Transverse Emittance Reduction in Muon Beams by Ionization Cooling

TL;DR

This paper demonstrates ionization cooling of muon beams, showing a significant reduction in transverse emittance, which is crucial for developing high-brightness muon sources for future high-energy physics applications.

Contribution

The study provides experimental evidence of ionization cooling in muon beams, validated by simulation and theory, advancing muon beam technology.

Findings

Transverse emittance reduction observed in muon beams

Experimental results match simulation and theoretical models

Progress towards muon-based high-energy facilities

Abstract

Accelerated muon beams have been considered for next-generation studies of high-energy lepton-antilepton collisions and neutrino oscillations. However, high-brightness muon beams have not yet been produced. The main challenge for muon acceleration and storage stems from the large phase-space volume occupied by the beam, derived from the muon production mechanism through the decay of pions from proton collisions. Ionization cooling is the technique proposed to decrease the muon beam phase-space volume. Here we demonstrate a clear signal of ionization cooling through the observation of transverse emittance reduction in beams that traverse lithium hydride or liquid hydrogen absorbers in the Muon Ionization Cooling Experiment (MICE). The measurement is well reproduced by the simulation of the experiment and the theoretical model. The results shown here represent a substantial advance towards the realization of muon-based facilities that could operate at the energy and intensity frontiers.