arXiv subjects

Longjie Ran

Publications and source records attributed to Longjie Ran.

5 recordsLinked to original sources

arXiv2025

Physical remnant of electroweak theta angles

In addition to the well-known quantum chromodynamical theta angle, we show that the Standard Model has another theta angle which is invariant under arbitrary chiral rotations of quarks and leptons. The new theta angle can be identified with the quantum electrodynamical theta angle, which should be viewed as an independent parameter of the Standard Model, and may be observable in spacetime with non-simply connected features, either beyond the visible universe or in an effective background from a laboratory setup.

hep-ph↗

arXiv2024

Non-Abelian R-symmetries in $\mathcal{N}=1$ supersymmetry

We investigate non-Abelian R-symmetries in $\mathcal{N}=1$ supersymmetric theory, where fields may transform under the R-symmetry in representations with dimension higher than one. While a continuous non-Abelian R-symmetry can always be decomposed to a $U(1)$ R-symmetry and non-R symmetries, there are non-trivial discrete non-Abelian R-symmetries that do not admit such a decomposition, and effective R-charges cannot be defined in such models. Previous results on sufficient conditions for R-symmetric supersymmetric vacua in Wess-Zumino models still hold, and do not depend on fields in representations of dimension greater than one. However, fields in higher-dimensional representations enter the sufficient conditions for supersymmetric vacua that break R-symmetry, but it is difficult to identify the independent variables which can be used to solve the F-flatness equation in this case, unless other conditions are fulfilled. We present examples with discrete non-Abelian R-symmetries of the lowest order in this case.

hep-th↗

arXiv2024

A brute-force search for R-symmetric Wess-Zumino models

This work makes an exhaustive search for generic renormalizable R-symmetric Wess-Zumino models with up to 5 chiral fields, and checks the consistency of their vacuum solutions with predictions from the Nelson-Seiberg theorem and its generalizations. Each model is recorded as the R-charge assignment of fields, which uniquely determines the cubic polynomial superpotentials with generic coefficients. Redundancy from permutation symmetries and reducible models are properly eliminated in the searching algorithm. We found that among 859 models in total, 19 of them have supersymmetric vacua unpredicted by the Nelson-Seiberg theorem and its generalizations. These exceptional models have their specific R-charge assignments covered by constructions found in previous literature. The search result can be used to estimate the accuracy of the field counting method for finding supersymmetric models in the string landscape. More applications of the dataset are expected in future work.

hep-th↗

arXiv2023

Gaugino masses from misaligned supersymmetry breaking and R-symmetry breaking spurions

In gauge mediation models with multiple spurion fields breaking SUSY and the R-symmetry separately, we show that it is possible to generate gaugino masses at one loop if the R-charge arrangement satisfies a certain condition. The resulting gaugino masses are calculated and suppressed by some power of the messenger mass scale. We present two simple examples to demonstrate this possibility, and discuss possible phenomenology implications.

hep-ph↗

arXiv2021

The quirk signal at FASER and FASER 2

We study FASER and FASER 2 sensitivities to the quirk signal by simulating the motions of quirks that are travelling through several infrastructures from the ATLAS interaction point to the FASER (2) detector. The ionization energy losses for a charged quirk travelling in different materials are treated carefully. We calculate the expected numbers of quirk events that can reach the FASER (2) detector for an integrated luminosity of 150 (3000) fb$^{-1}$. Scenarios for quirks with four different quantum numbers, and different masses and confinement scales are studied.

hep-ph↗