Abstract
Now that the mass of the Higgs boson is known, circular electron positron colliders, able to measure the properties of these particles with high accuracy, are receiving considerable attention. Design studies have been launched (i) at CERN with the Future Circular Colliders (FCC), of which an e+e- collider is a potential first step (FCC-ee, formerly caller TLEP) and (ii) in China with the Circular Electron Positron Collider (CEPC). Hosted in a tunnel of at least 50 km (CEPC) or 80-100 km (FCC), both projects can deliver very high luminosity from the Z peak to HZ threshold (CEPC) and even to the top pair threshold and above (FCC-ee).At the ZH production optimum, around 240 GeV, the FCC-ee (CEPC) will be able to deliver 10 (5) ab-1 integrated luminosity in 5 (10) years with 4 (2) interaction points: hence to produce millions of Higgs bosons through the Higgsstrahlung process and vector boson fusion processes. This sample opens the possibility of sub-per-cent precision absolute measurements of the Higgs boson couplings to fermions and to gauge-bosons, and of the Higgs boson width. These precision measurements are potentially sensitive to multi-TeV range new physics interacting with the scalar sector. The ZH production mechanism also gives access to the invisible or exotic branching ratios down to the per mil level, and with a more limited precision to the triple Higgs coupling. For the FCC-ee, the luminosity expected at the top pair production threshold (s∼340–350 GeV) further improves some of these accuracies significantly, and is sensitive to the Higgs boson coupling to the top quark.
Highlights
The Higgs boson is the last found piece of the Standard Model (SM) [1, 2], and an extremely strange object
The Future Circular Colliders (FCC)-ee and Circular Electron Positron Collider (CEPC) will be operated at several centre-of-mass energies, of which √s = 240-250 GeV is suitable for the Higgs boson precision measurements
A circular electron positron collider that can be upgraded to proton collider with much high centreof-mass energy is a very attractive option
Summary
The Higgs boson is the last found piece of the Standard Model (SM) [1, 2], and an extremely strange object. The Higgs measurement program at the two proposed circular electron-positron collider facilities, FCC-ee [5] and CEPC [6], is given. The FCC-ee and CEPC will be operated at several centre-of-mass energies, of which √s = 240-250 GeV is suitable for the Higgs boson precision measurements. The FCC-ee design and programme include a very important run at the top production threshold, towards a precise measurement of the top quark mass, essential for the interpretation of the electroweak measurements. The FCC-ee is plan to accomplish its Higgs measurement through the top runs, where the precision on the Higgs total width will be reduced by a factor three, down to better than a per-cent, which in turn further constrains the Higgs couplings
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
