Naturally Light Hidden Photons in LARGE Volume String Compactifications

TL;DR

This work analyzes hidden U(1) gauge bosons in LARGE volume string compactifications and their kinetic mixing with the Standard Model photon. It derives the generic one-loop kinetic-mixing scale chi and shows how geometry (hyperweak vs collapsed cycles) and moduli control its size, including special cancellations in particular setups. The authors explore mass-generation mechanisms—Stückelberg and Higgs—for hidden photons, estimating masses from the string scale and supersymmetry-breaking mediation, and discuss the resulting phenomenology, including minicharged particles and DM-related scenarios. The results map out a broad, testable landscape for hidden photons across TeV to GUT string scales, guiding upcoming laboratory and astrophysical searches.

Abstract

Extra "hidden" U(1) gauge factors are a generic feature of string theory that is of particular phenomenological interest. They can kinetically mix with the Standard Model photon and are thereby accessible to a wide variety of astrophysical and cosmological observations and laboratory experiments. In this paper we investigate the masses and the kinetic mixing of hidden U(1)s in LARGE volume compactifications of string theory. We find that in these scenarios the hidden photons can be naturally light and that their kinetic mixing with the ordinary electromagnetic photon can be of a size interesting for near future experiments and observations.

Figures (12)

• Figure 1: Current experimental limits on the possible existence of a hidden photon of mass $m_{\gamma^\prime}$, mixing kinetically with the photon, with a mixing parameter $\chi$. Strong constraints arise from the non-observation of deviations from the Coulomb law (yellow) Williams:1971msBartlett:1988yy, from Cosmic Microwave Background (CMB) measurements of the effective number of neutrinos and the blackbody nature of the spectrum (black) Jaeckel:2008fiMirizzi:2009iz, from light-shining-through-walls (LSW) experiments (grey) Ruoso:1992nxCameron:1993mrRobilliard:2007bqAhlers:2007rdChou:2007zzcAhlers:2007qfAfanasev:2008jtFouche:2008jkAfanasev:2008fvEhret:2009sq, and from searches of solar hidden photons with the CAST experiment (purple) Andriamonje:2007ewRedondo:2008aa. The white region in parameter space is currently unexplored, but may be accessed by experiments in the very near future, in particular by improvements in LSW experiments (for proposed experiments probing this region, see Refs. Jaeckel:2007chGninenko:2008pzJaeckel:2008szYaleDaresburytobarCaspers:2009cj). The yellow regions indicate some especially interesting regions as described in the main text.
• Figure 2: Hidden U(1)s in LARGE volume scenarios realized in type IIB orientifold flux compactifications. A common feature of the geometry of the extra dimensions in these scenarios is that they have a minimum of four cycles: a large one to control the overall volume, a small one to allow for non-perturbative effects stabilising the large volume, and two small cycles, exchanged by the orientifold, wrapped by the visible branes Conlon:2008wa. This leaves various possibilities for hidden U(1)s. In \ref{['scenario1']} the hidden U(1) gauge group is located on a LARGE cycle extending through the full LARGE volume. In \ref{['scenario2']} the hidden U(1) is located on a collapsed cycle. The black dashed line indicates the existence of a LARGE cycle. We do not necessarily have a brane wrapping around this cycle. Finally, in the last scenario \ref{['scenario3']} the hidden U(1) sits on an anti D3-brane which is often exploited for uplifting to a de Sitter vacuum Kachru:2003aw.
• Figure 3: Gauge coupling $g_{(q)}$ of a hidden U(1) as a function of the string scale $M_s$, for different dimensions of the wrapping cycle of the brane hosting the hidden U(1): $q=0$ (blue) corresponding to an (anti) D3 brane (cf. Fig. \ref{['scenario3']}) or a collapsed D7 brane (cf. Fig. \ref{['scenario2']}), and $q=4$ (red) for a D7 brane (cf. Fig. \ref{['scenario1']}). The string coupling has been set to $g_s=0.1$, such that $g_{(0)}$ corresponds to the hypercharge gauge coupling at the string scale, $\alpha_Y(M_s)\equiv g_Y^2(M_s)/(4\pi )\approx 1/20$.
• Figure 4: Kinetic mixing between the visible electromagnetic U(1) and a U(1) sitting on a collapsed cycle (blue) or a hyperweak U(1) on a LARGE cycle (red), as a function of the string scale.
• Figure 5: Contributions from SUSY breaking to the kinetic mixing between the visible electromagnetic U(1) and a U(1) on a hidden $\overline{\rm D3}$ brane (turquoise) or a hidden collapsed brane through non-vanishing $D$-terms in the electroweak sector (light blue) or in the hidden sector (dark blue).