Light stringy states and the $g-2$ of the muon

Abstract

In this work, we evaluate the contributions to the anomalous magnetic moment of the muon ($(g-2{)}_{\mu }$) coming from light stringy states in a D-brane semi-realistic configuration. A scalar which couples only to the muon can have a mass sufficiently light to provide a significant contribution to the $(g-2{)}_{\mu }$. This scenario can arise in intersecting D-brane models, where such light scalars correspond to the first stringy excitations of an open string stretched between two D-branes intersecting with a very small angle. In this article, we show that there is a region in the space of the geometric parameters of the internal manifold where such scalar light stringy states can explain (part) of the observed discrepancy in the $(g-2{)}_{\mu }$. In a low string scale framework with $M_s\sim 10\mathrm{TeV}$, we show that an excited Higgs with mass $\mathcal{O}(250\mathrm{MeV})$, living in an intersection with an angle of order $\mathcal{O}(10^{-10})$, can provide a significant contribution of one-tenth of the $(g-2{)}_{\mu }$ discrepancy. This leads to a lower bound for the compact dimension where the branes intersect of order $\mathcal{O}(10^{-8}{\mathrm{GeV}}^{-1})$. We also study patterns in D-brane configurations that realize our proposal, both in three and four stacks models.

26 pages, 9 figures. Published version

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