The Electron-Ion Collider in China (EicC), a cutting-edge facility under development, aims to unveil the internal structure of nucleons and nuclei by leveraging collisions of high-intensity polarized electrons and ions (polarized protons, polarized deuterons, polarized 3He, and unpolarized heavy ions up to Uranium) at center-of-mass energies of 15-20 GeV and luminosity of (2–4)×1033 cm−2s−1. Its primary physics objectives include 3D tomography of nucleon spin and momentum structure, fundamental questions regarding the origin of nucleon mass, partonic structure of nuclei and parton interactions with the nuclear environment, and exploration of exotic hadronic states. In this paper, we review the physics potential of the EicC and highlight its unique capabilities for advancing precision nucleon structure studies by combining its specialized kinematic coverage and high luminosity. Since traditional topics like 3D nucleon structure have already been well-covered by several extensive reviews, we have deliberately dedicated significant space to recent progress in nucleon mass decomposition, nucleon energy-energy correlation, quantum information, and artificial intelligence applications in high-energy nuclear physics, which have been emerging rapidly and attracted a tremendous amount of attention in the community.
The emergence of exotic nuclear structures, such as deformation, one- and two-neutron halos, and bubble configurations, marks a paradigm shift in our understanding of light- to medium-mass nuclei far from stability, particularly near and within the island of inversion extending across N=20–28. In this review, we integrate microscopic structure calculations using the antisymmetrized molecular dynamics method with reaction theories such as the Glauber model for high-energy collisions, and highlight the use of the fully quantum mechanical finite-range distorted wave Born approximation for calculating both inclusive and exclusive Coulomb breakup observables for these medium mass systems. These theoretical frameworks enable precise probing of nuclear density profiles through observables such as total reaction cross sections, neutron removal cross sections, relative energy spectra, parallel momentum distributions, and angular distributions. Applications to several nuclei in the island of inversion reveal enhanced halo extensions, neutron–neutron correlations in Borromean nuclei, and central density depletions in bubbles, challenging traditional shell-model paradigms. Furthermore, the sensitivity of astrophysical reaction rates to these exotic inputs is explored, demonstrating their role in the refinement of r-process nucleosynthesis models and elemental abundance predictions. This unified approach not only bridges nuclear structure and reactions, but also highlights the driplines as frontiers for unraveling nuclear matter under extreme conditions, with implications for rare-isotope beam experiments and beyond.
The FASER experiment is located in the Large Hadron Collider (LHC) complex at CERN, 480 m downstream of the ATLAS collision point and aligned with the beam-collision-axis. The experiment was designed to search for light, weakly-interacting new-particles which could be produced in the LHC collisions, and, for the first-time, to study high-energy neutrinos of all flavors originating at a particle collider. This review article presents the status of FASER up to early-2026. This includes details of the FASER detector design, operation, performance and physics results, as well as briefly mentioning upgrades that have been installed since the start of FASER. In addition, future plans for the experiment are detailed.
The strong interaction, described within the Standard Model of particle physics by quantum chromodynamics (QCD), plays a fundamental role in understanding the structure and the stability of matter. Despite significant advances, the low-energy QCD regime remains poorly understood due to its non-perturbative nature. Kaonic atoms, in which a negatively charged kaon is bound to a nucleus via electromagnetic interaction, offer a unique experimental tool to investigate the strong interactions in the strangeness sector. Their study provides key information on the antikaon–nucleon interaction at threshold energy, essential for refining the relative theoretical models. This work reviews the current status of kaonic atom research, highlighting recent experimental findings and their impact on our understanding of the strong interaction. We discuss the formation processes, the role of X-ray spectroscopy in probing strong-interaction effects, and the latest results from DAΦNE and J-PARC experimental facilities. Future perspectives, including planned experiments aimed at further improving the precision of the measurements and the potentiality of also measuring the high-n transitions as precision probes for quantum electrodynamics (QED) with strangeness, are also reviewed.
In this review, we discuss recent applications of the ab initio symmetry-adapted no-core shell-model (SA-NCSM) theory for study and prediction of structure and reactions of stable and unstable nuclei from light to medium mass range. We explore structure properties of neutron-rich He, Li, and Mg isotopes, with a focus on nuclear collectivity, clustering, and spectroscopic factors, as well as multi-particle excitations of utmost significance in the proximity of the drip lines. In addition, we present extensions of the SA-NCSM with continuum for determining the microscopic structure of reaction fragments, which enables calculations of reaction cross sections for targets from the lightest 4,6He to 40Ca, rooted in first principles. We illustrate this for neutron and proton elastic scattering, deuteron and alpha capture reactions, and alpha knock-out reactions. Furthermore, we discuss microscopic optical potentials with uncertainty quantification, a critical ingredient in many reaction models. We also discuss the impact of alpha clustering on reactions of significance to nuclear astrophysics, as well as on beta decays and beyond-the-standard-model physics.
Theory can provide important support at all the stages of spectroscopic experiments, from planning the measurements to the interpretation of the results. Such support is particularly valuable for the challenging experiments on heavy, unstable, and superheavy elements and for precision measurements aimed at testing the Standard Model of particle physics. To be reliable and useful in experimental context, theoretical predictions should be based on high-accuracy calculations. For heavy elements, such calculations must treat both relativistic effects and electron correlation on the highest possible level. Relativistic coupled cluster is considered one of the most powerful methods for accurate calculations on heavy many-electron atoms and molecules. This approach is highly accurate and versatile and can be used to obtain energies and a variety of atomic and molecular properties. Furthermore, its robust and transparent formulation allows for systematic improvement of the accuracy of the calculated results and for assigning uncertainties on theoretical values. The Fock-space coupled cluster (FSCC) variant of this method is particularly useful in the context of spectroscopic measurements as it provides access to atomic spectra and properties of the excited states. In this review, we present in detail the relativistic coupled cluster approach and its FSCC variant. We provide a description of the computational procedure used for accurate calculations and for assigning uncertainties. Outstanding recent examples of application to atomic properties, focusing on the experimental context are presented. Finally, we provide a brief discussion of the perspectives for future developments and applications of the CC approach.
The origin of the universal asymmetry between matter and antimatter remains a mystery. Electroweak baryogenesis is a well-motivated mechanism for generating the asymmetry dynamically, using interesting features of the Standard Model. In addition, it relies on beyond-the-Standard Model physics active around the electroweak scale: new physics coupling to the Higgs to make the electroweak phase transition first order, and a new mechanism of CP violation. The relatively low energy scale at which electroweak baryogenesis occurs makes certain aspects of the mechanism testable through collider experiments, electric dipole moment measurements, and gravitational wave observations. However, scenarios of electroweak baryogenesis are increasingly challenged by results from contemporary experiments. The developing experimental programs will play a crucial role in either falsifying or detecting the new physics responsible for electroweak baryogenesis. To achieve this, it is essential to make precise predictions for the baryon asymmetry and the corresponding experimental signatures within specific scenarios. This review aims to provide a comprehensive overview of the rich physics involved in these predictions. Our goal is to offer a practical computational guide, with a focus on recent developments in the field.
Hypernuclei are bound states of neutrons, protons and one or two hyperons, thus extending the nuclear landscape to a third dimension. They also encode information about the baryon-baryon and three-baryon interactions. Here, we review recent work on chiral effective field theory for two- and three-baryon interactions and their application in nuclei based on ab initio methods. These include the Faddeev-Yakubovsky equations, the no-core–shell-model (NCSM) and nuclear lattice effective field theory (NLEFT). Besides of providing an overview of the formalisms explicit results for the separation energies of light Λ hypernuclei are provided. Two-body and three-body forces are included consistently, in line with the underlying power counting. Calculations of Λ hypernuclei within the NCSM, performed up to A=7 so far, suggest that agreement with the experimental binding energies can be achieved once appropriate three-body forces are taken into account. Similar conclusions are drawn from the study based on NLEFT, where even hypernuclei up to A=16 can be computed. Additionally, applications of ab initio approaches in calculations of ΛΛ and Ξ hypernuclei are discussed and possible candidates for the lightest systems that could be bound are identified, namely ΛΛ5He and Ξ4H.
We review the role of the anomalous magnetic moment of the muon aμ as a powerful probe of physics beyond the Standard Model (BSM), taking advantage of the final result of the Fermilab g−2 experiment and the recently updated Standard Model value. This review provides both a comprehensive summary of the current status, as well as an accessible entry point for phenomenologists with interests in dark matter, Higgs and electroweak or neutrino and flavour physics in the context of a wide range of BSM scenarios. It begins with a qualitative overview of the field and a collection of key properties and typical results. It then focuses on model-independent, generic formulas and classifies types of BSM scenarios with or without chiral enhancements. A strong emphasis of the review are the connections to a large number of other observables — ranging from the muon mass and the muon–Higgs coupling and related dipole observables to dark matter, neutrino masses and high-energy collider observables. Finally, we survey a number of well-motivated BSM scenarios such as dark photons, axion-like particles, the two-Higgs doublet model, supersymmetric models and models with leptoquarks, vector-like leptons or neutrino mass models. We discuss the impact of the updated Standard Model value for aμ and of complementary constraints, exploring the phenomenology and identifying excluded and viable parameter regions.
We review recent progress in our understanding of the nucleon excitation spectrum. Thanks to dedicated efforts at facilities such as ELSA, MAMI and Jefferson Lab, several new nucleon resonances have been discovered, and evidence for previously elusive states has been significantly improved. Numerous decay channels have been observed for the first time, and resonance properties are being extracted from these data by several groups through coupled-channel analyses of varying complexity. Electroproduction experiments have provided further insights into the internal structure of light baryon resonances — for example, the long-debated Roper resonance N(1440) is observed as a three-quark state with a significant meson-cloud component. While the non-relativistic quark model remains a valuable tool for organizing the spectrum of nucleon and Δ resonances, a variety of theoretical frameworks have emerged to offer deeper understanding, including phenomenological quark models, holographic QCD, functional methods, effective field theories, and lattice QCD. We examine the interplay between these approaches, highlight their respective strengths and explore how they complement each other in shaping our knowledge of light baryon resonances. We address several open questions in baryon spectroscopy, including the nature of the enigmatic Λ(1405), ongoing searches for exotic states such as hybrid baryons and pentaquarks, and the dichotomy between microscopic descriptions of baryons in terms of quarks and gluons versus effective hadronic descriptions based on meson–baryon dynamics.
Dynamical coupled-channel (DCC) approaches parametrize the interactions and dynamics of two and more hadrons and their response to different electroweak probes. The inclusion of unitarity, three-body channels, and other properties from scattering theory allows for a reliable extraction of resonance spectra and their properties from data. We review the formalism and application of the ANL-Osaka, the Juelich-Bonn-Washington, and other DCC approaches in the context of light baryon resonances from meson, (virtual) photon, and neutrino-induced reactions, as well as production reactions, strange baryons, light mesons, heavy meson systems, exotics, and baryon-baryon interactions. Finally, we also provide a connection of the formalism to study finite-volume spectra obtained in Lattice QCD, and review applications involving modern statistical and machine learning tools.
This review has explored the fundamental principles of thermal field theory in the context of a background magnetic field, highlighting its theoretical framework and some of its applications to the thermo-magnetic QCD plasma generated in heavy-ion collisions. Our discussion has been limited to equilibrium systems for clarity and conciseness. We analyzed bulk thermodynamic characteristics including the phase diagram as well as real-time observables, shedding light on the behaviour and dynamics of the thermo-magnetic QCD medium relevant to heavy-ion physics.
Magnetic fields are ubiquitous across different physical systems of current interest; from the early Universe, compact astrophysical objects, and heavy-ion collisions to condensed matter systems. A proper treatment of the effects produced by magnetic fields during the dynamical evolution of these systems can help to understand observables that otherwise show puzzling behavior. Furthermore, when these fields are comparable to or stronger than ΛQCD, they serve as excellent probes to help elucidate the physics of strongly interacting matter under extreme conditions of temperature and density. This work provides a detailed report that contains in-depth analysis and expert insights into the specific topic of the effects of strong magnetic fields on QED and QCD systems. In this sense, the report is intended as a white paper contribution to the field. The subjects developed include the modification of meson static properties such as masses and form factors, the chiral magnetic effect, the description of anomalous transport coefficients, superconductivity in extreme magnetic fields, the properties of neutron stars, the evolution of heavy-ion collisions, as well as effects on the QCD phase diagram. We describe recent theory and phenomenological developments using effective models as well as LQCD methods. The work was motivated by presentations and discussions during the “Workshop on Strongly Interacting Matter in Strong Electromagnetic Fields” that took place in the European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT*) in the city of Trento, Italy, September 25–29, 2023.
The discoveries of the pentaquark states and XYZ mesons in the charm quark sector initiated a new epoch in hadron physics, where the existence of exotic multi-quark states beyond conventional valence three quark and quark–antiquark systems has been unambiguously confirmed. Such states could manifest as single colour bound objects, or evolve from meson–baryon and meson–meson interactions, creating molecular like systems and re-scattering effects near production thresholds. Molecular-like structures may be apparent over the full quark flavour and mass range, with equivalent states evidenced in the light, uds quark sector. This is the focus of the BGOOD photoproduction experiment at the ELSA electron accelerator at the University of Bonn. The combination of a central electromagnetic calorimeter and forward charged particle spectrometer permits access to low momentum exchange kinematics and corresponding forward meson production angles, which is crucial to study spatially extended, molecular-like structure which may manifest in reaction mechanisms.The reviewed publications span two areas of research connected via the kinematics associated with molecular-like hadron structure. The first is in the strangeness sector where meson–baryon dynamics may play prominent roles. Forward angle differential cross section measurements from threshold for K+Λ, K+Σ0, K+Σ(1385)0, K+Λ(1405) and K+Λ(1520) indicate an equivalence to the PC states observed at the DΣC, DΣC∗ and D∗ΣC thresholds. The second area of research is in the non-strange baryon-baryon sector, where coherent meson photoproduction off the deuteron enables access to proposed dibaryon states, including the recently discovered d∗(2380). The forward angle acceptance of deuterons enables differential cross section measurements that challenge conventional descriptions of coherent photoproduction, which should be suppressed due to the large momentum transfer.
The luminosity frontier in particle physics, in particular the high-luminosity LHC, poses a new level of challenges for the detection of muons. In consequence, muon systems had to evolve into large-scale tracking systems with high spatial and time resolution. Especially the forward regions of the LHC experiments ATLAS and CMS will be challenged by high particle rates and the resulting irradiation, while they need to identify and efficiently trigger the muons from signal events. A new type of gaseous detectors – micro-pattern gas detectors – plays a crucial role in the quest of meeting these goals. This next generation of muon systems had to overcome several technological challenges, like mass production of large-area detectors and high-voltage stability. Two technologies of micropattern gas detectors were identified for the upgrades of the muon forward systems of ATLAS and CMS. This article focuses on their development, implementation and performance. At the end, examples of promising R&D for further developments of future muon systems are summarized.
A review of neutron sources for large scale user facilities is provided, aimed at users of neutron sources who need to understand the characteristics and peculiarities of the different types of neutron sources in order to select the most suitable source for their needs and to optimize their experimental setups for their specific scientific requirements. To this end, we provide an overview of (i) the main nuclear processes used at user facilities to release neutrons from nuclei, namely fission, spallation, and low-energy nuclear reactions, (ii) the various possibilities to tailor the time structure and spectrum of free neutrons, from pulsing to moderation, (iii) the mechanisms to extract and transport neutron beams with desired properties in terms of flux, brilliance/brightness, spectrum, pulse shape, etc., (iii) the applications and related experimental requirements in major scientific fields, with emphasis on those with a larger user community, (iv) the technology and realization of research reactors and neutron spallation sources, and (v) the progress made in Compact Accelerator-driven Neutron Sources (CANS), but especially in High Current Accelerator-driven Neutron Sources (HiCANS).HiCANS are the focus of the current review, as this entirely new type of facility could in the future play the role in the neutron ecosystem that national reactor-based sources have played in the past. As such, HiCANS do not aim for the highest neutron brightness, but rather for parameters such as resilience, reliability, flexibility, ease of access, minimization of radioactive waste, excellent signal-to-noise ratio and optimization of the price/performance ratio. These are key features needed to further expand the community of neutron users from science and industry to whom this review is addressed.
This is a review on the nature of low-lying 0+ states in the excitation spectra of deformed nuclei. Early in the history of the field, Bohr-Mottelson-Rainwater won the 1975 Nobel prize in physics for connecting nucleon motion to the emergent collective behavior observed in nuclei. They essentially described the nucleus as a geometric shape with rotational and vibrational degrees of freedom. The lowest shape affecting vibrations in nuclei would be quadrupole (A =2). In spherical nuclei, the oscillations of the ground state shape were expected to yield an energy spectrum that could be described in terms of single and multiple quadrupole phonons. In deformed nuclei, rotational motion is prominent and could be described in terms of a rigid rotor. The question in nuclear structure physics that has remained unanswered for decades is the viability of a deformed nucleus to sustain oscillations or vibrations built on the ground state. The quadrupole oscillations in deformed nuclei could result in two types of vibrations: /3-vibrations resulting from oscillations along the symmetry axis with Kn = 0+ and y-vibrations breaking axial symmetry with a projection of Kn = 2+ on the symmetry axis. The Kn = 2+ or y-vibrational bands are well characterized and accepted as oscillations around the g.s. The question which has remained open is the nature of the Kn = 0+ bands. Historically, 0+ states were difficult to observe and to measure, more recently however, there has been a large abundance of states identified. The discussions have shifted towards the characterization of these 0+ states. The systematics of the observed B(E2) values depopulating the Kn = 0+ bands were shown to be weaker than the Kn = 2+ band decays. Questions arose about the nature of the Kn = 0+ bands. Were they indeed vibrations built on the ground state? Or are they coexisting minima of other shapes? The debates and discussions have led to a reexamination of the nature of vibrational excitations. A /3-vibrational band built on the ground state shape of a deformed nucleus is expected to show the same degree of deformation, hence the same dynamic moment of inertia, and perhaps even the same intrinsic quadrupole moment. Geometric, microscopic, and algebraic theoretical nuclear models have revisited the predictions and expectations of a /3-vibration in contrast to a coexisting minimum of a different shape. The topic continues to be of great interest in nuclear structure studies as evidenced by the hundreds of theoretical and experimental publications on the topic. The ability of deformed nuclei to sustain oscillations or vibrations is fundamental to understanding the properties of the nuclear quantum system. This review brings together the extensive data sets from the numerous 0+ states that have been observed in the past six decades, their lifetime measurements, transition probabilities, transfer reaction populations, dynamic moments of inertia, and the extracted intrinsic quadrupole moments to clearly identify /3 vibrations. Two-neutron transfer reactions were expected to elucidate the nature of 0+ states. However as shown in this extensive data collection effort, they do not provide the definitive answers to the open question regarding the nature of these states. The studies reported here are confined to the Z=50-82 region of the chart of nuclides with the largest demonstrated regions of deformation. The discussion has specifically only focused on highly deformed nuclei in order to avoid any confusion with coexisting minima which are not expected in high deformation regions. The theory section explores and briefly presents a tour of the numerous relevant theoretical models and the resulting constraints or assertions with respect to the nature of vibrations built on a deformed ground state. The interpretation and discussion chapters present the analysis of the vast body of knowledge that has been developed. The result is the identification of a large number of 0+ bands as fl-vibrations in the spectra of well-deformed nuclei. The list includes 152,154Sm, 154,156,158Gd, 162Dy, 168Er, 168Yb, 178Hf, and the 182,184W nuclei.
We review the status and perspectives of indirect methods that make use of transfer reactions. We focus on two of them that have been extensively used in the past decades to determine cross sections of reactions of astrophysical relevance: the Trojan Horse method and the Asymptotic Normalization Coefficients method. We provide a comprehensive description of the theory behind each of these techniques, followed by an overview of a selection of experiments carried out using these indirect tools.
The Beijing Radioactive Ion-beam Facility (BRIF), based on the Isotope Separation On-Line (ISOL) technique, consists of a 100 MeV proton cyclotron as the driving accelerator, a two-stage ISOL system for ion separation, a 13-MV tandem accelerator for post-acceleration, a superconducting linac for further boosting beam energies. It is capable of providing ISOL beams in the energy range from 60 to 300 keV, and post-accelerated beams in the energy range from 3 to 10 MeV/u for nuclei with mass numbers of A < 80. For nuclei with A up to 170, energies are still able to reach 3 MeV/u. This facility offers opportunities to address key questions of current interest in nuclear astrophysics, nuclear structure and reactions of unstable nuclei. In this review we present a comprehensive introduction to the BRIF and the typical experimental instruments installed on it, and then summarize current experimental results on unstable Na and Rb isotopes and future plan for development of the BRIF to improve its performance.
