New measurements of proton number cumulants from the Beam Energy Scan Phase II (BES-II) program at RHIC by the STAR Collaboration provide unprecedented precision and insights into the properties of strongly interacting matter. This report discusses the measurements in the context of predictions from hydrodynamics, emphasizing the enhanced sensitivity of factorial cumulants and their implications for the search for the QCD critical point. The experimental data shows enhancement of second-order factorial cumulants and suppression of third-order factorial cumulants relative to the non-critical baseline at $7.7 < \sqrt{s_{\rm NN}} \lesssim 10$ GeV. We discuss implications of this observation for the possible location of the critical point in the QCD phase diagram and opportunities for future measurements of acceptance dependence of factorial cumulants.
A cross section deficit phenomenon has been observed in $^{12}$C+$^{12}$C fusion reactions at astrophysical energies, at which fusion cross sections are suppressed in the off-resonance regions as compared to fusion cross sections for the $^{12}$C+$^{13}$C system. I here construct a simple schematic model which simulates this phenomenon. The model consists of a random matrix Hamiltonian based on the Gaussian Orthogonal Ensemble (GOE), which is coupled to an entrance channel Hamiltonian in the discrete basis representation. I show that the transmission coefficients are almost unity when both the level density and the decay widths of the GOE configurations are large, realizing the strong absorption regime. On the other hand, when these parameters are small, the transmission coefficients are significantly structured as a function of energy. In that situation, the transmission coefficients at resonance energies reach unity in this model, that is consistent with the experimental finding of the cross section deficit.
By employing the Coulomb proximity potential model (CPPM) in conjunction with 22 distinct proximity potential models, we investigated the temperature dependence and the effects of proton number and neutron number on the diffusion parameters that determine the {\alpha}-decay half-lives of superheavy nuclei. The results indicate that the Prox.77-3 T-DEP proximity potential model yields the best performance, with the lowest root mean square deviation ({\sigma}=0.515), reflecting a high consistency with experimental data. In contrast, Bass77, AW95, Ngo80, and Guo2013 display larger deviations. The inclusion of temperature dependence significantly improves the accuracy of models such as Prox.77-3, Prox.77-6, and Prox.77-7. The -decay half-lives of 36 potential superheavy nuclei were further predicted using the five most accurate proximity potential models and Ni's empirical formula, with the results aligning well with experimental data. These predictions underscore the high reliability of the CPPM combined with proximity potential models in the theoretical calculation of {\alpha}-decay half-lives of superheavy nuclei, offering valuable theoretical insights for future experimental investigations of superheavy nuclei.
The straightforward calculations of the reaction and interaction cross sections of the nuclear scattering are carried out in Glauber approach using the generating function method. It allows for the resummation of all orders of Glauber theory. The results are obtained for $^4$He, $^{11}$Li, $^{12}$C scattering on $^{12}$C target. The difference between the reaction and the differential cross section is shown to be not exceeding several percents
We apply the non-equilibrium Green function (NEGF) method to microscopically evaluate fission cross sections for the neutron induced $^{235}$U$(n,f)$ reaction. While the model space was restricted only to seniority zero configurations in the previous applications of the NEGF method, we remove this restriction and include seniority non-zero configurations as well. In such model space, a proton-neutron interaction is active, for which we introduce a random interaction. We find that the seniority non-zero configurations significantly increase the fission cross sections, and thus the fission-to-capture branching ratios, even though they are still underestimated by about one order of magnitude as compared to the experimental data. In addition, we also find that the fission dynamics is governed by only a small number of eigenstates of the model Hamiltonian.
Density Functional Theory (DFT) is a robust framework for modeling interacting many-body systems, including the equation of state (EoS) of dense matter. Many models, however, rely on energy functionals based on assumptions that have not been rigorously validated. We critically analyze a commonly used ansatz for confinement, where the energy functional scales with density as $U \propto n^{\frac{2}{3}}$ . Our findings, derived from a systematic non-local energy functional, reveal that this scaling does not capture the dynamics of confinement. Instead, the energy functional evolves from $n^2$ at low densities to $n$ at high densities, governed by an infrared cutoff. These results suggest that models relying on such assumptions should be revisited to ensure more reliable EoS construction.
The nucleon matrix elements (NMEs) associated with quark chromo-magnetic dipole moments (cMDMs) play a crucial role in determining the CP-odd pion-nucleon couplings induced by quark chromo-electric dipole moments. In recent years, it has been argued that the NMEs of cMDMs can be related to the third moment of the nucleon's higher-twist (specifically, twist-three) parton distribution function (PDF) $e(x)$, which can, in principle, be measured through dihadron production in semi-inclusive deep inelastic scattering processes. By applying the spin-flavor expansion to the cMDM operators in the large-$N_c$ limit, where $N_c$ is the number of quark colors, we show that the NMEs receive contributions not only from the twist-three PDF $e(x)$ but also from an additional, previously neglected nucleon form factor. Incorporating constraints from the spin-flavor expansion, recent experimental data on $e(x)$, as well as model calculations of $e(x)$, we estimate the NMEs of the cMDM operators. Our analysis indicates that the NMEs are dominated by the nucleon form factors, and the cMDM contributions to pion-nucleon couplings can be comparable to those from the quark sigma terms.
We present the first calculation of the momentum-transfer dependence of the pion gravitational form factors (GFFs) within a top-down holographic QCD framework. These form factors encode essential information about the internal stress distribution of hadrons and may serve as a tool to explore the non-perturbatice dyanmics responsible for quark and gluon confinement in QCD. In particular, we evaluate the forward-limit value of the GFFs, known as the D-term, within the framework of the Sakai-Sugimoto model. Our analysis also reveals glueball dominance, wherein the pion's gravitational interaction is mediated by an infinite tower of glueball excitations.
We investigate the effect of the glasma classical color fields, produced in the very early stage of heavy-ion collisions, on the transport of heavy quarks. The glasma fields evolve according to the classical Yang-Mills equations, while the dynamics of heavy quarks is described by Wong's equations. We numerically solve these equations and compute the transport coefficient $\kappa$, which is anisotropic and initially very large. Further, we extract observables sensitive to the initial glasma stage. The heavy quark nuclear modification factor $R_{AA}$ is affected by the glasma but the effect is moderate compared to the nPDF contribution. Our main finding is that the glasma has a large impact on the azimuthal correlation between $Q\overline{Q}$ pairs, initially produced back-to-back.
Contemplating to register signature of a new vector boson unambiguously from the measured non-linear isotope shift (IS) effects in three recent experiments [Phys. Rev. X {\bf 12}, 021033 (2022); Phys. Rev. Lett. {\bf 128}, 163201 (2022) and Phys. Rev. Lett. {\bf 134}, 063002 (2025)], very precise values of quadrupole moments and IS constants for the $6s ~ ^2S_{1/2} \rightarrow 5d ~ ^2D_{3/2}$ and $6s ~ ^2S_{1/2} \rightarrow 5d ~ ^2D_{5/2}$ clock transitions of $^{171}$Yb$^+$ are presented. This is accomplished by incorporating contributions from the computationally challenging triply excited configurations through the relativistic coupled-cluster (RCC) theory. Testament of quality atomic wave functions of states of the above transitions, obtained using the RCC theory, are gauged by comparing the calculated energies and magnetic dipole hyperfine structure constants with their measurements. The improved quadrupole moments from this work will be immensely useful to estimate quadrupole shifts of the clock transitions of Yb$^+$. Complementary approaches are employed to ascertain accuracy and comprehend roles of orbital relaxation and correlation effects in evaluating the IS constants. Combining these constants with the IS measurements from Phys. Rev. Lett. {\bf 128}, 163201 (2022), differential nuclear charge radii of the Yb isotopes are inferred that deviate by 6-7\% from the literature data.
Isospin asymmetric nuclear matter is introduced to V-QCD, a bottom-up holographic Quantum Chromodynamics (QCD) model. Using a small isospin chemical potential we extract the symmetry energy in the model, finding excellent agreement with experimental results for some of the potentials. Extending the calculation for finite and arbitrary sized isospin chemical potentials, we construct beta-equilibrated neutron stars via the usual Tolman-Oppenheimer-Volkov (TOV) equations. We find, pleasingly, that the neutron stars passing the mass/radius and tidal deformability constraints are those with the potentials that also lead to excellent symmetry energies.
We recently reported new results on the $\gamma^{(*)} + N(940)\frac{1}{2}^+ \to \Delta(1700)\frac{3}{2}^{-}$ transition form factors using a symmetry-preserving treatment of a vector$\,\otimes\,$vector contact interaction (SCI) within a coupled formalism based on the Dyson-Schwinger, Bethe-Salpeter, and Faddeev equations. In this work, we extend our investigation to the $\gamma^{(*)} + N(940)\frac{1}{2}^+ \to N(1520)\frac{3}{2}^{-}$ transition. Our computed transition form factors show reasonable agreement with experimental data at large photon virtualities. However, deviations emerge at low $Q^2$, where experimental results exhibit a sharper variation than theoretical predictions. This discrepancy is expected, as these continuum QCD analyses account only for the quark-core of baryons, while low photon virtualities are dominated by meson cloud effects. We anticipate that these analytical predictions, based on the simplified SCI framework, will serve as a valuable benchmark for more refined studies and QCD-based truncations that incorporate quark angular momentum and the contributions of scalar and vector diquarks.