We investigated the effect of an isospin chemical potential ( $ \mu_{I} $ ) within the quark-meson model, which approximates quantum chromodynamics (QCD) by modeling low-energy phenomena such as chiral symmetry breaking and phase structure under varying conditions of temperature and chemical potential. Using the functional renormalization group (FRG) flow equations, we calculated the phase diagram in the chiral limit within the two-flavor quark-meson model in a finite $ \mu_{I} $ with $\textit{ρ}$ vector meson interactions. Fluctuation effects significantly decrease the critical chemical potential from the mean-field (MF) value $\mu_{I,{\rm MF}} \gt m_\rho$ to a lower value at which the $\textit{ρ}$ vector meson condensates alongside the chiral condensate once the isospin chemical potential exceeds the critical value $ \mu_{I}^{{\rm{crit}}} $ . This $\textit{ρ}$ condensation was investigated numerically for different meson coupling strengths. The $\textit{ρ}$ meson dominated region is delineated from other phases by a second-order phase transition at lower $ \mu_{I} $ and a first-order transition at slightly higher $ \mu_{I} $ .

China

Mohammed Osman

Defu Hou

Wentao Wang

United States

Hui Zhang

Functional renormalization group study of $\textit{ρ}$ meson condensate at a finite isospin chemical potential in the quark meson model * Supported in part by the National Key Research and Development Program of China (2022YFA1604900). This work is also partly supported by the National Natural Science Foundation of China (NSFC) (12435009, 12275104). Hui Zhang acknowledges the financial support from the Guangdong Major Project of Basic and Applied Basic Research (2020B0301030008) and the National Natural Science Foundation of China (12047523, 12105107)

We introduce FANG (Focused Angular $\textit{N}$ -body event Generator), a new Monte Carlo tool for efficient event generation in restricted Lorentz-Invariant Phase Space (LIPS). Unlike conventional approaches that sample the full 4$\textit{π}$ solid angle, FANG directly generates events in which selected final-state particles are constrained to fixed directions or finite angular regions in the laboratory frame. Because of the way the generator is constructed, angular constraints can be imposed directly in the laboratory frame while maintaining the correct LIPS structure, enabling differential and total cross sections or decay rates to be computed with high efficiency. The method is validated against analytic results and existing event generators, showing excellent agreement. By reducing the computational cost of full phase-space event generation by several orders of magnitude, FANG provides a robust and versatile framework applicable to particle, nuclear, and detector physics.

Israel

Itay Horin

Arik Kreisel

Or Alon

Focused angular $\textit{N}$ -body event generator (FANG)

We present an investigation on cosmological implications resulting from spontaneous dark $ S U(2)_d $ symmetry breaking in conjunction with the Witten effect. Furthermore, we examine the mass of hidden monopoles generated by phase transition as well as the impact of axion-monopole interactions on the axion mass. Following spontaneous breaking of the PQ symmetry, axions emitted by cosmic strings or domain walls as well as hidden monopoles generated during this transition may collectively contribute to the observed dark matter relic density. Additionally, the stochastic gravitational wave background generated by sub-GeV phase transitions and by the decay of axionic domain walls formed during sub-ZeV phase transitions could account for the low-frequency gravitational wave signals detected by PTA experiments.

Ruiyu Zhou

Ligong Bian

Gravitational waves and dark matter with Witten effect * Supported by the National Key Research and Development Program of China (2021YFC2203004). Ruiyu Zhou is supported by the National Natural Science Foundation of China (12305109, 12147102), Chongqing Natural Science Foundation project (CSTB2022NSCQ-MSX0534), and Science and Technology Research Project of Chongqing Municipal Education Commission (KJQN202300614). Ligong Bian is supported by the National Natural Science Foundation of China (12322505, 12347101). Ligong Bian also acknowledges Chongqing Natural Science Foundation (CSTB2024NSCQ-JQX0022) and Chongqing Talents: Exceptional Young Talents Project (cstc2024ycjhbgzxm0020).

The neutrino floor, a theoretical sensitivity limit for dark matter (DM) direct detection, is being redefined as the boundary of a dynamic ''neutrino fog,'' where neutrino signals become inevitable, obscuring DM detection due to statistical and systematic uncertainties. This study provides the first site-specific analysis of the neutrino floor at China Jinping Underground Laboratory (CJPL), leveraging its unique geographic and environmental characteristics. We quantify how CJPL’s suppressed atmospheric neutrino flux (approximately 30% lower than that of Laboratori Nazionali del Gran Sasso (LNGS)) reshapes the neutrino floor, thereby enabling improved sensitivity to high-mass WIMPs (mass > 10 GeV). Using a gradient-based framework, we derive the CJPL’s neutrino floor and estimate the detection prospects for the PandaX-xT experiment. Our results demonstrate that a 500 tonne-year exposure with PandaX-xT could reach the floor, probing spin independent cross-sections down to $ \sigma_{n}\sim 3\times 10^{-49}\; {\rm{cm}}^2$ at a DM mass of 70 GeV/$\textit{c}$ $^{2}$.

Yingjie Fan

Xuewen Liu

Ning Zhou

Characterizing the CJPL’s site-specific neutrino floor as the neutrino fog boundary * Xuewen Liu is supported by the Project of Shandong Province Higher Educational Science and Technology Program (2022KJ271). Ning Zhou is supported by National Science Foundation of China (12325505)

We study $ \cos2\phi $ azimuthal asymmetry in doubly longitudinally polarized proton-proton Drell-Yan collisions within the transverse momentum dependent factorization framework. The asymmetry arises from the convolution of the longitudinal transversity distribution $ h_{1L}^{\perp} $ for both protons. Using the Bacchetta-Delcarro-Pisano-Radici-Signori parameterization for the nonperturbative Sudakov form factor and the Wandzura-Wilczek approximation for collinear $ h_{1L}^{\perp} $ , we predict the double spin asymmetry $ A_{LL}^{\cos2\phi} $ at RHIC and NICA kinematics. Our results demonstrate sensitivity to sea quark distributions, with the asymmetry reaching up to 25% for maximal sea quark contributions. These predictions highlight the potential of polarized Drell-Yan measurements to probe sea quark dynamics and advance our understanding of nucleon structures.

Hui Li

Ting Hu

Liang-Liang Liu

Xiao-Yu Wang

Zhun Lu

Asymmetry ${{\boldsymbol A}_{\boldsymbol{LL}}^{\bf\cos2\boldsymbol\phi}} $ in the polarized proton-proton Drell-Yan process within TMD factorization * Hui Li is supported by Fundamental Research Program of Shanxi Province (202203021222224) and Natural Science Foundation of Shanxi Normal University (JCYJ2023021). Xiao-Yu Wang is supported by the Natural Science Foundation of Henan Province (242300421377, 232300421140)

In this study, we investigate the $R^2$ corrections to the dissociation of heavy quarkonium in the Gauss-Bonnet gravitational background. We analyze the impact of the Gauss-Bonnet parameter $\lambda_{\rm GB}$ on the spectral function of charmonium and bottomonium and examine the effect of $\lambda_{\rm GB}$ on the dissociation of heavy quarkonium. Our results show that $\lambda_{\rm GB}$ reduces the peak height and increases the peak width of the spectral function, suggesting that $\lambda_{\rm GB}$ enhances the dissociation of heavy quarkonium. We also discuss the variation in the dissociation of heavy quarkonium with the ratio of shear viscosity to entropy density and observe that the dissociation is easier in more perfect plasma. Additionally, we observe that the temperature decreases the peak height and widens the peak, thereby accelerating the dissociation.

Zhou-Run Zhu

Manman Sun

Rui Zhou

Jinzhong Han

$\textit{R}$ $^{2}$ corrections to holographic heavy quarkonium dissociation * Rui Zhou supported by the Science and Technology Development Plan Project of Henan Province, China (242102230085), the National Natural Science Foundation of China (12404470), the High Level Talents Research and Startup Foundation Projects for Doctors of Zhoukou Normal University, China (ZKNUC2023017). Manman Sun supported by the National Natural Science Foundation of China (12305076). Zhou-Run Zhu supported by the High Level Talents Research and Startup Foundation Projects for Doctors of Zhoukou Normal University, China (ZKNUC2023018)

In this work, the production of the hidden-strange pentaquarklike state, <math><msup><mi>N</mi><mo>*</mo></msup><mo>(</mo><mn>2080</mn><mo>)</mo></math>, via the <math><msup><mi>π</mi><mo>−</mo></msup><mi>p</mi></math> scattering process is studied by the effective Lagrangian approach. Concretely, we consider the <math><mi>ρ</mi></math> meson exchange of <math><mi>t</mi></math>-channel and the nucleon exchange of <math><mi>u</mi></math>-channel, which are treated as the background terms, and take into account the contribution of the <math><msup><mi>N</mi><mo>*</mo></msup><mo>(</mo><mn>2080</mn><mo>)</mo></math> via the <math><mi>s</mi></math>-channel as a signal term. By global fitting of the total and differential cross sections of the <math><msup><mi>π</mi><mo>−</mo></msup><mi>p</mi><mo>→</mo><mi>ϕ</mi><mi>n</mi></math> process, it is shown that the <math><msup><mi>N</mi><mo>*</mo></msup><mo>(</mo><mn>2080</mn><mo>)</mo></math> contributes an obvious peak at the threshold energy point of the differential cross section at the forward angle (<math><mi>cos</mi><mi>θ</mi><mo>=</mo><mn>1</mn></math>), which provides clues to the detection of the <math><msup><mi>N</mi><mo>*</mo></msup><mo>(</mo><mn>2080</mn><mo>)</mo></math> by the <math><msup><mi>π</mi><mo>−</mo></msup><mi>p</mi></math> scattering process. However, due to the limited accuracy of the experimental data, it is an objective limitation for us to determine the properties of the <math><msup><mi>N</mi><mo>*</mo></msup><mo>(</mo><mn>2080</mn><mo>)</mo></math> by the <math><msup><mi>π</mi><mo>−</mo></msup><mi>p</mi></math> scattering process. Therefore, more accurate experimental measurements of the <math><msup><mi>π</mi><mo>−</mo></msup><mi>p</mi><mo>→</mo><mi>ϕ</mi><mi>n</mi></math> reaction are highly desirable, and we have also proposed that correlation measurements can be performed on J-PARC, AMBER, and future HIKE and HIAF meson beam experiments.

Xiao-Yun Wang

Hui-Fang Zhou

Xiang Liu

Prospects for detecting the hidden-strange pentaquarklike state <math><msup><mi>N</mi><mo>*</mo></msup><mo>(</mo><mn>2080</mn><mo>)</mo></math> in the <math><msup><mi>π</mi><mo>−</mo></msup><mi>p</mi><mo>→</mo><mi>ϕ</mi><mi>n</mi></math> reaction

In this work, we investigate the production of isovector scalar meson <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>1817</mn><mo>)</mo></math> by the effective Lagrangian approach. Specifically, we employ the Reggeized <math><mi>t</mi></math> channel Born term to calculate the total and differential cross sections for the reaction <math><msup><mi>K</mi><mo>−</mo></msup><mi>p</mi><mo>→</mo><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>1817</mn><mo>)</mo><mi>Λ</mi></math>. Our analysis reveals that the optimal energy range for detecting the <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>1817</mn><mo>)</mo></math> meson lies between <math><mi>W</mi><mo>=</mo><mn>3.4</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and <math><mi>W</mi><mo>=</mo><mn>3.6</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, where the predicted total cross section reaches a minimum value of 112 nb. Notably, the <math><mi>t</mi></math> channel, as predicted by the Regge model, significantly enhances the differential cross sections, particularly at extreme forward angles. Furthermore, we investigate the Dalitz processes of <math><mn>2</mn><mo>→</mo><mn>3</mn></math> and discuss the feasibility of detecting the <math><msub><mi>a</mi><mn>0</mn></msub><mo>(</mo><mn>1817</mn><mo>)</mo></math> meson in experiments like J-PARC.

Exploring kaon induced reactions for unraveling the nature of the scalar meson <math><mrow><msub><mrow><mi>a</mi></mrow><mrow><mn>0</mn></mrow></msub><mo>(</mo><mn>1817</mn><mo>)</mo></mrow></math>

A special class of four-point correlation functions in the maximally supersymmetric Yang-Mills theory is given by the square of the Fredholm determinant of a generalized Bessel kernel. In this note, we re-express its logarithmic derivatives in terms of a two-dimensional Riemann-Hilbert problem. We solve the latter in the null limit making use of the Deift-Zhou steepest descent. We reproduce the exact octagonal anomalous dimension in 't Hooft coupling and provide its novel formulation as the convolution of a non-linear quasiclassical phase with the Fermi distribution in the limit of the infinite chemical potential.

A.V. Belitsky

Null octagon from Deift-Zhou steepest descent

We study the quasi-two-body decays 
					 by employing the perturbative QCD (PQCD) factorization approach, where the charmonia 
					 represents 
					 and 
					. The corresponding decay channels are studied by constructing the kaon-pion distribution amplitude (DA) 
					, which comprises important final state interactions between the kaon and pion in the resonant region. Relativistic Breit-Wigner formulas are adopted to parameterize the time-like form factor 
					 appearing in the kaon-pion DAs. The SU(3) flavor symmetry breaking effect resulting from the mass difference between the kaon and pion is taken into account, which makes significant contributions to the longitudinal polarizations. The observed branching ratios and the polarization fractions of 
					 are accommodated by tuning hadronic parameters for the kaon-pion DAs. The PQCD predictions for 
					 modes from the same set of parameters can be tested by precise data obtained in the future from LHCb and Belle II experiments.
				

Ya Li

Zhou Rui

Zhen-Jun Xiao

P-wave contributions to B(s)→ψKπ decays in perturbative QCD approach Supported by the National Natural Science Foundation of China (11947013, 11605060, 11775117, 11547020); Ya Li is also Supported by the Natural Science Foundation of Jiangsu Province (BK20190508) and the Research Start-up Funding of Nanjing Agricultural University; Zhou Rui is Supported in part by the Natural Science Foundation of Hebei Province (A2019209449)