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arXiv · 2607.02405

Measurement of solar $pp$ neutrino flux with the new PandaX-4T data

PandaX Collaboration·Peiyuan Chen·Wei Chen·Xiaohua Chen·Xun Chen·Yunhua Chen·Chen Cheng·Xiangyi Cui·Yuxin Cui·Manna Deng·Roni Dey·Yingjie Fan·Deqing Fang·Xuanye Fu·Zhixing Gao·Yujie Ge·Lisheng Geng·Xunan Guo·Xuyuan Guo·Zichao Guo·Chencheng Han·Ke Han·Changda He·Jinrong He·Ruquan Hou·Houqi Huang·Junting Huang·Yule Huang·Xiangdong Ji·Yonglin Ju·Xiaorun Lan·Chenxiang Li·Mingchuan Li·Peiyuan Li·Shuaijie Li·Tao Li·Yangdong Li·Yuan Li·Zhiyuan Li·Qing Lin·Jianglai Liu·Yuanchun Liu·Yunyang Luo·Yugang Ma·Yajun Mao·Yue Meng·Binyu Pang·Ningchun Qi·Xiangxiang Ren·Dong Shan·Xiyuan Shao·Manbin Shen·Wenliang Sun·Xuyan Sun·Yi Tao·Yueqiang Tian·Yuxin Tian·Anqing Wang·Guanbo Wang·Hao Wang·Haoyu Wang·Jiamin Wang·Lei Wang·Meng Wang·Qiuhong Wang·Shaobo Wang·Shibo Wang·Siguang Wang·Wei Wang·Xu Wang·Zhou Wang·Yuehuan Wei·Weihao Wu·Yuan Wu·Mengjiao Xiao·Xiang Xiao·Yuhan Xie·Kaizhi Xiong·Jianqin Xu·Yifan Xu·Binbin Yan·Xiyu Yan·Yong Yang·Shunyu Yao·Peihua Ye·Chunxu Yu·Zhe Yuan·Youhui Yun·Minzhen Zhang·Peng Zhang·Shibo Zhang·Shu Zhang·Siyuan Zhang·Tao Zhang·Wei Zhang·Yang Zhang·Yingxin Zhang·Yuanyuan Zhang·Kangkang Zhao·Li Zhao
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Abstract

We report a new measurement of the solar proton--proton ($pp$) neutrino flux via neutrino--electron elastic scattering using the PandaX-4T Run 2 data set collected between 2024 and 2026, corresponding to an exposure of 1.9 tonne$\cdot$yr. Before Run 2 data taking, the detector underwent a series of upgrades to improve its response and background conditions. Time variations of radioactive noble-gas impurities are constrained using the physics data themselves, complemented by measurements from the gas-assay system. The analysis introduced improvements in the data processing chain, detector response characterization, and background models. A blind spectral analysis was then performed on the electronic-recoil data across a wide energy range from 20 to 1000 keV. In combination with the Run 0 data published earlier, the fitted $pp$ flux is $(8.5 \pm 3.5)\times 10^{10}$ $\mathrm{cm^{-2}s^{-1}}$, consistent with the prediction of the Standard Solar Model. With a statistical significance of $2.2\sigma$ above background, this marks the first positive indication of solar $pp$ neutrino--electron scattering below an electronic-recoil energy of 165 keV.

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PandaX Collaboration, Peiyuan Chen, Wei Chen, Xiaohua Chen, Xun Chen, Yunhua Chen, Chen Cheng, Xiangyi Cui, Yuxin Cui, Manna Deng, Roni Dey, Yingjie Fan, Deqing Fang, Xuanye Fu, Zhixing Gao, Yujie Ge, Lisheng Geng, Xunan Guo, Xuyuan Guo, Zichao Guo, Chencheng Han, Ke Han, Changda He, Jinrong He, Ruquan Hou, Houqi Huang, Junting Huang, Yule Huang, Xiangdong Ji, Yonglin Ju, Xiaorun Lan, Chenxiang Li, Mingchuan Li, Peiyuan Li, Shuaijie Li, Tao Li, Yangdong Li, Yuan Li, Zhiyuan Li, Qing Lin, Jianglai Liu, Yuanchun Liu, Yunyang Luo, Yugang Ma, Yajun Mao, Yue Meng, Binyu Pang, Ningchun Qi, Xiangxiang Ren, Dong Shan, Xiyuan Shao, Manbin Shen, Wenliang Sun, Xuyan Sun, Yi Tao, Yueqiang Tian, Yuxin Tian, Anqing Wang, Guanbo Wang, Hao Wang, Haoyu Wang, Jiamin Wang, Lei Wang, Meng Wang, Qiuhong Wang, Shaobo Wang, Shibo Wang, Siguang Wang, Wei Wang, Xu Wang, Zhou Wang, Yuehuan Wei, Weihao Wu, Yuan Wu, Mengjiao Xiao, Xiang Xiao, Yuhan Xie, Kaizhi Xiong, Jianqin Xu, Yifan Xu, Binbin Yan, Xiyu Yan, Yong Yang, Shunyu Yao, Peihua Ye, Chunxu Yu, Zhe Yuan, Youhui Yun, Minzhen Zhang, Peng Zhang, Shibo Zhang, Shu Zhang, Siyuan Zhang, Tao Zhang, Wei Zhang, Yang Zhang, Yingxin Zhang, Yuanyuan Zhang, Kangkang Zhao, Li Zhao. 2026-07-02. Measurement of solar $pp$ neutrino flux with the new PandaX-4T data. https://arxiv.org/abs/2607.02405

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