In this study, we investigate the possibility of enhancing the di-jet resonance searches by tagging the final state radiation (FSR) jet using an event-level deep neural network. It is found that solely relying on the 4-momenta of the leading three jets allows the algorithm to achieve good discriminating power that can identify the hardest FSR jet in the signal while rejecting other soft jets. Once the invariant mass is corrected with the tagged FSR jet, the mass resolution of the signal is greatly enhanced, and the sensitivity of the search is also improved by more than 10%. By crafting the input variables carefully, the algorithm introduces minimal mass sculpting for the background, and its applicability extends to a broad mass range. This work proves that FSR jet tagging can potentially enhance di-jet resonance searches, suiting various stages of the physics programmes at the Large Hadron Collider (LHC) and High-Luminosity LHC (HL-LHC).

China

Bingxuan Liu

Yuxuan Shen

Yuanshunzi Sui

Enhancing di-jet resonance searches via a final-state radiation jet tagging algorithm * Bingxuan Liu is supported by Shenzhen Campus of the Sun Yat-sen University under project 74140-12255011, and by the Young Scientists Fund (C Class) of the National Natural Science Foundation of China (12405122). Both Yuxuan Shen and Yuanshunzi Sui are supported by College Students’ Innovative Entrepreneurial Training Plan Program

Jet quenching is studied in a background magnetic field and finite baryon chemical potential. The production of energetic partons is calculated using the next-to-leading order (NLO) perturbative Quantum Chromodynamics (pQCD) parton model, whereas the parton energy loss formula is obtained from the AdS/CFT correspondence incorporating the magnetic field and baryon chemical potential effects. Using Bayesian inference, we systemically compare theoretical calculations with experimental data for the nuclear modification factor $ R_{AA}$ of large transverse momentum hadrons in different centralities of nucleus-nucleus collisions at 0.2, 2.76, and 5.02 TeV, respectively. The holographic calculation leads to a strong negative correlation between the magnetic field and chemical potential for a fixed amount of energy loss. This degeneracy can be observed after model calibration. Finally, we discussed the sensitivity of jet quenching phenomena to the external magnetic field and background baryon chemical potential.

Liqiang Zhu

Zhan Gao

Weiyao Ke

Hanzhong Zhang

Bayesian inference of the magnetic field and chemical potential on holographic jet quenching in heavy-ion collisions * Supported by National Natural Science Foundation of China (12535010, 11935007)

Small neutrino masses can be generated through the well-known seesaw mechanisms, among which the type-II scenario predicts a triplet scalar with doubly charged components. Except for the Drell-Yan production at the Large Hadron Collider (LHC), the doubly charged scalars $\Delta^{\pm\pm}$ can also be produced through photon fusion along with the ultraperipheral collision of protons, from which the outgoing protons can be detected by forward detectors at the LHC, providing a promising means to explore related new physics. We study the pair production through such processes at the 14 TeV LHC, focusing on the final states of $\mu^{+}\mu^{+}\mu^{-}\mu^{-}$ and $e^{+}e^{+}e^{-}e^{-}$ under the normal hierarchy (NH) and inverted hierarchy (IH) of the neutrino mass spectra, respectively. Promising sensitivity can be reached via our proposed search strategy. At a luminosity of 36.1 fb$^{-1}$(100 fb $^{-1}$ ), $m_{\Delta}\sim430(520)$ GeV can be excluded at 95% C.L. under the NH via $\mu^{+}\mu^{+}\mu^{-}\mu^{-}$ state searching, while the mass bound can be extended to 730(880) GeV under the IH via $e^{+}e^{+}e^{-}e^{-}$ states. The exclusion limits on $m_{\Delta}$ can be improved up to 1 TeV and even higher with integrated luminosity accumulated to 3 ab $^{-1}$ .

Hang Zhou

Ning Liu

Search for doubly charged scalars in type-II seesaw mechanism through photon fusion at the LHC * Supported by the National Natural Science Foundation of China (12405118) and the Natural Science Foundation of Jiangsu Province (BK20230623)

We investigate the collider signatures of a maximally flavor-violating $ U(1)_{L_\mu-L_\tau} $ model, where a new gauge boson $ Z^\prime $ and scalar triplets induce lepton flavor-changing interactions in the $\textit{μ}$-$\textit{τ}$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $ m_{Z^\prime} $ and the effective parameters $ \tilde{g}/m_{Z^\prime} $ , whereas it remains largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $ m_{Z^\prime} $ , and beam polarization can significantly suppress the Standard Model backgrounds while enhancing new physics contributions. We find that, in the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results show that multi-lepton final states are powerful probes of the $ U(1)_{L\mu - L_\tau} $ framework and can offer valuable guidance for future searches at muon and electron-positron colliders.

Jianing Qin

Fei Huang

Honglei Li

Zhi-Long Han

Jin Sun

Collider probes of four-lepton final states in maximally flavor-violating ${U(1)_{L_\mu-L_\tau}} $ model * Supported by National Natural Science Foundation of China (12505112, 11805081), Shandong Province Natural Science Foundation (ZR2024QA138, ZR2022MA056) and State Key Laboratory of Dark Matter Physics, University of Jinan Disciplinary Cross-Convergence Construction Project 2024 (XKJC- 202404) and Jin Sun is supported by IBS under the project code, (IBS-R018-D1)

We investigate thermal photon production in the quark-gluon plasma (QGP) under strong magnetic fields using a magnetohydrodynamic (MHD) framework. We employ relativistic ideal fluid dynamics under the non-resistive approximation by adopting the Bjorken flow model with power-law decaying magnetic fields $ \mathbf{B}(\tau) = \mathbf{B}_0 (\tau_0/\tau)^a $ , span> $\textit{a}$ controls the decay rate, $ B_0 = \sqrt{\sigma} T_0^2 $ , and $\textit{σ}$ characterizes the initial field strength. The resulting QGP temperature evolution exhibits distinct $\textit{a}$- and $\textit{σ}$-dependent behaviors. Thermal photon production rates are calculated for three dominant processes: Compton scattering with $ q\bar{q} $ annihilation (C+A), bremsstrahlung (Brems), and $ q\bar{q} $ annihilation with additional scattering (A+S). These rates are integrated over the space-time volume to obtain the photon transverse momentum $ (p_T) $ spectrum. Our results demonstrate that increasing $\textit{a}$ enhances photon yields across all $ p_T $ , with $ a \to \infty $ (super-fast decay) providing an upper bound. For $ a = 2/3 $ , a larger $\textit{σ}$ suppresses yields through accelerated cooling, whereas for $ a \to \infty $ , a larger $\textit{σ}$ enhances yields via prolonged thermal emission. Low- $ p_T $ photons receive significant contributions from all QGP evolution stages, while high- $ p_T $ photons originate predominantly from early times. The central rapidity region $ (y=0) $ dominates the total yield. This work extends the photon yield studies to the MHD regime under strong magnetic fields, clarifying the magnetic field effects on QGP electromagnetic signatures and establishing foundations for future investigations of magnetization and dissipative phenomena.

Jie Xiong

Xiang Fan

Jing Jing

Weishan Yang

Duan She

Ze-Fang Jiang

Thermal photon emission from quark-gluon plasma: 1+1D magnetohydrodynamics results * Supported by the National Natural Science Foundation of China (NSFC) (12305138). Duan She's research is funded by the Startup Research Fund of Henan Academy of Sciences (231820058) and the 2024 Henan Province International Science and Technology Cooperation Projects (242102521068)

We investigated the effect of an isospin chemical potential ( $ \mu_{I} $ ) within the quark-meson model, which approximates quantum chromodynamics (QCD) by modeling low-energy phenomena such as chiral symmetry breaking and phase structure under varying conditions of temperature and chemical potential. Using the functional renormalization group (FRG) flow equations, we calculated the phase diagram in the chiral limit within the two-flavor quark-meson model in a finite $ \mu_{I} $ with $\textit{ρ}$ vector meson interactions. Fluctuation effects significantly decrease the critical chemical potential from the mean-field (MF) value $\mu_{I,{\rm MF}} \gt m_\rho$ to a lower value at which the $\textit{ρ}$ vector meson condensates alongside the chiral condensate once the isospin chemical potential exceeds the critical value $ \mu_{I}^{{\rm{crit}}} $ . This $\textit{ρ}$ condensation was investigated numerically for different meson coupling strengths. The $\textit{ρ}$ meson dominated region is delineated from other phases by a second-order phase transition at lower $ \mu_{I} $ and a first-order transition at slightly higher $ \mu_{I} $ .

Mohammed Osman

Defu Hou

Wentao Wang

United States

Hui Zhang

Functional renormalization group study of $\textit{ρ}$ meson condensate at a finite isospin chemical potential in the quark meson model * Supported in part by the National Key Research and Development Program of China (2022YFA1604900). This work is also partly supported by the National Natural Science Foundation of China (NSFC) (12435009, 12275104). Hui Zhang acknowledges the financial support from the Guangdong Major Project of Basic and Applied Basic Research (2020B0301030008) and the National Natural Science Foundation of China (12047523, 12105107)

The CREDO-Maze project, which is being carried out at the University of Łódź, has at least two important objectives. The first is purely scientific. It involves searching for the Cosmic Ray Ensemble, more specifically, identifying long-range correlations between extensive air showers. The distances involved can be hundreds or even thousands of kilometres. Observing these hypothetical phenomena would necessitate a significant revision of our views on the universe and its origins. The second goal is equally important and has an educational focus. The aim is to establish an experimental base that will enable a large number of young people to learn about modern physics and become familiar with scientific methods, thereby stimulating their interest in science – particularly physics. The project is based on Linsley’s concept of a distributed air shower array, but on a global scale. This involves installing small particle arrays in numerous locations via a network of high schools. In this paper, we discuss the design of a single detector and the ’minimal’, local (school) shower array, as well as the structure of the entire CREDO-Maze network. We present the results of some detector tests, as well as selected results of the apparatus operating in atypical geometries. These results confirm the validity of our assumptions and demonstrate the significant potential of the apparatus for non-trivial and unusual measurements, including the search for Cosmic Ray Ensembles.

Poland

Tadeusz Wibig

Michał Karbowiak

Łukasz Radecki

Kacper Dorszewski

Jan Pabisiak

Patryk Siekierski

Bartłomiej Witaszczyk

CREDO-Maze project: global network of small extensive air shower arrays

This paper investigates the dynamical behavior of a quintom dark energy model, which combines quintessence and phantom scalar fields, across four distinct interacting scenarios: (I) quintessence-matter interaction, (II) phantom-matter interaction, (III) coupled quintessence-phantom-matter interaction, and (IV) intra-dark energy interaction (quintessence-phantom energy exchange). By constructing autonomous dynamical systems for each case, we analyze the stability of critical points and evaluate the cosmological evolution using the statefinder diagnostic pair $$\{r, s\}$$ . The exponential potentials for both scalar fields and interaction terms proportional to the matter density $$(Q_1, Q_2)$$ are adopted to derive fixed points, revealing that all scenarios admit late-time phantom-dominated attractors, consistent with accelerated expansion. Notably, interactions between dark sectors significantly alter transient regimes: energy transfer from dark matter to dark energy prolongs matter-quintessence coexistence phases, while reverse transfer accelerates phantom dominance. The statefinder diagnostic, however, fails to distinguish interactions due to overlapping $$s-r$$ trajectories across cases. Numerical simulations further demonstrate epochs of negative phantom energy density in scenarios involving phantom coupling, linked to non-physical fixed points. These results highlight quintom’s flexibility in mimicking observed dark energy behavior while emphasizing the limited discriminatory power of $$\{r, s\}$$ for coupling-specific dynamics. The study underscores the role of interactions in alleviating cosmic coincidence problems and shaping multi-phase cosmic histories.

Jianwen Liu

Fabao Gao

Ruifang Wang

Dynamics of an interacting quintom dark energy model in four scenarios and statefinder diagnostic

We investigate quasinormal modes (QNMs) of scalar, electromagnetic, and axial gravitational perturbations in slowly rotating Kalb–Ramond (KR) black holes, where an antisymmetric tensor field induces spontaneous Lorentz symmetry breaking. Working consistently to first order in the dimensionless spin parameter, we derive the corresponding master equations and compute the QNM spectrum using both the continued-fraction and matrix methods, finding excellent agreement. Lorentz violation modifies the oscillation and damping rates in a unified manner across all perturbative sectors: the real part of the QNM frequency increases monotonically with the Lorentz-violating parameter $$\ell $$ , while the imaginary part becomes more negative. Axial gravitational modes exhibit the strongest response, revealing an intrinsic theoretical bound $$\ell < 0.5$$ , beyond which the spectrum approaches an extremal behavior. Our results highlight the potential of gravitational-wave spectroscopy to probe Lorentz-violating signatures in KR gravity.

Weike Deng

Wentao Liu

Kui Xiao

Jiliang Jing

Quasinormal modes of scalar, electromagnetic, and gravitational perturbations in slowly rotating Kalb–Ramond black holes

<p>In the experiment with the SND at the VEPP-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2000</mn><mtext> </mtext><mtext> </mtext><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> collider, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi>γ</mi></math> cross section is measured in the energy range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>E</mi><mo>=</mo><mn>980</mn><mi>–</mi><mn>1060</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math>. The measurement is carried out in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>η</mi><mo stretchy="false">→</mo><mn>2</mn><mi>γ</mi></math> decay mode. Data with an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>73</mn><mtext> </mtext><mtext> </mtext><msup><mi>pb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> collected in 2018 and 2024 are used in the analysis. The measured cross section is the most accurate to date and is higher compared to other measurements. From the fit to the cross section data with the vector meson dominance model, the value of the product of the branching fractions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">(</mo><mi>ϕ</mi><mo stretchy="false">→</mo><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">)</mo><mi>B</mi><mo stretchy="false">(</mo><mi>ϕ</mi><mo stretchy="false">→</mo><mi>η</mi><mi>γ</mi><mo stretchy="false">)</mo></math> has been obtained.</p>

Russia

M.N. Achasov

A.E. Alizzi

A. Yu. Barnyakov

E.V. Bedarev

K.I. Beloborodov

A.V. Berdyugin

A.G. Bogdanchikov

A.A. Botov

D.E. Chistyakov

T.V. Dimova

V.P. Druzhinin

L.V. Kardapoltsev

A.S. Kasaev

A.A. Kattsin

A.G. Kharlamov

I.A. Koop

A.A. Korol

D.P. Kovrizhin

A.S. Kupich

A.P. Kryukov

N.A. Melnikova

N. Yu. Muchnoi

A.E. Obrazovsky

A.A. Oorzhak

E.V. Pakhtusova

I.A. Polomoshnov

K.V. Pugachev

S.A. Rastigeev

Yu. A. Rogovsky

A.I. Senchenko

S.I. Serednyakov

Yu. M. Shatunov

D.A. Shtol

Z.K. Silagadze

K.D. Sungurov

I.K. Surin

Yu. V. Usov

V.N. Zhabin

Yu. M. Zharinov

V.V. Zhulanov

Measurement of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>η</mi><mi>γ</mi></math> cross section near the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ϕ</mi><mo stretchy="false">(</mo><mn>1020</mn><mo stretchy="false">)</mo></math> resonance with the SND detector