A Lattice Computation of the First Moment of the Kaon's Distribution Amplitude

We present a lattice computation of the first moment of the kaon's leading-twist distribution amplitude. The results were computed using ensembles with 2+1 dynamical flavours with the domain wall fermion action and Iwasaki gauge action from the RBC and UKQCD joint dataset. The first moment is non-zero because of SU(3)-breaking effects, and we find that we are able to measure these effects very clearly. We observe the expected chiral behaviour and finally obtain <\xi>(2GeV) = 3/5*a_K^1(2GeV) = 0.032(3), which agrees very well with results obtained using sum-rules, but with a significantly smaller error.