The interference between amplitudes corresponding to different intermediate resonances plays an important role in generating large CP asymmetries in the phase space in multi-body decays of bottom and charmed mesons. In this study, we examine the CP violation in the decay channel $ {\overline{B}}^{0}\rightarrow K^{-}\pi^{+}\pi^{0} $ in the phase-space region where the intermediate resonances $ \overline{K}^{*}(892)^{0} $ and $ {\overline{K}^{*}_{0}(700)} $ dominate. In particular, the forward-backward asymmetry (FBA) and the CP asymmetry induced by FBA (FB-CPA), which are closely related to the interference effects between the two aforementioned resonances, are investigated. The nontrivial correlation between FBA and FB-CPA is analyzed. The analysis indicates that FB-CPAs around the resonance $ \overline{K}^{*}(892)^{0} $ can be as large as approximately 35%, which can be potentially accessible by Belle and Belle-II collaborations in the near future.

China

Jian-Yu Yang

Yu-Jie Zhao

Jing-Juan Qi

Zhen-Hua Zhang

The forward-backward asymmetry induced CP asymmetry in ${{\overline{B}}^{0}\rightarrow K^{-}\pi^{+}\pi^{0}}$ in phase space around the resonances ${{\overline{K}}^{*}(892)^{0}}$ and ${{\overline{K}}^{*}_{0}(700)}$ * Supported by National Natural Science Foundation of China (12475096, 12405115, 12192261) and Scientific Research Fund of Hunan Provincial Education Department (22A0319)

Motivated by the observation of the doubly charmed tetraquark $ T_{cc}(3875)^+ $ , we present a systematic study of doubly heavy tetraquarks ( $ T_{QQ'\bar{q}\bar{q}'} $ ) using heavy antiquark-diquark symmetry (HADS) within a constituent quark model. By calibrating model parameters to known hadron spectra and incorporating the effective mass formula, we predict the masses for 38 ground-state tetraquarks with $ cc $ , $ bb $ , and $ bc $ heavy quark pairs, including the non-strange, single-strange, and double-strange configurations with quantum numbers $ J^P = 0^+, 1^+ $ and $ 2^+ $ . Notably, we identify several stable states below the relevant meson-meson thresholds, particularly in the $ bb\bar{q}\bar{q}' $ sector. The explicit connection between the doubly heavy tetraquark and the heavy baryon spectra through HADS reduces model dependence and reveals the fundamental systematics in the heavy-quark hadron landscape.

Liu-Yu Zhang

Tian-Wei Wu

Yong-Liang Ma

Bridging doubly heavy tetraquark mass spectrum with heavy baryons utilizing heavy antiquark-diquark symmetry * The work of Tian-Wei Wu is supported by the National Natural Science Foundation of China (12405108). Yong-Liang Ma is supported in part by the National Science Foundation of China (NSFC) (12347103) and Gusu Talent Innovation Program (ZXL2024363)

The Schwinger effect, a non-perturbative mechanism for particle production in strong fields, plays a crucial role in understanding quantum vacuum decay and high-energy phenomena, including heavy-ion collisions (HIC). Although holographic quantum chromodynamics (QCD) models have been widely used to study this effect, most treatments assume isotropy or consider only a single type of anisotropy, neglecting the interplay between spatial and magnetic anisotropies that arise in realistic HIC scenarios. A unified framework accounting for both anisotropies is needed to accurately model particle production. We investigate the Schwinger effect in a twice anisotropic holographic QCD model incorporating both spatial and magnetic anisotropies. Using the anti-de Sitter/conformal field theory correspondence, we compute the total potential of a particle-antiparticle pair to quantify how these anisotropies influence pair production. Our results show that the magnetic field (parameterized by $c_B$ and $q_3$ ) enhances the Schwinger effect by lowering and narrowing the potential barrier, while increasing spatial anisotropy (controlled by $\nu$ ) suppresses the process by raising and widening the barrier. These findings demonstrate that magnetic and spatial anisotropies exert competing effects on particle production, emphasizing the necessity of treating both concurrently in holographic models. This work advances the theoretical description of the Schwinger effect in anisotropic environments, with implications for understanding non-equilibrium dynamics in HIC and other strongly coupled systems.

Wen-Bin Chang

Defu Hou

Schwinger effect in a twice anisotropic holographic model * Defu Hou's research is supported in part by the National Key Research and Development Program of China (2022YFA1604900). Additionally, Defu Hou receives partial support from the National Natural Science Foundation of China (NSFC) (12435009, 12275104). Wen-Bin Chang is supported by the Ph.D. Research Startup Project at Hubei Minzu University (RZ2500000857)

Several proposed future lepton colliders are capable of producing trillions of Z-bosons, including FCC-ee, CEPC, LEP3 and LEP-Z. Such Tera-Z factories can discover new elementary particles with couplings to the Z-boson that are orders of magnitude smaller than current bounds. For couplings near the currently excluded parameter regions they could produce sufficiently large samples to study the new particles’ properties in detail, thereby serving as both a discovery and precision machine in one. Using simple analytic estimates, we quantify the dependence of the expected event yield in long-lived particle searches on the number of produced Z-bosons and on the detector dimensions. From this, we derive estimates for both the discovery reach and the measurement precision attainable at such facilities. While the precision of such estimates of course falls short of proper simulations, the analytic approach is suitable for a quick assessment of the sensitivity for a given design. We illustrate this with two examples, heavy neutral leptons and axion-like particles. Under optimistic assumptions, these could be produced in the millions and billions, respectively, effectively turning future lepton colliders into exotics factories.

Belgium

Germany

Marco Drewes

Croatia

Juraj Klarić

Yuan-Zhen Li

New particles at the Z-pole:

The notion of time in general relativity must arise from an internal clock, i.e., a degree of freedom in the gravitational theory internal to the system that can serve the role of a physical clock. One such internal notion of time is the York time, corresponding to constant extrinsic curvature slicing of spacetime. We study the Hartle-Hawking wavefunction of asymptotically $\textit{AdS}$ JT gravity as a function of York time. Using both canonical quantization and the JT gravity path integral, we explicitly calculate this wavefunction and show that it satisfies a Schrodinger equation with respect to York time. We find the corresponding York Hamiltonian, which turns out to be manifestly Hermitian. Our analysis cleanly avoids operator ordering ambiguities. The dependence of the wavefunction on York time should be thought of as emerging from a unitary basis transformation of the gravitational length basis states used to compute the wavefunction, and not from time evolution of the state in the dual boundary theory.

India

Onkar Parrikar

Japan

Sunil Sake

York time in JT gravity

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.

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)