Connected and disconnected contributions to nucleon axial form factors using Nf = 2 twisted mass fermions at the physical point

We present results on the isovector and isoscalar nucleon axial form factors including disconnected contributions, using an ensemble of Nf = 2 twisted mass cloverimproved Wilson fermions simulated with approximately the physical value of the pion mass. The light disconnected quark loops are computed using exact deflation, while the strange and the charm quark loops are evaluated using the truncated solver method. Techniques such as the summation and the two-state fits have been employed to access ground-state dominance.

Contribution of charm to rare radiative leptonic B-decays

We revisit rare radiative leptonic decays Bd,s → γμ+μ- and Bd,s → γe+e- in the Standard Model and obtain predictions for a number of differential distributions in these decays with special emphasis on the contribution of charm-quark loops.

η and η′ masses and decay constants

We present preliminary results for the masses and decay constants of the η and η′ mesons using CLS Nf = 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.