{
  "id": 15729653,
  "title": "One-positron quantum cyclotron could put the Standard Model to the test",
  "url": "https://urgent.news/2026/10/20/one-positron-quantum-cyclotron-could-put-the-standard-model-to-the",
  "topic": "science",
  "section": "Science",
  "published": "2026-10-20T10:23:18.000Z",
  "source": {
    "name": "Physics World",
    "slug": "physics-world",
    "url": "https://physicsworld.com/a/one-positron-quantum-cyclotron-could-put-the-standard-model-to-the-test/"
  },
  "original_language": "en",
  "account": "Physicists in the United States have, for the first time, successfully trapped a single positron, allowing them to fully observe its lowest-energy quantum states. This achievement is made possible by a device known as a \"one-positron quantum cyclotron.\" The team, led by Gerald Gabrielse and colleagues from Northwestern University, aims to measure the positron's magnetic moment with unprecedented precision. This precise measurement could offer an extremely stringent test of a fundamental symmetry within the Standard Model of particle physics. While the Standard Model has been highly successful in describing fundamental particles and their interactions, it struggles to explain why the observable universe contains much more matter than antimatter. The Standard Model is renowned for its ability to make extremely precise predictions about measurable quantities, but it is inconsistent with basic features of the universe. As a result, physicists continuously test the Standard Model, seeking situations where it fails to predict particle properties accurately, with the potential to discover new physics. One common method for testing the Standard Model is through colliding particles at higher and higher energies in an attempt to spot deviations from predictions. However, recent advancements have seen physicists employing low-energy experiments to trap particles using magnetic and electric fields, enabling highly precise measurements of properties like the magnetic moment. A key aspect of the Standard Model is CPT invariance, which posits that a universe undergoing charge conjugation (swapping particles for their antiparticles), parity (mirroring everything), and time reversal (running time backwards) would exhibit the same physical laws as our own. If true, every particle would be an exact mirror of its antiparticle, sharing identical masses and magnetic moments of equal size but opposite sign. To develop a test of CPT invariance for the electron and its antiparticle—the positron—Gabrielse's team introduced a single positron into a Penning trap. The trap, cooled to just 300 mK, places the positron in its lowest-energy quantum states. High-speed positrons, generated from the decay of a sodium nucleus, are slowed and captured within this cold environment, where they can be observed as they make one-quantum jumps between their lowest quantum states. This technique allows the researchers to hold the positron in its cyclotron ground state and also excite it to higher-energy states using a driving electromagnetic force. These low-energy states are determined by the size of the positron's cyclotron orbit and the relative orientation of its magnetic moment to the cyclotron's magnetic field. By measuring the energy difference between spin states, the team can determine the size of the positron's magnetic moment. The researchers believe that future single-positron cyclotron measurements will yield a value for the positron's magnetic moment to one part in 10¹³. According to Gabrielse, \"The one-positron quantum cyclotron should enable the first quantum measurements of the positron magnetic moment.\" If CPT invariance holds, the results should match the size of the electron's magnetic moment, which has been measured to 1 part in 10¹³ using a one-electron quantum cyclotron. By pushing the positron up to the electron's level of precision, Gabrielse and colleagues hope to deliver the most stringent test yet of CPT invariance for leptons, potentially unveiling new observations that might finally prove to break the Standard Model's predictions.",
  "summary": "Magnetic moment could be measured at unprecedented precision The post One-positron quantum cyclotron could put the Standard Model to the test appeared first on Physics World .",
  "key_points": [
    "First-ever trapping of a single positron achieved",
    "One-positron quantum cyclotron used for observation",
    "Measurement aims to test CPT invariance in the Standard Model"
  ],
  "editors_take": "Achieving unprecedented precision in low-energy measurements allows physicists to challenge the Standard Model by testing whether antimatter particles behave as exact mirrors of their matter counterparts.",
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}