China plans construction of LHC 100 km circumference
China is seriously considering building an LHC equivalent of 100 kilometers in circumference and looks set to achieve, by 2030, an electron-positron collider of similar size as a prelude, as the Europeans had done with LEP . The usefulness of these machines is unfortunately not self-evident ...
China has just let it be known that it still intends to rob Europeans of leadership in the high energy race in particle physics. Already in 2012, just after the announcement of the discovery of the Brout-Englert-Higgs boson (BEH), she had announced that she was embarking on preliminary studies for the construction of a circular collider larger than LEP ( Large Electron Positron Collider), a large electron-positron collider of 27 km circumference, according to 1989 to 2000 in the tunnel where subsequently replaced the LHC
With a circumference of 50 to 70 km, the Chinese Circular Electron Positron Collider (CEPC) was planned to make collisions between electron beams and anti-electrons at energies of 240 GeV. A review of six years of research has just been published, implying that the circumference envisaged was now 100 km and that prototypes of certain elements of the machine were really going to be built. Work on CRCI infrastructure is expected to begin in 2022 with inauguration by 2030.
If this roadmap is successful, the Chinese will initially have a plant capable of producing in about 10 years a million BEH bosons, 100 million W bosons and a thousand billion Z bosons. LEP, the CEPC would then be dismantled to make way for the Super Proton Proton Collider (SPPC), a 100 km circumferential LHC equivalent producing 70 TeV (70,000 GeV) collisions.
As Futura pointed out in the previous article below, the Europeans, too, have in their box studies for an LHC 100 km in circumference. A project, not a circular but linear collider of electrons and positrons, has already been completed for preliminary studies for years and is waiting for a green light to be built. This is the International Linear Collider (ILC). The Japanese in particular were very involved.
New particles out of reach even with a PPSC?
Futura had explained in detail the reasons for the completion of these machines and they are the same as for the CEPC and the PPSC. However, one can wonder today if the construction of these machines is very serious.
Already in 2016, the Chinese physicist Chen-Ning Yang - a famous physicist for having won the Nobel Prize in Physics for his work on the violation of parity in particle physics with his colleague Tsung-Dao Lee, and for having been at the origin of famous Yang-Mills theories of all the physics of the standard model - had indicated that he was not in favor of the realization of the PPSC.
Although we can qualify and even refute some of the criticisms made by Yang for the construction of the two machines, as explained by the physicist and mathematician John Baez, we can not help but lean in favor of Yang.
Indeed, by the time the LHC entered service, there were many good reasons to expect a major revolution in fundamental physics. Indeed, several very credible theoretical arguments gave hope for the discovery, in a few years at most, of new particles predicted by the theory of supersymmetry, string theory and especially the production of black minitrous that evaporate by Hawking effect. energies of the order of a few TeV.
The LHC routinely made 13 TeV collisions, with beam brightness already high ... and no new particle showed even the tip of its nose. We have no theoretical arguments to really hope for new particles above 10 TeV, except for a few predicted by split supersymmetry, but recent experiments on electron dipole moment are more like a shower. cold in this respect. Worse, the low mass of the BEH boson suggests that the standard model may well be valid up to the Planck energy, which means that no new physics should appear in the colliders that humanity could build. , or at least no new particle.
We can therefore legitimately ask ourselves, in the absence of new theoretical and experimental arguments and the crisis that humanity is facing with global warming, energy and resources, if billions will not be better used for development of new nuclear reactors, eg thorium. It is true, however, that China has also engaged in this type of research.
WHAT YOU MUST REMEMBER
Proton colliders at higher and higher energies make it possible to track new physics by producing particles of high masses.
But they also produce a lot of already known particles, which make a background noise that is not compatible with precise studies. Collisions between electrons and positrons are then more suitable for a fine study of particles already discovered.
Europeans and Chinese are therefore considering colliders of these types even more powerful in the decades to come.
