Neutron-rich nuclei around 78Ni provide an important testing ground for the <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>50</mn></mrow></math> shell closure and cross-shell correlations. We develop a nuclear-structure implementation of the semistochastic heat-bath configuration interaction (SHCI) method and apply it, for the first time, to nuclear structure calculations with <italic>ab initio</italic> valence-space Hamiltonians. SHCI builds a compact variational space through heat-bath selection and accounts for remaining correlations using semistochastic second-order perturbation theory. Combined with valence-space in-medium similarity renormalization group Hamiltonians derived from chiral two- and three-nucleon interactions, SHCI provides a large-space solver for extended proton- <italic>pf</italic> and neutron- <italic>gds</italic> valence spaces beyond conventional exact diagonalization. Benchmark calculations for 78Ni show that SHCI achieves faster convergence of low-lying spectra than comparable particle-hole truncations, demonstrating the efficiency of determinant-based selection. We further study the <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>50</mn></mrow></math> isotones and the Ni, Cu, and Zn isotopic chains toward the predicted neutron-rich limits. The results indicate a robust but gradually weakened <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>50</mn></mrow></math> shell closure from Ni to Zn, predict the drip-line nuclei, and suggest a possible weak subshell structure near <math altimg='si4.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>58</mn></mrow></math>. This work establishes SHCI as a systematically improvable large-space solver for <italic>ab initio</italic> nuclear structure.

China

P.Y. Wang

K.H. Li

Q. Yuan

W.J. Huang

J.G. Li

Semistochastic heat-bath configuration interaction with <italic>ab initio</italic> valence-space Hamiltonians for neutron-rich Ni, Cu, and Zn isotopes

We evaluate discovery prospects for photophobic axion-like particles (ALPs) in the $\textit{WWjj}$ final state at the High-Luminosity LHC (HL-LHC; $\sqrt{s}=14\ {\rm{TeV}}$ , ${\cal{L}}=3\ {\rm{ab}}^{-1}$ ). In the photophobic limit ( $g_{a\gamma\gamma}=0$ ), ALPs couple to electroweak gauge bosons and are produced in association with two jets ( $ pp\to jj\ a $ ) via both $\textit{s}$-channel electroweak exchange and vector boson fusion (VBF)–like topologies, followed by $a\to W^+W^-$ decay. We target the different-flavour dilepton mode $W^+W^- \to e^\pm\mu^\mp\nu \bar{\nu}$ with two jets and moderate missing transverse momentum. The analysis employs a two-step strategy: initial preselection that defines the signal-like final state, followed by a multivariate analysis (MVA) trained on dijet and dileptonic-$\textit{WW}$ kinematics from both the $\textit{s}$-channel and VBF-like production mechanisms to separate signal from background; the MVA threshold is optimized independently at each $m_a$ . We present 2$\textit{σ}$ and 5$\textit{σ}$ discovery sensitivities for the ALP–$\textit{W}$ coupling $g_{aWW}$ across the 170–4000 GeV mass range. For $260\ {\rm{GeV}}\le m_a\le1500\ {\rm{GeV}}$ , the 2$\textit{σ}$ (5$\textit{σ}$) sensitivity is approximately flat around $ 0.61(0.76)\ {\rm{TeV}}^{-1}$ . At large masses/couplings, the mapping between an experimental rate and a single EFT parameter $g_{aWW}$ can become UV sensitive, and we treat the extreme high-mass/high-coupling corner as an extrapolation; therefore, we also report model-independent discovery thresholds for the fiducial quantity $ \sigma(pp\to jj\ a)\times\rm{Br}(a\to W^+W^-) $ over the same mass range to enable reinterpretation for other models. These results indicate that the $WWjj$ topology offers competitive and complementary sensitivity to heavy photophobic ALPs at the HL-LHC.

Jiaojiao Feng

Ying-nan Mao

Kechen Wang

Discovery prospects for photophobic axion-like particles in the $\textit{WWjj}$ final state at the High-Luminosity LHC * Jiaojiao Feng and Kechen Wang are supported by the National Natural Science Foundation of China (11905162), the Excellent Young Talents Program of the Wuhan University of Technology (40122102, 40122103) and the research program of the Wuhan University of Technology (2020IB024, 104972025KFYjc0101). Ying-nan Mao is supported by the National Natural Science Foundation of China (12205227). The simulation and analysis work of this article was completed with the computational cluster provided by the Theoretical Physics Group at the Department of Physics, School of Physics and Mechanics, Wuhan University of Technology

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

We investigate proton-rich systems beyond the proton drip line, focusing on the notably poorly known 13F and 15Ne and the yet unobserved 14Ne, whose structure properties remain weakly constrained. Using the Gamow shell model (GSM), which consistently incorporates both inter-nucleon correlations and couplings to the particle continuum, we study oxygen, fluorine, and neon isotopes with mass <math altimg='si1.svg'><mrow><mi>A</mi><mo linebreak='goodbreak'>=</mo><mn>12</mn><mo linebreak='goodbreak'>&#8722;</mo><mn>16</mn></mrow></math>. Taking 8C as an inert core, the GSM Hamiltonian based on an effective field theory nucleon-nucleon interaction is optimized for this proton-rich region. The constructed Hamiltonian reproduces the low-lying spectra and decay properties of fluorine and neon isotopes beyond the proton drip line. We quantify many-body configuration and average partial-wave occupancies to elucidate the structural evolution of the drip line nuclei 12&#8211;14O, 13&#8211;15F, and 14&#8211;16Ne. In particular, multi-proton separation energies and spectroscopic factors are analyzed in detail, leading to a prediction for the unresolved ground state of 13F. Furthermore, the candidate 4 <italic>p</italic> emitter 14Ne is theoretically predicted for the first time, providing valuable guidance for future experimental investigations.

N. Chen

M.R. Xie

N. Michel

Probing exotic multi-proton emitters: A Gamow shell model study of proton-rich fluorine and neon isotopes beyond the drip line

Several possible excesses around $ 95 $ GeV hint at an additional light scalar beyond the Standard Model. We examine the capability of the Circular Electron-Positron Collider (CEPC) to test this hypothesis in the Higgs-strahlung channel $ e^{+}e^{-} \to ZS $ with $ Z \to\mu^{+}\mu^{-} $ and $ S \to\tau^{+}\tau^{-} $ . A full detector simulation shows that the optimal center-of-mass energy for studying the 95 GeV light scalar is 210 GeV. A deep neural network classifier reduces the luminosity required for discovery by half. At $ L = 20\; \mathrm{ab}^{-1} $ , the $ 5\sigma $ sensitivity of the CEPC to the signal strength $ \mu_{\tau\tau}^{ZS} $ reaches 0.016 and 0.020 for $ \sqrt{s} = 210 $ GeV and 240 GeV, respectively. The corresponding thresholds for a 5% precision measurement are $ \mu_{\tau\tau}^{ZS} \gt 0.10 $ and $ \gt 0.12 $ . At $ \sqrt{s}=210 $ GeV (240 GeV), the $ 5\sigma $ coverage of all N2HDM-Flipped samples with $ \chi^2_{h_{95}} \lt 7.82 $ requires $ L=800\ \mathrm{fb}^{-1} $ (1.22 $ \mathrm{ab}^{-1} $ ). These results establish a 210 GeV run, augmented by machine-learning selection, as the most efficient strategy to confirm or refute the 95 GeV excess at future lepton colliders.

Yabo Dong

Manqi Ruan

Kun Wang

Haijun Yang

Jingya Zhu

Testing a 95 GeV Scalar at the CEPC with Machine Learning * This work was supported by the National Natural Science Foundation of China under Grant No. 12275066 and by the startup research funds of Henan University. The work of K. Wang was also supported by the Open Project of the Shanghai Key Laboratory of Particle Physics and Cosmology under Grant No. 22DZ2229013-3. The work of M. Ruan was also supported by the National Key Program for S&T Research and Development under Contract No. 2024YFA1610603. The work of H. Yang was also supported by the National Natural Science Foundation of China under Grant No. W2441004.

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)

Proton-rich nuclei beyond the proton drip line are of great interest in nuclear structure physics, due to exotic phenomena such as proton emissions and the Thomas-Ehrman shift (TES). In this work, we employ the Gamow shell model (GSM) to investigate the structure and decay of 20Si, a candidate for six-proton (6 <italic>p</italic>) emission, which can be produced via two-neutron knockout from the drip line nucleus 22Si. We predict that its ground state decays via 6 <italic>p</italic> emission to the ground state of 14O, with a decay energy <math altimg='si21.svg'><mrow><msub><mi>E</mi><mrow><mn>6</mn><mi>p</mi></mrow></msub><mo linebreak='goodbreak'>=</mo><mn>10.125</mn></mrow></math> MeV and a width of 371 keV. A <math altimg='si22.svg'><msup><mn>2</mn><mo>+</mo></msup></math> state is predicted at 1.7 MeV, comparable with that in 18Mg, indicating the disappearance of the <math altimg='si23.svg'><mrow><mi>Z</mi><mo linebreak='goodbreak'>=</mo><mn>14</mn></mrow></math> magic number in 20Si. Instead, analyses of the many-body configurations and the average occupancies of the mirror states suggest the presence of <italic>dynamic</italic> TES in low-lying states of 19Al/ 19C and 20Si/ 20C. Further evidence is provided by analyzing the contributions of different components of the GSM Hamiltonian. Moreover, this study offers the first theoretical description of 20Si and guidance for future experiments.

J.L. Wang

Gamow shell model predictions for six-proton unbound nucleus 20Si

We study $ \cos2\phi $ azimuthal asymmetry in doubly longitudinally polarized proton-proton Drell-Yan collisions within the transverse momentum dependent factorization framework. The asymmetry arises from the convolution of the longitudinal transversity distribution $ h_{1L}^{\perp} $ for both protons. Using the Bacchetta-Delcarro-Pisano-Radici-Signori parameterization for the nonperturbative Sudakov form factor and the Wandzura-Wilczek approximation for collinear $ h_{1L}^{\perp} $ , we predict the double spin asymmetry $ A_{LL}^{\cos2\phi} $ at RHIC and NICA kinematics. Our results demonstrate sensitivity to sea quark distributions, with the asymmetry reaching up to 25% for maximal sea quark contributions. These predictions highlight the potential of polarized Drell-Yan measurements to probe sea quark dynamics and advance our understanding of nucleon structures.

Hui Li

Ting Hu

Liang-Liang Liu

Xiao-Yu Wang

Zhun Lu

Asymmetry ${{\boldsymbol A}_{\boldsymbol{LL}}^{\bf\cos2\boldsymbol\phi}} $ in the polarized proton-proton Drell-Yan process within TMD factorization * Hui Li is supported by Fundamental Research Program of Shanxi Province (202203021222224) and Natural Science Foundation of Shanxi Normal University (JCYJ2023021). Xiao-Yu Wang is supported by the Natural Science Foundation of Henan Province (242300421377, 232300421140)

We propose a search strategy at the HL-LHC for a new neutral particle $\textit{X}$ that couples to $\textit{W}$-bosons, using the process $ p p \to W^{\pm} X (\to W^{+} W^{-}) $ with a tri-$\textit{W}$-boson final state. Focusing on events with two same-sign leptonic $\textit{W}$-boson decays into muons and a hadronically decaying $\textit{W}$-boson, our method leverages the enhanced signal-to-background discrimination achieved through a machine-learning-based multivariate analysis. Using the heavy photophobic axion-like particle (ALP) as a benchmark, we evaluate the discovery sensitivities on both production cross section times branching ratio $ \sigma(p p \to W^{\pm} X) \times \text{Br}(X \to W^{+} W^{-}) $ and the coupling $ g_{aWW} $ for particle mass over a wide range of 170–3000 GeV at the HL-LHC with center-of-mass energy $ \sqrt{s} = 14 \, \text{ TeV} $ and integrated luminosity $ {\cal{L}} = 3 \, \text{ab}^{-1} $ . Our results show significant improvements in discovery sensitivity, particularly for masses above 300 GeV, compared to existing limits derived from CMS analyses of Standard Model (SM) tri-$\textit{W}$-boson production at $ \sqrt{s} = 13 \, \text{ TeV} $ . This study demonstrates the potential of advanced selection techniques in probing the coupling of new particles to $\textit{W}$-bosons and highlights the HL-LHC's capability to explore physics beyond the SM.

Yiheng Xiong

Sensitivities of new resonance couplings to $\textit{W}$-bosons at the LHC * Ying-nan Mao and Yihen Xiong are supported by the National Natural Science Foundation of China (12205227). Kechen Wang is supported by the National Natural Science Foundation of China (11905162), the Excellent Young Talents Program of the Wuhan University of Technology (40122102), and the research program of the Wuhan University of Technology (2020IB024). The simulation and analysis work of this article was completed with the computational cluster provided by the Theoretical Physics Group at the Department of Physics, School of Physics and Mechanics, Wuhan University of Technology

The production of heavy-quark (HQ) jets is a new area that addresses the mass effect of jet quenching in heavy-ion physics. This paper presents a theoretical study of HQ jet yield suppression in Pb+Pb collisions at the Large Hadron Collider (LHC) and focuses on the energy loss of HQ jets produced by different mechanisms. The $\textit{p+p}$ baseline is provided by the generator simulation of high-energy reactions of particles (SHERPA), and the jet-medium interactions are described by the SHELL transport model, which considers the elastic and inelastic partonic energy loss in the quark-gluon plasma (QGP). In $\textit{p+p}$ collisions, our numerical results indicate that the HQ jets from gluon splitting ( $ g \rightarrow Q $ -jet) are the dominant contribution at high $ p_T $ , displaying more dispersive structures than the HQ-initiated ( $ Q \rightarrow Q $ -jet). In nucleus-nucleus collisions, our calculations were consistent with the inclusive and b-jet $ R_{AA} $ recently measured by the ATLAS collaboration, revealing a remarkable manifestation of the mass effect of jet energy loss. As a result of the dispersive substructure, the $ g \rightarrow Q $ -jet loses more energy than the $ Q \rightarrow Q $ -jet in the QGP. Due to the significant contribution of $ g \rightarrow c $ -jet, the $ R_{AA} $ of $\textit{c}$-jet is comparable or even smaller than that of inclusive jet. To experimentally distinguish the $ g \rightarrow Q $ -jet and $ Q \rightarrow Q $ -jet, we propose event selection strategies based on their topological features and test their performances. By isolating the $ c \rightarrow c $ -jet, $ b \rightarrow b $ -jet, and the jets initiated by heavy quarks, we predicted that the order of their $ R_{AA} $ are in line with the mass hierarchy of energy loss. Future measurements on the $ R_{AA} $ of $ Q \rightarrow Q $ -jet and $ g \rightarrow Q $ -jet will provide a unique opportunity for testing the flavor/mass dependence of energy loss at the jet level.

Sa Wang

Shuang Li

Yao Li

Ben-Wei Zhang

Enke Wang

Probing the mass effect of heavy quark jets in high-energy nuclear collisions * Supported by the MajorProject of Basic and Applied Basic Research of Guangdong Province, China (2020B0301030008, 2023A1515011460), and the National Natural Science Foundation of China (11935007, 12035007, 12247127, 12375137). Sa Wang is supported by the Open Foundation of Key Laboratory of Quark and Lepton Physics (MOE) (QLPL2023P01) and the Talent Scientific Star-up Foundation of the China Three Gorges University, China (CTGU) (2024RCKJ013)