The Jiangmen Underground Neutrino Observatory (JUNO) started physics data taking on 26 August 2025. JUNO consists of a 20-kton liquid scintillator central detector, surrounded by a 35 kton water pool serving as a Cherenkov veto, and almost 1000 m$^{2}$ of plastic scintillator veto on top. The detector is located in a shallow underground laboratory with an overburden of 1800 m.w.e. This paper presents the performance results of the detector, extensively studied during the commissioning of the water phase, the subsequent liquid scintillator filling phase, and the first physics runs. The liquid scintillator achieved an attenuation length of 20.6 m at 430 nm, while the high coverage PMT system and scintillator together yielded about 1785 photoelectrons per MeV of energy deposit at the detector centre, measured using the 2.223 MeV $\textit{γ}$ from neutron captures on hydrogen with an Am-C calibration source. The reconstructed energy resolution is 3.4% for two 0.511 MeV $\textit{γ}$ at the detector centre and 2.9% for the 0.93 MeV quenched $^{214}$Po alpha decays from natural radioactive sources. The energy non-linearity is calibrated to better than 1%. Intrinsic contaminations of $^{238}$U and $^{232}$Th in the liquid scintillator are below 10$^{-16}$ g/g, assuming secular equilibrium. The water Cherenkov detector achieves a muon detection efficiency better than 99.9% for muons traversing the liquid scintillator volume. During the initial science runs, the data acquisition duty cycle exceeded 97.8%, demonstrating the excellent stability and readiness of JUNO for high-precision neutrino physics.

Chile

Angel Abusleme

France

Thomas Adam

Germany

Kai Adamowicz

China

David Adey

Pakistan

Shakeel Ahmad

Rizwan Ahmed

Finland

Timo Ahola

Italy

Sebastiano Aiello

Fengpeng An

Guangpeng An

United Kingdom

Costas Andreopoulos

Giuseppe Andronico

João Pedro Athayde Marcondes de André

Russia

Nikolay Anfimov

Vito Antonelli

Tatiana Antoshkina

Thailand

Burin Asavapibhop

Didier Auguste

Margherita Buizza Avanzini

Slovakia

Andrej Babic

Jingzhi Bai

Weidong Bai

Nikita Balashov

Roberto Barbera

Andrea Barresi

Davide Basilico

Eric Baussan

Beatrice Bellantonio

Marco Bellato

JeanLuc Beney

Marco Beretta

Antonio Bergnoli

Enrico Bernieri

Nikita Bessonov

David Biaré

Daniel Bick

Lukas Bieger

Svetlana Biktemerova

Thilo Birkenfeld

David Blum

Simon Blyth

Sara Boarin

Manuel Boehles

Anastasia Bolshakova

Mathieu Bongrand

Aurélie Bonhomme

Clément Bordereau

Matteo Borghesi

Augusto Brigatti

Timothee Brugiere

Riccardo Brugnera

Riccardo Bruno

Jonas Buchholz

Antonio Budano

Max Buesken

Mario Buscemi

Severino Bussino

Jose Busto

Ilya Butorov

Marcel Büchner

Anatael Cabrera

Barbara Caccianiga

Boshuai Cai

Hao Cai

Xiao Cai

Yanke Cai

Yi-zhou Cai

Zhiyan Cai

Stéphane Callier

Steven Calvez

Antonio Cammi

Agustin Campeny

Dechang Cai

Chuanya Cao

Dewen Cao

Guofu Cao

Jun Cao

Yaoqi Cao

Rossella Caruso

Aurelio Caslini

Cédric Cerna

Vanessa Cerrone

Daniele Cesini

Chi Chan

Jinfan Chang

Yun Chang

Milo Charavet

Tim Charissé

Auttakit Chatrabhuti

Chao Chen

Guoming Chen

Haitao Chen

Haotian Chen

Jiahui Chen

Jian Chen

Jing Chen

Junyou Chen

Lihao Chen

Mali Chen

Mingming Chen

Initial performance results of the JUNO detector * We acknowledge financial and institutional supportfrom the Chinese Academy of Sciences, the National KeyR&D Program of China, the People's Government of Guangdong Province, and the Tsung–Dao Lee Institute of Shanghai Jiao Tong University in China.We appreciate the contributions from the Institut Na-tional de Physique Nucléaire et de Physique des Partic-ules (IN2P3) in France, the Istituto Nazionale di Fisica Nucleare (INFN) in Italy, the Fonds de la Recherche Sci-entifique (F.R.S.–FNRS) and the Institut Interuni-versitaire des Sciences Nucléaires (IISN) in Belgium, and the Conselho Nacional de Desenvolvimento Científico eTecnológico (CNPq) in Brazil.We also acknowledge the support of the AgenciaNacional de Investigación y Desarrollo (ANID) and the ANID–Millennium Science Initiative Program (ICN2019044) in Chile; the European Structural and In-vestment Funds, the Ministry of Education, Youth and Sports, and the Charles University Research Center inthe Czech Republic; the Deutsche Forschungsgemeinsch-aft (DFG), the Helmholtz Association, and the Cluster ofExcellence PRISMA+ in Germany; and the Joint Insti-tute for Nuclear Research (JINR) and Lomonosov Mo-scow State University in Russia.We further thank the Slovak Research and Develop-ment Agency in the Slovak Republic, the National Science and Technology Council (NSCT) and MOE, China, the Program Management Unit for Hu-man Resources & Institutional Development, Research and Innovation (PMU–B), Chulalongkorn University, and Suranaree University of Technology in Thailand, the Science and Technology Facilities Council (STFC) in the United Kingdom, and the University of California atIrvine and the National Science Foundation (NSF) in the United States

In this paper, we employ a ray-tracing algorithm to simulate the shadows of three equal-mass black holes in static equilibrium across a wide parameter space. We find that the shadows consist of a larger primary shadow and several distorted, eyebrow-like secondary shadows. The boundaries of these profiles exhibit self-similar fractal structures, which can be attributed to the photon chaotic scattering. In certain parameter spaces, we also observe the ring-like shadows, with the ring diameter associated with the spacing of black holes. Furthermore, when the black holes approach each other sufficiently, their shadows can merge into a standard disk, suggesting a shadow degeneracy between closely arranged triple black holes and a single massive, spherically symmetric black hole. The shadow features of the triple black holes revealed in this study have potential implications for analyzing the shadow formation mechanisms, as well as the gravitational lensing during the merger and inspiral of black holes.

Dan Li

Yuxiang Zuo

Shiyang Hu

Chen Deng

Yu Wang

Wenfu Cao

Shadows of three black holes in static equilibrium configuration

In this work, gravitational lensing in the weak and strong field limits is investigated for black hole spacetime within the framework of Hu–Sawicki ( ) gravity. We employ the Ishihara et al. approach for weak lensing and adopt Bozza’s method for strong lensing to explore the impact of Hu–Sawicki model parameters on lensing phenomenon. The deflection angles are computed and analyzed in both the field limits. Our investigation in the weak as well as the strong lensing reveals that in the case of Hu–Sawicki black holes, photons exhibit divergence at smaller impact parameters for different values of the model parameters compared to the Schwarzschild scenario and the photon experiences negative deflection angle when impact parameter moves towards the larger impact parameter values. Additionally, by calculating strong lensing coefficients we study their behavior with model parameters. The strong lensing key observables associated with the lensing effect viz. the angular position $$\vartheta _{\infty }$$ , angular separation and relative magnification $$r_\text {mag}$$ are estimated numerically by extending the analysis to supermassive black holes $$\text {SgrA}^*$$ and $$\text {M87}^*$$ and analyzed their behavior concerning the parameters for each black hole. The analysis shows that $$\text {SgrA}^*$$ demonstrates larger values of $$\vartheta _{\infty }$$ and relative to $$\text {M87}^*$$ .

India

Gayatri Mohan

Nashiba Parbin

Umananda Goswami

Investigating the effects of gravitational lensing by Hu-Sawicki $$\varvec{f(R)}$$ gravity black holes

We study the propagation of massless fermionic fields, implementing a family of special functions: Heun functions, in solving the wave equation in three three-dimensional backgrounds, including the BTZ black hole in string theory and Lifshitz black hole solutions in conformal gravity and Hu–Sawicki ( ) theory. The main properties of the selected black hole solutions is that their line elements are Weyl related to that of a homogeneous spacetime, whose spatial part possesses Lie symmetry, described by Lobachevsky-type geometry with arbitrary negative Gaussian curvature. Using the Weyl symmetry of massless Dirac action, we consider the perturbation equations of fermionic fields in relation to those of the homogeneous background, which having definite singularities, are transformed into Heun’s equation. We point out the existence of quasinormal modes labeled by the accessory parameter of the Heun function. The distribution of the quasinormal modes has been clarified to satisfy the boundary conditions that require ingoing and decaying waves at the event horizon and conformal infinity, respectively. It turned out that the procedure based on the Heun function, beside reproducing the previously known results obtained via hypergeometric function for the BTZ and Lifshitz black hole solution in conformal gravity, brings up new families of quasinormal frequencies, which can also contain purely imaginary modes. Also, the analysis of the quasinormal modes shows that with the negative imaginary part of complex frequencies $$\omega =\omega _{Re}+i\omega _{Im}$$ , the fermionic perturbations are stable in this background.

Iran

F. Naderi

A. Rezaei-Aghdam

Quasinormal modes of three $$(2+1)$$ -dimensional black holes in string theory, conformal gravity, and Hu–Sawicki

We derive novel black hole solutions in a modified gravity theory, namely the Hu–Sawicki model of f(R) gravity. After obtaining the black hole solution, we study the horizon radius of the black hole from the metric and then analyse the dependence of the model parameters on the horizon. We then use the 6th order WKB method to study the quasinormal modes of oscillations (QNMs) of the black hole perturbed by a scalar field. The dependence of the amplitude and damping part of the QNMs are analysed with respect to variations in model parameters and the error associated with the QNMs are also computed. After that we study some thermodynamic properties associated with the black hole such as its thermodynamic temperature as well as greybody factors. It is found that the black hole has the possibility of showcasing negative temperatures and is thermodynamically unstable for feasible values of model parameters. Then we analyse the geodesics and derive the photon sphere radius as well as the shadow radius of the black hole. The photon radius is independent of the model parameters while shadow radius showed fair amount of dependence on the model parameters. We tried to constrain the parameters with the help of Keck and VLTI observational data and obtained some bounds on m and  $$c_{2}$$  <math> <msub> <mi>c</mi> <mn>2</mn> </msub> </math>   parameters.

Ronit Karmakar

Quasinormal modes, thermodynamics and shadow of black holes in Hu–Sawicki  $$\varvec{f(R)}$$  <math> <mrow> <mi>f</mi> <mo>(</mo> <mi>R</mi> <mo>)</mo> </mrow> </math>   gravity theory

The present paper contains the investigations with respect to the optical appearance, redshift distribution, and observed energy flux of the thin accretion disk described by the Novikov-Thorne model in modified gravity (MOG) proposed by Moffat. The results show that the gravity coupling parameter  $$\alpha $$  <math> <mi>α</mi> </math>   plays an indispensable role in the size of direct and secondary images of the accretion disk, while the image profile is mainly affected by the observational angles. In addition, an increase of the parameter  $$\alpha $$  <math> <mi>α</mi> </math>   leads to that of the redshift factor, but a decrease in the radiation energy flux of the accretion disk. These results are due to the enhancement of the parameter  $$\alpha $$  <math> <mi>α</mi> </math>   that strengthens the black hole’s gravitational effects. By comparing the accretion disk images of the Schwarzschild-MOG black hole, the Schwarzschild black hole, and the Reissner–Nordström black hole, we point out that the Schwarzschild-MOG black hole exhibits the largest inner shadow and the lowest luminosity. This finding provides a potential way to distinguish Schwarzschild-MOG black holes from their counterparts in General Relativity.

Sen Guo

Xin Wu

Enwei Liang

Observational signatures of Schwarzschild-MOG black holes in scalar–tensor–vector gravity: images of the accretion disk

We study the influence of parameter  $$\alpha $$  <math> <mi>α</mi> </math>   on the optical features of Schwarzschild-MOG black holes with different thin accretions in scalar-tensor-vector gravity. As  $$\alpha $$  <math> <mi>α</mi> </math>   increases from 0, the radii of the event horizon, photon sphere, and observed shadow increase in comparison with the Schwarzschild black hole. We constrain the parameter  $$\alpha $$  <math> <mi>α</mi> </math>   with the experimental data reported by the Event Horizon Telescope Collaboration for M87 $$^{*}$$  <math> <msup> <mrow></mrow> <mrow> <mrow></mrow> <mo>∗</mo> </mrow> </msup> </math>   and Sagittarius A $$^{*}$$  <math> <msup> <mrow></mrow> <mrow> <mrow></mrow> <mo>∗</mo> </mrow> </msup> </math>  . In the situation of spherical accretions, we unveil that the parameter  $$\alpha $$  <math> <mi>α</mi> </math>   has a positive effect on the shadow size but a negative effect on the observed specific intensities. Considering that the Schwarzschild-MOG black hole is surrounded by an optical and geometrically thin accretion disk, we find that the total observed specific intensities are mainly contributed by the direct emissions, while the photon rings and lensed rings provide small contributions. It is also found that with the increase of  $$\alpha $$  <math> <mi>α</mi> </math>  , the black hole shadow expands, the photon rings and lensed rings become larger and thicker. Besides, we emphasize that the boundary of the observed shadow cast by the aim black hole in the disk accretion scenario is determined by the direct emissions rather than the photon ring emissions. Consequently, we unveil that there is a linear relationship involving the critical impact parameter and the starting point of the direct emissions. This finding helps to use the experimental results of the Event Horizon Telescope to infer the critical impact parameter and to test General Relativity.

Observational signatures of Schwarzschild-MOG black holes in scalar-tensor-vector gravity: shadows and rings with different accretions