Narrow Results

One item on the agenda of future colliders is certain to be the Higgs boson. What is it trying to tell us? The primary objective of any future collider must surely be to identify physics beyond the Standard Model, and supersymmetry is one of the most studied options. Is supersymmetry waiting for us and, if so, can LHC Run 2 find it? The big surprise from the initial 13 TeV LHC data has been the appearance of a possible signal for a new boson $X$ with a mass $\simeq$ 750 GeV. What are the prospects for future colliders if the X(750) exists? One of the most intriguing possibilities in electroweak physics would be the discovery of nonperturbative phenomena. What are the prospects for observing sphalerons at the LHC or a future collider?

I give an overview of the physics potential at possible future $e^{+}{e}^{-}$ colliders, including the ILC, FCC-ee, and CEPC. The goal is to explain some of the measurements that can be done in the context of electroweak precision tests and Higgs couplings, to compare some of the options under consideration, and to put the measurements in context by summarizing their implications for some new physics scenarios. This is a writeup of a plenary talk at the Hong Kong University of Science and Technology Jockey Club Institute for Advanced Study Program on High Energy Physics Conference, 18–21 January 2016. Some previously unpublished electroweak precision results for FCC-ee and CEPC are included.

The answer to the question in the title is: in search of new physics beyond the Standard Model, for which there are many motivations, including the likely instability of the electroweak vacuum, dark matter, the origin of matter, the masses of neutrinos, the naturalness of the hierarchy of mass scales, cosmological inflation and the search for quantum gravity. So far, however, there are no clear indications about the theoretical solutions to these problems, nor the experimental strategies to resolve them. It makes sense now to prepare various projects for possible future accelerators, so as to be ready for decisions when the physics outlook becomes clearer. Paraphrasing George Harrison, “If you don’t yet know where you’re going, any road may take you there.”

Sterile neutrinos are among the most attractive extensions of the SM to generate the light neutrino masses observed in neutrino oscillation experiments. When the sterile neutrinos are subject to a protective symmetry, they can have masses around the electroweak scale and potentially large neutrino Yukawa couplings, which makes them testable at planned future particle colliders. We systematically discuss the production and decay channels at electron–positron, proton–proton and electron–proton colliders and provide a complete list of the leading order signatures for sterile neutrino searches. Among other things, we discuss several novel search channels, and present a first look at the possible sensitivities for the active-sterile mixings and the heavy neutrino masses. We compare the performance of the different collider types and discuss their complementarity.

We discuss the physics opportunities and challenges presented by high energy lepton colliders in the range of center-of-mass energy between few and several tens of TeV. The focus is on the progress attainable on the study of weak and Higgs interactions in connection with new physics scenarios motivated by the shortcomings of the Standard Model.

In this talk I give a snapshot of the ongoing discussion on new physics searches at future colliders. I discuss the unique opportunities of a high energy lepton collider operating at multi-TeV center-of-mass energy and in particular its peculiar capability to carry out at the same time "intensity'' searches with the copious production of Standard Model states as well as directly producing heavy new physics states or probing still heavier new physics via indirect effects.

International Linear Collider (ILC) is a viable option for realization of a future Higgs factory. With proven accelerator technology and technically mature detector design, ILC offers well-understood physics program in the top, EW and Higgs sectors. Clean environment of electron–positron collisions, together with beam polarization of both beams and center-of-mass reach at a TeV scale, will make ILC a precision tool to probe realizations of new physics. The above will be illustrated on examples of fully simulated measurements in the Higgs sector, including Higgs couplings, Higgs self-coupling, CP violation measurements and Higgs exotic decay studies at ILC.

In this paper we trace the origins of the International Committee for Future Accelerators (ICFA), and outline its structure and mandate, its activities and accomplishments. We also discuss ICFA’s anticipated activities related to the future directions of the field of particle physics.

In this paper we trace the origins of the International Committee for Future Accelerators (ICFA), and outline its structure and mandate, its activities and accomplishments. We also discuss ICFA’s anticipated activities related to the future directions of the field of particle physics.

One item on the agenda of future colliders is certain to be the Higgs boson. What is it trying to tell us? The primary objective of any future collider must surely be to identify physics beyond the Standard Model, and supersymmetry is one of the most studied options. Is supersymmetry waiting for us and, if so, can LHC Run 2 find it? The big surprise from the initial 13 TeV LHC data has been the appearance of a possible signal for a new boson X with a mass ≃750 GeV. What are the prospects for future colliders if the X(750) exists? One of the most intriguing possibilities in electroweak physics would be the discovery of nonperturbative phenomena. What are the prospects for observing sphalerons at the LHC or a future collider?

I give an overview of the physics potential at possible future e⁺e⁻ colliders, including the ILC, FCC-ee, and CEPC. The goal is to explain some of the measurements that can be done in the context of electroweak precision tests and Higgs couplings, to compare some of the options under consideration, and to put the measurements in context by summarizing their implications for some new physics scenarios. This is a writeup of a plenary talk at the Hong Kong University of Science and Technology Jockey Club Institute for Advanced Study Program on High Energy Physics Conference, 18–21 January 2016. Some previously unpublished electroweak precision results for FCC-ee and CEPC are included.