Testing String Vacua in the Lab: From a Hidden CMB to Dark Forces in Flux Compactifications

TL;DR

The paper demonstrates that hidden U(1) gauge bosons with kinetic mixing can naturally arise in type IIB flux compactifications and that their phenomenology is strongly shaped by moduli stabilisation. By comparing isotropic and anisotropic Calabi–Yau geometries, it shows that anisotropic (K3-fibration) setups can decouple the hidden photon mass from its mixing, allowing GeV-scale dark forces or meV-scale hidden CMB states to emerge in plausible string-scale regimes. Moduli stabilisation via the LARGE Volume Scenario, including α′, loop, and non-perturbative corrections, is essential to making concrete predictions, while D-term effects impose stringent constraints that can be navigated in multi-cycle geometries or via vanishing FI-terms. The work supplies concrete mass–mixing relations and identifies regions in parameter space that upcoming laboratory and fixed-target experiments could probe, linking high-scale string theory to low-energy hidden-sector phenomenology.

Abstract

We perform a detailed analysis of the phenomenological properties of hidden Abelian gauge bosons with a kinetic mixing with the ordinary photon within type IIB flux compactifications. We study the interplay between moduli stabilisation and the Green-Schwarz mechanism that gives mass to the hidden photon paying particular attention to the role of D-terms. We present two generic classes of explicit Calabi-Yau examples with an isotropic and an anisotropic shape of the extra dimensions showing how the last case turns out to be very promising to make contact with current experiments. In fact, anisotropic compactifications lead naturally to a GeV-scale hidden photon ("dark forces" that can be searched for in beam dump experiments) for an intermediate string scale; or even to an meV-scale hidden photon (which could lead to a "hidden CMB" and can be tested by light-shining-through-a-wall experiments) in the case of TeV-scale strings.

Figures (3)

• Figure 1: Constraints on the kinetic mixing parameter $\chi$ vs. hidden photon mass $m_{\gamma^\prime}$ from astrophysics, cosmology and laboratory experiments. Phenomenologically interesting regions are marked in yellow. Compilation from Jaeckel:2010ni.
• Figure 2: Pictorial view of the K3 fibred Calabi-Yau three-fold and the brane set-up under consideration. Four-cycles are shown as surfaces and two-cycles as lines.
• Figure 3: Predictions from anisotropic compactifications. The area predicted by models with vanishing FI-terms is shown in light blue and marked as "Stückelberg anisotropic". The lines denote different values of from bottom to top, $\kappa=1,10^{-3},10^{-6}\ldots10^{-21}$. The red line denotes a natural $\kappa=10^{-6}$. The green area marked "KK anisotropic" denotes the region where we expect the corresponding Kaluza-Klein modes. Finally the light red area "Non-zero FI-terms" corresponds to parameter values expected in models with non-vanishing Fayet-Iliopoulos terms. The existing experimental and observational constraints are marked in grey. As in Fig. 1 we have marked phenomenologically interesting areas in yellow.