Chinese Physics C

Highlights

Tilted-axis-cranking covariant density functional theory for high-spin spectroscopy of ⁶⁹Ga
Y. P. Wang, Y. K. Wang, P. W. Zhao

2026, 50(1): 014112. doi: 10.1088/1674-1137/ae07b8

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The tilted-axis-cranking covariant density functional theory is applied to investigate the three newly-observed positive-parity bands SI, SII, and SIII in ⁶⁹Ga. The energy spectra and angular momenta are calculated, and they agree closely with experimental data. For band SI, pairing correlations are crucial for the states with spin $I\leq 23/2\hbar$. Bands SII and SIII are suggested to be signature partner bands with positive and negative signatures, respectively. By analyzing the angular momentum alignments, we reveal that the $g_{9/2}$ protons and neutrons are crucial in the collective structures of ⁶⁹Ga. The transition probabilities $B(E2)$ for these bands are predicted, awaiting further experimental verification.
Null test of cosmic curvature using deep learning method
Li Tang, Liang Liu, Ying Wu

2026, 50(1): 015107. doi: 10.1088/1674-1137/ae0b42

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Determining the spatial curvature of the Universe, a fundamental parameter defining the global geometry of spacetime, remains crucial yet contentious due to existing observational tensions. Although Planck satellite measurements have provided precise constraints on spatial curvature, discrepancies persist regarding whether the Universe is flat or closed. Here, we introduce a model-independent approach leveraging deep learning techniques, specifically residual neural networks (ResNet), to reconstruct the dimensionless Hubble parameter E(z) and the normalized comoving distance D(z) from H(z) data and multiple SNe Ia compilations. Our dual-block ResNet architecture, which integrates a model-driven block informed by $ \Lambda $CDM and a purely data-driven block, yields smooth and robust reconstructions and enables the derivation of D'(z). By combining these reconstructed quantities, we assess the curvature diagnostic function $ {\cal{O}}_k(z) $. Analyses of the Pantheon+ sample support spatial flatness at the 1$ \sigma $ level over 0 < z < 2.5, with a mild tendency toward negative curvature at high redshift. Reconstructions based on Union3 and DESY5, however, show stronger departures toward negative curvature at intermediate and high redshifts. These results highlight the need for expanded and refined observational datasets to conclusively resolve these tensions and comprehensively investigate cosmic geometry.
Extracting the kinetic freeze-out properties of high energy pp collisions at the LHC with event shape classifiers
Jialin He, Xinye Peng, Zhongbao Yin, Liang Zheng

2026, 50(1): 014108. doi: 10.1088/1674-1137/ae07ba

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Event shape measurements are crucial for understanding the underlying event and multiple-parton interactions (MPIs) in high energy proton-proton (pp) collisions. In this study, the Tsallis blast-wave model with independent non-extensive parameters for mesons and baryons was applied to analyze the transverse momentum spectra of charged pions, kaons, and protons in pp collision events at $ \sqrt{s}=13 $ TeV classified by event shape estimators such as relative transverse event activity, unweighted transverse spherocity, and flattenicity. Our analysis reveals consistent trends in the kinetic freeze-out temperature and non-extensive parameter across different collision systems and event shape classes. The use of diverse event-shape observables in pp collisions has significantly expanded the accessible freeze-out parameter space, enabling a more comprehensive exploration of its boundaries. Among these event shape classifiers, flattenicity emerges as a unique observable for disentangling hard process contributions from additive MPI effects, which helps isolate collective motion effects encoded by the radial flow velocity. Through the analysis of the interplay between event-shape measurements and kinetic freeze-out properties, we gain deeper insights into mechanisms responsible for flow-like signatures in pp collisions.

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Exploring Thermalization and Multi-Freeze-Out Effects in Pb–Pb Collisions Based on Tsallis p_T Distributions
Haifa I. Alrebdi, Muhammad Ajaz, Murad Badshah, Mohammad Ayaz Ahmad

Published: 2026-01-22

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Published: 2026-01-22

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Fusion Reaction of ¹⁹O + ¹²C Studied with an Active-Target Time Projection Chamber in the Energy Range 9.7 < E_c.m. < 16.9 MeV
J. L. Zhang, C. G. Lu, Z. C. Zhang, Z. Bai, F. F. Duan, L. M. Duan, B. S. Gao, B. F. Ji, K. A. Li, Y. T. Li, W. H. Long, J. B. Ma, S. B. Ma, K. Meng, H. J. Ong, T. L. Pu, L. H. Ru, X. D. Tang, K. Wang, X. Y. Wang, S. W. Xu, X. D. Xu, G. Yang, Y. Y. Yang, L. Y. Zhang, N. T. Zhang

Published: 2026-01-22, doi: 10.1088/1674-1137/ae368b

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Published: 2026-01-22, doi: 10.1088/1674-1137/ae368b

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Dynamical System and Statefinder Analysis of Cosmological Models in f(T, B) Gravity
Jianwen Liu, Fabao Gao, Aqeela Razzaq

Published: 2026-01-18

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Published: 2026-01-18

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Searching for the toponium ${{\boldsymbol\eta}_{\boldsymbol t}}$ with the ${{\boldsymbol\eta}_{\boldsymbol t}}$ ${\boldsymbol\to}$ ${{\boldsymbol W}^{\bf +}{\boldsymbol W}^{\bf -}}$ decay
Yueling Yang, Bingbing Yang, Jiazhi Li, Zhaojie Lü, Junfeng Sun

2026, 50(3): 033101-033101-5. doi: 10.1088/1674-1137/ae18aa

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Inspired by the observation of the ${\eta}_{t}$ meson at the LHC and the promising prospect of the ${\eta}_{t}$ meson available at the approaching HL-LHC, branching ratios for the ${\eta}_{t}$ ${\to}$ $f\bar{f}$, $gg$, ${\gamma}{\gamma}$, $W^{+}W^{-}$, $Z^{0}Z^{0}$, $Z^{0}{\gamma}$, and $Z^{0}H$ decays are roughly estimated. It is found that tens of opposite-charge dilepton events from the ${\eta}_{t}$ ${\to}$ $W^{+}W^{-}$ decay and hundreds of events from the ${\eta}_{t}$ ${\to}$ $Z^{0}H$ ${\to}$ ${\ell}^{+}{\ell}^{-}H$ decay using the single $Z^{0}$ boson tagging method are expected to be accessible. This estimation provides a reference for future experimental study on the ${\eta}_{t}$ meson.

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One texture zero for Dirac neutrinos in a diagonal charged lepton basis
Richard H. Benavides, Yessica Lenis, John D. Gómez, William A. Ponce

2026, 50(3): 033111-033111-9. doi: 10.1088/1674-1137/ae2b5c

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An analytical and numerical systematic study of the neutrino mass matrix with one texture zero is presented in a basis where the charged leptons are diagonal. Under the assumption that neutrinos are Dirac particles, the analysis is conducted in detail for the normal and inverted hierarchy mass spectra. Our study is performed without any approximations, first analytically and then numerically, using current neutrino oscillation data. The analysis constrains the parameter space in such a way that, among the six possible one-texture-zero patterns, only four are favored in the normal hierarchy and one in the inverted hierarchy by current oscillation data at the $3 \sigma$ level. Phenomenological implications for the lepton CP-violating phase and neutrino masses are also explored.

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Search potential for direct slepton pair production at the CEPC with ${ \sqrt{\boldsymbol s}}$ = 360 GeV
Feng Lyu, Jiarong Yuan, Huajie Cheng, Jianxiong Wang, Rabia Hameed, Da Xu, Xuai Zhuang

2026, 50(3): 033001-033001-12. doi: 10.1088/1674-1137/ae2f4e

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The Circular Electron Positron Collider (CEPC) is designed to operate at key center-of-mass energies: 91.2 GeV as a Z factory for precision Z boson studies, ≈ 160 GeV at the threshold for W boson pair production, and 240 GeV as a Higgs factory for copious Higgs boson production. It can be upgraded to 360 GeV (CEPC-360 GeV) for enabling top quark-antiquark ($ t\bar{t}$) pair production. Beyond enabling high-precision measurements of the Standard Model (SM), CEPC-360 GeV is uniquely positioned to perform searches for new physics beyond the SM (BSM), serving as a valuable complement to hadron colliders. This paper presents a sensitivity study on the direct pair production of staus and smuons at the CEPC with $ \sqrt{s}$ = 360 GeV, conducted via full Monte Carlo simulation. Under the assumptions of 1.0 ab⁻¹ integrated luminosity and a flat 5% systematic uncertainty, CEPC-360 GeV could potentially discover the combined production of left-handed and right-handed staus up to a mass of 170 GeV (if they exist) or up to 169 for pure left-handed staus and 162 GeV for pure right-handed staus. For direct smuon production, the discovery potential reaches up to 178 GeV under the same conditions.

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Current Issued

2026 Vol. 50, No. 1
Published: 25 December 2025

Particles And Fields
Nuclear Physics
Particle And Nuclear Astrophysics And Cosmology