Physicists Achieve New Milestone in Antimatter Research

Researchers at CERN have achieved a groundbreaking milestone in antimatter research by performing coherent spin spectroscopy on a single antiproton. This significant advancement, led by the BASE (Baryon Antibaryon Symmetry Experiment) collaboration, allows scientists to measure the magnetic properties of antimatter with unprecedented precision. The findings could illuminate the longstanding mystery of why our universe contains far more matter than antimatter.

The experiment’s success lies in its ability to manipulate the spin states of a single antiproton using a technique known as coherent spectroscopy. According to Stefan Ulmer, a senior member of BASE and head of the Ulmer Fundamental Symmetries Laboratory at RIKEN in Japan, “This is of highest importance in studying the fundamental properties of the particle.” The research demonstrates a resonance peak that is 16 times narrower than any previous antiproton measurements, enhancing the precision of the transition frequency.

The baryon asymmetry problem remains one of the most pressing questions in physics. Theoretical models suggest that the universe should have originated with equal amounts of matter and antimatter. Yet, all observable matter, including stars, galaxies, and planets, is predominantly composed of matter. As Dmitry Budker, a physicist at the University of California, Berkeley, noted, the level of control achieved in this experiment is unprecedented, paving the way for more precise tests of fundamental symmetries in nature.

Exploring the Fundamental Symmetries

The BASE team’s work focuses on comparing the properties of matter and antimatter particles, specifically protons and antiprotons. The Standard Model of particle physics posits that protons and antiprotons should have identical masses while exhibiting equal and opposite electrical charges. Any deviations from this model could provide crucial insights into the baryon asymmetry.

Ulmer elaborated on the experimental setup, stating, “We were doing spectroscopy on the spin of a single trapped antiproton, stored in a cryogenic Penning trap system.” By applying microwave radiation at a specific frequency, the team induced Rabi oscillations, which are periodic fluctuations of the antiproton’s spin, allowing them to observe resonances with remarkable clarity.

The measurements yielded a 1.5-fold improvement in the signal-to-noise ratio, potentially leading to at least a tenfold increase in the precision of antiproton magnetic moment measurements. Ulmer suggested that with further technological advancements, they could reduce the linewidth by an additional factor of ten, further enhancing the experiment’s accuracy.

Future Implications and Applications

The implications of this research extend beyond antimatter studies. Testing CPT invariance, which asserts that the laws of physics remain unchanged when charge, parity, and time are reversed, is crucial for identifying discrepancies in the Standard Model. Ulmer reported that the team observed antiproton spin coherence times of up to 50 seconds, indicating a stable quantum spin state necessary for high-precision measurements.

Conducting magnetic moment measurements on nuclear particles is notoriously challenging, but the complexities increase significantly when dealing with antimatter. Ulmer noted that these measurements require developing experiments that are three orders of magnitude more sensitive than previously established methods.

The BASE collaboration has been on this path since 2005, achieving early successes with proton measurements by 2011. Significant strides in antiproton studies began in 2017, culminating in the current achievement of coherent spin control through innovations that include ultra-homogeneous magnetic fields and cryogenic temperatures.

Looking ahead, the BASE team aims to utilize their transportable trap system, BASE STEP, for more detailed offline studies of antiprotons. As Budker stated, “The BASE collaboration keeps a steady course on increasing the precision of fundamental symmetry tests. This is an important step in that direction.”

The study is detailed in a recent publication in the journal Nature, marking a pivotal moment in the quest to unlock the secrets of antimatter and its role in the universe.