Mixing of axino and goldstino, and axino mass

TL;DR

This paper explores the mixing between axino and goldstino in supersymmetric models, providing a general framework for defining axion and axino, and analyzing the resulting axino mass spectrum under various conditions.

Contribution

It offers a comprehensive definition of axion and axino in the presence of SUSY breaking and calculates the QCD axino mass considering non-minimal Kähler potentials and different SUSY breaking scenarios.

Findings

Axino can mix with goldstino when certain superfields develop scalar VEVs and F-terms.

The axino mass depends on the Kähler potential and SUSY breaking details, ranging from eV to multi-TeV.

In gauge mediation, the gaugino mass dominates the axino mass, allowing it to be a free parameter.

Abstract

Axino, related to the SUSY transformation of axion, can mix with goldstino in principle. This case is realized when some superfields carrying nonvanishing Peccei-Quinn charges develop both scalar VEVs and F-terms. In this case, we present a proper definition of axion and axino. With this definition, we present the QCD axino mass in the most general framework, including non-minimal K\"ahler potential. The axino mass is known to have a hierarchical mass structure depending on accidental symmetries. With only one axino, if $G_A=0$ where $G=K+\ln|W|^2$, we obtain $m_{\tilde a}=m_{3/2}$. For $G_A\ne 0$, the axino mass depends on the details of the K\"ahler potential. In the gauge mediation scenario, the gaugino mass is the dominant axino mass parameter. Therefore, we can take the theoretical QCD axino mass as a free parameter in the study of its cosmological effects, ranging from eV to multi-TeV scales, without a present knowledge on its ultraviolet completion.