The neutrino exerts the same mysterious attractive force on physicists and laypersons alike. The author found himself drawn in by that force in the 1970s and set about trying to resolve the solar neutrino problem and to determine the neutrino mass. His experiences as a foot soldier in the revolution that followed are the subject of this article.
Supersymmetry has long played a central role in the search for physics beyond the Standard Model at colliders, providing a comprehensive and internally consistent framework for generating well-motivated experimental signatures. For more than fifteen years of LHC operation, the CMS and ATLAS collaborations have achieved remarkable sensitivity to a wide range of supersymmetric signatures. Despite this unprecedented reach, no conclusive evidence for supersymmetry has emerged. If supersymmetry is nature's solution to outstanding questions in particle physics, it is necessarily challenging to find. In this article, we review supersymmetric signatures that are particularly rare or otherwise challenging, with a focus on searches at the Large Hadron Collider. We highlight experimental challenges relating to detector constraints and analysis difficulties, in addition to model challenges in the interpretation and optimization of searches. We also identify regions of signature space that remain comparatively unconstrained and therefore represent promising targets for future exploration.
Over the past six decades, accelerator-based neutrino beams have revolutionized particle physics. Neutrinos created with accelerators have been used to discover the muon neutrino and tau neutrinos was discovered and to confirm the existence of neutrino oscillations. More recently, long-baseline experiments have offered the first experimental hint of CP violation in the neutrino sector. Building and operating such beams is an enormous technical challenge, yet they remain our most versatile tool for studying neutrinos. With new experiments such as DUNE and Hyper-Kamiokande, and ideas such as neutrino factories, the next generation of beams will address open questions about neutrino mass ordering, CP violation, and possible physics beyond the standard model.
The discovery of the Higgs boson at the Large Hadron Collider has opened the door to a new realm of physics, where high-energy accelerators are essential to explore more fundamental laws. In this article, we share our vision regarding the future of high-energy physics and accelerators, particularly focusing on the Circular Electron Positron Collider (CEPC) and Super Proton-Proton Collider (SPPC) projects proposed by Chinese scientists in September 2012. Following the recent completion of the CEPC accelerator's technical design report, we review its main physics drives, technical design, and related technology development. The construction of the CEPC will become technologically viable upon the completion of its engineering design report, expected in approximately 3 years. Efforts are also underway to advance technologies for the SPPC.
Detectors for relativistic nuclear interactions have significantly increased in size and sophistication over the last few decades, primarily owing to rising collision energies and rates. Common across most particle physics experiments is the need to measure collision vertex, particle momentum, and particle energy. To accurately measure momenta at the very low level of 100 MeV/ c , tracking detectors with a very low material budget are required. Additionally, particle identification requires detector systems that use time-of-flight, energy loss, and Cherenkov radiation measurements. Compared to high-luminosity proton–proton experiments, these detectors face considerably lower radiation levels, enabling the use of a wider range of sensor technologies and leading to innovative developments in this area. Technological advancements in data transport and processing over recent decades now enable continuous data readout and online processing, eliminating the need for selective triggering, which has significantly enhanced detector performance. This article provides an overview of current and future detectors for relativistic nuclear collisions along with a discussion of key technological advancements in this context. Given the similarity in detector requirements for future e + e − Higgs factories, the conclusions drawn here are also relevant to developments in that domain.
Ultra-relativistic heavy-ion collisions are used to create a deconfined state of quarks and gluons, the quark-gluon plasma (QGP), similar to the matter in the early universe. Dileptons are a unique probe of the QGP. Being emitted during all stages of the collision without interacting strongly with the surrounding matter, they carry undistorted information about the medium evolution. The mass of the lepton-antilepton pair gives a unique mean to separate partonic from hadronic radiation. Thus, dileptons can be used to study the QGP equilibration time, its average temperature but also effects related to the restoration of chiral symmetry in the hot medium via vector meson decays. This information is not accessible with hadrons. The price to pay is a large background from ordinary hadron decays. We summarize the potential of dilepton measurements, the results obtained so far at colliders, and the ongoing efforts for future experiments with further increased sensitivity.
This article reviews the development and achievements of the Jinping Underground Nuclear Astrophysics (JUNA) experimental platform and focuses on the direct measurement of reaction rates within or near the Gamow window in deep-underground astrophysical experiments. It discusses the advantages of conducting experiments in the deep-underground environment of the China Jinping Underground Laboratory (CJPL), which provides significant shielding from cosmic rays along with milliampere-level intensity from the JUNA accelerator. This shielding and the high beam intensity are crucial for accurately measuring very-low-cross-section nuclear reactions essential to understanding astrophysical processes, such as the synthesis of heavy elements in stars from neutron sources and CNO cycle leakage. The manuscript also covers technological achievements, including advancements in ion sources, accelerators, detectors, and targets used in the JUNA experiment. The physics results from these experiments provide valuable data for key reactions, such as neutron source reactions and radiative capture reactions, as well as for the production of heavy elements in early stars. Future plans for the JUNA experiment are also outlined.
Exploding stars have long been considered a threat to life on Earth. While early studies were speculative, modern research is based on advanced observations, theory, and modeling. This review examines supernova explosions, γ-ray bursts (GRBs), and kilonova outbursts, which are major sources of ionizing radiation in galaxies. This radiation can harm Earth-like biospheres by destroying stratospheric ozone, increasing exposure to solar ultraviolet radiation, and producing cosmic-ray muons that penetrate belowground and underwater. Using recent work, we calculate rates for nearby explosions based on distance from the Earth and ionizing radiation dose. Over the Earth's history, core-collapse supernova cosmic rays, γ-rays from Type Ia supernovae, X-rays from Type IIn supernovae, and γ-rays from long GRBs have likely caused significant biosphere damage. However, short GRBs and kilonovae are less concerning. Future research could address open questions through nuclear and particle experiments, astronomical observations, and studies in climate, geology, radiation, and evolutionary biology.
While a variety of laboratory-based fusion schemes have been studied for decades, the only fusion scheme yet to demonstrate fusion ignition and significant energy gain has been X-ray-driven inertially confined fusion. Ignition was demonstrated to occur at the thermodynamic conditions where it had long been expected, but the energy required for the implosion system to reach these conditions was more than projected years ago. This short review gives a status update on the three principal inertial confinement fusion schemes and research challenges going forward.
The dark sector offers a compelling theoretical framework for addressing the nature of dark matter while potentially solving other fundamental problems in physics. This review focuses on light dark flavored sector models, which are those where the flavor structure of the interactions with the standard model is non-trivial and distinguish among different fermion families. Such scenarios feature flavor violation leading to unique experimental signatures, such as flavor-changing neutral current decays of heavy hadrons (kaons, D and B mesons, baryons) and leptons (muons and taus) with missing energy carried away by light dark-sector particles. In this article, we review their motivation, summarize current constraints, highlight discovery opportunities in ongoing and future flavor experiments, and discuss implications for astrophysics and cosmology.
Solid-state phonon and charge detectors probe the scattering of weakly interacting particles, such as dark matter and neutrinos, through their low recoil thresholds. Recent advancements have pushed sensitivity to eV-scale energy depositions, uncovering previously-unseen low-energy excess backgrounds. While some arise from known processes such as thermal radiation, luminescence, and stress, others remain unexplained. This review examines these backgrounds, their possible origins, and parallels to low-energy effects in solids. Their understanding is essential for interpreting particle interactions at and below the eV-scale.
Accurate neutrino transport is crucial for reliably modeling explosive astrophysical events like core-collapse supernovae (CCSNe) and neutron star mergers (NSMs). However, in these extremely neutrino-dense systems, flavor oscillations exhibit challenging nonlinear effects rooted in neutrino–neutrino forward scattering. Evidence is quickly accumulating that these collective phenomena can substantially affect explosion dynamics, neutrino and gravitational-wave signals, nucleosynthesis, and kilonova light curves. We review the progress made so far on the difficult and conceptually deep question of how to correctly include this physics in simulations of CCSNe and NSMs. Our aim is to take a broad view of where the problem stands and provide a critical assessment of where it is headed.
Self-consistent, multidimensional core-collapse supernova (SN) simulations, especially in 3D, have achieved tremendous progress over the past 10 years. They are now able to follow the entire evolution from core collapse through bounce, neutrino-triggered shock revival, shock breakout at the stellar surface to the electromagnetic SN outburst and the subsequent SN remnant phase. Thus they provide general support for the neutrino-driven explosion mechanism by reproducing observed SN energies, neutron-star (NS) kicks, and diagnostically relevant radioactive isotope yields; they allow to predict neutrino and gravitational-wave signals for many seconds of proto-NS cooling; they confirm correlations between explosion and progenitor or remnant properties already expected from previous spherically symmetric (1D) and 2D models; and they carve out various scenarios for stellar-mass black-hole (BH) formation. Despite these successes it is currently unclear which stars explode or form BHs, because different modeling approaches disagree and suggest the possible importance of the 3D nature of the progenitors and of magnetic fields. The role of neutrino flavor conversion in SN cores still needs to be better understood, the nuclear equation of state including potential phase transitions implies major uncertainties, the SN 1987A neutrino measurements raise new puzzles, and tracing a possible correlation of NS spins and kicks requires still more refined SN simulations.
The proton-proton collisions at the Large Hadron Collider (LHC) produce an intense, high-energy beam of neutrinos of all flavors, collimated in the forward direction. Recently two dedicated neutrino experiments, FASER and SND@LHC, have started operating to take advantage of the TeV energy LHC neutrino beam, with first results released in 2023 and further results released in 2024. The first detection of neutrinos produced at a particle collider opens up a new avenue of research, allowing to study the highest energy neutrinos produced in a controlled laboratory environment, with an associated broad and rich physics program. Neutrino measurements at the LHC will provide important contributions to QCD, neutrino and BSM physics, with impactful implications for astro-particle physics. This review article summarizes the physics motivation, status and plans of, present and future neutrino experiments at the LHC.
In this report, we present an experimental overview of quarkonium results obtained in nucleus-nucleus heavy-ion collisions, with a focus on the data collected at the LHC. We discuss the current understanding of charmonium and bottomonium behavior in the deconfined medium produced in such collisions, comparing the various observables now accessible to state-of-the-art theoretical models. We also discuss the open points and how future heavy-ion experiments aim to clarify these aspects.
Lattice effective field theory applies the principles of effective field theory in a lattice framework where space and time are discretized. Nucleons are placed on the lattice sites, and the interactions are tuned to replicate the observed features of the nuclear force. Monte Carlo simulations are then employed to predict the properties of nuclear few- and many-body systems. We review the basic methods and several theoretical and algorithmic advances that have been used to further our understanding of atomic nuclei.
This paper reviews the calculation of nuclear Schiff moments, which one must know in order to interpret experiments that search for time-reversal-violating electric dipole moments in certain atoms and molecules. After briefly reviewing the connection between dipole moments and CP violation in and beyond the Standard Model of particle physics, Schiff's theorem, which concerns the screening of nuclear electric dipole moments by electrons, Schiff moments, and experiments to measure dipole moments in atoms and molecules, the paper examines attempts to compute Schiff moments in nuclei such as ^199Hg and octupole-deformed isotopes such as ^225Ra, which are particularly useful in experiments. It then turns to ab initio nuclear-structure theory, describing ways in which both the In-Medium Similarity Renormalization Group and coupled-cluster theory can be used to compute important Schiff moments more accurately than the less controlled methods that have been applied so far.
The search for dark matter and physics beyond the Standard Model has grown to encompass a highly interdisciplinary approach. In this review, we survey recent searches for light, weakly-coupled particles - axions and dark photons - over the past decade, focusing on new experimental results and the incorporation of technologies and techniques from fields as diverse as quantum science, microwave engineering, precision magnetometry, and condensed matter physics. We also review theoretical progress which has been useful in identifying new experimental directions, and identify the areas of most rapid experimental progress and the technological advances required to continue exploring the parameter space for axions and dark photons.
