Sayan Sen @ssc_combater007 · Jan 25, 2026 01:02 EST0

For decades, scientists have sought to understand why matter dominates over antimatter in the universe. A key concept in this search is CP violation, which refers to differences in the behavior of particles and their antiparticles.

CP violation happens when particles and their antimatter counterparts don’t behave identically under charge (C) and parity (P) transformations. In practice, certain decays occur more often than their CP-conjugates due to interference between weak and strong interaction phases. This asymmetry is crucial for explaining the matter–antimatter imbalance in our universe.

Earlier studies revealed unexpectedly large CP violation effects in charmed meson decays, but results for charmed baryon decays remained inconclusive. To address this gap, Professor Xiao-Gang He and Dr. Chia-Wei Liu of the Tsung-Dao Lee Institute (TDLI) at Shanghai Jiao Tong University conducted a systematic analysis. Using SU(3) flavor symmetry theory together with the framework of final-state re-scattering, they predicted significantly stronger CP violation effects in charmed baryon decays than previously estimated.

A baryon is a subatomic particle made of three quarks bound together by the strong nuclear force. It carries a baryon number of +1, distinguishing it from mesons. Protons (uud) and neutrons (udd) are the lightest baryons, forming atomic nuclei, while heavier baryons include strange, charm, or bottom quarks and decay into lighter ones.

The study emphasizes the role of final-state re-scattering in CP violation. This process allows secondary interactions among particles, which generate strong phases essential for CP violation to occur. According to their findings, the matter-antimatter asymmetry in charmed baryon decays could reach a level of one-thousandth, a magnitude far greater than earlier theoretical expectations.

Founded in 2017, TDLI has focused on advancing fundamental physics research. Professor He, who leads the Particle and Nuclear Physics division, explained, “The research on charm CP violation opens new pathways for experimental exploration and provides deeper insights into the fundamental mechanisms underlying the universe’s matter-antimatter asymmetry. It offers important opportunities for further tests of the Standard Model and potential discoveries of new physics.”

The Standard Model explains how the basic building blocks of matter interact, governed by four fundamental forces—gravity, electromagnetism, the strong nuclear force, and the weak nuclear force.

The predictions now await experimental confirmation. Current facilities such as BESIII in China, LHCb at CERN, and Belle II in Japan already possess some capability to detect CP violation in charm decays. Looking ahead, China’s planned Super Tau-Charm Facility (STCF) is expected to provide enhanced sensitivity, enabling more precise measurements.

The study represents a step forward in understanding one of the most fundamental questions in physics: why matter exists in greater abundance than antimatter. By pointing to larger CP violation effects in charmed baryons, the research offers new directions for experiments and potential insights into physics beyond the Standard Model.

Source: Science China Press

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• Science china press
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