Speaker
Description
I will review the signal-to-noise ratio problem for the electromagnetic current correlator, which hampers the accurate determination of the leading-order hadronic vacuum polarization contribution to the muon anomaly from first principles, among other physically-interesting matrix elements. Thanks to the recent factorization of the fermionic determinant, multi-level integration can be performed in QCD which offers exponential improvement in the precision in many correlation functions at long distances. In the work with Dalla Brida, Giusti and Pepe, we investigated the variance reduction in the current correlator in a two-level QCD simulation with light quarks corresponding to a pion mass of about 270 MeV and in a large volume of 3fm. The best estimate is obtained by using translation averaging for the correlator, and some time will be devoted discussing its implementation in our simulation.
