Groundbreaking Discovery in Japan: The Future of Particle Physics!

In an exciting development hailing from Japan, researchers have achieved a milestone by accelerating muons into the most precise and high-intensity beam ever recorded, reaching impressive energy levels of 100 keV. This groundbreaking feat holds transformative potential for next-generation experiments—including refined measurements of the muon’s anomalous magnetic moment—which could unveil new realms of physics beyond the established Standard Model.

What Are Muons and Why Do They Matter?

Muons are intriguing subatomic particles, akin to electrons but weighing in at about 200 times more. This additional mass comes with a significant advantage: muons lose less energy as they spiral through accelerators, making them prime candidates for generating more vigorous collisions than traditional electron machines, assuming equal energy inputs.

The Challenges of Working with Muons

However, harnessing the power of muons is not without its hurdles. Scientists predominantly produce high-intensity muon beams through the decay of pions, yet these beams require precision cooling to equalize the particles' speeds before they can be accelerated to the high velocities needed in colliders. Unlike electrons, muons pose a unique challenge due to their fleeting existence—they last only about 2 milliseconds. Conventional cooling methods simply don’t apply.

A Game-Changing Cooling Technique!

To tackle these issues, researchers at the MUon Science Facility (MUSE) within the Japan Proton Accelerator Research Complex (J-PARC) have introduced an innovative cooling and acceleration method. Their approach involves cooling positively charged muons, or antimuons, to thermal energies of 25 meV before utilizing radio-frequency cavities for acceleration.

Uniqueness in Silica Aerogel!

In their recent experiments, a team led by physicist Shusei Kamioka directed antimuons into a unique silica aerogel. This remarkable material causes stopped muons to be re-emitted as muonium atoms (exotic atoms comprising an antimuon and an electron) at remarkably low thermal energy. They then targeted these low-energy muonium atoms with lasers to eject their electrons, resulting in antimuons with significantly reduced, more uniform velocities.

Measurable Success!

The results are astounding: the newly formed beam boasts an intensity of 2 × 10⁻³ μ+ per pulse and a drastically reduced measured emittance—2.0 × 10² times lower in the horizontal and 4.1 × 10² times lower vertically compared to the initial beam. This reduction marks a monumental two-orders-of-magnitude improvement in both position and momentum spread, enhancing muon acceleration efficiency.

What's Next?

The findings, published in Physical Review Letters, signal promising strides towards developing a functioning muon collider. However, the researchers are clear: they need to further boost both the energy and intensity of the beam—an ambitious challenge ahead.

Kamioka reveals, “We’re gearing up for the next acceleration test in a newly dedicated experimental area. Plans for 2027 include a 4 MeV acceleration with 1000 muons per second, escalating to 212 MeV and 105 muons per second by 2029. The future of muon research is looking bright!”