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How far can you go ? Surprises and pitfalls in three-flavour chiral extrapolations

Presenter: Sébastien Descotes-Genon — LPT (CNRS/Univ. Paris-Sud 11)

S. Descotes-Genon

Chiral symmetry breaking may exhibit significantly different patterns in two chiral limits: Nf=2 massless flavours (mu=md=0, ms physical) and Nf=3 massless flavours (mu=md=0=ms=0). Such a difference may arise due to vacuum fluctuations of ss pairs related to the violation of the Zweig rule in the scalar sector. It could yield a numerical competition between contributions counted as leading and next-to-leading orders in the chiral expansions of observables. Such a situation would require a more careful treatment of chiral series, specially for observables in the kaon sector. I will summarise experimental indications for such a scenario, and outline some of its implications for the chiral extrapolation of lattice results.

Related work : hep-ph/0012221, hep-ph/0310283, hep-ph/0410233, hep-ph/0703154