Abstract Using e + e − collision data corresponding to an integrated luminosity of 22.7 fb −1, collected at center-of-mass energies between 3.7 and 4.7 GeV with the BESIII detector at the BEPCII storage ring, we measure the energy-dependent Born cross sections of e + e − → Ω − Ω ¯ + $$ {e}^{+}{e}^{-}\to {\varOmega}^{-}{\overline{\varOmega}}^{+} $$ and the effective form factors of the Ω − baryon. The analysis employs a single baryon tagging method, and the results are consistent with theoretical predictions, providing critical constraints on the electromagnetic structure of the Ω − hyperon. No significant signal of charmonium or charmonium-like states decaying to Ω − Ω ¯ + $$ {\varOmega}^{-}{\overline{\varOmega}}^{+} $$ is observed in the investigated energy range.

The landmark detection of neutrinos from SN1987A marked the dawn of neutrino astrophysics. The neutrino burst provided essential insights into fundamental properties of neutrinos, and served as key probes of stellar evolution and supernova dynamics. The recent advancement in coherent elastic neutrino-nucleus scattering enables the detection of core-collapse supernova burst neutrinos using tonne-scale liquid xenon detectors originally designed for dark matter direct detection. Leveraging this capability, we developed and deployed an online supernova monitoring system for the PandaX-4T experiment. This system features a GPS module with millisecond-level timing precision, a low false-alarm rate, and high sensitivity to galactic core-collapse supernova explosion events. The methodology is robust, directly scalable, and planned for implementation in the next-generation PandaX-20T experiment.

Scalar-mediated interactions may exist among neutrinos, dark matter particles, or between the two. Double β-decay experiments provide a powerful tool to probe such exotic interactions. Using ^{136}Xe double β-decay data from PandaX-4T, we perform the first direct spectral search in the energy range of 20 to 2800 keV, setting the most stringent limits to date on scalar-mediated neutrino self-interactions for mediator masses below 2  MeV/c^{2}. These results place significant constraints on models invoking such interactions to alleviate the Hubble tension. Assuming the same scalar also mediates dark matter self-interactions, constraints on the dark matter-scalar interactions can be placed in conjunction with cosmological constraints.

We report a precise measurement of Po-216 half-life using the PandaX-4T liquid-xenon time-projection chamber (TPC). Rn-220, emanating from a Th-228 calibration source, is injected to the detector and undergoes successive alpha decays, first to Po-216 and then to Pb-212. The PandaX-4T detector measures the five-dimensional (5D) information of each decay, including time, energy, and three-dimensional position. Therefore, we can identify the Rn-220 and Po-216 decay events and pair them exactly to extract the lifetime of each Po-216. With a large data set and high-precision Rn-220 - Po-216 pairing technique, we measure the Po-216 half-life to be 143.7 +/- 0.5 ms, which is the most precise result to date and agrees with previously published values. The leading precision of this measurement demonstrates the power of the 5D calorimeter and the potential of exact parent-daughter pairing in the xenon TPC.

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator-based, low-radioactivity, multi-purpose neutrino detector located 693 meters (1800 m.w.e.) underground in the Guangdong province, China. To detect scintillation light produced in the target, the detector is equipped with 17,612 20-inch photomultipliers (PMTs), forming the Large PMT system (LPMT). In addition, 25,600 3-inch photomultipliers (the Small Photomultiplier System or SPMT) are deployed in the gaps between the LPMTs. This paper presents the design and performance of the underwater front-end electronics developed for the SPMT system. It details the individual electronics boards and their key components, the inter-board interfaces, the system-level design, and the firmware architecture that supports data acquisition and control. It also outlines mechanical and thermal integration, board validation procedures, and system performance metrics. The readout chain includes digitization of 128 PMT channels per unit, synchronized time-stamping, charge measurement, event packaging, and bandwidth management. Comprehensive validation confirms the system's readiness to meet JUNO's stringent physics goals. The underwater electronics achieve noise levels as low as 0.04 photoelectrons with minimal crosstalk (below 0.4

The continuous spectrum of double beta decay (ββ) provides a sensitive probe to test the predictions of the standard model and to search for signatures of new physics beyond it. We present a comprehensive analysis of the ^{136}Xe ββ spectrum utilizing 39.1±0.7  kg·yr of ^{136}Xe exposure from the PandaX-4T experiment. The analysis yields the most precise measurement to date of the ^{136}Xe two-neutrino double beta decay (2νββ) half-life, (2.14±0.05)×10^{21}  years, the uncertainty of which is reduced by a factor of 2 compared to our previous result. We measure the parameter ξ_{31}^{2ν}, defined as the ratio between the subleading and leading components of the ^{136}Xe 2νββ nuclear matrix element, to be 0.59_{-0.38}^{+0.41}, which is consistent with theoretical predictions. We also search for Majoron-emitting modes of ^{136}Xe ββ, establishing the most stringent limit for the spectral index n=7.

Cosmic-ray muons, owing to their high penetration power and abundance, have been widely employed as a natural probe in experimental particle physics. We developed a meter-scale cosmic-ray muon telescope, consisting of two parallel super-layers (1 m & times; 1 m) separated vertically by one meter. A super-layer is composed of two orthogonal detection layers, each one consisting of eighteen modules arranged in parallel and packed closely together. A module consists of a plastic scintillating bar precisely aligned and stacked on top of an underlying scintillating fiber mat in which fibers are arranged in a row of bundles. For a detection layer, each scintillator bar is coupled to a PMT while fiber bundles at the same position within all modules are coupled to a single PMT. Signals from scintillating bars and fibers are combined together to determine hit positions. With this detection scheme, the telescope can meet the requirement of spatial resolution and reduce the number of readout electronic channels. This article presents the comprehensive development of the telescope, encompassing its geometric design, data acquisition system, and performance evaluation. Experimental results show that the telescope achieves a position resolution better than 2 mm and an overall detection efficiency of similar to 85%. The innovative design keeps the manufacturing cost low while maintaining high spatial resolution and detection efficiency.

Over 25,600 3-inch photomultiplier tubes (PMTs) have been instrumented for the central detector of the Jiangmen Underground Neutrino Observatory. Each PMT is equipped with a high-voltage divider and a frontend cable with waterproof sealing. Groups of sixteen PMTs are connected to the underwater frontend readout electronics via specialized multi-channel waterproof connectors. This paper outlines the design and mass production processes for the high-voltage divider, the cable and connector, as well as the waterproof potting of the PMT bases. The results of the acceptance tests of all the integrated PMTs are also presented.

This corrects the article DOI: 10.1103/rtnh-jn8s.

This paper introduces a new charge reconstruction combination method used Bayesian for multilayer detectors to enhance the charge identification capability. The method employs a Landau convoluted Gaussian function to fit charge distributions of each layer, deriving the probability density function (PDF) which serves as a likelihood function. By combining the likelihood function of the same nucleus in different layers, the joint likelihood function is obtained for each nucleus sample. The combined charge of the incident particle is built according to the Bayesian approach. The new method is used to combine the charge reconstruction results of two layers of plastic scintillator detector, and the effectiveness of the method is verified with the beam test and simulation data. By comparing the performance with the traditional direct averaging method, the Bayesian method is significantly better than the traditional method.

This paper presents an energy resolution study of the JUNO experiment, incorporating the latest knowledge acquired during the detector construction phase. The determination of neutrino mass ordering in JUNO requires an exceptional energy resolution better than 3% at 1 MeV. To achieve this ambitious goal, significant efforts have been undertaken in the design and production of the key components of the JUNO detector. Various factors affecting the detection of inverse beta decay signals have an impact on the energy resolution, extending beyond the statistical fluctuations of the detected number of photons, such as the properties of the liquid scintillator, performance of photomultiplier tubes, and the energy reconstruction algorithm. To account for these effects, a full JUNO simulation and reconstruction approach is employed. This enables the modeling of all relevant effects and the evaluation of associated inputs to accurately estimate the energy resolution. The results of this study reveal an energy resolution of 2.95% at 1 MeV. Furthermore, this study assesses the contribution of major effects to the overall energy resolution budget. This analysis serves as a reference for interpreting future measurements of energy resolution during JUNO data collection. Moreover, it provides a guideline for comprehending the energy resolution characteristics of liquid scintillator-based detectors.

We perform a search of double beta decay of Xe-136 to the excited state, 0(1)(+), of Ba-136 (2 nu beta beta-0(1)(+)), using the dual-phase xenon detector of PandaX-4T with the first 94.9-day commissioning data. The multi-site events are reconstructed up to the MeV energy scale, which helps to improve the background model significantly. The background contribution from the stainless steel platform outside PandaX-4T cryostat is evaluated for the first time. No significant evidence for 2 nu beta beta-0(1)(+) is observed, resulting in a lower limit on half-life of 7.5 x 1022 yr at the 90% confidence level. This is the first experimental limit on such a rare decay in a natural xenon-based detector.

The inclusive cross sections of prompt J/psi and psi(3686) production are measured at center-of-mass energies from 3.808 to 4.951 GeV. The dataset used is 22 fb(-1) of e(+)e(-) annihilation data collected with the BESIII detector operating at the BEPCII storage ring. The results obtained are in agreement with the previous BESIII measurements of exclusive J/psi and psi(3686) production. The average values obtained for the cross sections measured in the center-of-mass energy ranges from 4.527 to 4.951 GeV for J/psi and from 4.843 to 4.951 GeV for psi(3686), where the impact of known resonances is negligible, are 14.0 +/- 1.7 +/- 3.1 pb and 15.3 +/- 3.0 pb, respectively. For J/psi, the first and the second uncertainties are statistical and systematic, respectively. For psi(3686), the uncertainty is total. These values are useful for testing charmonium production models.

Based on (2712.4 +/- 14.1) x 10(6) psi(3686) decays collected with the BESIII detector, we have observed, for the first time, the hadronic decays of S- and P-wave charmonium states into 2(pi(+) pi(-))eta via radiative transitions from psi(3686). The branching fraction of the decay eta(c)(1S) -> 2(pi(+) pi(-))eta has a significant dependence on the interference pattern between eta(c)(1S) and non-eta(c)(1S) processes. We measure it in both the destructive and constructive interference scenarios for the first time. The mass and width of the eta(c)(1S) are measured to be M = (2984.14 +/- 0.13 +/- 0.38) MeV/c(2) and Gamma = (28.82 +/- 0.11 +/- 0.82) MeV, respectively. Clear signals for the decays of the chi(cJ)(J = 0, 1, 2) and the eta(c)(2S) to 2(pi(+) pi(-))eta are also observed for the first time, and the corresponding branching fractions are measured. The ratio of the branching fractions between the eta(c)(2S) and eta(c)(1S) decays is significantly lower than the theoretical prediction, which might suggest different dynamics in their decays.

We perform a search of double beta decay of 136Xe to the excited state, 0_1^+ , of 136Ba (2νββ- 0_1^+ ), using the dual-phase xenon detector of PandaX-4T with the first 94.9-day commissioning data. The multi-site events are reconstructed up to the MeV energy scale, which helps to improve the background model significantly. The background contribution from the stainless steel platform outside PandaX-4T cryostat is evaluated for the first time. No significant evidence for 2νββ- 0_1^+ is observed, resulting in a lower limit on half-life of 7.5 × 1022 yr at the 90

We present a novel constraint on light dark matter utilizing 1.54 metric ton/year of data acquired from the PandaX-4T dual-phase xenon time projection chamber. This constraint is derived through detecting electronic recoil signals resulting from the interaction with solar-enhanced dark matter flux. Low-mass dark matter particles, lighter than a few MeV/c^{2}, can scatter with the thermal electrons in the Sun. Consequently, with higher kinetic energy, the boosted dark matter component becomes detectable via contact scattering with xenon electrons, resulting in a few keV energy deposition that exceeds the threshold of PandaX-4T. We calculate the expected recoil energy in PandaX-4T considering the Sun's acceleration with heavy mediators and the detection capabilities of the xenon detector. The first experimental search results using the xenon detector yield the most stringent upper limits cross section of 3.51×10^{-39}  cm^{2} at 0.08  MeV/c^{2} for a solar boosted dark matter mass ranging from 0.02 to 10  MeV/c^{2}, achieving a 23-fold improvement compared with earlier experimental studies.

We measure the Born cross section for the reaction e+e−→ηhc from s=4.129 to 4.600 GeV using datasets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross-section line shape near 4.200 GeV is observed with a statistical significance of 7σ. The parameters of this resonance are measured to be M=4188.8±4.7±8.0 MeV/c2 and Γ=49±16±19 MeV, where the first uncertainties are statistical and the second systematic. Published by the American Physical Society 2025

The characteristics of capacitor dividers of disk and coaxial configurations are investigated. The amplitude-frequency response properties of two disk capacitor dividers obtained during the experiments indicate that the upper-limited response frequency of the disk sensor could be improved by decreasing its diameter. This might be due to the transit time of the measured high-voltage pulse propagating through the sensor being non-negligible if it is comparable to the rise time of the measured pulse. Both the experimental and circuit simulation results demonstrate that the upper-limited response frequency of the coaxial monitor is improved with respect to decreasing its length. A coaxial sensor is employed to diagnose the high-voltage pulse with a rise time of about 100 ps, and the corresponding upper-limited response frequency of this monitor is about 12 GHz. We have proposed a numerical post-processing method to compensate for the low-frequency response property of the capacitor divider, and the high-voltage pulse with a rise time of about 100 ps can be accurately measured.

We report the search for neutrinoless double-beta decay of 136Xe from the PandaX-4T experiment with a 3.7-tonne natural xenon target. The data reconstruction and the background modeling are optimized in the MeV energy region. A blind analysis is performed with data from the commissioning run and the first science run. No significant excess of signal over the background is observed. A lower limit on the half-life of 136Xe neutrinoless double-beta decay is established to be 2.1×1024 yr at the 90% confidence level, with a 136Xe exposure of 44.6 kg⋅yr. Our result represents the most stringent constraint from a natural xenon detector to date.

Axionlike particles (ALPs) and dark photons (DPs) are viable dark matter particle candidates. We have searched for possible ALP/DP signals in the PandaX-4T liquid xenon detector using 440 kg·yr of data. A binned likelihood fit is constructed to search for possible mono-energetic peaks induced by the absorption processes between ALPs/DPs and atomic electrons of xenon. A detailed temporal model of decays associated with xenon isotopes is introduced to constrain the number of background events. No signal excess over background expectations is observed, and we have established the most stringent exclusion limits for most ALP/DP masses across the range of 150 keV/c^2 to 1 MeV/c^2. The improvement is particularly significant within the mass range of 150-400 keV/c^2, with the average factor of 3.5 compared to previous results.