The European Physical Journal A最新文献

We systematically investigate the resonant states of kaonic nuclei using the relativistic mean-field complex momentum representation (RMF–CMR) method. Validation with different integration contours confirms that the RMF–CMR method is effective and reliable for calculating resonant states in kaonic nuclei. The strong (K^-)-nucleon attraction in light kaonic nuclei induces a pronounced core compression effect and a sharp increase in nuclear potential depth; this effect weakens as the nucleon number increases. A new (1d_{5/2}) resonant state is identified just above the neutron continuum threshold in (^{13}_{K^-}) C; its single-particle density is strongly extended at finite distances, exhibiting a halo-like spatial distribution in the light kaonic nucleus. We also find that nuclear matter softening shifts d-orbital resonant levels closer to the continuum threshold and generally weakens their coupling to the continuum, and the (1d_{5/2}) state, lying much closer to the continuum threshold than the (1d_{3/2}) state under the common (ell =2) centrifugal barrier owing to the spin-orbit splitting, retains an extremely narrow width over the whole investigated parameter range and is more sensitive to nuclear matter softening. The widths discussed in this work refer to the neutron-emission widths of single-particle shape resonances; the mesonic (bar{K}N) decay of the kaonic nucleus itself is not included.

We investigate the performance of quantum algorithms for light nuclear systems by studying the deuteron (²H), triton (³H), and helium-3 (³He) nuclei within a lattice formulation of pionless effective field theory (EFT). We first compute ground-state energies using classical exact diagonalization (ED), serving as a benchmark reference for variational quantum algorithms. We then perform Variational Quantum Eigensolver (VQE) calculations using noiseless statevector simulations of quantum circuits, enabling a controlled assessment of algorithmic performance in the absence of hardware-induced noise. We calibrate the two-body low-energy constant using the deuteron system and fit the three-body interaction strength to the triton, then consistently apply the resulting Hamiltonian parameters to the helium-3 nucleus. Our VQE calculations employ physically motivated ansätze targeting the relevant particle-number sectors, with explicit particle-number-conserving constructions implemented for the triton and helium-3 systems. The variational optimization includes an analysis of the Hamiltonian energy variance, ⟨H²⟩−⟨H⟩², providing insight into convergence behavior and the quality of the variational states. The deuteron VQE energy agrees with the ED reference within the reported numerical precision, whereas the triton and helium-3 calculations retain deviations of 0.1016 MeV and 0.1128 MeV, respectively, together with nonzero Hamiltonian variances. The results therefore provide a controlled, one-dimensional small-system benchmark of the implemented VQE workflow rather than a demonstration of quantum advantage, scalability, or independent validation of the nuclear interaction. Additionally, we perform noisy evaluations of noiseless-optimized triton circuits using a depolarizing noise model to illustrate the impact of representative Noisy Intermediate-Scale Quantum (NISQ)-era hardware noise on variational energy estimation.

Poincaré-covariant Bethe–Salpeter wave functions are used to calculate light-front wave functions (LFWFs) of the pion, (pi ), and an analogue state, (pi _{sbar{s}}). The current masses of the degenerate valence constituents in the (pi _{sbar{s}}) are around 25-times larger than those of the pion’s valence constituents. Both valence spin-antialigned () and spin-aligned () components are obtained and combined to produce the complete LFWF for each system. Comparing predictions delivered by two distinct Bethe–Salpeter kernels, the impact of nonperturbative dynamical effects contained in the more sophisticated (bRL) kernel are seen to be significant; and contrasts between (pi ), (pi _{s bar{s}}) results reveal the interplay between emergent hadron mass and mass effects owing to Higgs-boson couplings. Amongst the results, one finds that for (pi ), (pi _{sbar{s}}), the LFWFs can be approximated by a separable form, with that representation being pointwise reliable in the bRL cases. Moreover, the component is important; so a LFWF obtained after omission of this piece is typically a poor representation of the system. These features are naturally expressed in (pi , pi _{sbar{s}}) transverse momentum dependent parton distribution functions (TMDs). In this connection, it is found that a Gaussian Ansatz can only provide a rough guide to TMD pointwise behaviour: magnitude deviations between Ansatz and prediction exceed a factor of two on (k_perp ^2 gtrsim 0.55,text { GeV}^2). One should therefore be cautious in interpreting conclusions drawn from phenomenological analyses based upon Gaussian Ansätze.

Hadronic vacuum polarization (hVP) enters simple atomic systems at a level that is small yet decisive for the precision spectroscopy now underway. We evaluate the hVP contributions to the Lamb shift and the hyperfine splitting (HFS) in ordinary and muonic hydrogen (H and (mu )H) and hydrogen-like helium-3 ions ((^3)He(^+) and (mu ^3)He(^+)), using the dispersive data-driven approach and state-of-the-art empirical parametrizations of the R ratio. At the centre of the analysis is the interplay of recoil and finite-size effects: the recoil corrections that dominate the HFS in muonium (Mu), where both constituents are pointlike, are shown to be suppressed by the nuclear elastic form factors (FFs). Our results for the leading hVP contribution to the Lamb shift agree with the literature within uncertainties. Furthermore, we present a first evaluation of the subleading (O(Z^5alpha ^6)) hVP-finite-size correction, which is by no means negligible in (mu ^3)He(^+). Our results for the hVP contribution to the HFS in H, (mu )H, and (mu ^3)He(^+) deviate significantly from previous evaluations. For the ground-state HFS, we obtain 2.153(11) (upmu )eV in (mu )H and (-15.19(57)) (upmu )eV in (mu ^3)He(^+), as well as 0.0860(4) kHz and (-0.476(17)) kHz in ordinary H and (^3)He(^+), respectively. Notably, our result for (mu )H differs from previous evaluations by roughly ten times the experimental precision anticipated by the upcoming CREMA and FAMU measurements.

Accurate measurement of critical data for astrophysical modeling, such as ((alpha ), n) and ((gamma ), n) cross-sections and (beta )-delayed neutron emission probabilities, depends heavily on overcoming the low and energy/emission-angle-dependent efficiency of current polyethylene-moderated (^3)He neutron detectors. We proposed a novel detector that replaces polyethylene with a large spherical heavy-water-moderator and substitutes (^3)He tubes with a layer of “(^3)He + CF(_4)” scintillation gas coupled to photomultipliers for thermal neutron detection. Simulations performed with MCNPX under varied moderator configurations show that a design employing 7.0 cm boron-11, 0.9 cm beryllium, and 50.0 cm heavy water achieves a neutron capture efficiency of 85.1%, with less sensitivity to neutron energy and emission angle. The newly designed neutron detector demonstrates its potential to replace the conventional polyethylene moderated (^{3})He neutron detector and may enable the researchers to make accurate measurements of ((alpha ), n), ((gamma ), n) cross-sections and (beta )-delayed neutron emission probabilities.

By varying the symmetry energy slope (L), I investigate how the exotic content within the interiors of neutron stars changes and how it affects both macroscopic and microscopic quantities. Using two different parametrizations (L3(omega rho ) and BigApple), and three different possibilities about the neutron star core (nucleons + hyperons, nucleons+deltas, nucleons + hyperons + deltas), I show that, for the models analyzed in this work, changing the slope barely changes the amount of hyperons, but it can strongly suppress the (Delta ) resonances for large values of L. I also show that, in general, the presence of exotic content will be more evident for lower values of L than for large ones. Differences and similarities between the two parametrizations are also analyzed.

The question of why quantum matter exhibits hierarchical structures—from quarks, hadrons, and nuclei to atoms and molecules—is one of the fundamental problems in modern physics, yet it has not been widely discussed in a unified manner. One reason may be that each hierarchical level has traditionally been studied independently, and apparent connections between different scales were not clearly recognized. On the other hand, the concept of “clusters” may provide a common framework linking these hierarchical regimes. Namely, a cluster formed within one hierarchy can itself become a constituent particle in the next hierarchy, as nucleons in the hadronic hierarchy form atomic nuclei.

We present a gate-based quantum computing solution of the homogeneous Bethe–Salpeter equation (hBSE) for the bound state of two massive relativistic scalar particles interacting via ladder-approximation scalar exchange. After Wick rotation to Euclidean space and O(4) S-wave partial-wave projection, the hBSE is reduced to a symmetric matrix eigenvalue problem of dimension (N = 2^n). We decompose the resulting Hamiltonian into a sum of n-qubit Pauli operators and solve it with the Variational Quantum Eigensolver (VQE) using a Matrix Product State (MPS) tensor-network ansatz. For (N=16) ((n=4) qubits), the VQE recovers the maximum eigenvalue – which encodes the minimum coupling constant for binding – to better than (1%) mean relative error compared to classical diagonalization. Entanglement analysis of the BSE amplitude shows low, area-law-like entanglement over the tested sizes, which motivates the MPS ansatz. A critical analysis of three independent barriers – exponential Pauli overhead, approximately size-independent low entanglement, and decreasing VQE gradient scales for the tested ansatz, consistent with generic barren-plateau concerns at larger n – reveals that the specific problem studied here lies in a classically tractable regime: over the tested range it is well described by low-bond-dimension tensor networks and efficiently handled by MPS/Lanczos methods. This negative result provides, to our knowledge, the first entanglement quantification of the BSE amplitude in qubit encoding, establishes the Pauli Hamiltonian framework for future BSE variants, and identifies 2D Minkowski-space BSE, N-body bound states, and non-ladder kernels as physically motivated extensions where genuine quantum advantage may become plausible.

The double differential thick target neutron yields (TTNY) for 500 MeV/u (^9)Be ions incident on a lead target were measured at emission angles from (0^{circ }) to (75^{circ }) using the time-of-flight (TOF) method with organic liquid scintillators. The angular distribution of neutron yields was obtained by integrating the neutron energy spectrum above the detection threshold. The experimental data were then compared with results calculated using the Monte Carlo simulation codes GEANT4, PHITS, and FLUKA with different physics models. The results show that the neutron energy spectrum in the forward direction exhibits a broad peak centered around 60–70% of the incident particle energy per nucleon and spread up to nearly twice the projectile energy per nucleon. All calculations overestimate the neutron yields near this broad peak except at (0^{circ },) and overestimate the neutron energy corresponding to the peak center at all angles. The GEANT4 results show good agreement with the experimental data from a few tens of MeV to around 100 MeV at angles from (5^{circ }) to (60^{circ },) while PHITS and FLUKA results slightly overestimate the yields. Regarding the angular distribution, the predictions from GEANT4, PHITS, and FLUKA differ from the experimental data by less than a factor of 2 except at (75^{circ }.)