Using the pinch technique, we determine the one-loop vertices of weak interactions in the B-LSSM and incorporate their pinch contributions into the gauge boson self-energies. Compared to the definitions of the $\textit{S}$, $\textit{T}$, and $\textit{U}$ parameters in the Standard Model based on the $S U(2)_L \otimes U(1)_Y$ group, the corresponding parameters in the local B-L gauge symmetry (B-LSSM) are modified. We present these redefined $\textit{S}$, $\textit{T}$, and $\textit{U}$ parameters and demonstrate the convergence of the results. In the framework of the low-energy effective Lagrangian for weak interactions, the $\textit{S}$, $\textit{T}$, and $\textit{U}$ parameters can be expressed as functions of specific parameters in the B-LSSM. The updated experimental and fitting results strongly constrain the parameter space of the B-LSSM.

China

Sheng-Kai Cui

Ke-Sheng Sun

Yu-Li Yan

Jin-Lei Yang

Tai-Fu Feng

$\textit{S}$, $\textit{T}$, $\textit{U}$ parameters in the B-LSSM * Supported by the Natural Science Foundation of Guangxi Autonomous Region (2022GXNSFDA035068), the Natural Science Foundation of Hebei Province (A2022104001), and the Foundation of Baoding University (2023Z01)

The processes of $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ and $ K^- p \to \pi^0 \Lambda(1405) $ are studied within the effective Lagrangian approach. In addition to the “background” contribution from the $\textit{u}$-channel nucleon pole term, the contribution from the $ \Sigma(1660) $ resonance with spin-parity $ J^P=1/2^+ $ is also considered. For the $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ reaction, we perform a calculation for the total and differential cross sections by considering the contribution from the $ \Sigma(1660) $ intermediate resonance decaying into $ \pi^0 \Lambda(1405) $ with $ \Lambda(1405) $ decaying into $ \pi^0 \Sigma^0 $ . With our model parameters, the available experimental data on both the $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ and $ K^- p \to \pi^0 \Lambda(1405) $ reactions can be fairly well reproduced. It is shown that the contribution from the $ \Sigma(1660) $ resonance is necessary, and that these experimental measurements could be used to determine some properties of the $ \Sigma(1660) $ resonance.

Xing-Yi Ji

Si-Wei Liu

Wen-Tao Lyu

De-Min Li

En Wang

Ju-Jun Xie

Role of Σ(1660) in the $\textit{K}$ $^{−}$ $\textit{p}$ → $\textit{π}$ $^{0}$ $\textit{π}$ $^{0}$Σ$^{0}$ reaction * Supported by the National Key R&D Program of China (2023YFA1606703, 2024YFE0105200), the National Natural Science Foundation of China (12435007, 12475086, 12192263, 12361141819, 1252200936), the Natural Science Foundation of Henan (232300421140, 252300423951) and the Zhengzhou University Young Student Basic Research Projects (PhD students) (ZDBJ202522)

Right-handed neutrinos are naturally induced by dark extra dimension models and play an essential role in neutrino oscillations. The model parameters can be examined by the long-baseline neutrino oscillation experiments. In this work, we compute the predicted neutrino oscillation spectra within/without extra dimension models and compare them with the experimental data. We find that the neutrino data in the T2K and NOvA experiments are compatible with the standard neutrino oscillation hypothesis. The results set the stringent exclusion limit on the extra dimension model parameters at a high confidence level. The derived constraints on dark dimension right-handed neutrinos are complementary to those results from the collider experiments and cosmological observations.

Ai-Yu Bai

Thailand

Auttakit Chatrabhuti

Yin-Yuan Huang

Hiroshi Isono

Jian Tang

Dark dimension right-handed neutrinos confronted with long-baseline oscillation experiments

The effects of polarization transfer from the initial electron to the bremsstrahlung photon in electron-nucleus scattering (Bethe-Heitler process) are considered. The calculation is carried out without the assumption of smallness of the electron mass. A detailed comparison with previous well-known works is made. Some issues related to neglecting the electron mass are shown and commented on. The results are applicable to the modeling of polarized cross sections at energies down to the electron mass scale.

JINR

Yu. M. Bystritskiy

Belarus

V.A. Zykunov

Bremsstrahlung photon polarization observables in Bethe-Heitler process: Calculation in an exact kinematics

We determine the parametric conditions (pulse strength and duration) under which Schwinger’s prediction for the pair-creation current—and therefore the probability—is significantly altered.

Russia

E.T. Akhmedov

P.S. Zavgorodny

Does Schwinger’s value for the current of created pairs get modified for a long and strong enough pulse?

Dark-matter halos can significantly influence the physical properties of black holes, particularly when realistic density profiles are taken into account. In this work, we consider a static, spherically symmetric black hole embedded in a Dehnen $$\left( 1,4,\frac{5}{2}\right) $$ dark-matter halo. This configuration is the steepest analytically tractable Dehnen model with inner density slope $$\gamma <3$$ , providing a natural setting to probe strong-gravity effects in cuspy dark-matter environments. Unlike previous analyses that rely on linear expansions in the halo parameters, we derive the null geodesics directly from the variational principle and obtain an exact description of photon motion in the full black hole-halo spacetime. This approach allows the light-ring structure and the associated gravitational lensing properties to be determined without perturbative approximations. We further examine the thermodynamic behavior of the system by constructing the enthalpy, entropy, temperature, heat capacity, and Gibbs free energy. We find that the dark-matter environment substantially modifies the thermodynamic structure of the black hole. In particular, increasing the halo density or size enhances thermodynamic stability and can trigger phase-transition that is absent in linearized approximation.

David Senjaya

Optical and thermodynamic properties of an analytical black hole solution in the steep Dehnen $$\left( 1,4,\frac{5}{2}\right) $$ dark-matter halo

We investigate massive scalar perturbations and several characteristics of particle motion in the spacetime of regular black holes arising in four-dimensional quasi-topological gravity. Quasinormal modes are computed using high-order WKB approximations with Padé resummation and verified through time-domain integration. For moderate values of the scalar-field mass, the time-domain profiles confirm the WKB results with excellent accuracy. As the mass increases, the damping rate decreases substantially, indicating the approach to the quasi-resonant regime of long-lived modes. For sufficiently large masses, the late-time signal becomes dominated by oscillatory power-law tails, which mask the quasi-resonant mode in the time-domain profile. In addition, we analyze photon motion and circular geodesics, including the photon-sphere radius, shadow size, Lyapunov exponent, and ISCO characteristics. These quantities exhibit only moderate deviations from their Schwarzschild values, unlike the Hawking temperature of the black hole.

Czechia

Bekir Lütfüoğlu

Long-lived quasinormal modes, shadows and particle motion in four-dimensional quasi-topological gravity

Effective field theories (EFTs) provide a powerful framework to parametrise unknown aspects of possible ultraviolet (UV) physics. For scalar fields in de Sitter space, however, new emergent phenomena can arise when the cut-off scale of the theory lies below the horizon scale $\textit{H}$, as seen in the stochastic formalism of inflation. In this work, we study EFTs that, at leading order, reproduce the standard quartic theory in de Sitter, but with a variable cut-off identified with the mass of an integrated-out hidden sector. We perform the complete analytic computation for the tree- and loop-level matching between the effective $\textit{λϕ}$ theory and two possible UV realisations. We find that when the cut-off is much larger than the horizon, the theory admits a unitary description, up to exponentially suppressed corrections. In contrast, when the cut-off is lowered below $\textit{H}$, the system evolves into a mixed state and diffusive effects emerge. Nevertheless, at leading order, the EFT remains local and reproduces the same effective quartic coefficient as in the unitary regime. Furthermore, for the EFT matching at the loop-level, the effective quartic coupling changes sign and becomes negative as the cut-off decreases, in agreement with the result obtained from the stochastic formalism. In general, for cosmological EFTs, our findings highlight the role of non-unitary effects and illustrate their regimes of validity, within and beyond perturbation theory.

United Kingdom

Sebastián Céspedes

Zhehan Qin

Dong-Gang Wang

λ$\textit{ϕ}$ 4 as an effective theory in de Sitter

We argue that interacting conformal line defects in free quantum field theories can exist, provided that inversion symmetry is broken. Important for our demonstration is the existence of a special cross ratio for bulk-defect-defect three point functions that is invariant under the conformal group but picks up a sign under inversion. We examine the particular case of a free scalar field in detail, and provide a toy model example where this bulk field interacts via a Yukawa term with fermions on the line. We expect nontrivial line defects may also exist for free Maxwell theory in four dimensions and free bulk fermions.

Samuel Bartlett-Tisdall

Japan

Dongsheng Ge

Christopher Herzog

How to get an interacting conformal line defect for free theories

Using (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mo>+</mo><mn>1</mn></mrow></math>)-flavor lattice QCD data, we refine the parameters of an analytical holographic model via gradient descent optimization to precisely locate the critical endpoint in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>T</mi><mtext>−</mtext><mi>μ</mi></mrow></math> plane. Specifically, we calibrate the model using input data for the speed of sound at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>B</mi></msub><mo>=</mo><mn>0</mn></math>, the second-order baryon number susceptibility <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>χ</mi><mn>2</mn><mi>B</mi></msubsup></math>, and the baryon number density at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>μ</mi><mi>B</mi></msub><mo>/</mo><mi>T</mi><mo>=</mo><mn>1</mn></math>. With these parameters fixed, we calculate pressure and energy density versus temperature at small chemical potentials and compare the results with lattice QCD data using Taylor expansion techniques. This comparison validates the robustness of our model upon extension to finite chemical potentials, as the results show broad consistency with lattice QCD data in this regime. Finally, we employ the calibrated model to determine the coordinates of the critical endpoint in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>T</mi><mtext>−</mtext><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow></math> plane, finding it located at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub><mo>=</mo><mn>0.678</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo>,</mo><mi>T</mi><mo>=</mo><mn>0.110</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi><mo stretchy="false">)</mo></mrow></math>.

Italy

Xun Chen

Floriana Giannuzzi

Stefano Nicotri

Data-driven refinement of an analytical holographic model for the QCD phase transition