Unveiling Ghost Particles: Breakthrough Discovery Holds Promise for Solving a Perplexing Physics Enigma

A team of theoretical physicists from the University of Minnesota has introduced an innovative approach to detect axions, hypothetical particles that could provide a solution to the enigmatic “Strong CP Problem” in physics. This novel strategy involves tracking the decay of axions into two muons, opening up new avenues for particle collider experiments.

The quest for answers to one of the most baffling questions in physics has led theoretical physicists to expand the search for elusive particles called “axions.” At the heart of this pursuit lies the perplexing Strong CP Problem, which arises from the peculiar observation that neutrons, composed of quarks—fundamental particles with electric charges—do not interact with electric fields. This discrepancy challenges the existing framework of the Standard Model, the prevailing set of theories that scientists have relied on for years to explain the fundamental laws of nature.

Led by theoretical physicists from the University of Minnesota Twin Cities, a team of researchers has made a significant breakthrough in the search for axions. Collaborating with experimental scientists at the Fermilab National Accelerator Laboratory, they have devised a fresh strategy that opens up unexplored possibilities for detecting axions in particle collider experiments.

The groundbreaking research conducted by the University of Minnesota researchers has been published in Physical Review Letters, a respected peer-reviewed scientific journal published by the American Physical Society. The article highlights their new method of searching for hypothetical axions, which involves measuring the decay of these particles into two muons—a heavier version of the electron, as depicted in the accompanying image. Credit: Raymond Co, University of Minnesota

Zhen Liu, co-author of the paper and an assistant professor in the University of Minnesota School of Physics and Astronomy, commented, “As particle physicists, our goal is to deepen our understanding of nature. Over the past century, scientists have achieved tremendous success in discovering elementary particles through established theoretical frameworks. Hence, it is extremely perplexing why neutrons do not couple to electric fields, as our existing theory would predict. The discovery of the axion would represent a remarkable advancement in our fundamental comprehension of the structure of the natural world.”

Collider experiments play a crucial role in the study of subatomic particles and offer the potential for discovering new particles. Essentially, scientists collide beams of particles, and the resulting energy generates other particles that can be analyzed through detectors to investigate their properties.

Liu and his team’s proposed method involves measuring the decay product of axions into two muons—an observable transformation that occurs when an unstable heavy particle breaks down into multiple lighter particles. By reconstructing these decays from the muon tracks detected, the researchers believe they have a chance to pinpoint the axion and provide evidence for its existence.

Raymond Co, co-author of the paper and a postdoctoral researcher at the University of Minnesota School of Physics and Astronomy and William Fine Theoretical Physics Institute, elaborated, “This research expands the avenues through which we can search for the axion particle. Until now, no one has utilized the decay of axions into muons as a means to probe these elusive particles in neutrino or collider experiments. Our research opens up new possibilities and paves the way for future endeavors in our field.”

Contributing to the theoretical aspect of the research alongside Liu and Co are Kun-Feng Lyu, a postdoctoral researcher in physics and astronomy at the University of Minnesota, and Soubhik Kumar, a postdoctoral researcher at the University of California, Berkeley. Together, they form part of the ArgoNeuT collaboration, which brings together theorists and experimentalists from various institutions across the country to study particles through experiments at Fermilab.

In this paper, the University of Minnesota-led theoretical team collaborated with experimental researchers to conduct a search for axions using their innovative method and existing data from the ArgoNeuT experiment. The researchers intend to employ the experimental results to further refine their theoretical calculations of axion production rates in future studies.

The research received funding from the U.S. Department of Energy’s Office of Science, the National Science Foundation, the United Kingdom Research and Innovation’s Science and Technology Facilities Council, and the UK’s Royal Society.

In addition to Liu, Co, Lyu, and Kumar, the paper’s team included researchers from various institutions, including Fermi National Accelerator Laboratory, Argonne National Laboratory, University of Michigan, Yale University, University of Manchester, University of Oxford, European Organization for Nuclear Research (CERN), University of Texas at Austin, Rutgers University, University of California, Santa Barbara, Syracuse University, and the University of Edinburgh.

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• Physical Review Letters
• University of Minnesota School of Physics and Astronomy
• Fermilab National Accelerator Laboratory
• Standard Model of Particle Physics
• Strong CP Problem
• Axions
• Particle Collider Experiments