Chinese Physics C

Highlights

Searches for heavy neutrinos at a 3 TeV CLIC in fat jet final states
Yao-Bei Liu, Jing-Wei Lian

2026, 50(3): 033110. doi: 10.1088/1674-1137/ae2d24

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Heavy Majorana neutrinos (N) are predicted in many models of physics beyond the Standard Model. In this work, we explore the production and detection prospects of TeV-scale heavy neutrinos ($ m_N \gtrsim 1 $ TeV) at a future 3 TeV Compact Linear Collider (CLIC). We focus on two distinct decay topologies: (i) $ N \to \ell^\pm W^\mp $ with hadronic W boson decay, leading to a final state with one charged lepton and a hadronic fat jet $ J_W $; and (ii) $ N \to \nu h $ with subsequent Higgs decay $ h \to b\bar{b} $, yielding a Higgs-tagged fat jet $ J_h $ and $\not{E}_T$. Based on comprehensive detector-level simulations and background analysis, we present both $ 2\sigma $ exclusion limits and $ 5\sigma $ discovery reaches in the $ m_N $–$ |V_{\ell N}|^2 $ plane. We further extract 95% confidence level upper limits on the mixing parameter $ |V_{\ell N}|^2 $ and perform a detailed comparison with existing constraints from direct searches at future colliders and indirect global fits. Our findings demonstrate that a 3 TeV CLIC can improve the sensitivity to $ |V_{\ell N}|^2 $ by about two orders of magnitude compared with the projected reaches of future hadron colliders while remaining competitive with other CLIC search channels.
Particle-number conserving analysis of the πd_5/2 band in ^{117,119,121,123,125}Cs
Qing-Qing Zhang, Anshul Dadwal, Xiao-Tao He

2026, 50(3): 034107. doi: 10.1088/1674-1137/ae1de6

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The $ \pi d_{5/2} $ rotational bands in odd-even nuclei ^{117,119,121,123,125}Cs are systematically investigated using the cranked shell model (CSM) with the pairing correlations modeled with a particle number conserving (PNC) method. In this PNC method, the particle number is conserved exactly while considering the blocking effects. The experimental observations of the $ \pi d_{5/2} $ bands with two upbendings for ^117,119Cs and one backbending for ¹²⁵Cs are reproduced very well by the PNC-CSM method. Furthermore, $ \pi d_{5/2} $ configuration bands with two upbendings for ¹²¹Cs and one backbending for ¹²³Cs are predicted by the PNC-CSM calculations. The difference between the lighter ^117,119,121Cs and heavier ^123,125Cs isotopes is caused by the evolution of single-particle orbitals near the Fermi surface, and the high-j low-Ω orbital $ \pi [550]1/2 $ plays an important role. The proton shell gap of lighter isotopes is at $ Z=50 $, whereas it appears at $ Z=48 $ for heavier ones. For lighter isotopes ^117,119,121Cs, the first upbending is primarily due to the off-diagonal contributions of protons $ j_{x}(\pi5/2^{-}[532]\pi3/2^{-}[541]) $ and $ j_{x}(\pi1/2^{-}[550]\pi3/2^{-}[541]) $. The second upbending is mainly effected by the off-diagonal contributions of neutrons $ j_{x}(\nu7/2^{-}[523] \nu5/2^{-}[532]) $ and $ j_{x}(\nu3/2^{-}[541] \nu5/2^{-}[532]) $ for ^117,119Cs and $ j_{x}(\nu1/2^{-}[541] \nu5/2^{-}[532]) $ for ¹²¹Cs, respectively. For heavier isotopes such as ^123,125Cs, the backbending is attributed mainly to the diagonal parts of proton $ j_{x}(\pi1/2^{-}[550]) $ and neutron $ \nu7/2^{-}[523] $ orbital related terms of diagonal $ j_{x}(\nu7/2^{-}[523]) $ and off-diagonal $ j_{x}(\nu7/2^{-}[523] \nu5/2^{-}[532]) $ contributions.
Comprehensive investigation on baryon number violating nucleon decays involving an axion-like particle
Wei-Qi Fan, Yi Liao, Xiao-Dong Ma, Hao-Lin Wang

2026, 50(3): 033103. doi: 10.1088/1674-1137/ae25c9

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In this study, we systematically investigate baryon number violating (BNV) nucleon decays into an axion-like particle (ALP) within a low energy effective field theory extended with an ALP, which is referred to as aLEFT. Unlike previous studies in the literature, we consider contributions to nucleon decays from a complete set of dimension-eight BNV aLEFT operators involving light u, d, and s quarks. We perform the chiral irreducible representation (irrep) decomposition of these interactions under the QCD chiral group ${S U}(3)_{\mathtt{L}}\times {S U}(3)_{\mathtt{R}}$ and match them onto the recently developed chiral framework to obtain nucleon-level effective interactions among the ALP, octet baryons, and octet pseudoscalar mesons. Within this framework, we derive general expressions for the decay widths of nucleon two- and three-body decays involving an ALP. Subsequently, we analyze momentum distributions for three-body modes and find that operators belonging to the newly identified chiral irreps ${\bf{6}}_{{\mathtt{L}}({\mathtt{R}})}\times {\bf{3}}_{{\mathtt{R}}({\mathtt{L}})}$ exhibit markedly different behavior compared to that in the usual irreps ${\bf{8}}_{{\mathtt{L}}({\mathtt{R}})}\times \pmb{1}_{{\mathtt{R}}({\mathtt{L}})}$ and ${\bf{3}}_{{\mathtt{L}}({\mathtt{R}})}\times \bar{{\bf{3}}}_{{\mathtt{R}}({\mathtt{L}})}$. In addition, we reanalyze experimental data collected by Super-Kamiokande and establish bounds on the inverse decay widths of these new modes by properly accounting for experimental efficiencies and Cherenkov threshold effects because of the lack of direct constraints on those exotic decay modes. Our recasting constraints are several orders of magnitude more stringent than inclusive bounds used in the literature. Based on these improved bounds, we set conservative limits on associated effective scales across a broad range of ALP mass and predict stringent bounds on certain neutron and hyperon decays involving an ALP.

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Predictions of nuclear charge radii with the radial basis function approach and linear relationship
Tao Li, Min Liu, Ning Wang

Published: 2026-02-26

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Published: 2026-02-26

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Gluon Wigner distributions with transverse polarization at non-zero skewness
Sujit Jana, Kenil Solanki, Vikash Kumar Ojha

Published: 2026-02-26

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Published: 2026-02-26

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Minimal lepton models with non-holomorphic modular A₄ symmetry
Xiang-Yan Gao, Cai-Chang Li

Published: 2026-02-26

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Published: 2026-02-26

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Measurement and systematic analysis of the cross sections of the ⁸²Kr(n, p)⁸²Br reaction induced by d-T neutrons
Junhua Luo, Long He, Li Jiang

2026, 50(4): 044001-044001-9. doi: 10.1088/1674-1137/ae3601

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The cross section of the ⁸²Kr(n, p)⁸²Br reaction induced by d-T neutrons was measured using the activation method. Incident neutrons are generated through the ³H(d, n)⁴He reaction. High-purity natural krypton gas held at high pressure was used as the target sample. The neutron energy and its uncertainty were determined based on the Q-value equation of the ³H(d, n)⁴He reaction and the experimental conditions. The neutron fluence incident on the sample is monitored by the ²⁷Al(n, α)²⁴Na reaction. The eight characteristic gamma rays of the ⁸²Br daughter nucleus were selected to determine its activity by off-line gamma spectrometry using an HPGe detector. The ⁸²Kr(n, p)⁸²Br reaction cross sections with lower uncertainties were finally determined at five neutron energies by the weighted method. The measured cross sections were compared with previous experimental studies, theoretical values from Talys-2.0, calculation results from the systematics (empirical and semi-empirical) formulas, and evaluation results. The present high-precision cross sections for the ⁸²Kr(n, p)⁸²Br reaction over a wide energy range not only help to validate and evaluate nuclear reaction models, but also substantially enrich the neutron-induced nuclear reaction cross sections database.

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Improving nuclear mass predictions by correcting mass residuals using eXtreme Gradient Boosting
X. Y. Zhang, W. F. Li, J. Y. Fang

2026, 50(4): 044101-044101-8. doi: 10.1088/1674-1137/ae25cd

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Nuclear masses are investigated for the first time using the eXtreme Gradient Boosting (XGBoost) method. Nucleon numbers, valence nucleon numbers, and physical quantities related to the magic number are used as input features for the decision tree, which learns the residuals of experimental binding energies with respect to the Bethe-Weizsäcker (BW2) formula predictions, and the XGBoost method can achieve high accuracy predictions of nuclear binding energy. For nuclear masses of magic number nuclei with prediction challenges, XGBoost can better capture the physical information associated with the magic number compared to that using BW2, and the root mean square deviation of its predicted nuclear mass ranges from 2.769 to 0.732 MeV. Comparing the results of BW2* and XGBoost* with the pseudo-experimental data of Finite-Range Droplet Model (FRDM12) suggests that the XGBoost* method may have better extrapolation abilities.

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Sub-barrier fusion enhancement caused by positive Q-value four-neutron transfer
Ning Wang, Yi-Jie Duan, Hong Yao, Hui-Ming Jia

2026, 50(4): 044110-044110-10. doi: 10.1088/1674-1137/ae3731

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The effect of positive Q-value four-neutron transfer (PQ4NT) on the sub-barrier capture cross sections is investigated systematically using the empirical barrier distribution (EBD2) method. For 13 fusion reactions with $Q_{4{\rm n}}>0$, the sustained neutron-pair transfer reduces barrier heights and enhances capture cross sections at sub-barrier energies. In contrast, reactions such as ¹⁸O+⁵⁸Ni, which have $Q_{2{\rm n}}>0$ and $Q_{4{\rm n}}<0$, exhibit no enhancement due to stalling of subsequent neutron-pair transfer after the initial 2n transfer. Incorporating PQ4NT effects into EBD2 for systems with $Q_{4{\rm n}}>0$ significantly reduces the average deviation between the predicted and experimental capture cross sections (113 datasets) by 20%. In comparison with those in reactions induced by ⁴⁸Ca ($Q_{4{\rm n}}<0$), the neutron pickup probabilities in the quasi-elastic scattering of ⁴⁰Ca-induced reactions ($Q_{4{\rm n}}>0$) are considerably larger, according to the time-dependent Hartree-Fock calculations.

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Current Issued

2026 Vol. 50, No. 3
Published: 27 February 2026

Particles And Fields
Nuclear Physics
Particle And Nuclear Astrophysics And Cosmology