Abstract
Following the discovery of the Higgs boson at the LHC in 2012, new large colliders are being considered and studied by the international high-energy community to explore the Higgs boson in details and to probe new physics beyond the Standard Model. In China, a two-stage circular collider project, CEPC-SPPC was proposed and is under study. The first stage, CEPC (Circular Electron Positron Collier, a so-called Higgs factory) is focused on the Higgs physics, and the second stage, SPPC (Super Proton-Proton Collider) will be an energy frontier collider and a discovery machine beyond the LHC. The two colliders will share a same tunnel of 100 km in circumference, with a goal of 250 GeV in center-of-mass for CEPC and 75 TeV for SPPC Phase-I and 125–150 TeV for the SPPC ultimate goal. This article presents the design concept of the SPPC and some study results about the key accelerator physics problems and technical issues, which include luminosity optimization, beam collimation, beam-beam effects, longitudinal beam dynamics, high-field magnets and beam screen.
Highlights
Given the 100 km circumference tunnel which is jointly defined by CEPC and SPPC, we will try to achieve the modest center-of-mass energy in proton-proton collisions with the anticipated accelerator technology and modest cost in late 2030s, but a more ambitious goal to go to higher energy is preserved
Smaller beam sizes at the IPs are favorable for luminosity, the emittances cannot be allowed to fall freely without limit because of beam-beam tune shift and detector data pileup that is caused by too high number of events per bunch crossing to be handled by the detector
To avoid the critical single diffractive effects (SDE) which becomes more important at higher energy, we developed a novel concept by combining the betatron collimation and momentum collimation in a same long straight section [41]
Summary
SPPC (Super Proton-Proton Collider) is envisioned to be an extremely powerful machine, far beyond the scope of the Large Hadron Collider (abbr. as LHC), with a center-of-mass energy of 75 TeV, a nominal luminosity of 1.0 × 1035 cm−2s−1 per interactive point (abbr. as IP) at the collision start, and an integrated luminosity of 30 ab−1 assuming 2 interaction points and 10–15 years of operation. Solutions to the naturalness problem almost inevitably predict the existence of a plethora of new fundamental particles not far from the electroweak scale Such new particles will shed light on the underlying physics principles that link the low energy scale of the electroweak processes, including the light Higgs boson mass, with respect to the extremely high value of the Planck scale that sets the upper energy limit of applicability of quantum physics as we know it. Searching for these possible new particles at the LHC can probe the level of fine-tuning down to 10–2, while SPPC would push this down to the unprecedented level of 10–4, beyond the common concept of the naturalness principle. Understanding SM processes in such an unprecedented environment poses new challenges and offers unique opportunities for sharpening our tools in the search for new physics at higher energy scales
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