Figure 5.10: Spectra used to determine Rlh. The measured background plus simulated p -> e n ( g ) spectrum were fit to the measured spectrum containing both event types.
or very near the high energy edge of the Michel spectrum. The low threshold events represent the whole spectrum of Michel energies above a small threshold due to positron energy loss in the target. A weighted, least-squares minimization with a single varying parameter Rlh was performed for channels between 1400 and 2500. This range was chosen to include everything on the high energy side of the high threshold Michel peak while excluding any events in the region of the discriminator threshold. The value of Rlh was determined to be (7.31 ± 0.13) × 10-3 where the uncertainty was returned by the CERNLIB fitting routine. Figure 5.11 shows a plot of the results of this fit.
Figure 5.11: Spectra used to determine Rlh. The curves were fit between channels 1400 and 2500.