$\eta$ and $\eta^\prime$ masses and decay constants

Understand

We present preliminary results for the masses and decay constants of the $\eta$ and $\eta^\prime$ mesons using CLS $N_f = 2+1$ ensembles.

• One of the major challenges in these calculations are the large statistical fluctuations due to disconnected quark loops.
• We tackle these by employing a combination of noise reduction techniques which are tuned to minimize the statistical error at a fixed cost.
• On the analysis side we carefully assess excited states contributions by using a direct fit approach.