Highlights
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Tests of amorphous carbon-coated storage cells for a polarized gas target at LHCb and further results
2025, 49(8): 084002. doi: 10.1088/1674-1137/add70e
As the LHC beams cannot be polarized, introducing a dense polarized gas target at the LHCb experiment at CERN, to be operated concurrently with beam-beam collisions, will facilitate fixed-target interactions to explore a new energy regime of spin physics measurements. Unfortunately, typical surface coatings used to avoid polarization losses, such as water, Teflon, or aluminum, are prohibited due to restrictions imposed by vacuum and beam policies. The former atomic beam source for the polarized target at ANKE@COSY (Forschungszentrum Jülich), an accompanying Lamb-shift polarimeter, and a storage cell chamber inside a superconducting magnet provide a perfect test stand to investigate the properties of a storage cell coated with amorphous carbon. A significant recombination rate, ranging from 93% to 100%, and preservation of polarization during recombination surpassing 74% were observed. We successfully produced$ \mathrm{H}_2 $ molecules with a nuclear polarization of$ P\sim 0.59 $ . In addition, we could produce polarized$ \mathrm{H}_3^+ $ ions for the first time and observed the shift of the axis of rotation within$ \mathrm{HD} $ molecules. -
B(E2) anomaly and triaxial deformation within a two-fluid
${{\boldsymbol S} {\boldsymbol U} }$ (3) symmetry2025, 49(8): 084106. doi: 10.1088/1674-1137/adcd4a
The correlation between$ B(E2) $ structure and triaxial deformation has been investigated within the framework of the proton-neutron boson model. The analysis reveals that the distinctive feature, characterized by$ B(E2;4_1^+\rightarrow2_1^+)/B(E2;2_1^+\rightarrow0_1^+)<1.0 $ along with$ E(4_1^+)/E(2_1^+)>2.0 $ , can emerge from the triaxial$ S U$ (3) symmetry inherent in two-fluid boson systems, attributed to band-mixing effects. This suggests a symmetry-based understanding of the anomalous$ E2 $ transitions observed in experiments. -
Lepton-number-violating pion decay and type-I seesaw mechanism in chiral perturbation theory
2025, 49(8): 083103. doi: 10.1088/1674-1137/add5c6
We investigate the process of lepton-number-violating pion decay, which dominates the nuclear neutrinoless double beta decay induced by the short-range operator within the type-I seesaw mechanism. The type-I seesaw mechanism leads to the Dirac and Majorana mass terms of neutrinos by introducing the gauge-singlet right-handed neutrinos, which are often called sterile neutrinos. Applying the chiral perturbation theory, we calculate the transition amplitudes for light and heavy sterile neutrinos up to$ \mathcal{O}(Q^2/\Lambda^2_\chi) $ , where Q is the typical low-energy scale in this process and$ \Lambda_\chi $ the chiral symmetry breaking scale. We then adopt a naive interpolation formula of mass dependence to obtain the amplitude in the full mass range and briefly discuss its validity.
Just Accepted
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On the pole trajectory of the subthreshold negative parity nucleon with varying pion masses
Published: 2025-08-16
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Measurement of separate electron and positron spectra from 10 GeV to 20 GeV with the geomagnetic field on DAMPE
Published: 2025-08-15
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Constraints on Lorentz Invariance Violation from GRB 221009A Using the DisCan Method
Published: 2025-08-15
Recent
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Detecting cosmological phase transitions with Taiji: sensitivity analysis and parameter estimation
2025, 49(10): 105103-105103-12. doi: 10.1088/1674-1137/ade65fShow AbstractWe investigate the capability of the Taiji space-based gravitational wave observatory to detect stochastic gravitational wave backgrounds produced by first-order phase transitions in the early universe. Using a comprehensive simulation framework that incorporates realistic instrumental noise, galactic double white dwarf confusion noise, and extragalactic compact binary backgrounds, we systematically analyze Taiji's sensitivity across a range of signal parameters. Our Bayesian analysis demonstrates that Taiji can robustly detect and characterize phase transition signals with energy densities exceeding
$\Omega_{\text{PT}} \gtrsim 1.4 \times 10^{-11}$ across most of its frequency band, with strong sensitivity at approximately$10^{-3}$ to$10^{-2}$ Hz. For signals with amplitudes above$\Omega_{\text{PT}} \gtrsim 1.1 \times 10^{-10}$ , Taiji can determine the peak frequency with relative precision better than 10%. These detection capabilities would enable Taiji to probe electroweak-scale phase transitions in various beyond-Standard-Model scenarios, potentially revealing new physics connected to baryogenesis and dark matter production. We quantify detection confidence using both Bayes factors and the Deviance Information Criterion, obtaining consistent results that validate our statistical methodology. -
Nuclear mass predictions with a Bayesian neural network
2025, 49(10): 104106-104106-7. doi: 10.1088/1674-1137/ade958Show AbstractThe Bayesian neural network (BNN) has been widely used to study nuclear physics in recent years. In this study, a BNN was applied to optimize seven theoretical nuclear mass models, namely, six global models and one local model. The accuracy of these models in describing and predicting masses of nuclei with both the proton number and the neutron number greater than or equal to eight was improved effectively for two types of numerical experiments, particularly for the liquid drop model and the relativistic mean-field theory, whose root mean square deviations (RMSDs) for describing (predicting) nuclear masses were reduced by 81.5%−90.6% (66.9%−84.2%). Additionally, the relatively stable RMSDs as nuclei move away from the β-stability line and the good agreement with experimental single-neutron separation energies further confirm the reliability of the BNN.
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Exploring axion-like particle from observation of FSRQ Ton 599 by Fermi-LAT
2025, 49(10): 105107-105107-9. doi: 10.1088/1674-1137/ade6d2Show AbstractHigh energy photons traveling through astrophysical magnetic fields have the potential to undergo oscillations with axion-like particles (ALPs), resulting in modifications to the observed photon spectrum. High energy
$ \gamma $ -ray sources with significant magnetic field strengths provide an ideal environment to investigate this phenomenon. Ton 599, a flat spectrum radio quasar with a magnetic field strength on the order of Gauss in its emission region, presents a promising opportunity for studying ALP-photon oscillations. In this study, we analyze the effects of ALP-photon oscillations on the γ-ray spectrum of Ton 599, as observed by Fermi-LAT. Our investigation considers the potential influences of the broad-line region and dusty torus on the$ \gamma $ -ray spectrum of Ton 599. We set the constraints on the ALP parameters at a 95% confidence level and show that the constraints on$ g_{a\gamma} $ can reach approximately$ 2 \times 10^{-12}\; \text{GeV}^{-1} $ for$ m_a \sim 10^{-9}\; \text{eV} $ .
Current Issued
2025 Vol. 49, No. 8
Published: 01 August 2025
Published: 01 August 2025
Archive
IF: 3.1
Monthly issued, founded in 1977
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ISSN 1674-1137 CN 11-5641/O4
Original research articles, Ietters and reviews Covering theory and experiments in the fieids of
- Particle physics
- Nuclear physics
- Particle and nuclear astrophysics
- Cosmology
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Cover Story
- Cover Story (Issue 1, 2025) Comments on Prediction of Energy Resolution inthe JUNO Experiment
- Cover Story (Issue 12, 2024) | Doubly heavy meson puzzle: precise prediction of the mass spectra and hadronic decay with coupled channel effects to hunt for beauty-charm family
- Cover Story (Issue 9, 2024) Measurement of solar pp neutrino flux using electron recoil data from PandaX-4T commissioning run
- Cover Story (Issue 11, 2024) ｜ Form factor for Dalitz decays from J/ψ to light pseudoscalars
- Cover Story (Issue 3, 2024) | First measurement of the ground-state mass of 22Al helps to evaluate the ab-initio theory
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