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 achieve the optimal noise reduction per cost.

On the analysis side we carefully assess excited states contributions by using a direct fit approach and investigate effects arising from long autocorrelation times in the pseudoscalar channel.

Hadron Spectroscopy and Interactions