With data at ±|E| at each temperature, this gives eight data points for a given momentum Q and energy transfer |E|. Assuming temperature independent background parameters of B1 and B2 and four values of S(|E|, T = 2, 20, 50, and 80 K), this is a closed problem of fitting six parameters to eight data points for each momentum and energy transfer. To obtain the temperature independent background we performed a least-squares fit to each Q and |E| to obtain the temperature independent background parameters B1,2. We then used this to subtract off the background from the data, leaving the structure factor S(|E|, T) which can be computed theoretically and compared to first principle calculations as discussed below.