Chinese Physics C

Highlights

Spontaneous scalarization of regular Hayward black holes in Einstein-nonlinear electromagnetic-scalar gravity
Lan-Lan Cai, Meng-Yun Lai, De-Cheng Zou, Lina Zhang, Hyat Huang

2026, 50(9): 095104. doi: 10.1088/1674-1137/ae836d

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Regular Hayward black holes provide a useful setting for investigating scalarization in theories with nonminimally coupled matter sectors. Within the framework of Einstein-nonlinear electromagnetic-scalar gravity, we identify the tachyonic threshold that signals the bifurcation from the bald Hayward background and then obtain scalarized charged black holes for both quadratic $ (1-\alpha\phi^2) $ and exponential $ ({\rm e}^{-\alpha \phi^2}) $ couplings. These configurations form a discrete set of branches classified by the number of nodes in the scalar field. The branch with $ n=0 $ is the fundamental branch, whereas solutions with $ n\geq 1 $ are excited branches. By studying radial perturbations, we find that the fundamental branch is stable for both coupling choices, which makes it the most relevant branch for future phenomenological and observational studies.
LHC shines on positivity
Zhen Liu, Kun-Feng Lyu, Tong Arthur Wu

2026, 50(9): 091003. doi: 10.1088/1674-1137/ae74be

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We show that hadron colliders have an excellent reach for positivity tests on a class of diphoton operators. Due to the helicity selection rules, the relevant dimension-6 operators either do not contribute or are highly constrained by other experimental observables. We demonstrate, for the first time, that the LHC can probe the positivity of the dimension-8 operators involving colored particles. The kinematic differential distributions of the diphoton final states are utilized to perform the $ \chi^2$ analysis. Through a global fit, the effective scale for these operators can be inclusively probed up to around 2 TeV at HL-LHC and over 5 TeV at future 100 TeV FCC-hh at 95% C.L., providing a powerful test of the positivity bounds up to the multi-TeV scale.
Covariant canonical-spinor amplitudes for partial wave analysis
Hong Huang, Yi-Ning Wang, Jiang-Hao Yu

2026, 50(9): 093110. doi: 10.1088/1674-1137/ae6a86

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We propose a covariant orbital-spin (LS) decomposed amplitude for the partial wave analysis using the massive spinor-helicity formalism. First, we review the traditional-LS method in the little group space and the Zemach tensor method in the double cover of the $ S O(3) $ space. To recover the $S O(3,1)$ Lorentz covariance, several Lorentz covariant $LS$ tensors have been constructed through different methods: covariant tensor, covariant projection tensor in pure-spin and general-spin schemes. However, performing an intrinsic separation between $LS$ coupling while maintaining covariance is not straightforward. We utilize the massive canonical-spinor variables to determine general three-point amplitudes, where the $LS$ decomposition is realized in a single little group space by projecting little group indices of each particle into one, while ensuring Lorentz covariance by the spinor form naturally. This covariant spinor method allows direct evaluation in any frame and offers a streamlined treatment of cascade decays within a single frame without additional alignment rotations needed in non-covariant approaches. As a benchmark, we implement the method in TF-PWA and analyze $\Lambda_c^+\to\Lambda\pi^+\pi^0$, finding consistent fit results across the helicity, traditional-$LS$, and canonical-spinor amplitudes. This validates the canonical-spinor amplitude as a practical tool for modern partial wave analyses of complex decay chains.

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Constraints on the canonical single-field slow-roll inflation model from observations
Jun Li, Guanghai Guo, Pengfei Yan, Xiong Yang

Published: 2026-08-19, doi: 10.1088/1674-1137/ae8cf2

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Published: 2026-08-19, doi: 10.1088/1674-1137/ae8cf2

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The resonance effect for the CP asymmetry associated with the process ${\boldsymbol\omega{\bf\to}{\boldsymbol\pi}^+{\boldsymbol\pi}^-{\boldsymbol\pi}^{\bf 0} }$
Xi-Liang Yuan, Gang Lü, Na Wang, Chao Wang

Published: 2025-05-26, doi: 10.1088/1674-1137/ad8ec2

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Published: 2025-05-26, doi: 10.1088/1674-1137/ad8ec2

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Neutron-induced reaction cross sections of selenium isotopes at 14−15 MeV: Activation measurements and covariance analysis
Vandana, Shivani Sharma, N. L. Singh, Mayur Mehta, Mitul Abhangi, Ratnesh Kumar, Himanshu Sharma, Sudhirsinh Vala, R. K. Singh, R. J. Makwana, R. D. Chauhan, K. Katovsky, Pargin Bangotra

2026, 50(10): 104003-104003-18. doi: 10.1088/1674-1137/ae7a19

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Neutron-induced reaction cross sections of Se isotopes were investigated using the activation technique via ³H(D, n)⁴He (D-T) fusion reaction at the Neutron and Ion Irradiation Facility (NIIF) of the Institute for Plasma Research (IPR), India. The emitted gamma (γ) ray from a radioactive sample (Se) was examined using a High Purity Germanium (HPGe) detector. The measured cross sections of ⁷⁶Se(n, p)⁷⁶As, ⁷⁸Se(n, p)⁷⁸As, ⁸²Se(n, 2n)⁸¹Se^g, ⁷⁶Se(n, 2n)⁷⁵Se, and ⁸⁰Se(n, α)⁷⁷Ge are 55.30 ± 4.09 mb, 18.77 ± 1.12 mb, 529.78 ± 51.23 mb, 903.98 ± 55.99 mb, and 2.01 ± 0.12 mb, respectively, at the neutron energy of 14.96 ± 0.22 MeV. The detailed uncertainty propagation from the various parameters and cross-correlation of the aforementioned reactions was estimated using covariance analysis. Furthermore, the measured cross sections were compared with the EXFOR database and evaluated nuclear libraries (ENDF/B-VIII.1, JEFF-4.0, JENDL-5, TENDL-2023 and CENDL-3.2). The cross sections were also reproduced theoretically using TALYS 2.0 code with an adjusted (optimized) set of parameters, and the contributions of various nuclear reaction mechanisms to the cross section were systematically analyzed and discussed. In addition, the measured reaction cross sections were quantified using various established semi-empirical systematic formulae. This study also performed statistical validation via chi-square minimization to identify the theoretical models and semi-empirical formulae that accurately reproduce the best measured cross section.

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Lesser Green’s function and chirality-reduced entropy via the In-Medium NJL model
Seung-il Nam

2026, 50(10): 103109-103109-9. doi: 10.1088/1674-1137/ae8825

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We investigate chiral symmetry restoration in finite-temperature and finite-density quark matter using a correlator-based chirality-reduced entropy within the in-medium Nambu–Jona-Lasinio (NJL) model. Starting from the lesser Green's function $G^{<}(k)$ in the real-time formalism, we construct the equal-time correlation matrix $C({\boldsymbol{k}})$ and define the left-handed reduced correlator $C_L({\boldsymbol{k}}) = P_L C({\boldsymbol{k}}) P_L$. The corresponding von Neumann entropy, $S_\chi = -\mathrm{Tr}\left[C_L \ln C_L + (1-C_L)\ln(1-C_L)\right]$, characterizes the mixedness of the chirality-reduced subsystem. We show that the reduced correlator retains a nontrivial helicity structure and therefore must be described by its full eigenvalue spectrum rather than by a single scalar occupation probability. The self-consistent dynamical quark mass $M_q(T,\mu_q)$ reproduces the expected QCD-like phase structure, with a second-order transition in the chiral limit and a smooth crossover for finite current quark mass. The chirality-reduced entropy correlates with chiral restoration but is not an order parameter; instead, it provides complementary information through the full spectrum of the reduced correlator. Our numerical results show that $S_\chi$ exhibits characteristic nontrivial behavior across the chiral transition region and serves as an information-theoretic diagnostic of reduced chiral-sector mixedness.

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Nature of ${K^*(1680)}$ and ${q\bar{q}}$-hybrid mixing as the SU(3) partner of ${\eta_{1}(1855)}$ in the strange sector
Samee Ullah, Ye Cao, Ming-Xiao Duan, Hai-Bing Fu, Qiang Zhao

2026, 50(10): 103105-103105-12. doi: 10.1088/1674-1137/ae71a8

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We present an investigation of the $ K^*(1680) $ state in its strong decays into two-body final states within the flux-tube model and quark pair creation model. Since charge conjugation parity is not conserved in the strange sector, the conventional $ q\bar{q} $ states with $ J^{P(C)}=1^{-(-)} $ can mix with the lowest hybrid states with $ J^{P(C)}=1^{-(+)} $. Our analysis of the $ K^*(1680) $ two-body strong decays indicates that the decay pattern of $ K^*(1680) $ cannot be explained by the conventional $ q\bar{q} $ scenario. Moreover, there is strong evidence for the $ q\bar{q} $-hybrid mixing mechanism in the strange sector. The phenomenological consequences of such mixing are also discussed. Our study can provide guidance for future searches for hybrid multiplets in experiments at BESIII, LHCb, and Belle II.

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Current Issued

2026 Vol. 50, No. 9
Published: 31 August 2026

Particles And Fields
Nuclear Physics
Particle And Nuclear Astrophysics And Cosmology