Physics – High Energy Physics – High Energy Physics - Lattice
Scientific paper
2001-07-30
Phys.Lett.B518:243-251,2001
Physics
High Energy Physics
High Energy Physics - Lattice
references added, typos corrected
Scientific paper
10.1016/S0370-2693(01)01062-0
We report on determinations of the low-energy constants alpha5 and alpha8 in the effective chiral Lagrangian at O(p^4), using lattice simulations with N_f=2 flavours of dynamical quarks. Precise knowledge of these constants is required to test the hypothesis whether or not the up-quark is massless. Our results are obtained by studying the quark mass dependence of suitably defined ratios of pseudoscalar meson masses and matrix elements. Although comparisons with an earlier study in the quenched approximation reveal small qualitative differences in the quark mass behaviour, numerical estimates for alpha5 and alpha8 show only a weak dependence on the number of dynamical quark flavours. Our results disfavour the possibility of a massless up-quark, provided that the quark mass dependence in the physical three-flavour case is not fundamentally different from the two-flavour case studied here.
Irving Alan C.
McNeile Craig
Michael Carpentier
Sharkey K. J.
UKQCD Collaboration
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