Physicists from the USA and South Korea described a possible scenario for the evolution of the Universe after the Big Bang, which differs from the one generally accepted by science. According to this scenario, it will no longer be possible to detect new elementary particles at the Large Hadron Collider (LHC) at CERN. Also, an alternative scenario allows you to solve the problem of the hierarchy of masses. Research published on arXiv.org
The theory is called Nnaturalness. It is determined on the scale of energies of the order of the electroweak interaction, after the separation of the electromagnetic and weak interactions. This was about ten at minus thirty-two - ten at minus twelve seconds after the Big Bang. Then, according to the authors of the new concept, a hypothetical elementary particle existed in the Universe - rechiton (or reheaton, from the English reheaton), the disintegration of which led to the formation of the physics observed today.
As the Universe became colder (the temperature of matter and radiation decreased) and flat (the geometry of space approached Euclidean), the Rechiton disintegrated into many other particles. They formed groups of particles that almost do not interact with each other, almost identical in species set, but differing in the mass of the Higgs boson, and therefore in their own masses.
The number of such groups of particles, which, according to scientists, exist in the modern universe, reaches several thousand trillion. The physics described by the Standard Model (SM) and the particles and interactions observed in experiments at the LHC belong to one of these families. The new theory allows one to abandon supersymmetry, which is still trying to find unsuccessfully, and solves the problem of the hierarchy of particles.
In particular, if the mass of the Higgs boson formed as a result of the rechiton decay is small, then the mass of the remaining particles will be large, and vice versa. This is what solves the problem of the electroweak hierarchy associated with the large gap between the experimentally observed masses of elementary particles and the energy scales of the early Universe. For example, the question of why an electron with a mass of 0.5 megaelectronvolt is almost 200 times lighter than a muon with the same quantum numbers disappears by itself - in the Universe there are exactly the same sets of particles, where this difference is not so strong.
According to the new theory, the Higgs boson observed in experiments at the LHC is the lightest particle of this type, formed as a result of the decay of a rechiton. Heavier bosons are associated with other groups of not yet discovered particles - analogs of today discovered and well-studied leptons (not participating in the strong interaction) and hadrons (participating in the strong interaction).
Nima Arkani-Hamed
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The new theory does not cancel, but makes it not so necessary to introduce supersymmetry, which implies doubling (at least) the number of known elementary particles due to the presence of super partners. For example, for a photon - a photino, a quark - a squark, a Higgs - a Higgsino, and so on. The spin of the superpartners should differ by half an integer from the spin of the original particle.
Mathematically, a particle and a superparticle are combined into one system (supermultiplet); all quantum parameters and masses of particles and their partners coincide in exact supersymmetry. It is believed that supersymmetry is broken in nature, and therefore the mass of superpartners is much greater than the mass of their particles. To detect supersymmetric particles, powerful accelerators like the LHC were needed.
If supersymmetry or any new particles or interactions do exist, then, according to the authors of the new study, they can be discovered on a scale of ten teraelectronvolts. This is almost at the border of the LHC's capabilities, and if the proposed theory is correct, the discovery of new particles there is extremely unlikely.
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A signal near 750 gigaelectronvolts, which could indicate the decay of a heavy particle into two gamma photons, as reported by the scientists of the CMS (Compact Muon Solenoid) and ATLAS (A Toroidal LHC ApparatuS) collaborations working at the LHC in December 2015 and March 2016, recognized as statistical noise. After 2012, when it became known about the discovery of the Higgs boson at CERN, no new fundamental particles predicted by the SM extensions have been revealed.
Therefore, the emergence of theories in which the need for supersymmetry disappears is expected. "There are many theorists, including myself, who believe that now is a completely unique time when we are solving important and systemic issues, and not concerning the details of any next elementary particle," said the lead author of the new study, physicist Nima Arkani-Hamed from Princeton University (USA).
His optimism is not shared by everyone. For example, physicist Matt Strassler of Harvard University believes the mathematical justification of the new theory to be contrived. Meanwhile, Paddy Fox of the Enrico Fermi National Accelerator Laboratory in Batavia (USA) believes that the new theory can be tested in the next ten years. In his opinion, particles formed in a group with any heavy Higgs boson should leave their traces on the relic radiation - the ancient microwave radiation predicted by the Big Bang theory.
Andrey Borisov