Early in its history, shortly after the Big Bang, the universe was filled with equal amounts of matter and "antimatter" — particles that are matter counterparts but with opposite charge. But then, as space expanded, the universe cooled. Today's universe is full of galaxies and stars which are made of matter. Where did the antimatter go, and how did matter come to dominate the universe? This cosmic origin of matter continues to puzzle scientists.
Physicists at the University of California, Riverside, and Tsinghua University in China have now opened a new pathway for probing the cosmic origin of matter by invoking the "cosmological collider."
[...] "Cosmic inflation provided a highly energetic environment, enabling the production of heavy new particles as well as their interactions," Cui said. "The inflationary universe behaved just like a cosmological collider, except that the energy was up to 10 billion times larger than any human-made collider."
[...] "The fact that our current-day universe is dominated by matter remains among the most perplexing, longstanding mysteries in modern physics," Cui said. "A subtle imbalance or asymmetry between matter and antimatter in the early universe is required to achieve today's matter dominance but cannot be realized within the known framework of fundamental physics."
Cui and Xianyu propose testing leptogenesis, a well-known mechanism that explains the origin of the baryon — visible gas and stars — asymmetry in our universe. Had the universe begun with equal amounts of matter and antimatter, they would have annihilated each other into photon radiation, leaving nothing. Since matter far exceeds antimatter today, asymmetry is required to explain the imbalance.
"Leptogenesis is among the most compelling mechanisms generating the matter-antimatter asymmetry," Cui said. "It involves a new fundamental particle, the right-handed neutrino. It was long thought, however, that testing leptogenesis is next to impossible because the mass of the right-handed neutrino is typically many orders of magnitudes beyond the reach of the highest energy collider ever built, the Large Hadron Collider."
[...] "Specifically, we demonstrate that essential conditions for the asymmetry generation, including the interactions and masses of the right-handed neutrino, which is the key player here, can leave distinctive fingerprints in the statistics of the spatial distribution of galaxies or cosmic microwave background and can be precisely measured," Cui said. "The astrophysical observations anticipated in the coming years can potentially detect such signals and unravel the cosmic origin of matter."
Journal Reference:
Yanou Cui and Zhong-Zhi Xianyu, Probing Leptogenesis with the Cosmological Collider [open], Phys Rev Lett, 129, 111301, 2022. DOI: 10.1103/PhysRevLett.129.111301
(Score: 3, Interesting) by khallow on Thursday October 13 2022, @07:32PM
Their hypothesis is that the features of the universe we can see now, particularly the cosmic microwave background and the distribution of matter into galaxies, can be used to reconstruct the early perturbations of the universe - which they speculate are in good part particle interactions, perhaps even particle interactions we've never seen before. In particular, they speculate that there may be enough information lying around to reconstruct particle interactions at energies vastly above ("up to 10 billion times larger") what we can achieve today.
(Score: 3, Informative) by Immerman on Thursday October 13 2022, @08:16PM
It occurs to me that matter-antimatter pairs must have formed from the preexisting incredibly dense, high-energy photonic energy, so as long as the universe remained dense enough it wouldn't really make much difference whether they rapidly annihilated back into it again - the resulting photons would contribute to spawning another matter-antimatter pair soon enough.
Depending on just how long the universe remained in that initial high-density state, even a very slight imbalance in any reaction path that favored matter might very rapidly convert all available energy to matter.
Accepted wisdom is that the high-density phase didn't last long, but realistically that's all extrapolation into time long before the CMBR, we have very little direct evidence, and it's generally accepted that physics as we know it must have broken down at some point before then.