Next Generation Muon g-2 Experiments

TL;DR

This paper discusses the progress of two advanced muon g-2 experiments, Fermilab E989 and J-PARC E34, aiming to measure the muon anomalous magnetic moment with higher precision using different innovative methods.

Contribution

It introduces two new experimental approaches for measuring muon g-2, with significant hardware upgrades at Fermilab and a novel ultra-cold muon beam method at J-PARC.

Findings

Fermilab E989 aims to reduce uncertainty by a factor of 4.

J-PARC E34 employs a new ultra-cold muon beam technique.

Both experiments target improved precision in muon g-2 measurement.

Abstract

I report on the progress of two new muon anomalous magnetic moment experiments, which are in advanced design and construction phases. The goal of Fermilab E989 is to reduce the experimental uncertainty of $a_\mu$ from Brookhaven E821 by a factor of 4; that is, $\delta a_\mu \sim 16 \times 10^{-11}$, a relative uncertainty of 140~ppb. The method follows the same magic-momentum storage ring concept used at BNL, and pioneered previously at CERN, but muon beam preparation, storage ring internal hardware, field measuring equipment, and detector and electronics systems are all new or upgraded significantly. In contrast, J-PARC E34 will employ a novel approach based on injection of an ultra-cold, low-energy, muon beam injected into a small, but highly uniform magnet. Only a small magnetic focusing field is needed to maintain storage, which distinguishes it from CERN, BNL and Fermilab. E34 aims to roughly match the previous BNL precision in their Phase~1 installation.