On the Effective Theory of Low Scale Orientifold String Vacua

TL;DR

This paper formulates and analyzes the minimal Low Scale Orientifold Model (mLSOM) EFT, which augments the SM with a MSSM-like Higgs sector and three anomalous U(1) gauge bosons arising from TeV-scale orientifold vacua. It derives the effective action, performs a basis change to a hypercharge-aligned frame, and details the Green-Schwarz anomaly-cancellation structure, including Stueckelberg masses and axion couplings. Electroweak breaking then induces mixing among the photon, Z, and the anomalous U(1)s, producing shifted Z couplings, small Z′ admixtures, and a rich axion–gauge sector that yields distinctive tree-level processes, including a potentially observable axi-Higgs χ with mass fixed by the Higgs–axion potential. The work provides explicit tree-level decay rates and Drell–Yan cross sections, illustrating how Z and Z′ signals, along with χ-related channels, could probe TeV-scale stringy physics and constrain the UV mass eigenvalues and mixing angles in future collider experiments.

Abstract

The effective field theory of the minimal Low Scale Orientifold Models is developed. It describes universal features of related orientifold vacua in string theory. It contains, beyond the Standard Model fields, an MSSM-like Higgs sector and three anomalous (massive) U(1) gauge bosons. All renormalizable couplings are included as well as some dimension-five couplings that are important for anomaly cancellation. The Higgs symmetry breaking induces mixing between the anomalous U(1) gauge bosons and the photon and $Z^0$. This mixing as well as the anomaly generated cubic vector boson couplings is potentially important for discriminating such models from other theories containing Z's. Some interesting tree-level processes are also evaluated.

Figures (2)

• Figure 1: Pictorial representation of models$A, A'$.
• Figure 2: Pictorial representation of models $B$ and $B'$.