Abstract
The potential discovery of unparticles could have far-reaching implications for particle physics and cosmology. For over a decade, high-energy physicists have extensively studied the effects of unparticles. In this study, we derive six types of nonrelativistic potentials between fermions induced by unparticle exchange in coordinate space. We consider all possible combinations of scalar, pseudo-scalar, vector, and axial-vector couplings to explore the full range of possibilities. Previous studies have only examined scalar-scalar (SS), pseudoscalar-pseudoscalar (PP), vector-vector (VV), and axial-axial-vector (AA) type interactions, which are all parity even. We propose SP and VA interactions to extend our understanding of unparticle physics, noting that parity conservation is not always guaranteed in modern physics. We explore the possibilities of detecting unparticles through the long-range interactions they may mediate with ordinary matter. Dedicated experiments using precision measurement methods can be employed to search for such interactions. We discuss the properties of these potentials and estimate constraints on their coupling constants based on existing experimental data. Our findings indicate that for some particular values of the scaling dimension \( {d}_{\mathcal{U}} \), the coupling between scalar or vector unparticles and fermions is constrained by several orders of magnitude more tightly than the previous limits. The underlying reason for this improvement is analyzed. Limits are also set on the newly proposed SP and VA interactions for continuous \( {d}_{\mathcal{U}} \) values, allowing the exploration of the \( {d}_{\mathcal{U}} \) dependence of the constraints. It turns out that the bounds exhibit an exponential decay trend with the increasing \( {d}_{\mathcal{U}} \).
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Acknowledgments
We acknowledge support from the National Natural Science Foundation of China under grants U2230207, U2030209, and 12305125 and the National Key Program for Research and Development of China under grants 2020YFA0406001 and 2020YFA0406002. This work was also supported by the Natural Science Foundation of Sichuan Province under grant 24NSFSC5910. We thank Dr. Y. Liao and Dr. Z. Xiao for providing us their valuable notes and for their helpful discussions.
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Wu, L.Y., Zhang, K.Y. & Yan, H. Exotic spin-dependent interactions through unparticle exchange. J. High Energ. Phys. 2024, 83 (2024). https://doi.org/10.1007/JHEP01(2024)083
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DOI: https://doi.org/10.1007/JHEP01(2024)083