This exotic particle could finally explain why matter has mass

Science News from research organizations This exotic particle could finally explain why matter has mass A newly spotted exotic particle state could finally expose how the universe gives matter its mass. Date: April 25, 2026 Source: The University of Osaka Summary: A major physics experiment has uncovered evidence for a strange new form of matter, where a fleeting particle gets trapped inside a nucleus. This exotic state may reveal how mass is generated, suggesting that particles can weigh less when surrounded by dense nuclear matter. The findings support long-standing theories about how the vacuum of space influences mass. Share: Facebook Twitter Pinterest LinkedIN Email FULL STORY Physicists may have found a new exotic particle state that reveals how mass changes inside atomic nuclei. The discovery hints that the “empty” vacuum of space plays a powerful role in shaping the weight of matter. Credit: Shutterstock Everything around us has mass, but its origin is still one of physics' biggest unanswered questions. According to modern theories, mass does not simply come from matter itself. Instead, it is tied to the nature of the vacuum, which is not empty space but a dynamic environment with a complex structure. Studying special particle systems can help scientists better understand this hidden framework and how mass is generated. One promising approach involves mesons, which are particles made of a quark and an anti-quark, bound together with an atomic nucleus. This combination is known as a mesic nucleus. By examining these systems, researchers can probe the vacuum structure and the mechanisms that give particles their mass. Now, new experimental results have brought scientists closer to that goal by revealing evidence for a completely new type of mesic nucleus. Evidence for a Rare and Exotic Particle State An international team of researchers has reported signs of a previously unseen but theoretically predicted state called an η′-mesic nucleus. Their findings, which will appear in Physical Review Letters, point to the possible existence of this unusual bound system. Under certain conditions, short-lived particles known as mesons, which exist for less than ten-millionth of a second, can become temporarily trapped inside an atomic nucleus. When this happens, they form a rare and exotic state. Studying these mesic nuclei can help scientists understand how the strong nuclear force behaves and how the vacuum changes in extremely dense environments. "One particle of particular interest is the η′ meson," says senior author Kenta Itahashi. "It is unusually heavy compared with related particles, and physicists expect that its mass changes when it exists inside nuclear matter. Observing this phenomenon would provide valuable information about how particle masses are generated in the universe." High Precision Experiment Inside a Particle Accelerator To search for η′-mesic nuclei, the team carried out a high-precision experiment at the GSI Helmholtzzentrum für Schwerionenforschung in Germany. The researchers directed a beam of high-energy protons onto a carbon target. This process excited the carbon nuclei and produced η′ mesons, which in some cases became bound to the nucleus. To study these interactions, the team measured the excitation energy of the carbon nuclei by analyzing deuterons -the simplest atomic nucleus made of one proton and one neutron- that were emitted during the reaction. These measurements were made using a high-resolution spectrometer called the Fragment Separator (FRS). The experiment also relied on a specialized detector known as WASA, originally developed in Uppsala, Sweden. This device allowed scientists to detect high-energy protons leaving the target and identify signals that indicate an η′ meson had been created and captured within the nucleus. These signals, known as decay signatures, were critical for identifying the exotic state. "With our new experimental setup combining the FRS and the WASA, we can identify structures in the data that match theoretical signatures of η′-mesic nuclei," explains lead author Ryohei Sekiya. "Our analysis suggests that these bound states were indeed formed." What the Results Reveal About Mass The excitation spectrum of the carbon nucleus measured in the experiment shows patterns consistent with the formation of η′-mesic nuclei. The results also suggest that the mass of the η′ meson may decrease when it is inside nuclear matter. This finding supports theoretical predictions and offers rare experimental insight into how particle properties can change under extreme conditions. "Our measurements provide important new clues about how mesons behave in nuclear matter," says Itahashi. "This brings us closer to answering deep, fundamental questions about how matter acquires mass, as well as how the vacuum structure changes inside atomic nuclei." What Comes Next The team plans to carry out further experiments to improve measurement accuracy and look for additional decay signals that could confirm the existence of η′-mesic nuclei. Each new result will help refine our understanding of the fundamental laws that govern matter and the universe. The article, "Excitation Spectra of the 12C(p,d) Reaction near the η'-Meson Emission Threshold Measured in Coincidence with High-Momentum Protons," was published in Physical Review Letters. RELATED TOPICS Space & Time Space Exploration NASA Space Station Cosmology Matter & Energy Physics Detectors Quantum Physics Telecommunications RELATED TERMS Particle physics Introduction to quantum mechanics Dark energy Physics Dark matter Big Bang Subatomic particle Nuclear fission Story Source: Materials provided by The University of Osaka. Note: Content may be edited for style and length. Journal Reference: R. Sekiya, K. Itahashi, Y. K. Tanaka, S. Hirenzaki, N. Ikeno, V. Metag, M. Nanova, J. Yamagata-Sekihara, V. Drozd, H. Ekawa, H. Geissel, E. Haettner, A. Kasagi, E. Liu, M. Nakagawa, S. Purushothaman, C. Rappold, T. R. Saito, H. Alibrahim Alfaki, F. Amjad, M. Armstrong, K.-H. Behr, J. Benlliure, Z. Brencic, T. Dickel, S. Dubey, S. Escrig, M. Feijoo-Fontán, H. Fujioka, Y. Gao, F. Goldenbaum, A. Graña González, M. N. Harakeh, Y. He, H. Heggen, C. Hornung, N. Hubbard, M. Iwasaki, N. Kalantar-Nayestanaki, M. Kavatsyuk, E. Kazantseva, A. Khreptak, B. Kindler, H. Kollmus, D. Kostyleva, S. Kraft-Bermuth, N. Kurz, B. Lommel, S. Minami, D. J. Morrissey, P. Moskal, I. Mukha, C. Nociforo, H. J. Ong, S. Pietri, E. Rocco, J. L. Rodríguez-Sánchez, P. Roy, R. Ruber, S. Schadmand, C. Scheidenberger, P. Schwarz, V. Serdyuk, M. Skurzok, B. Streicher, K. Suzuki, B. Szczepanczyk, X. Tang, N. Tortorelli, M. Vencelj, T. Weber, H. Weick, M. Will, K. Wimmer, A. Yamamoto, A. Yanai, J. Zhao. Excitation Spectra of the C12(p,d) Reaction near the η′-Meson Emission Threshold Measured in Coincidence with High-Momentum Protons.

Physical Review Letters, 2026; 136 (14) DOI: 10.1103/6vsl-ng7x Cite This Page: MLA APA Chicago The University of Osaka. "This exotic particle could finally explain why matter has mass." ScienceDaily. ScienceDaily, 25 April 2026. . The University of Osaka. (2026, April 25). This exotic particle could finally explain why matter has mass. ScienceDaily. Retrieved April 25, 2026 from www.sciencedaily.com/releases/2026/04/260424233214.htm The University of Osaka. "This exotic particle could finally explain why matter has mass." ScienceDaily. www.sciencedaily.com/releases/2026/04/260424233214.htm (accessed April 25, 2026). Explore More from ScienceDaily RELATED STORIES Scientists May Have Found Dark Matter After 100 Years of Searching Nov. 29, 2025 — Nearly a century after astronomers first proposed dark matter to explain the strange motions of galaxies, scientists may finally be catching a glimpse of it. A University of Tokyo researcher ...

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