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The Rotating Reference Frame

It is often convenient to fit the measured asymmetry in a rotating reference frame (RRF). To do this, one subtracts a phase $\phi_{RRF} = \omega_{RRF} t$ from the phase of Eq. (3.39), where $\omega_{RRF}
= 2 \pi \nu_{RRF}$ is the chosen RRF frequency. The RRF frequency is taken to be slightly lower than the average Larmor-precession frequency $\overline{\omega}_{\mu}$ of the muon. The precession signal viewed in this rotating reference frame has only low frequency components on the order of $\overline{\omega}_{\mu} - \omega_{RRF}$, where $\overline{\omega}_{\mu}$is the average precession frequency in the lab frame. This has two important consequences. The first is that the quality of the fit can be visually inspected. Second and most important, it allows the data to be packed into much fewer bins, greatly enhancing the speed of fitting.

Jess H. Brewer