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<div>Theory Center Seminar<br>
Wednesday, Dec. 13, 2017<br>
2:00 p.m. (coffee at 1:45 p.m.)<br>
CEBAF Center, Room F224-225<br>
<font color="#0f61c8"><br>
</font>Peter Stoffer (UCSD)<br>
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<b>Dispersion relation for hadronic light-by-light scattering</b><br>
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The anomalous magnetic moment of the muon g-2 has been measured
and computed to very high precision of about 0.5 ppm. For more
than a decade, a discrepancy has persisted between experiment
and Standard Model prediction, now of about 3-4 sigma. The main
uncertainty of the theory prediction is due to strong
interaction effects. With improved input for hadronic vacuum
polarisation, the subleading hadronic light-by-light (HLbL)
contribution starts to dominate the theory error. While some
constraints from QCD exist, the calculation of the HLbL
contribution to g-2 is plagued by a substantial model
dependence. In this talk, I will present a dispersive approach
to HLbL scattering, based on the fundamental principles of
unitarity and analyticity. Our dispersive formalism recently
allowed us to evaluate two-pion contributions including
rescattering effects and it shows a path towards a data-driven
determination of the HLbL contribution to g-2 of the muon.</div>
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