The roles of the $ \Delta (1232) $ , $ {N}^{*}(1520) $ , and $ {N}^{*}(1650) $ resonances in the $ \gamma p\to{\pi }^{0}{\pi }^{0}p $ reaction near threshold is investigated within an effective Lagrangian approach. The differential cross sections of the $ \gamma p\to{\pi }^{0}{\pi }^{0}p $ reaction was calculated including contributions from the $ \Delta (1232) $ , $ {N}^{*}(1520) $ , and $ {N}^{*}(1650) $ intermediate states decaying into $ \pi^0 p $ via the $\textit{s}$-channel nucleon pole and $\textit{t}$-channel $\textit{ρ}$ exchange. Current experimental measurements were well reproduced. The production of $ \Delta(1232) $ was mainly from the mechanism of the $\textit{s}$-channel nucleon pole, while the $ {N}^{*}(1520) $ and $ {N}^{*}(1650) $ were produced from the mechanism of the $\textit{t}$-channel $\textit{ρ}$ exchange. More experimental data on the $ \gamma p \to \pi^0 \pi^0 p $ reaction could be used to explore the properties of the low-lying excited baryon state.

China

Meng-Yuan Dai

Si-Wei Liu

Cheng Chen

De-Min Li

En Wang

Ju-Jun Xie

Roles of ${\boldsymbol\Delta(\bf 1232)}$ , ${\boldsymbol N^*(\bf 1520)}$ , and ${\boldsymbol N^*(\bf 1650)}$ resonances in ${\boldsymbol\gamma \boldsymbol p\to \boldsymbol\pi^{\bf 0} \boldsymbol\pi^{\bf 0}\boldsymbol p}$ reaction within an effective Lagrangian approach * Supported by the National Key R&D Program of China (2023YFA1606703, 2024YFE0105200), the Natural Science Foundation of Henan Province, China (232300421140, 222300420554), and the National Natural Science Foundation of China (12435007, 12361141819, 12475086, 12192263)

The total cross sections of the process   $ e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^- $   close to the threshold are calculated within the vector meson dominance model. It is found that the theoretical results can describe the current experimental measurements. The nontrivial near-threshold energy dependence of the total cross sections of the process   $ e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^- $   can be well reproduced by considering the contributions from charmonium-like states and the Coulomb factor. In particular, the results for the angular distribution parameters about the differential cross section are consistent with the experiments from the BESIII Collaboration. In addition, the relative phase   $ e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^- $   of the electromagnetic form factors is given, and the spin polarization of   $ e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^- $   is predicted at center-mass energy   $ e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^- $  . It is hopeful that this work will provide a new perspective on the characteristics of the charmed baryon   $ e^+ e^-\to \Lambda_c^+ \bar{\Lambda}_c^- $  .

Bing Yan

The electromagnetic form factors and spin polarization of In the Process   

We study the properties of the lowest multiplet of light-flavor tensor meson resonances, i.e., <math><msub><mi>f</mi><mn>2</mn></msub><mo>(</mo><mn>1270</mn><mo>)</mo></math>, <math><msub><mi>a</mi><mn>2</mn></msub><mo>(</mo><mn>1320</mn><mo>)</mo></math>, <math><msubsup><mi>K</mi><mn>2</mn><mo>*</mo></msubsup><mo>(</mo><mn>1430</mn><mo>)</mo></math>, and <math><msubsup><mi>f</mi><mn>2</mn><mo>′</mo></msubsup><mo>(</mo><mn>1525</mn><mo>)</mo></math>, within the resonance chiral theory approach. The higher-order resonance chiral operators, including the light-quark mass and <math><mn>1</mn><mo>/</mo><msub><mi>N</mi><mi>C</mi></msub></math> corrections, are simultaneously incorporated in our study. The use of resonance chiral expressions allows us to analyze not only the relevant experimental data but also in the meantime the lattice results at unphysical quark masses, including the masses of the lowest multiplet of tensor resonances and their decay widths into two pseudoscalar mesons. In addition, the radiative decays of the tensor resonances into one photon plus one pseudoscalar meson and two photons are also studied.

Nai-Qian Cheng

Lin-Wan Yan

Chun-Gui Duan

Zhi-Hui Guo

Revisiting the tensor-meson nonet in resonance chiral theory

We propose a phenomenological extended vector meson dominance model for the baryon electromagnetic structure, and it is found that the current experimental data on the <math><mi>Σ</mi></math> and <math><mrow><mi>Ξ</mi></mrow></math> electromagnetic form factors in the timelike region can be well described. Meanwhile, we can also reproduce the ratios of the total cross sections of reactions <math><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><msup><mrow><mi>Σ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mover><mrow><mi>Σ</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mo>−</mo></mrow></msup></mrow></math>, <math><msup><mi>Σ</mi><mn>0</mn></msup><msup><mover><mi>Σ</mi><mo>¯</mo></mover><mn>0</mn></msup></math>, and <math><msup><mi>Σ</mi><mo>−</mo></msup><msup><mover><mi>Σ</mi><mo>¯</mo></mover><mo>+</mo></msup></math>, which are <math><mrow><mn>9.7</mn><mo>±</mo><mn>1.3</mn><mo>∶</mo><mn>3.3</mn><mo>±</mo><mn>0.7</mn><mo>∶</mo><mn>1</mn></mrow></math> at center-of-mass energies from 2.3864 GeV to 3.02 GeV. We also analytically continue the expression of the form factors to spacelike region and estimate the charge radii of the <math><mi>Σ</mi></math> and <math><mi>Ξ</mi></math> hyperons. The obtained result of the charge radius for the <math><msup><mi>Σ</mi><mo>−</mo></msup></math> is in agreement with the experimental data.

<math><mrow><mi>Σ</mi></mrow></math> and <math><mrow><mi>Ξ</mi></mrow></math> electromagnetic form factors in the extended vector meson dominance model

Abstract The open N = 2 string theory is defined on the 4D space-time with the split signature (+, +, −, −). The string field theory action of the open N = 2 string theory is described by the 4D Wess–Zumino–Witten (WZW$_{4}$) model. The equation of motion of the WZW$_{4}$ model is the Yang equation, which is equivalent to the anti-self-dual Yang–Mills equation. In this paper, we study soliton-type classical solutions of the WZW$_{4}$ model in the split signature by calculating the action density of the WZW$_{4}$ model. We find that the action density of the one-soliton solutions is localized on a 3D hyperplane. This shows that there would be codimension-one-solitonic objects, or equivalently some kind of three-branes in the open N = 2 string theory. We also prove that, in the asymptotic region of the space-time, the action density of the n-soliton solutions is a “non-linear superposition” of n one-solitons. This suggests the existence of n intersecting three-branes in the N = 2 strings. Finally we make a reduction to a (1 + 2)D real space-time to calculate the energy densities of the soliton solutions. We can successfully evaluate the energy distribution for the two-soliton solutions and find that there is no singularity in the interacting region. This implies the existence of smooth intersecting codimension-one branes in the whole region. Soliton solutions in the Euclidean signature are also discussed.

Japan

Masashi Hamanaka

Shan-Chi Huang

Hiroaki Kanno

Solitons in open = 2 String Theory Kahler-Chen-Simons theory A tour through N=2 strings On soliton solutions of the anti-self-dual Yang-Mills equations from the perspective of integrable systems Soliton solutions in an integrable chiral model in 2+1 dimensions On the space-time monopole equation A review on tachyon condensation in open string field theories Soliton equations as dynamical systems on infinite dimensional Grassmann manifold

Here we study the quark orbital angular momentum of the ground octet baryons employing an extended chiral constituent quark model, within which the baryon wave functions are taken to be superposition of the traditional <math><mrow><mi>q</mi><mi>q</mi><mi>q</mi></mrow></math> and the <math><mrow><mi>q</mi><mi>q</mi><mi>q</mi><mi>q</mi><mover><mi>q</mi><mo>¯</mo></mover></mrow></math> higher Fock components. Coupling between the two configurations is estimated using the <math><mmultiscripts><mi>P</mi><mn>0</mn><none></none><mprescripts></mprescripts><none></none><mn>3</mn></mmultiscripts></math> quark-antiquark creation mechanism, and the corresponding coupling strength is determined by fitting the sea flavor asymmetry of the nucleon. The obtained numerical results show that the quark angular momentum of the nucleon, <math><mi>Σ</mi><mo>,</mo><mo> </mo><mi>Λ</mi></math>, and <math><mi>Ξ</mi></math> hyperons, are in the range 0.10–0.30. In addition, the quark angular momentum of all the hyperons are a little bit smaller than that of the nucleon. And the octet baryons spin fractions taken by the intrinsic quark orbital angular momentum could be up to <math><mrow><mn>60</mn><mo>%</mo></mrow></math> in present model.

Jing-Feng Li

Gang Li

Chun-Sheng An

Cheng-Rong Deng

Quark orbital angular momentum of ground-state octet baryons

In this work, we perform a detailed study of the τ  −  → π  −  π 0 γν decay process within the resonance chiral theory. We pay special attention to the triple-product asymmetry in the τ  −  → π  −  π 0 γν process. The minimal resonance chiral Lagrangian and the odd-intrinsic parity resonance operators are simultaneously included to calculate the decay amplitudes. Various invariant-mass distributions in the π  −  π 0, π  −  γ and π 0 γ systems are studied and they reveal different resonance dynamics. We further predict the intriguing nonzero triple-product asymmetry distributions, which may provide useful guidelines for future experimental measurements conducted at the Belle-II and super tau-charm facilities.

Triple-product asymmetry in the radiative two-pion tau decay

In the present paper, the exact solutions of spherically symmetrical Einstein field equations describing wormholes supported by phantom energy that violates the null energy condition from Shan–Chen background fluid are obtained. We have considered the important case of the model parameter ψ≈1 , which corresponds to the “saturation effect”, and this regime corresponds to an effective form of “asymptotic freedom” for the fluids, but occurring at cosmological rather than subnuclear scales. Then we investigate the allowed range for the values of the model parameters g and ω when the spacetime metrics describe wormholes and discuss the possible singularities of the solutions, finding that the obtained spacetimes are geodesically complete. Furthermore, we construct two traversable wormholes through matching our obtained interior solutions to the exterior Schwarzschild solutions and analyze the traversablities of the wormholes. Finally, we consider the case of anisotropic pressure and discover that the transverse pressure also crosses the phantom divide -1 with the growth of the wormhole dimension, and it tends to be the same as the radial pressure with the growth of the wormhole radius.