Coherent elastic neutrino-nucleus scattering (<math><mrow><mi>CE</mi><mi>ν</mi><mi>NS</mi></mrow></math>) provides a unique probe for neutrino properties beyond the Standard Model physics. The reactor neutrino liquid xenon coherent scattering experiment (RELICS), a proposed reactor neutrino program using liquid xenon time projection chamber technology, aims to investigate the <math><mrow><mi>CE</mi><mi>ν</mi><mi>NS</mi></mrow></math> process of antineutrinos off xenon atomic nuclei. In this work, the design of the experiment is studied and optimized based on Monte Carlo simulations. To achieve a sufficiently low-energy threshold for <math><mrow><mi>CE</mi><mi>ν</mi><mi>NS</mi></mrow></math> detection, an ionization-only analysis channel is adopted for RELICS. A high emission rate of delayed electrons after a big ionization signal is the major background, leading to an analysis threshold of 120 photoelectrons in the <math><mrow><mi>CE</mi><mi>ν</mi><mi>NS</mi></mrow></math> search. The second largest background, nuclear recoils induced by cosmic-ray neutrons, is suppressed via a passive water shield. The physics potential of RELICS is explored with a <math><mrow><mn>30</mn><mtext> </mtext><mtext> </mtext><mi>kg</mi><mo>·</mo><mi>yr</mi></mrow></math> exposure at a baseline of 25 m from a reactor core with a 3 GW thermal power. In an energy range of 120–300 photoelectrons, corresponding to an average nuclear recoil from 0.63 to 1.36 keV considering the liquid xenon response and detector-related effect, we expect 4639.7 <math><mrow><mi>CE</mi><mi>ν</mi><mi>NS</mi></mrow></math> and 1687.8 background events. The sensitivity of RELICS to the weak mixing angle is investigated at a low momentum transfer. Our study shows that RELICS can further improve the constraints on the nonstandard neutrino interaction compared to the current best results.

China

Chang Cai

Guocai Chen

Jiangyu Chen

Rundong Fang

Fei Gao

Xiaoran Guo

Jiheng Guo

Hong Kong

Tingyi He

Chengjie Jia

Gaojun Jin

Yipin Jing

Gaojun Ju

Yang Lei

Jiayi Li

Kaihang Li

Meng Li

Minhua Li

Shengchao Li

Siyin Li

Tao Li

Qing Lin

Jiajun Liu

Minghao Liu

Sheng Lv

Guang Luo

Jian Ma

Chuanping Shen

Mingzhuo Song

Lijun Tong

Xiaoyu Wang

Wei Wang

Xiaoping Wang

Zihu Wang

Yuehuan Wei

Liming Weng

Xiang Xiao

Lingfeng Xie

Dacheng Xu

Jijun Yang

Litao Yang

Long Yang

Jingqiang Ye

Jiachen Yu

Qian Yue

Yuyong Yue

Bingwei Zhang

Shuhao Zhang

Yifei Zhao

Chenhui Zhu

Reactor neutrino liquid xenon coherent elastic scattering experiment

Recent studies have proposed using a geocentric muon spin force to account for the <math><mrow><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><msub><mrow><mo>)</mo></mrow><mrow><mi>μ</mi></mrow></msub></mrow></math> anomaly, with the long-range force mediator being a light axionlike particle. The mediator exhibits a <math><mi>C</mi><mi>P</mi></math>-violating scalar coupling to nucleons and a normal derivative coupling to muons. Due to the weak symmetry, this axion inevitably couples to neutrinos, providing potential impact on neutrino oscillations. By utilizing neutrino data from BOREXINO, IceCube DeepCore, Super-Kamiokande, and SNO, we have identified that both atmospheric and solar neutrino data can impose stringent constraints on the long-range muon spin force model and the <math><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><msub><mo>)</mo><mi>μ</mi></msub></math> parameter space. With optimized data analysis techniques and the potential from future experiments, such as JUNO, Hyper-Kamiokande, <math><mrow><mi>SNO</mi><mo>+</mo></mrow></math>, and IceCube PINGU, there exists a promising opportunity to achieve even greater sensitivities. Indeed, neutrino oscillations offer a robust and distinctive cross-check for the model, offering stringent constraints on the <math><mo>(</mo><mi>g</mi><mo>−</mo><mn>2</mn><msub><mo>)</mo><mi>μ</mi></msub></math> parameter space.

Ji-Heng Guo

Jia Liu

Xiao-Ping Wang

Muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math>, long-range muon spin force, and neutrino oscillations

Light millicharged particles can be copiously produced from meson decays in cosmic ray collisions with the atmosphere, leading to detectable signals in large underground neutrino detectors. In this paper we study a new channel for generating atmospheric millicharged particles, the proton bremsstrahlung process. We find that the proton bremsstrahlung process leads to a significantly higher flux of millicharged particles compared to meson decays and, for certain masses, results in a one-order-of-magnitude improvement in the flux. Consequently, Super-K constraints on ε 2 for sub-GeV MCPs are improved by half order of magnitude. We further note that the study on the proton bremsstrahlung process can be extended to a variety of new physics particle searches in atmospheric collisions and in low energy proton accelerators.

Mingxuan Du

Zuowei Liu

Millicharged particles from proton bremsstrahlung in the atmosphere

Long-lived particles that are present in many new physics models beyond the standard model, can be searched for in a number of newly proposed lifetime frontier experiments at the LHC. The signals of the long-lived dark photons can be significantly enhanced in a new dark photon model in which dark photons are copiously produced in the hidden radiation process. We investigate the capability of various lifetime frontier detectors in probing the parameter space of this model, including the far forward detectors FACET and FASER, the far transverse detector MATHUSLA, and the precision timing detector CMS-MTD. We find that the accessible parameter space is significantly enlarged by the hidden radiation process so that FACET, MATHUSLA, and CMS-MTD can probe a much larger parameter space than the so-called minimal model. The parameter space probed by FACET is found to be much larger than FASER, which is largely due to the fact that the former has a larger decay volume and is closer to the interaction point. There also exists some parameter space that can be probed both by the far detectors and by precision timing detectors, so that different experiments can be complementary to each other. A brief overview of the lifetime frontier detectors is also given.

Vietnam

Van Que Tran

Enhanced long-lived dark photon signals at lifetime frontier detectors