Early in its history, shortly after the Big Bang, the universe was filled with equal amounts of matter and “antimatter” – particles that are isotopes of matter but with opposite charge. But then, as space expanded, the universe cooled. Today’s world is full of galaxies and stars made of matter. Where did antimatter go, and how did matter take over the universe? This cosmic origin of matter continues to baffle scientists.
Physicists at the University of California, Riverside, and Tsinghua University in China have now opened a new path to exploring the cosmic origin of matter by calling the “cosmic collider.”
Not just any collider
High-energy colliders, such as the Large Hadron Collider, are built to produce extremely heavy subatomic elementary particles that may reveal new physics. But some new physics, such as the one that explains dark matter and the origin of matter, can involve much heavier particles, and require far more energy than a man-made collider can provide. It turns out that the early universe could have been a super collider.
It is widely believed that cosmic inflation, an era in which the universe expanded at an accelerating rate, preceded the Big Bang, explained Yano Koi, associate professor of physics and astronomy at the University of California.
“Cosmic inflation provided a very energetic environment, allowing the production of new heavy particles in addition to their interactions,” Coy said. “The inflationary universe behaved just like the cosmic collider, except that the energy was up to 10 billion times greater than any man-made collider.”
According to Cui, the microscopic structures created by energetic events during inflation expanded as the universe expanded, resulting in regions of varying density in a homogeneous universe. Subsequently, these microscopic structures seeded the large-scale structure of our universe, which today is manifested in the form of the distribution of galaxies across the sky. Cui explained that the new subatomic particle physics may be revealed by studying the signature of the Cosmic Collider in the contents of the universe today, such as galaxies and the cosmic microwave background.
Cui and Zhong-Zhi Xianyu, assistant professor of physics at Tsinghua University, report in the journal physical review messages That by applying the physics of the Cosmic Collider and using accurate data to measure the structure of our universe from upcoming experiments such as SPHEREx and the 21cm line tomography, the mystery of the cosmic origin of matter may be revealed.
“The fact that our current universe is dominated by matter remains among the most long-standing mysteries of modern physics,” Coy said. “A subtle imbalance or asymmetry between matter and antimatter in the early universe is required to achieve the dominance of matter today but cannot be achieved within the known framework of fundamental physics.”
Leptogenesis composition to the rescue
Cui and Xianyu suggest testing hematopoiesis, a well-known mechanism that explains the origin of the baryon asymmetry — gas and visible stars — in our universe. If the universe had started with equal amounts of matter and antimatter, they would have annihilated each other in photon radiation, leaving nothing behind. Since matter far exceeds today’s antimatter, asymmetry is required to explain the imbalance.
“The process of leptin formation is one of the most urgent mechanisms for generating matter-antimatter asymmetry,” Coy said. “It includes a new fundamental particle, the right-handed neutrino. However, it has long been thought that testing leptin formation is next to impossible because the mass of the right-hand neutrino is usually in large numbers beyond the power of the largest energy collider ever built, the Large Hadron Collider. .”
The new work proposes to test lap-formation by decoding detailed statistical properties of the spatial distribution of objects in the cosmic structure observed today, reminiscent of the microscopic physics during cosmic inflation. The researchers argue that the impact of the Cosmic Collider enables the production of super-heavy, right-handed neutrinos during the inflationary era.
“Specifically, we show that the prerequisites for asymmetry generation, including the interactions and masses of the right-hand neutrino, which is the key player here, can leave distinctive imprints in the statistics of the spatial distribution of galaxies or the cosmic microwave background and can be precisely measured,” Coy said. “Astrophysical observations expected in the coming years can detect such signals and reveal the cosmic origin of matter.”
Cui was supported in the research by a grant from the US Department of Energy.
The title of the paper is “Examination of Leptogenesis Using the Cosmic Collider.”