We report measurements of the tensor analyzing power T 20 for incoherent neutral pion photoproduction on the deuteron, γd → pnπ 0 , at photon energies 300–600 MeV. The data reveal a clear kinematic transition in the reaction mechanism. At low neutron momenta (p n < 200 MeV/c), T 20 is governed by the deuteron D-wave component, providing a direct probe of the deuteron structure. At high neutron momenta (p n > 200 MeV/c), the observable becomes sensitive to the reaction dynamics, with final state interactions dominating the production mechanism. This transition demonstrates that T 20 can discriminate between quasi-free and rescattering-dominated processes. The results are compared with theoretical calculations based on the MAID2007 model with explicit inclusion of NN and πN rescattering, showing good agreement across both kinematic regimes.
Accurate prediction of nuclear proton separation energies is very important to understand the fundamental nuclear structure and rapid proton capture (rp-process) astrophysical simulations. While standard global mass models are built on powerful theoretical bases, the complex interaction between the macroscopic liquid-drop behavior and discrete quantum shell effects is still a major computational challenge. Moreover, the ability of such highly localized phenomena at the microscopic level by continuous or discrete machine learning (ML) structures requires a strict comparative analysis. In this research, we quantitatively evaluate two different predictive models of a continuous-mapping Feedforward Neural Network (FNN) and a tree based piecewise-discrete Natural Gradient Boosting (NGBoost) algorithm. Both architectures were trained using comprehensive NUBASE2020 data of 3378 empirically assessed nuclides, using a physics-informed feature space, which explicitly captures macroscopic, microscopic, and non-linear correlational effects. Both algorithms were able to map the overall nuclear dynamics with a high score of over 0.98 on R 2 . The FNN showed that it can generalize well and effectively learn smooth macroscopic trends. However, NGBoost achieved higher predictive precision, resulting in a significant reduction of test error when compared to the continuous model. Our analysis provides evidence that continuous FNN structures tend to be better at capturing high-level structural trends, while discrete additive tree NGBoost structures are better suited to capturing extreme, non-linear microscopic discontinuities. As a result, NGBoost develops a calculation system that is widely accurate and strong to calibrate the predictions of nuclear masses and analyze the characteristics of carried out exotic nuclei.
High-energy proton-proton collisions provide an important probe of small-x gluon dynamics in quantum chromodynamics. In this work, charged-particle pseudorapidity distributions in high-energy pp collisions are studied within a two-component model. The central component is described by gluon-gluon fusion using unintegrated gluon distributions constructed with the Kimber-Martin-Ryskin prescription, while the fragmentation component is modeled through quark recombination with collinear parton distributions. The integrated PDFs are evolved using the modified DGLAP equations including nonlinear gluon-recombination corrections. The calculated (1/N ev ) dN ch /dη distributions are compared with ATLAS data at [Formula: see text] = 0.9, 2.36, 7, and 13 TeV. After normalization at midrapidity, the model reproduces the main features of the measured distributions, with gluon fusion dominating the central rapidity region. Comparisons with CT18, MSHT20, NNPDF, HERAPDF2.0, and GRV98 PDFs show that the pseudorapidity shape is sensitive to the small-x behavior of the gluon distribution. The results suggest that charged-particle pseudorapidity distributions can serve as a useful phenomenological test of small-x gluon PDFs within two-component models.
The analysis of the directly measured experimental cross-section for the radiative capture reaction [Formula: see text]C[Formula: see text]C, leading to the ground and first excited states of the [Formula: see text]C nucleus, has been performed within the modified two body potential approach. The peripheral character of the [Formula: see text]C[Formula: see text]C reaction has been demonstrated and new values of the asymptotic normalization coefficients (ANCs) for the [Formula: see text]C+n[Formula: see text]C configuration, corresponding to the ground and first excited states of the [Formula: see text]C, together with their associated uncertainties, have been obtained. The new values of the ANCs obtained in this work have been used for the extrapolation of the cross-sections to low energies within the modified two body potential approach. The total neutron capture cross-section at energy of [Formula: see text] [Formula: see text]keV has been determined to be [Formula: see text] [Formula: see text] [Formula: see text]b.
Within the framework of the multiple-scattering Glauber model and using a proton wave function in which quark–quark short-range correlations and three-quark forces are taken into account, the proton–proton elastic scattering differential cross-section at ISR energies [Formula: see text]–[Formula: see text] [Formula: see text]GeV and at LHC energies 7, 8 and 13[Formula: see text]TeV is calculated. The proton radius is taken in two measured values, 0.87 and 0.84 fm. The proton core radii in these two cases are 0.50 and 0.485 fm, respectively. A single set of quark–quark amplitude parameters is used in both cases. The [Formula: see text] values are calculated using two well-known formulas at each energy. A good agreement with the experimental data for the elastic scattering differential cross-section in both cases is obtained at all energies considered. Analyzing our results, we show that the three valence quarks are confined in a deep core with radius [Formula: see text] [Formula: see text]fm at ISR energies and radius [Formula: see text] [Formula: see text]fm at LHC energies, respectively. The short-range correlation radius [Formula: see text] is [Formula: see text] [Formula: see text]fm at ISR energies and [Formula: see text] [Formula: see text]fm at LHC energies. The results are the same for the two assumed values of the proton radius. A fine structure of the proton is represented by the inequality [Formula: see text].
This paper presents a study of multiplicity distribution of the backward grey particles emitted in central 22Ne-emulsion collisions at 4.1AGeV/c using nuclear emulsion detectors. Applying the Heckman criteria in the present study, the central events of 22Ne-emulsion collisions have been selected. Basic observables related to the multiplicity distribution, including multiplicity moments, variance, and the scaled variance, have been calculated to characterize the shape of the multiplicity distribution quantitatively. This work attempts to model the backward grey particle multiplicity distribution using the Gamma distribution, Negative Binomial Distribution (NBD) and the KNO-type parametrization. In addition, a detailed analysis of R & eacute;nyi and Shannon entropies has been carried out to gain further insight into the underlying multiplicity distribution.
In this paper, we investigate the cooling properties of dark-matter-admixed Neutron Stars (NSs) with antikaon (including K- and K & strns;0) condensations. Dark Matter (DM) is assumed to be made of non-self annihilating, but weakly self-interacting fermions. Results show that the neutrino luminosity of NSs dependence strongly on the neutron star mass, and antikaon condensations decrease it for any DM particle mass significantly. DM improves the cooling rate of high-mass NSs but reduces it for low-mass NSs, whereas antikaon condensations depress the cooling of NSs with medium and low masses. Overall, the effects of DM and antikaon condensations on NS cooling are mutually suppressive.
The chiral imbalance, coupled with the presence of a strong magnetic field produced during heavy-ion collisions, can result in charge separation along the magnetic field axis, referred to as the Chiral Magnetic Effect (CME). A novel technique, the Sliding Dumbbell Method (SDM) is employed to investigate the CME within the RHIC isobar program. The SDM enables the selection of events corresponding to various charge separations ([Formula: see text]) across the dumbbell. The charge separation distributions for each collision centrality are divided into ten percentile bins to identify potential CME-like events corresponding to the highest charge separation. The study reports the results on CME sensitive [Formula: see text]-correlator ([Formula: see text]) and [Formula: see text]-correlator ([Formula: see text]) evaluated in each [Formula: see text] bin for different centralities in isobaric collisions ([Formula: see text] and [Formula: see text]) at [Formula: see text] measured with the STAR detector. Furthermore, the background scaled ratio ([Formula: see text]/[Formula: see text]) is presented to check for the expected enhancement of the CME in [Formula: see text] collisions as compared to [Formula: see text] collisions.
Neutron–proton pairing correlations occupy a central position in nuclear structure physics. While likeparticle pairing between neutrons or protons in the isovector ([Formula: see text]) channel is firmly established and accounts for many systematic features of nuclear spectra, the role of neutron–proton correlations, particularly in the isoscalar ([Formula: see text]) channel, remains a subject of ongoing debate in both experiment and theory. In this review, we examine the theoretical foundations and current understanding of neutron–proton pairing, beginning with the conceptual distinctions among several phenomena that are often conflated in the literature: the residual neutron–proton interaction, isovector pairing correlations and possible isoscalar pairing condensates. We discuss how these different forms of correlation emerge in the shell–model framework and how they are represented in BCS mean-field approaches. Special attention is given to the pedagogical aspects of single-j pairing models, algebraic approaches, as well as the shell-model-like exact pairing diagonalization algorithms, which provide valuable benchmarks for understanding the limitations of mean-field descriptions and the interplay between isovector and isoscalar pairing channels. We also review experimental signatures that have been proposed as evidence for neutron–proton pairing, including spectroscopic patterns in [Formula: see text] nuclei, mass systematics and transfer reactions and discuss the extent to which these observations support or challenge current theoretical interpretations. The review highlights both the progress achieved in clarifying the mechanisms of neutron–proton correlations and the major open questions that remain, particularly regarding the existence and manifestation of collective [Formula: see text] pairing modes in finite nuclei. Finally, a practical computational scheme for the exact diagonalization of neutron–proton pairing is presented.
Gamma-ray transitions from excited states in [Formula: see text]Nb have been reported in [V. Kumar, R. Chapman, D. O’Donnell, J. Ollier, R. Orlandi, J. F. Smith, K.-M. Spohr, D. A. Torres, P. Wady, S. K. Tandel, S. J. Freeman, G. de Angelis, N. Mărginean, D. R. Napoli, J. J. Valiente-Dobón, S. Aydin, E. Farnea, R. Mărginean, D. Mengoni, T. Kröll and N. Thompson, Phys. Rev. C 108 (2023) 044313], and the yrast level scheme up to an excitation energy of 3034 keV has been established in [N. Fotiades, J. A. Cizewski, P. Fallon, P. G. Kevrekidis, R. Krücken and I. Y. Lee, Phys. Rev. C 111 (2025) 014316]. However, a detailed theoretical interpretation of the observed level structures is still lacking. In this work, the yrast states of [Formula: see text]Nb are investigated using large-scale shell-model calculations within the jj45pn model space employing the jj45pna effective interaction. To examine the role of the neutron 1h[Formula: see text] orbital on the nuclear structure, calculations were performed using two truncation schemes: one excluding the 1h[Formula: see text] orbital and the other allowing a maximum occupancy of two neutrons in this 1h[Formula: see text] orbital. The inclusion of the [Formula: see text]h[Formula: see text] orbital has only a minor influence on the low-spin states but significantly modifies the higher-spin positive- and negative-parity states. A comparison of the root-mean-square deviation values indicates that excluding the [Formula: see text]h[Formula: see text] orbital yields a slightly better description of the low-spin yrast states. The predicted (B(E2)) and (B(M1)) transition strengths further support the proposed microscopic structure.
A systematic study of the elastic scattering of deuterons from the [Formula: see text]Al target has been performed over a wide range of incident deuteron beam energies (5 to 85 MeV). The experimental angular distributions obtained from the elastic scattering reaction [Formula: see text]Al(d,d)[Formula: see text]Al were analyzed using the double-folding São Paulo potential (SPP) [L. C. Chamon et al., Phys. Rev. Lett. 79 (1997) 5218 and L. C. Chamon et al., Phys. Rev. C 66 (2002) 014610.], where double folding potentials were generated using the average matter and charge density. The experimental angular distributions were also analyzed using the modified São Paulo potential (SPP2), which employs realistic deuteron matter and charge density distributions, within the nuclear reaction code REGINA [L. C. Chamon, B. V. Carlson and L. R. Gasques, Comput. Phys. Commun. 267 (2021) 108061]. The sensitivity of the elastic scattering angular distributions of deuterons at each energy was investigated, and relevant potential parameters (Real, [Formula: see text] and Imaginary, [Formula: see text] normalization parameters) as well as total reaction cross-sections were extracted. The energy dependence of [Formula: see text] and [Formula: see text] was parameterized phenomenologically. Good agreement was obtained between the theoretical angular distributions of the cross-sections and the experimental angular distributions for the same. The extracted potential parameters were found to follow a systematic energy dependence. The SPP and SPP2 potentials were found to successfully describe deuteron elastic scattering angular distributions and provide useful constraints on the energy dependence of deuteron optical model potentials over a broad energy range.
The differential cross-sections (DCS) of the 9 Be([Formula: see text]Be and [Formula: see text]C( 9 Be,[Formula: see text]Be)[Formula: see text]C reactions at energies of 12 and 40[Formula: see text]MeV were analyzed within the framework of the modified distorted wave Born approximation. The peripheral character of the reactions was systematically investigated, and it was demonstrated that both reactions are predominantly peripheral in the region of the main peak of the angular distributions. The “experimental” asymptotic normalization coefficients (ANCs) for the [Formula: see text]Be[Formula: see text]Be[Formula: see text] configuration were extracted. Using the 9 Be(d,[Formula: see text]Be reaction, the ANCs values for both the ground and first excited states of the [Formula: see text]Be nucleus were determined, while the [Formula: see text]C( 9 Be,[Formula: see text]Be)[Formula: see text]C reaction was used to obtain the ANC value for the ground state of the [Formula: see text]Be nucleus. The extracted ANCs for the ground state obtained from the two independent reactions were found to be in good agreement with each other, confirming the reliability and consistency of the analysis.
The nuclear structure of [Formula: see text]P was investigated by detecting multi-[Formula: see text] coincidences along with charged light ions following the bombardment of an [Formula: see text]O target with a 30-MeV [Formula: see text]O beam from the Florida State University accelerator facility using the Clarion2-Trinity array of Clover [Formula: see text] spectrometers and GAGG (Gd-Al-Ga-garnet) scintillators for charged particles. A number of new states up to 12 MeV excitation and spins up to [Formula: see text] were observed by their [Formula: see text] decay patterns. Spins and parities were assigned by comparing measured [Formula: see text] angular distributions with polarizations inferred from Compton-scattering asymmetries between the Ge crystals in the Clover spectrometers. The new level scheme of [Formula: see text]P compares well with shell model calculations using the FSU cross-shell interaction and reasonably well with those using the sdpf-m interaction. In particular, structures with higher spin arise from promotion of more nucleons up to the f-p shell.
Atomic nuclei can take on asymmetric, triaxial shapes — a phenomenon known as triaxial deformation. One of the clearest signs of such asymmetry is a wobbling motion, similar to a spinning football that wobbles as it rotates. Wobbling has long been studied in heavy, strongly deformed nuclei, but its existence in lighter, normally deformed nuclei has remained unclear. Here we use the triaxial projected shell model (TPSM) to systematically investigate four odd-mass nuclei in the mass-130 region: [Formula: see text]Xe, [Formula: see text]Ba, [Formula: see text]La and [Formula: see text]Pr. We also present new TPSM calculations for [Formula: see text]Pm, extending the systematic investigation to include this recently studied wobbling nucleus. Our calculations reproduce the experimental data and reveal that wobbling in these systems can be of two types — transverse or longitudinal — depending on whether the unpaired neutron or proton aligns with the long, short, or medium axis of the nucleus. The same single-particle orbital ([Formula: see text]) can give rise to different wobbling behaviours depending on the occupation of the shell. These findings establish normally deformed nuclei as a new testing ground for wobbling excitations and provide a microscopic understanding of how triaxial shapes emerge in nuclear many-body systems. It should be noted that the assignments of two-phonon wobbling bands in these nuclei remain tentative, as definitive electromagnetic transition measurements are still awaited.
A Monte Carlo simulation of the process of bombarding titanium-tritium and titanium-deuterium targets with 160[Formula: see text]keV deuterons was performed using the Geant4 and SRIANG codes. The results of calculating the energy spectra of neutrons emitted from the target at different angles are presented. A comparison of the calculation results is carried out. The advantages and disadvantages of different approaches to modeling the DT and DD neutron source are analyzed.
The understanding structure and composition of compound nuclei provide valuable insights into nuclear reaction mechanisms, including decay modes and cross-sections. The compound nucleus is a transient state where the nucleons from the projectile and the target nuclei combine, leading to a complex system. The interpretation of the intricate structure of the nucleus necessitates a crucial factor that facilitates its construction. This knowledge enables the calculation for cross-sections of every decay particle in a nuclear reaction on individual basis. This factor is incorporated in the Dynamical Cluster-decay Model (DCM), known as the preformation probability, often denoted as [Formula: see text]. This is the key factor in determining the outcomes of nuclear reactions. Preformation probability refers to the plausibility of a specific configuration or state occurring in a system before a particular event or measurement. In theoretical models, the preformation probability aids in predicting fission fragment yields. One of the notable advantages of the DCM is its incorporation of preformation probability, making it a more comprehensive framework compared to other fission models. This study explores the significance of [Formula: see text], paving the way for breakthroughs in nuclear research and applications.
The yrast-band structures of 102 Pd and 106,108 Cd isotopes have been studied within collective and shell-model frameworks. Comparison with experimental excitation energies indicates that the shell-model calculations yield larger root-mean-square deviations, especially for nuclei characterized by higher R 4/2 ratios. In addition, the theoretical energy ratios E(I)/E[Formula: see text] are analyzed and compared with the predictions of E(5) symmetry.
The total and partial charge-changing cross-sections of projectile fragmentation of 28 Si on carbon and copper targets at 130 A MeV were measured using CR-39 nuclear track detectors. The latest experimental results were reported, which supplement the experimental data of the C and Cu targets in this energy region. It is shown that the total charge-changing cross-sections are in good agreement with the Bradt-Peters semi-empirical formula within the experimental error. The partial charge-changing cross-sections generally show a downward trend with the increase of ΔZ and do not exhibit the odd-even effect. The partial charge-changing cross-sections are also compared with those at higher beam energies and different theoretical models. It is found that the present experimental results for partial cross-sections of projectile fragments production are smaller than those at higher energies and the theoretical predictions.
We study the real-time dynamics of vacuum electron-positron pair production in a time-dependent Sauter-type electric field, focusing on the emergence of characteristic time scales associated with particle formation. From the time evolution of the transverse momentum distribution, we extract three distinct time scales corresponding to the onset of spectral deformation, the reorganization of interference structures and the final freeze-in of real particles. We show that these time scales depend on the external field parameters, with the peak field strength governing the dynamics and the pulse duration providing a secondary control. Our results provide a time-resolved characterization of transverse momentum formation and offer new insight into nonequilibrium dynamics in strong-field quantum electrodynamics (SFQED).
The Quantum Chromodynamics (QCD) phase diagram, characterized by temperature (T) and baryon chemical potential (mu(B)), features a transition from hadronic matter to a deconfined Quark Gluon Plasma (QGP) at certain values of T and mu(B). The Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) explores this phase structure by sys-tematically varying the collision energy of Au+ Au collisions, with a key focus on locating the QCD phase boundary and the critical point. During the first phase (BES-I, 2010 2014), STAR experiment measured the nuclear modifica tion factor (R-cp) of inclusive charged particles in Au + Au collisions in the energy range from root(NN)-N-S 7.7 to 39 GeV. In 2018, the STAR experiment initiated the second phase of the BES program (BES-II), which has a tenfold increase in statistics compared to the first phase. This enables better precision Rer measurements. By 2018 2019, STAR collected more than 500 million Au + Au events at root(NN)-N-S 19.6 and 27 GeV, two orders of magnitude larger than the BES-I dataset at these energies. In these proceedings, we present new measurements of charged-particle production and R-CP measurements on the high-statistics BES-II data at root(NN)-N-S 19.6 and 27 GeV, comparing them with BES-I results. We further evaluate theoretical expectations using UrQMD and hydrody-namic (SMASH + VHLLE) model predictions, testing their description of the experimental observations. By extending the analysis to higher transverse momenta (p(T)), we probe potential jet quenching effects and assess implications for QGP formation and properties at lower collision encrrics
