Theory Seminar: Christopher Kane

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Speaker: Christopher Kane (University of Arizona)

Title: Methods for high-precision determinations of radiative-leptonic decay form factors using lattice QCD

Abstract: In the region of hard photon energies, radiative leptonic decays of pseudoscalar mesons represent important probes of the internal structure of hadrons. Such decays are particularly interesting for heavy mesons, where currently only model-dependent calculations have been performed. Moreover, radiative decays can provide independent determinations of Cabibbo-Koboyashi-Maskawa matrix elements with respect to purely leptonic or semileptonic channels. In this talk, I present a study of lattice-QCD methods to determine the relevant hadronic form factors for radiative leptonic decays of pseudoscalar mesons. In particular, I discuss how to best control two sources of systematic error inherent in the calculation, specifically the unwanted excited states created by the meson interpolating field, and unwanted exponentials in the sum over intermediate states. From there, I describe a number of improvements, including the use of an infinite-volume approximation method which allows us to perform calculations over the entire allowed range of photon energies. Using our improved methods, I present in progress results for the structure-dependent form factors describing the $D_s \to \ell \nu_\ell \gamma$ process, using a domain-wall action for all quark flavors.

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