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

TL;DR

This paper investigates how light stringy states in D-brane models could account for part of the muon's anomalous magnetic moment discrepancy, proposing specific scalar excitations with particular geometric configurations.

Contribution

It demonstrates that light stringy scalars in intersecting D-brane models can significantly contribute to the muon g-2, providing a novel string-theoretic explanation for the discrepancy.

Findings

Light scalars can explain up to 10% of the muon g-2 discrepancy.

A scalar with mass around 250 MeV can arise in models with specific intersection angles.

Constraints on the compactification scale are derived from the muon g-2 contribution.

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 $M_s\sim 10~{\rm TeV}$, we show that an excited Higgs with mass $\mathcal{O}(250~{\rm MeV})$, 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 $\mathcal{O}(10^{-8}~{\rm GeV}^{-1})$. We also study patterns in D-brane configurations that realize our proposal, both in three and four stacks models.