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arXiv · 2606.06553

Hyperon-Nucleon Spectrometer

Abstract

Chirality lies at the heart of low-energy QCD, governing the symmetry structure that shapes hadron masses and strong interaction dynamics. Among the most compelling open questions tied to chiral dynamics and spontaneous chiral symmetry breaking is the longstanding $\Lambda$ polarization puzzle, in which $\Lambda$ hyperons produced in unpolarized hadronic collisions exhibit a surprisingly large transverse polarization that remains theoretically unexplained. This whitepaper presents the proposal for the Hyperon-Nucleon Spectrometer (H-NS) at the High-Intensity heavy-ion Accelerator Facility (HIAF). Leveraging the high energy and high intensity of HIAF's proton and heavy-ion beams, the H-NS experiment will perform systematic studies of hyperon polarization phenomena and their underlying mechanisms in proton-proton ($pp$), proton-nucleus ($pA$), and nucleus-nucleus ($AA$) collisions in the fixed target mode. A wide-range beam energy scan, including proton beams from 3 GeV up to 9.3 GeV (HIAF) and up to 32 GeV (upgraded HIAF), will be conducted to examine the dependence of polarization on collision energy. The spectrometer is designed with specialized detectors capable of high-precision reconstruction of final-state baryon polarizations. Among its many interesting and important measurements, H-NS will simultaneously measure hyperon and proton spin observables to explore the polarization mechanism in hadronic interactions and the spin structure of baryons. Furthermore, the use of $pA$ and $AA$ collisions will enable detailed investigations of cold and hot nuclear matter effects on spin polarization. Its physics program and detector development will significantly benefit the future Electron-ion Collider in China.

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Xiaozhi Bai, Xu Cao, Zhe Cao, Jinhui Chen, Kai Chen, Qibo Chen, Shi Chen, Xin Chen, Yuquan Chen, Zhenyu Chen, Jianping Dai, Heng-Tong Ding, Dongshuo Du, Shuxian Du, Limin Duan, Zhe Duan, Anhui Feng, Jie Feng, Yicheng Feng, Jinlin Fu, Xiaofeng Fu, Chaosong Gao, Liang Ge, Wenwen Ge, Lisheng Geng, Boxing Gou, An Gu, Yinghui Guan, Yutian Guan, Aiqiang Guo, Fengkun Guo, Lu Guo, Hao Han, Weijia Han, Yunxiang Hao, Wanbing He, Xionghong He, Zhixuan He, Defu Hou, Tingting Hou, Jinniu Hu, Shouyang Hu, Zhen Hu, Fei Huang, Kaixuan Huang, Linqin Huang, Mei Huang, Xuguang Huang, Yuanjing Ji, Xincai Kang, Jie Kong, Cheng Li, Demin Li, Haibo Li, Jibo Li, Lixuan Li, Min Li, Peilian Li, Peiyu Li, Ronghua Li, Suxian Li, Weilong Li, Wuyuan Li, Xin Li, Xiaomei Li, Xiaqing Li, Yang Li, Yangu Li, Yutie Liang, Zheng Liang, Zuotang Liang, Chuangxin Lin, Dexu Lin, Shoulong Lin, Ting Lin, Bo Liu, Bo-Chao Liu, Feng Liu, Hang Liu, Hongna Liu, Hui Liu, Kai Liu, Liuming Liu, Qian Liu, Tianbo Liu, Tong Liu, Xiang Liu, Yanwen Liu, Pengzhong Lu, Weijian Lu, Xiaofeng Luo, Xiao-Rui Lyu, Bo-Qiang Ma, Jianping Ma, Kuo Ma, Weihu Ma, Yugang Ma, Lijun Mao, Ruishi Mao, Yu Meng. 2026-06-04. Hyperon-Nucleon Spectrometer. https://arxiv.org/abs/2606.06553

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