This paper investigates the existence of cosmological black holes by analyzing the properties of trapping horizons in detail, based on Hayward’s formalism of future outer and past inner trapping horizons, in several dynamical spacetimes embedded in an expanding universe. Through a detailed examination of the McVittie, Culetu, and Sultana–Dyer metrics, as well as the generalized Glass–Mashhoon solution, we evaluate the existence and characteristics of trapping horizons and energy conditions. The Glass–Mashhoon solution provides an analytical model for spherical stellar collapse. However, it is shown that, as long as certain conditions are satisfied, it lacks suitable future outer trapping horizons, meaning it does not represent a cosmological black hole. As a result, the McVittie class of solutions also fails to describe a cosmological black hole. Conversely, the Culetu and Sultana–Dyer spacetimes can describe a cosmological black hole in the matter-dominated early universe, provided that the relevant energy conditions are satisfied.

Iran

Mahdi Esfandiar

Fatimah Shojai

Omid Jamshidi

Soran Zoorasna

Cosmological black hole candidates: a detailed analysis of McVittie, Culetu, Sultana–Dyer, and Glass–Mashhoon spacetimes

Global analyses of particle physics data are integral for validating and scrutinizing published results of experiments. Global fits of anomalous oscillation data which search for one or more eV-scale sterile neutrinos are particularly challenging both to evaluate and to reconcile in the global picture. Fits (especially joint ones) to oscillation data suffer from significant computational burdens, such as likelihood intractability, making traditional Markov Chain-Monte Carlo all but impossible. Given evidence both supporting and challenging beyond Standard Model physics across neutrino experiments of various baselines, energies, and detection techniques, the global search for sterile neutrinos requires additional tools in order to determine whether sterile neutrinos remain a viable solution to unexplained anomalies. Furthermore, both a Bayesian and frequentist interpretation of sterile neutrino data is needed for a complete assessment of longstanding tensions in the field. Techniques from the machine learning subfield of simulation-based inference have a natural application to such a problem. In this contribution, we illustrate some of the outstanding questions of the global picture of light sterile neutrinos by focusing on experiments searching with the disappearance of electron (anti)neutrinos, and look to posterior density estimation strategies to craft answers, including comparisons to a machine-learning-based frequentist approach.

United States

Joshua Villarreal

Julia Woodward

John Hardin

Janet Conrad

Machine learning-informed 3+1 sterile neutrino global fits using posterior density estimation of electron disappearance data

We compute the effective action for covariantly constant gauge fields that are solutions of the sourceless Yang–Mills equation and have the form of magnetic flux tubes. They represent a superposition of infinite many alternating monopole/anti-monopole pairs situated at infinity, with each pair having a structure similar to the Nielsen–Olesen magnetic flux tube. The chromomagnetic flux tubes condensation is stable and indicates that the Yang–Mills vacuum state is highly degenerate.

Greece

George Savvidy

QCD effective lagrangian and condensation of chromomagnetic flux tubes

We investigate the bound-state equations (BSEs) in two-dimensional QCD in the $ N_{\rm{c}}\to \infty$ limit, viewed from both the infinite momentum frame (IMF) and the finite momentum frame (FMF). The BSE of a meson in the original 't Hooft model, $\textit{viz.}$, spinor QCD$_{2}$ containing only fermionc quarks, has been extensively studied in literature. In this work, we focus on the BSEs pertaining to two types of ''exotic'' hadrons, a ''tetraquark'' which is composed of a bosonic quark and bosonic antiquark, and a ''baryon'' which is composed of a bosonic antiquark and a fermionic quark. Utilizing the Hamiltonian approach, we derive the corresponding BSEs for both types of ''exotic'' hadrons, from the perspectives of the light-front and equal-time quantization, and confirm the known results. The recently available BSEs for ''tetraquark'' in FMF has also been recovered with the aid of the diagrammatic approach. For the first time we also present the BSEs of a ''baryon'' in FMF in the extended 't Hooft model. By solving various BSEs numerically, we obtain the mass spectra pertaining to ''tetraquark'' and ''baryon'' and the corresponding bound-state wave functions of the lowest-lying states. It is numerically demonstrated that, when a ''tetraquark'' or ''baryon'' is continuously boosted, the forward-moving component of the bound-state wave function approaches the corresponding light-cone wave function, while the backward-moving component fades away.

China

Xiaolin Li

Yu Jia

Ying Li

Zhewen Mo

Solving bound-state equations in QCD$_{2}$ with bosonic and fermionic quarks * Supported in part by the National Science Foundation of China (12475090, 11925506, 12435004) and the Natural Science Foundation of Shandong province (ZR2022ZD26). The work of Zhewen Mo is also supported in part by the National Natural Science Foundation of China (12347145, 12347105)

The $ e^+e^- $ annihilation of unpolarized beams is free from initial hadron states or initial anisotropy around the azimuthal angle. Hence, it is ideal for studying the correlations of dynamical origin via final state jets. We investigate the planar properties of multi-jet events employing the relevant event-shape observables at next-to-next-to-leading order ( $ {\cal{O}} $ ( $ \alpha_{s}^{3} $ )) in perturbative Quantum Chromodynamics (QCD). In particular, the azimuthal angle correlations on the long pseudo-rapidity (polar angle) range (Ridge correlation) between the inclusive jet momenta are calculated. We demonstrate that the significant planar properties and the strong correlations as the consequence are natural results of the energy-momentum conservation of the perturbative QCD radiation dynamics. Our study provides benchmarks of a hard strong interaction background for investigating the collective and/or thermal effects via the Ridge-like correlation observables for various scattering processes.

Xuan Chen

Yuesheng Dai

Shi-Yuan Li

Zong-Guo Si

Huiting Sun

Planar property and long-range azimuthal correlation in $\textit{e}$ $^{+}$ $\textit{e}$ $^{–}$ annihilation * Supported by the National Science Foundation of China (NSFC) (12475085, 12275157, 12321005, 12235008)

In this paper, we systematically explore the mass spectrum of fully strange tetraquark candidates within the framework of QCD sum rules, focusing on states with quantum numbers $ J^{PC}=0^{++} $ , $ 0^{-+} $ , $ 0^{--} $ , $ 1^{--} $ , $ 1^{+-} $ , and $ 1^{++} $ . The analysis reveals the existence of fully strange tetraquark states with masses ranging from approximately $ 2.07 $ to $ 3.12 $ GeV. These predictions are compared with existing experimental observations of potential fully strange tetraquark resonances, notably the $ X(2300) $ recently reported by the BESIII Collaboration, which may be interpreted as a fully strange tetraquark state. Furthermore, the possible decay modes of these fully strange tetraquark states are analyzed, providing guidance for their identification in current and future high-energy experiments, such as BESIII, Belle II, and LHCb.

Bing-Dong Wan

Ji-Chong Yang

Fully strange tetraquark states via QCD sum rules * Supported in part by the National Natural Science Foundation of China (12575106, 12147214) and Specific Fund of Fundamental Scientific Research Operating Expenses for Undergraduate Universities in Liaoning Province (LJ212410165019)

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).

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)