The Galactic Center GeV Excess (GCE) remains a compelling but enigmatic signal from the inner regions of our galaxy. Muonphilic dark matter (DM), which couples exclusively to muons via a new mediator, provides a viable explanation for the GCE and relic density while naturally evading constraints from direct detection, collider searches, and other multimessenger observations. Based on the viable nonresonant parameter space identified in previous global fits, we perform a comprehensive study on the prospects for discovering such muonphilic DM in the context of a future 3 TeV muon collider, focusing on simplified models with a $Z_2$ -even mediator. Four distinct search strategies are investigated: visible on-shell mediator decays ( $\mu^{+}\mu^{-}\gamma$ final state), invisible on-shell mediator decays (mono-photon plus missing energy), mono-photon production via off-shell mediators, and vector boson fusion production. Through a detailed signal-background analysis using cut-and-count methods, we project the exclusion limits at $ 95 $ % confidence level for seven representative models across a wide range of mediator masses. Our results demonstrate that the projected limits cover a significant portion of viable parameter space that explains the GCE, establishing a muon collider as a decisive machine for testing the muonphilic DM hypothesis.

China

Wanyun Chen

Haoqi Li

Chih-Ting Lu

Qiulei Wang

Exploring muonphilic dark matter with the $\textit{Z}$ $_{2}$-even mediator at muon colliders * Chih-Ting Lu, Wanyun Chen and Haoqi Li are supported by the National Natural Science Foundation of China (NNSFC) (12335005, 12575118) and the Special funds for postdoctoral overseas recruitment, Ministry of Education of China

This study investigates the ultraviolet realization of semileptonic four-fermion operator $ O_{ledq}^{\alpha \beta 11} $ that incorporates Majorana dark matter (DM) in both lepton-flavor-conserving (LFC) and lepton-flavor-violating (LFV) scenarios at the one-loop level via box diagram, thereby effectively alleviating the lower bounds on the new physics scale. In addition, we investigate the interplay between model-independent constraints on the Wilson coefficients and DM direct detection, relic density, and collider searches in the context of fermion portal DM model with two mediators. We found that both the projected future constraint on the LFC Wilson coefficient $ C_{ledq}^{2211}/\Lambda^2 \lt $ $ (12.3\; \text{TeV})^{-2} $ from the measurements of neutrino non-standard interaction in the next-generation neutrino oscillation experiments, and the LFV constraint $ C_{ledq}^{1211}/\Lambda^2 \lt \left(2.2\times 10^3\; \text{TeV} \right)^{-2} $ from ongoing charged-lepton-flavor-violation searches, provide a complementary exploration of the parameter space encompassing the DM and scalar masses. With a colored mediator mass of approximately $ 2\; \text{TeV} $ , the sensitivity of the indirect constraints on the four-fermion operator can surpass those of collider searches and DM direct detection, in scenarios where the masses of the DM and scalar are close. By ensuring the correct DM relic density, however, we find that the collider searches and DM direct detection are more sensitive to the electroweak-scale DM and scalar than indirect constraints.

Yuxuan He

Gang Li

Jia Liu

Xiao-Ping Wang

Xiang Zhao

Lepton flavor of four-fermion operator and fermion portal dark matter * Gang Li and Xiang Zhao are supported by the National Natural Science Foundation of China (12347105, 12505127), the Guangdong Basic and Applied Basic Research Foundation (2024A1515012668). The work of Jia Liu is supported by the National Science Foundation of China (12235001, 12475103) and State Key Laboratory of Nuclear Physics and Technology (NPT2025ZX11). The work of Xiao-Ping Wang is supported by National Science Foundation of China (12375095) and the Fundamental Research Funds for the Central Universities

Within the framework of Dyson-Schwinger equations (DSEs) and by means of the Multiple Reflection Expansion approximation, we study the finite volume effects on the constituent quark mass in a strong external magnetic field. Since the magnetic field influences the coupling constant, which controls the strength of strong interactions in QCD, we adopt the magnetic-field-dependent running coupling constant in our simulations. The results show that, in addition to the magnetic field, the masses of constituent quarks also have a significant dependence on the volume and the running coupling constant. The model behaves closely to the infinite volume limit for large sizes, but the effect of the finite volume is significant when the system size $\textit{R}$ is about $ 2-6 $ fm. The finite volume effects and the magnetic-field-dependent running coupling constant have considerable influence on the phase transition.

Li-Juan Zhou

De-Xian Wei

Zhong-Yi Liu

Hong-Wei Zhong

Dynamical quark mass and finite volume effects in the Dyson-Schwinger equations * Li-Juan Zhou has been supported by the National Natural Science Foundation of China (11865005), the Natural Science Foundation of Guangxi (China) (2025GXNSFAA069552). De-Xian Wei has been supported by the National Natural Science Foundation of China (12105057), the Natural Science Foundation of Guangxi (China) (2023GXNSFAA026020)

Precise neutrino energy reconstruction is essential for next-generation long-baseline oscillation experiments, yet current methods remain limited by large uncertainties in neutrino-nucleus interaction modeling. Even so, it is well established that different interaction channels produce systematically varying amounts of missing energy and therefore yield different reconstruction performance–information that standard calorimetric approaches do not exploit. We introduce a strategy that incorporates this structure by classifying events according to their underlying interaction type prior to energy reconstruction. Using supervised machine-learning techniques trained on labeled generator events, we leverage intrinsic kinematic differences among quasielastic scattering, meson-exchange current, resonance production, and deep-inelastic scattering processes. A cross-generator testing framework demonstrates that this classification approach is robust to microphysics mismodeling and, when applied to a simulated DUNE <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ν</mi><mi>μ</mi></msub></math> disappearance analysis, yields improved accuracy and sensitivity at the 10%–20% level. These results highlight a practical path toward reducing reconstruction-driven systematics in future oscillation measurements.

Switzerland

United Kingdom

Sebastian A.R. Ellis

United States

Daniel C. Hackett

Shirley Weishi Li

Pedro A.N. Machado

Karla Tame-Narvaez

Improving neutrino oscillation measurements through event classification

We report an experimental investigation of an unexplored breakup pathway of 6Li proceeding via one-proton stripping to the unbound 5He nucleus, followed by its decay into <math altimg='si22.svg'><mrow><mi>&#945;</mi><mo linebreak='goodbreak'>+</mo><mi>n</mi></mrow></math>, in the 6Li + 112Sn reaction at <math altimg='si3.svg'><mrow><msub><mi>E</mi><mrow><mrow><mi mathvariant='normal'>b</mi></mrow><mi>e</mi><mi>a</mi><mi>m</mi></mrow></msub><mo linebreak='goodbreak'>=</mo><mn>30</mn></mrow></math> MeV. Coincident <italic>&#945;</italic>- <italic>n</italic> events were measured using an array of silicon strip telescopes in conjunction with liquid scintillator neutron detectors. Successive kinematical cuts on the reconstructed projectile-like, fragment energies and Q-values enabled a clear separation of contributions arising purely through 5He <math altimg='si6.svg'><mrow><mo>&#8594;</mo><mi>&#945;</mi><mo linebreak='goodbreak'>+</mo><mi>n</mi></mrow></math> from competing processes such as evaporation following complete and incomplete fusion. The resultant relative energy distributions exhibit a pronounced peak at 0.84 MeV, indicating sequential breakup through the first unbound resonance 5He(3/2 <math altimg='si23.svg'><msup><mrow /><mo>&#8722;</mo></msup></math>) and show good agreement with Monte-Carlo simulations. Absolute breakup cross-sections for the ( 6Li, 5He&#8239;&#8594;&#8239; <italic>&#945;n</italic>) channel are determined using the efficiency-corrected yields. In addition, angular distributions for elastic scattering and breakup cross sections are interpreted within coupled-channels (CDCC+CRC) framework. The present results provide valuable insight into transfer-induced breakup dynamics of weakly bound nuclei near the Coulomb barrier.

India

Tanya Singh

S. Santra

P.C. Rout

A. Pal

A. Baishya

H. Kumawat

T. Santhosh

M. Meher

Jyotisankar Das

Ramandeep Gandhi

Sequential breakup of 6Li via ( 6Li, 5He <math altimg='si6.svg'><mrow><mo>&#8594;</mo><mi>&#945;</mi><mo linebreak='goodbreak'>+</mo><mi>n</mi></mrow></math>) reaction

A wide range of scintillating bolometers are under investigation for applications in the search for rare events and processes beyond the Standard Model. In this work, we report the first measurement of a natural, non-molybdenum-doped, lithium tungstate (Li $$_2$$ WO $$_4$$ ) crystal operated underground as a scintillating cryogenic calorimeter. The detector achieved a baseline energy resolution of 0.5 keV RMS with a low-energy threshold of about 1.5 keV. The simultaneous readout of heat and light enabled particle identification, revealing a clear separation between $$\beta /\gamma ,$$ $$\alpha ,$$ and nuclear recoil populations above 300 keV, with a light-yield-based particle discrimination better than $$6\sigma .$$ These results, fully comparable with those achieved with other compounds in the field, demonstrate that Li $$_2$$ WO $$_4$$ is a promising candidate for rare-event searches. In particular, the combination of excellent radio-purity (with U/Th levels below 0.5 mBq/kg) and sensitivity to neutron interactions via the $$^6$$ Li(n, $$\alpha )$$ $$^3$$ H reaction makes this material an attractive option for next-generation experiments in dark matter, coherent elastic neutrino-nucleus scattering, and spin-dependent interactions.

Italy

D. Helis

A. Melchiorre

S. Nagorny

M. Noia

L. Pagnanini

S. Pirro

A. Puiu

G. Benato

P. Carniti

R. Elleboro

P. Gambacorta

C. Gotti

Russia

V. Grigorieva

S. Nisi

France

E. Olivieri

G. Pessina

S. Piacentini

Kazakhstan

M. Shafiee

V. Shlegel

Characterization of the Li $$_2$$ WO $$_4$$ crystal as a cryogenic scintillating calorimeter

KM3NeT has reported the detection of a remarkably high-energy through-going muon. Lighting up about a third of the detector, this muon likely originated from a neutrino exceeding 10 PeV in energy. The crucial question we need to answer is where this event comes from and what its source is. Intriguingly, IceCube has been operating with a much larger effective area for a considerably longer time, yet it has not reported neutrinos above 10 PeV. We quantify the tension between the KM3NeT event and the absence of similar high-energy events in IceCube under various assumptions of the origin for the neutrino including the isotropic diffuse flux, cosmogenic flux, and a steady or transient point source. Through a detailed analysis, we determine the most likely neutrino energy to be in the range of 23 – 2400 PeV, and find a tension between the experiments ranging from 3.6 to 3.1 <italic>&#963;</italic> for diffuse origins and 2.9 to 2.0 <italic>&#963;</italic> for point sources. The lack of observation of high-energy events in IceCube seriously challenges the explanation of this event coming from any known diffuse fluxes. Our results indicate the KM3NeT event is likely the first observation of a new astrophysical source.

Pedro Machado

Spain

Daniel Naredo-Tuero

Thomas Schwemberger

Clash of the titans: ultra-high energy KM3NeT event versus IceCube data

The competition between the breakup channels in the 6Li + 209Bi fusion reaction at the above-barrier energies has been investigated using a classical dynamic model. By incorporating the breakup processes from the short-lived nucleus formed via direct excitation and <italic>n</italic>-stripping, the model provides a comprehensive description of both complete and incomplete fusion cross sections. Although the <italic>n</italic>-stripping channel exhibits a higher probability, it contributes less to the complete fusion cross section compared to the direct excitation channel. An unexpected behavior was observed in incomplete fusion at the above barrier energies: the light-fragment capture predominantly occurs near the critical angular momentum, while the <italic>&#945;</italic> capture is favored at lower angular momenta, particularly in cases with large mass asymmetry between the two fragments. These findings provide further insight into the origin of fusion suppression in reactions involving weakly bound nuclei.

Kai-Xuan Cheng

Chun-Wang Ma

Mechanism of breakup channel competition in the 6Li+ 209Bi system at above-barrier energies

The 2HDM+S is the singlet extension of the two-Higgs-doublet model (2HDM). The singlet field and its mixing with the 2HDM Higgs sector lead to new contributions to the electroweak precision observables, in particular, the oblique parameters. In this study, we performed a systematic investigation of the impacts of each mixing angle on the oblique parameters. We adopted the mixing angles and physical Higgs masses as our parameters, which allow a mapping when a specific symmetry structure of the Higgs potential and various theoretical considerations are taken into account. We identified five benchmark cases, where at most one mixing angle was nonzero, and analyzed the 95% C.L. allowed parameter space using the oblique parameters. In the alignment limit of the 2HDM, we find that, other than the usual mass relations of $m_H\sim m_{H^\pm}$ or $m_A\sim m_{H^\pm}$ , electroweak precision measurements also impose an upper limit on the neutral Higgs masses. In the cases with nonzero singlet mixing with the 2HDM Higgses $\textit{H}$ or $\textit{A}$, we find approximate mass relations of $c^2_{\alpha_{HS}} m_{H} + s^2_{\alpha_{HS}}m_{h_S} = m_{H^\pm}$ or $c^2_{\alpha_{AS}} m_{A} + s^2_{\alpha_{AS}}m_{A_S} = m_{H^\pm}$ . These relations are universal to the 2HDM+S models, with or without further symmetry assumption. We also studied the non-alignment limit of the 2HDM+S, which typically has tighter constraints on the masses and mixing angles. Finally, we examined the complementarity between the electroweak precision analyses and the Higgs coupling precision measurements.

Cheng Li

Juxiang Li

Shufang Su

Wei Su

Electroweak precision constraints of the 2HDM+S * Cheng Li, Juxiang Li, and Wei Su are supported by the Natural Science Foundation of China (NSFC) (12305115), Shenzhen Science and Technology Program (202206193000001, 20220816094256002), Guangdong Provincial Key Laboratory of Gamma-Gamma Collider and Its Comprehensive Applications (2024KSYS001), and Guangdong Provincial Key Laboratory of Advanced Particle Detection Technology (2024B1212010005). Juxiang Li is also supported by the Fundamental Research Funds for the Central Universities, and the Sun Yat-sen University Science Foundation. Shufang Su is supported by the Department of Energy (DEFG02-13ER41976/DE-SC0009913)

Electroweak (EW) amplitudes in the gauge-Goldstone five-component formalism have a distinctive property: gauge symmetry is imprinted in the amplitudes, manifested as the massive Ward identity (MWI) $ k^M{\cal{M}}_M=0 $ . In this study, we used the HELAS package to numerically study gauge symmetry in EW amplitudes. First, we directly tested gauge symmetry by examining the MWI of amplitudes. Second, we modified the couplings within a vertex and among vertices to check if and how the MWI changes. Third, we tested gauge symmetry by considering the couplings modified by operators from the standard model effective field theory (SMEFT). Similar to the standard model, there are relations between different couplings that are protected by gauge symmetry. We observed that, if we modify the couplings to deviate from the relations, the MWI is violated. In contrast, the MWI is restored when the relations between couplings reduce to those in the SMEFT.

Wang-Fa Li

Junmou Chen

Qian-Jiu Wang

Zhao-Huan Yu

Numerical study on the gauge symmetry of electroweak amplitudes * Junmou Chen is supported by National Natural Science Foundation of China (12205118), Wang-Fa Li, Qian-Jiu Wang, and Zhao-Huan Yu are supported by the Guangzhou Science and Technology Planning Project (2024A04J4026)