenomena. To optimise its physics output CLIC is foreseen to be built and operated in several energy stages, ranging from ~350 GeV to 3 TeV centre-of mass energy. The CLIC physics potential has been studied using full detector simulations for several centre-of-mass energies. These include Higgs production through Higgsstahlung at a few hundred GeV, allowing for the couplings and width of the Higgs boson to be determined in a model-independent way through the recoil mass technique. While originally considering only leptonic Z decays in the recoil mass measurement, it was shown recently that significantly higher precisions on the couplings can be achieved by including the hadronic decay of the Z. Operation at higher centre-of-mass energies provides large statistics for the study of the Higgs boson through the WW-fusion production process. It also offers the potential to directly measure the top Yukawa coupling. At the highest centre-of-mass energy of 3 TeV, the Higgs self-coupling can be determined with 10% precision. The complete physics program for all measurements of accessible Higgs couplings is included in combined fits. Precision measurements of top quark production in e+e- collisions will significantly enhance our knowledge of top quark properties and will give new insight in physics beyond the Standard Model. The top mass can be measured at a 50 MeV accuracy level in a well-defined mass scheme by performing a scan of the top pair production threshold. For the study of the top quark couplings to electroweak gauge bosons, form factors can be determined to 1% precision, an order of magnitude better than the full LHC programme. Recent results extend the prospects to different centre-of-mass energies and to CP violating form factors. New studies of Flavour Changing Neutral Current decays of the top quark, such as the decay t -> cH, to a branching ratio BR(t->cH) ~ 10^-5, are also presented. The search for phenomena beyond the Standard Model through direct observation of new particles and precision measurements is a main motivation for the high-energy stages of CLIC. An overview of physics benchmark studies assuming different New Physics scenarios is given. New particles can be discovered in a model-independent way almost up to the kinematic limit of sqrt(s)/2. The low background conditions at CLIC provide extended discovery potential compared to hadron colliders, for example in the case of non-coloured TeV-scale SUSY particles. In addition to studying new particles directly, BSM models can be probed up to scales of tens of TeV through precision measurements. Examples, including recent results on the reaction e+ e- -> gamma gamma, are presented. Beam polarisation allows to constrain the underlying theory further in many cases. The talk will also include a discussion of LHC results relevant for the CLIC physics case.
The CLIC physics potential will be summarised.
Lucie Linssen (CERN)