CyberSec Research

Accurate comparisons between theoretical models and experimental data are critical for scientific progress. However, inferred model parameters can vary significantly with the chosen physics model, highlighting the importance of properly accounting for theoretical uncertainties. In this article, we explicitly incorporate these uncertainties using Gaussian processes that model the domain of validity of theoretical models, integrating prior knowledge about where a theory applies and where it does not. We demonstrate the effectiveness of this approach using two systems: a simple ball drop experiment and multi-stage heavy-ion simulations. In both cases incorporating model discrepancy leads to improved parameter estimates, with systematic improvements observed as additional experimental observables are integrated.

We study the Quantum Chromodynamics (QCD) phase transitions in the complex chemical potential plane in the framework of Dyson-Schwinger equation approach, in the presence of a constant gluonic background field that represents confining dynamics. We solve the quark gap equation and the background field equation self consistently, which allows us to directly explore the confinement phase transition and furthermore, evaluate the impact of the back-coupling of confinement on chiral symmetry breaking. Moreover, within such a coupled framework towards the complex chemical potential region, we demonstrate the emergence of Roberge-Weiss (RW) symmetry and investigate the trajectory of Lee-Yang edge singularities (LYES). Our analysis reveals that the LYES scaling behavior is similar to our previous findings without the background field condensate. However, a significant difference from our earlier work is that the trajectory of LYES terminates when the imaginary part of the singularity becomes $1/3 \, \pi T$. We elaborate that this cut-off behavior is caused by the RW symmetry that is symmetric to the imaginary chemical potential $\mu_i=1/3 \, \pi T$.

Based on an extended nuclear statistical equilibrium model, we investigate the properties of non-accreted crusts of young and warm neo-neutron stars, i.e., of finite-temperature inhomogeneous dense matter in beta equilibrium. We present two novel results and one known, but frequently ignored property of such matter. The first new feature is the appearance, in the deep inner crust, of an extensive and almost pure $^{14}$He layer that extends up to the density of the transition to homogeneous matter. This layer may challenge the idea of nuclear pasta phases, significantly impact the transport properties and the crust crystallization process. Second, we raise the question of the (in)stability of the inner crust with respect to diffusion of ions (buoyancy) and demonstrate that our crust is stable, in contrast with the predictions of some other models. Finally, we show that subsaturated stellar matter is thermodynamically stable with respect to density fluctuations, which rules out a first-order phase transition between inhomogeneous and homogeneous phases.

We report on the mass measurement of the rapid proton-capture process key nuclide ${}^{84}$Mo and its vicinity, such as ${}^{78}$Y${}^{\rm m}$, ${}^{79}$Y, ${}^{83}$Nb, and ${}^{88}$Ru, using the multi-reflection time-of-flight spectrograph at RIKEN RIBF. For ${}^{78}$Y${}^{\rm m}$, ${}^{84}$Mo, and ${}^{88}$Ru, their masses are experimentally determined for the first time with uncertainties of $\delta m \approx 20~{\rm keV}$. The mass precision of ${}^{79}$Y and ${}^{83}$Nb is improved to 13 keV and 9.6 keV, respectively. The new $\alpha$-separation energy of ${}^{84}$Mo, 1.434(83) MeV, unambiguously rules out the possibility of forming the ZrNb cycle. The X-ray burst simulation with the new masses shows that our measurements effectively remove the large final abundance uncertainties in the $A=80-90$ mass region. The new mass values improve the prediction power for the composition of the nuclear ashes in X-ray bursts, including the production of light $p$-nuclei.

We investigate the impact of chemical equilibration and the resulting bulk viscosity on non-radial oscillation modes of warm neutron stars at temperatures up to T~5 MeV, relevant for protoneutron stars and neutron-star post-merger remnants. In this regime, the relaxation rate of weak interactions becomes comparable to the characteristic frequencies of composition g-modes in the core, resulting in resonant damping. To capture this effect, we introduce the dynamic sound speed, a complex, frequency-dependent generalization of the adiabatic sound speed that encodes both the restoring force and the dissipative effects of bulk compression. Using realistic weak reaction rates and three representative equations of state, we compute the complex frequencies of composition g-modes with finite-temperature profiles. We find that bulk viscous damping becomes increasingly significant with temperature and can completely suppress composition g-modes. In contrast, the f-mode remains largely unaffected by bulk viscosity due to its nearly divergence-free character. Our results highlight the sensitivity of g-mode behavior to thermal structure, weak reaction rates, and the equation of state, and establish the dynamic sound speed as a valuable descriptor characterizing oscillation properties in dissipative neutron star matter.

Based on the model of three-fluid dynamics (3FD), the global $\Lambda$ polarization ($P_\Lambda$) is calculated in Au+Au collisions at 3 $\leq\sqrt{s_{NN}}\leq$ 9 GeV, in which high baryon density is achieved. Various contributions to $P_\Lambda$ are considered: those from the thermal vorticity, meson field, thermal shear and spin-Hall effect. Feed-down from higher-lying resonances is also taken into account. The results are compared with available data. Special attention is payed to the collision energies of $\sqrt{s_{NN}}=$ 3, 3.2, 3.5, 3.9, and 4.5 GeV, for which a thorough scan of the energy, rapidity, and centrality dependence of $P_\Lambda$ is performed. The results for 3 GeV reasonably well reproduce the corresponding STAR data. While the results at $\sqrt{s_{NN}}=$ 3.2, 3.5, 3.9, and 4.5 GeV can be considered as predictions for results of measurements within the STAR fixed-target (STAR-FXT) programthat are expected in the nearest future. It is predicted that a broad maximum of $P_\Lambda$ is reached at $\sqrt{s_{NN}}\approx$ 3--3.9 GeV, exact position of which depends on the centrality and width of the midrapidity range of observation. Impact of the meson-field, thermal-shear and spin-Hall-effect contributions to $P_\Lambda$ is also studied.

Nuclear charge radii of neutron-rich $^{47-49}$Sc isotopes were measured using collinear laser spectroscopy at CERN-ISOLDE. The new data reveal that the charge radii of scandium isotopes exhibit a distinct trend between $N=20$ and $N=28$, with $^{41}$Sc and $^{49}$Sc isotopes having similar values, mirroring the closeness of the charge radii of $^{40}$Ca and $^{48}$Ca. Theoretical models that successfully interpret the radii of calcium isotopes could not account for the observed behavior in scandium radii, in particular the reduced odd-even staggering. Remarkably, the inclusion of the new $^{49}$Sc radius data has unveiled a similar trend in the charge radii of $N=28$ isotones and $Z=20$ isotopes when adding the neutrons atop the $^{40}$Ca core and the protons atop the $^{48}$Ca core, respectively. We demonstrate that this trend is consistent with the prediction of the seniority model.

[Background] Pair condensation in finite nuclei generates a collective motion known as pair rotation. The moment of inertia of pair rotation (P-MoI) has been used as an indicator of pair condensation. [Purpose] We aim to elucidate the fundamental properties of the P-MoI, particularly its dependence on the particle number and the order parameter. [Method] The P-MoI was evaluated using the Bardeen-Cooper-Schrieffer (BCS) calculations with a monopole pairing Hamiltonian and Skyrme density functional theory calculations with different density-dependent pairing energy density functionals. [Results] In open-shell nuclei, a negative correlation was found between the P-MoI and the pair amplitude, which is the order parameter for the transition from the normal phase to the superconducting phase. Analysis based on the decomposition of the P-MoI into the orbital contributions within the BCS approximation shows that its orbital dependence is very similar to that of the pairing gap. [Conclusions] The P-MoI reflects the influence of both the level density near the Fermi energy and the pair amplitude.

Weak Gamow-Teller (GT) responses for low-lying states in ${}^{71}\mathrm{Ga}$ are crucial for studying low-energy solar neutrinos and the Ga anomaly, i.e., the possible transition to the sterile state. The responses for the ground state, the first excited state, and the second excited state are evaluated for the first time using the experimental electron capture rates, the experimental charge exchange reaction (CER) rates corrected for the tensor-interaction effect and the theoretical interacting shell model (ISM) calculations. The contributions from the two excited states to the solar and ${}^{51}\mathrm{Cr}$ neutrinos are found to be $4.2 \pm 1.2\%$ of that for the ground state. This is slightly larger than the ISM values but little smaller than the CER values without corrections for the tensor interaction effect. The Ga anomaly is far beyond the uncertainty of the obtained nuclear responses.

Some of the computational limitations in solving the nuclear many-body problem could be overcome by utilizing quantum computers. The nuclear shell-model calculations providing deeper insights into the properties of atomic nuclei, is one such case with high demand for resources as the size of the Hilbert space grows exponentially with the number of particles involved. Quantum algorithms are being developed to overcome these challenges and advance such calculations. To develop quantum circuits for the nuclear shell-model, leveraging the capabilities of noisy intermediate-scale quantum (NISQ) devices. We aim to minimize resource requirements (specifically in terms of qubits and gates) and strive to reduce the impact of noise by employing relevant mitigation techniques. We achieve noise resilience by designing an optimized ansatz for the variational quantum eigensolver (VQE) based on Givens rotations and incorporating qubit-ADAPT-VQE in combination with variational quantum deflation (VQD) to compute ground and excited states incorporating the zero-noise extrapolation mitigation technique. Furthermore, the qubit requirements are significantly reduced by mapping the basis states to qubits using Gray code encoding and generalizing transformations of fermionic operators to efficiently represent manybody states. By employing the noise-resilient protocols, we achieve the ground and excited state energy levels of 38Ar and 6Li with better accuracy. These energy levels are presented for noiseless simulations, noisy conditions, and after applying noise mitigation techniques. Results are compared for Jordan Wigner and Gray code encoding using VQE, qubit-ADAPT-VQE, and VQD. Our work highlights the potential of noise-resilient protocols to leverage the full potential of NISQ devices in scaling the nuclear shell model calculations.

The many-body nature of nuclear physics problems poses significant computational challenges. These challenges become even more pronounced when studying the resonance states of nuclear systems, which are governed by the non-Hermitian Hamiltonian. Quantum computing, particularly for quantum many-body systems, offers a promising alternative, especially within the constraints of current noisy intermediate-scale quantum (NISQ) devices. This work aims to simulate nuclear resonances using quantum algorithms by developing a variational framework compatible with non-Hermitian Hamiltonians and implementing it fully on a quantum simulator. We employ the complex scaling technique to extract resonance positions classically and adapt it for quantum simulations using a two-step algorithm. First, we transform the non-Hermitian Hamiltonian into a Hermitian form by using the energy variance as a cost function within a variational framework. Second, we perform theta-trajectory calculations to determine optimal resonance positions in the complex energy plane. To address resource constraints on NISQ devices, we utilize Gray Code (GC) encoding to reduce qubit requirements. We first validate our approach using a schematic potential model that mimics a nuclear potential, successfully reproducing known resonance energies with high fidelity. We then extend the method to a more realistic alpha-alpha nuclear potential and compute the resonance energies with a basis size of 16, using only four qubits. This study demonstrates, for the first time, that the complete theta-trajectory method can be implemented on a quantum computer without relying on any classical input beyond the Hamiltonian. The results establish a scalable and efficient quantum framework for simulating resonance phenomena in nuclear systems. This work represents a significant step toward quantum simulations of open quantum systems.

We formulate the relativistic dissipative hydrodynamics of a system of quasi-particles from the Boltzmann equation within the ambit of relaxation time approximation with modified collision kernels. We focus on two specific scenarios with single quasi-particle species, (i) the extended relaxation time approximation, and (ii) the novel relaxation time approximation. We find that both approaches lead to equivalent results up to first-order in spacetime gradients. We generalize the extended relaxation time approach to incorporate multiple quasi-particle species and obtain the corresponding expressions for the shear ($\eta_s$) and bulk ($\zeta_s$) viscous coefficients. As an application, we study the temperature dependence of the transport coefficients of hot QCD medium with quasi-gluon and (light and strange) quasi-quark sectors considering the power law ansatz for the momentum dependence of the relaxation time. We explore the impact of the power law exponent on the ratio $\zeta_s/\eta_s$. Our study suggests that in comparison to a constant exponent, a temperature dependent exponent in the power law ansatz is more suitable for modeling the quasi-particle dynamics in the relevant temperature regime of heavy ion collision.

The Positron Annihilation into Dark Matter Experiment at the Laboratori Nazionali di Frascati has reported an excess of $e^+e^-$ final-state events from positron annihilation on fixed-target atomic electrons. While the global significance remains at the $1.8\,\sigma$ level, the excess is centered around $\sqrt{s} \sim 17\,\text{MeV}$, coinciding with the invariant mass at which anomalous $e^+e^-$ pair production has previously been observed in nuclear transitions from excited to ground states in $^8$Be, $^4$He and $^{12}$C, thereby strengthening the case for a common underlying origin, possibly involving a hypothetical new $X_{17}$ boson. We discuss the significance of this independent accelerator-based evidence. Combining it with existing nuclear physics results, we obtain a value for the $X_{17}$ mass of $m_{X_{17}} = 16.88 \pm 0.05\,$ MeV, reducing the uncertainty from nuclear physics determinations alone by more than a factor of two.

We investigated the impact of a spatially varying matter potential $\lambda$, coming from neutrino-electron forward scattering, on the emergence of fast neutrino flavor conversion (FFC) triggered by the presence of zero crossings in the angular distribution of the neutrino electron lepton number (ELN). We find that FFC can be significantly affected as the spatial variation rate of $\lambda$ increases, and strong spatial variations can completely stabilize initially unstable systems. Using stability analysis based solely on initial conditions, we identified for the first time a critical variation rate above which no FFC occurs even if the flavor instability exists. By analyzing several representative matter profiles based on an 18 $M_{\odot}$ SN model, we show that spatially inhomogeneous $\lambda$ can suppress the occurrence of FFC associated with shallow ELN zero crossings in most of the SN's radial region, especially during the accretion phase. Our finding highlights the need to consider the impact of matter inhomogeneity in the development of improved SN models that aim to include the effect of neutrino flavor conversions.

We extend the multireference covariant density functional theory (MR-CDFT) to describe the low-lying states of the odd-mass nucleus $^{43}$S near the neutron magic number $N=28$ with shape coexistence. The wave functions of the low-lying states are constructed as superpositions of configurations with different intrinsic shapes and $K$ quantum numbers, projected onto good particle numbers and angular momenta. The MR-CDFT successfully reproduces the main features of the low-energy structure in $^{43}$S. Our results indicate that the ground state, $3/2^-_1$, is predominantly composed of the intruder prolate one-quasiparticle (1qp) configuration $\nu1/2^-[321]$. In contrast, the $7/2^-_1$ state is identified as a high-$K$ isomer, primarily built on the prolate 1qp configuration $\nu7/2^-[303]$. Additionally, the $3/2^-_2$ state is found to be an admixture dominated by an oblate configuration with $K^\pi = 1/2^-$, along with a small contribution from a prolate configuration with $K^\pi = 3/2^-$. These results demonstrate the capability of MR-CDFT to capture the intricate interplay among shape coexistence, $K$-mixing, and isomerism in the low-energy structure of odd-mass nuclei around $N = 28$.

A new method is proposed for fitting non-relativistic binary-scattering data and for extracting the parameters of possible quantum resonances in the compound system that is formed during the collision. The method combines the well-known $R$-matrix approach with the analysis based on the semi-analytic representation of the Jost functions. It is shown that such a combination has the advantages of both these approaches, namely, the number of the fitting parameters remains relatively small (as for the $R$-matrix approach) and the proper analytic structure of the $S$-matrix is preserved (as for the Jost function method). It is also shown that the new formalism, although closely related to the $R$-matrix method, has the benefit of no dependence on an arbitrary channel radius. The efficiency and accuracy of the proposed method are tested using a model single-channel potential. Artificial ``experimental'' data generated with this potential are fitted, and its known resonances are successfully recovered as zeros of the Jost function on the appropriate sheet of the Riemann surface of the energy.

The reactor antineutrino anomaly, discovered in 2011, means a noticeable difference between the observed rate of inverse beta decays and the expected (theoretical) rate of such processes based on the measurement of the spectra of electrons in beta decay of $^{235}$U, $^{239}$Pu, $^{241}$Pu, and $^{238}$U nuclei and their subsequent conversion into right-handed antineutrino spectra. This paper provides a rationale for the fact that both right-handed and left-handed antineutrinos are produced in beta decays of nuclei. But the conversion procedure in any case assigns a right-handed antineutrino to each electron, which leads to the superiority of the theoretical rate of inverse beta decays over the experimental one. The right-handed antineutrino is produced in the mode of beta decay of the nucleus due to the standard electroweak interaction. The left-handed antineutrino appears in the mode caused by the existence of a interaction, the carrier of which is a massless pseudoscalar boson having a Yukawa coupling with the electron neutrino and nucleons. The emission of such a boson from a virtual right-handed antineutrino converts it into a free left-handed antineutrino.

In this work, we present a comprehensive and systematic study of the statistical complexity, originally introduced by L\'opez-Ruiz, Mancini, and Calbet [Phys. Lett. A 209, 321-326 (1995)], across a broad range of compact star models. We explore how complexity correlates not only with macroscopic observables such as mass and radius, but also with the microscopic characteristics of the underlying equation of state. By incorporating both realistic equations of state and analytical solutions to Einstein's field equations, we demonstrate that gravitational mass plays a dominant role in determining the behavior of complexity. Furthermore, we show that strong phase transitions within the stellar interior, such as those hypothesized in hybrid stars, can manifest as distinct features in the complexity profile, offering a potential informational signature of such transitions. This work offers new insights into the link between information theory and compact object physics, highlighting complexity's potential as a diagnostic tool in astrophysics.