Annual Review of Nuclear and Particle Science - Volume 72, 2022
Volume 72, 2022
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The Road to Precision Cosmology
Vol. 72 (2022), pp. 1–35More LessIn the past 50 years, cosmology has gone from a field known for the errors being in the exponents to a precision science. The transformation—powered by ideas, technology, a paradigm shift, and culture change—has revolutionized our understanding of the Universe, with the Lambda cold dark matter (ΛCDM) paradigm as its crowning achievement. I chronicle the journey of precision cosmology and finish with thoughts about the next cosmological paradigm.
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B Flavor Anomalies: 2021 Theoretical Status Report
Vol. 72 (2022), pp. 37–68More LessAt the present time (2022), there are discrepancies with the predictions of the Standard Model in several observables involving b → sℓ+ℓ− and
decays. These are the B flavor anomalies. In this review, we summarize the data as of Moriond 2021 and present theoretical new physics explanations from both a model-independent effective field theory point of view and through the building of explicit models. Throughout, we stress the complementarity of these two approaches. In addition, we discuss combined explanations of both B anomalies and present models that also explain other problems, such as dark matter, (g − 2)μ, neutrino properties, and hadronic anomalies.
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Testing Lepton Flavor Universality with Pion, Kaon, Tau, and Beta Decays
Vol. 72 (2022), pp. 69–91More LessWe present an overview of searches for violation of lepton flavor universality with a focus on low energy precision probes using π, K, τ, and nuclear beta decays. We review the current experimental results, summarize the theoretical status within the context of the Standard Model, and discuss future prospects (both experimental and theoretical). We review the implications of these measurements for physics beyond the Standard Model by performing a global model-independent fit to modified W couplings to leptons and four-fermion operators. We also discuss new physics in the context of simplified models and review Standard Model extensions with a focus on those that can explain a possible deviation from unitarity of the Cabibbo–Kobayashi–Maskawa quark mixing matrix.
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Something Can Come of Nothing: Surface Approaches to Quantum Fluctuations and the Casimir Force
Vol. 72 (2022), pp. 93–118More LessThe Casimir force provides a striking example of the effects of quantum fluctuations in a mesoscopic system. Because it arises from the objects’ electromagnetic response, the necessary calculations in quantum field theory are most naturally expressed in terms of electromagnetic scattering from each object. In this review, we illustrate a variety of such techniques, with a focus on those that can be expressed in terms of surface effects, including both idealized boundary conditions and their physical realization in terms of material properties.
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Exotic Higgs Decays
Vol. 72 (2022), pp. 119–149More LessExotic decays of the Standard Model (SM)-like Higgs boson into beyond-the-SM particles are predicted in a wide range of well-motivated theories. The enormous samples of Higgs bosons that have been and will be produced at the Large Hadron Collider thus constitute one of the key discovery opportunities at that facility, particularly in the upcoming high-statistics, high-luminosity run. Here we review recent theoretical work on models that predict or accommodate exotic Higgs decays, survey the status of current experimental searches, and look forward to future capabilities at dedicated Higgs factories and beyond.
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Fundamental Neutron Physics at Spallation Sources
Vol. 72 (2022), pp. 151–176More LessLow-energy neutrons have been a useful probe in fundamental physics studies for more than 70 years. With advances in accelerator technology, many new sources are spallation based. These new, high-flux facilities are becoming the sites for many next-generation fundamental neutron physics experiments. In this review, we present an overview of the sources and the current and upcoming fundamental neutron physics programs.
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Exploring Stars in Underground Laboratories: Challenges and Solutions
Vol. 72 (2022), pp. 177–204More LessFor millennia, mankind has been fascinated by the marvel of the starry night sky. Yet, a proper scientific understanding of how stars form, shine, and die is a relatively recent achievement, made possible by the interplay of different disciplines as well as by significant technological, theoretical, and observational progress. We now know that stars are sustained by nuclear fusion reactions and are the furnaces where all chemical elements continue to be forged out of primordial hydrogen and helium. Studying these reactions in terrestrial laboratories presents serious challenges and often requires developing ingenious instrumentation and detection techniques. Here, we reveal how some of the major breakthroughs in our quest to unveil the inner workings of stars have come from the most unexpected of places: deep underground. As we celebrate 30 years of activity at the first underground laboratory for nuclear astrophysics, LUNA, we review some of the key milestones and anticipate future opportunities for further advances both at LUNA and at other underground laboratories worldwide.
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Status of Lattice QCD Determination of Nucleon Form Factors and Their Relevance for the Few-GeV Neutrino Program
Vol. 72 (2022), pp. 205–232More LessCalculations of neutrino–nucleus cross sections begin with the neutrino–nucleon interaction, making the latter critically important to flagship neutrino oscillation experiments despite limited measurements with poor statistics. Alternatively, lattice quantum chromodynamics (LQCD) can be used to determine these interactions from the Standard Model with quantifiable theoretical uncertainties. Recent LQCD results of gA are in excellent agreement with data, and results for the (quasi-)elastic nucleon form factors with full uncertainty budgets are expected within a few years. We review the status of the field and LQCD results for the nucleon axial form factor, FA(Q2), a major source of uncertainty in modeling sub-GeV neutrino–nucleon interactions. Results from different LQCD calculations are consistent but collectively disagree with existing models, with potential implications for current and future neutrino oscillation experiments. We describe a road map to solidify confidence in the LQCD results and discuss future calculations of more complicated processes, which are important to few-GeV neutrino oscillation experiments.
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Precision QCD Physics at the LHC
Vol. 72 (2022), pp. 233–258More LessThis review describes the current status of precision quantum chromodynamics (QCD) studies at the LHC. We introduce the main experimental and theoretical methods, and we discuss their cross-stimulated developments and recent advances. The different types of QCD observables that are measured at the LHC, including cross sections and event- and jet-level properties, for various final states, are summarized. Their relation to fundamental QCD dynamics and their impact on Standard Model parameter determinations are discussed using specific examples. The impact of QCD-related observables on direct and indirect searches for rare processes within and New Physics beyond the Standard Model is outlined.
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Probing the Neutrino-Mass Scale with the KATRIN Experiment
Vol. 72 (2022), pp. 259–282More LessThe absolute mass scale of neutrinos is an intriguing open question in contemporary physics. The as-yet-unknown mass of the lightest and, at the same time, most abundant massive elementary particle species bears fundamental relevance to theoretical particle physics, astrophysics, and cosmology. The most model-independent experimental approach consists of precision measurements of the kinematics of weak decays, notably tritium β decay. With the KATRIN experiment, this direct neutrino-mass measurement has entered the sub-eV domain, recently pushing the upper limit on the electron-based neutrino mass down to 0.8 eV (90% CL) on the basis of first-year data out of ongoing, multiyear operations. Here, we review the experimental apparatus of KATRIN, the progress of data taking, and initial results. While KATRIN is heading toward the target sensitivity of 0.2 eV, other scientific goals are pursued. We discuss the search for light sterile neutrinos and an outlook on future keV-scale sterile-neutrino searches as well as further physics opportunities beyond the Standard Model.
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Electroweak Penguin Decays of b-Flavored Hadrons
Vol. 72 (2022), pp. 283–305More LessIn the past decade, electroweak penguin decays have provided a number of precision measurements and have become one of the most competitive ways to search for New Physics describing phenomena beyond the Standard Model. An overview of the measurements made at the B factories and hadron colliders is given, and the experimental methods are presented. Experimental measurements required to provide further insight into present indications of New Physics are discussed.
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Progress in Understanding Short-Range Structure in Nuclei: An Experimental Perspective
Vol. 72 (2022), pp. 307–337More LessHigh-energy electron scattering is a clean, precise probe for measurements of hadronic and nuclear structure and plays a key role in understanding the role of high-momentum nucleons (and quarks) in nuclei. Jefferson Lab has dramatically expanded our knowledge of the high-momentum nucleons generated by short-range correlations, providing sufficient insight to model much of their impact on nuclear structure in neutron stars and in low- to medium-energy scattering observables, including neutrino oscillation measurements. These short-range correlations also seem related to the modification of the quark distributions in nuclei, and efforts to improve our understanding of the internal structure of these short-distance and high-momentum configurations in nuclei will provide important input on a wide range of high-energy observables.
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Short-Lived Nuclides in the Early Solar System: Abundances, Origins, and Applications
Vol. 72 (2022), pp. 339–363More LessSeveral short-lived radionuclides (SLRs) were present in the first few million years of Solar System history. Their abundances have profound impact on the timing of stellar nucleosynthesis events prior to Solar System formation, chronology of events in the early Solar System, early solar activity, heating of early-formed planetesimals, and chronology of planet formation. Isotopic analytical techniques have undergone dramatic improvements in the past decade, leading to tighter constraints on the levels of SLRs in the early Solar System and on the use of these nuclides for detailed chronological studies. This review emphasizes the abundances of SLRs when the Solar System formed and how we know them, and briefly discusses the origins of these nuclides and applications in planetary science.
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High-Energy Extragalactic Neutrino Astrophysics
Vol. 72 (2022), pp. 365–387More LessThe detection of an astrophysical flux of neutrinos in the TeV–PeV energy range by the IceCube Neutrino Observatory has opened new possibilities for the study of extreme cosmic accelerators. The apparent isotropy of the neutrino arrival directions favors an extragalactic origin for this flux, potentially created by a large population of distant sources. Recent evidence for the detection of neutrino emission from extragalactic sources includes the active galaxies TXS 0506+056 and NGC 1068. We here review the current status of the search for the sources of the high-energy neutrino flux, concentrating on its extragalactic contribution. We discuss the implications of these observations for multimessenger studies of cosmic sources and present an outlook for how additional observations by current and future instruments will help address fundamental questions in the emerging field of high-energy neutrino astronomy.
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The Proton Structure in and out of Muonic Hydrogen
Vol. 72 (2022), pp. 389–418More LessLaser spectroscopy of muonic atoms has been recently used to probe properties of light nuclei with unprecedented precision. We introduce nuclear effects in hydrogen-like atoms, nucleon structure quantities (form factors, structure functions, polarizabilities), and their effects in the Lamb shift and hyperfine splitting (HFS) of muonic hydrogen (μH). Updated theory predictions for the Lamb shift and HFS in μH are presented. We review the challenges of the ongoing effort to measure the ground-state HFS in μH and its impact on our understanding of the nucleon spin structure. To narrow down this search, we present a novel theory prediction obtained by scaling the measured HFS in hydrogen while leveraging radiative corrections. We also summarize recent developments in the spectroscopy of simple atomic and molecular systems and emphasize how they allow for precise determinations of fundamental constants, bound-state QED tests, and New Physics searches.
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Novel Quantum Sensors for Light Dark Matter and Neutrino Detection
Vol. 72 (2022), pp. 419–446More LessThe fields of light dark matter and neutrino physics offer compelling signals at recoil energies of eV to even meV, well below the
keV thresholds of many techniques currently employed in these fields. Sensing of such small energies can benefit from the emergence of so-called quantum sensors, which employ fundamentally quantum mechanical phenomena to transduce energy depositions into electrical signals. This review focuses on quantum sensors under development that will enhance and extend the search for “particle-like” interactions of dark matter or enable new measurements of neutrino properties in the coming years.
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Searches for Heavy Resonances with Substructure
Vol. 72 (2022), pp. 447–475More LessIn the past decade, the Large Hadron Collider (LHC) has probed a higher energy scale than ever before. Most models of physics beyond the standard model (BSM) predict the production of new heavy particles; the LHC results have excluded lower masses of such particles. This makes the high-mass regions especially interesting for current and future searches. In most BSM scenarios of interest, the new heavy resonances decay to standard model particles. In a subset of these models, the new particles have large couplings to the top quark, the W and Z bosons, or the Higgs boson. The top quark and W, Z, and Higgs bosons often decay to quarks, giving rise to jets of particles with substructure; event selection based on substructure is used to suppress standard model backgrounds. This review covers the key concepts in experimental searches based on the jet substructure and discusses recent results from the ATLAS and CMS experiments.
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Previous Volumes
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Volume 74 (2024)
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Volume 73 (2023)
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Volume 72 (2022)
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Volume 71 (2021)
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Volume 70 (2020)
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Volume 69 (2019)
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Volume 68 (2018)
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Volume 67 (2017)
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Volume 66 (2016)
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Volume 65 (2015)
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Volume 64 (2014)
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Volume 63 (2013)
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Volume 62 (2012)
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Volume 61 (2011)
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Volume 60 (2010)
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Volume 59 (2009)
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Volume 58 (2008)
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Volume 57 (2007)
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Volume 56 (2006)
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Volume 55 (2005)
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Volume 54 (2004)
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Volume 53 (2003)
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Volume 52 (2002)
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Volume 51 (2001)
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Volume 50 (2000)
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Volume 49 (1999)
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Volume 48 (1998)
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Volume 47 (1997)
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Volume 46 (1996)
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Volume 45 (1995)
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Volume 44 (1994)
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Volume 43 (1993)
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Volume 42 (1992)
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Volume 41 (1991)
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Volume 40 (1990)
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Volume 39 (1989)
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Volume 38 (1988)
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Volume 37 (1987)
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Volume 36 (1986)
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Volume 35 (1985)
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Volume 34 (1984)
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Volume 33 (1983)
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Volume 32 (1982)
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Volume 31 (1981)
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Volume 30 (1980)
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Volume 29 (1979)
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Volume 28 (1978)
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Volume 27 (1977)
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Volume 26 (1976)
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Volume 25 (1975)
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Volume 24 (1974)
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Volume 23 (1973)
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Volume 22 (1972)
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Volume 21 (1971)
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Volume 20 (1970)
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Volume 19 (1969)
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Volume 18 (1968)
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Volume 17 (1967)
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Volume 16 (1966)
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Volume 15 (1965)
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Volume 14 (1964)
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Volume 13 (1963)
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Volume 12 (1962)
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Volume 11 (1961)
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Volume 10 (1960)
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Volume 9 (1959)
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Volume 8 (1958)
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Volume 7 (1957)
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Volume 6 (1956)
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Volume 5 (1955)
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Volume 4 (1954)
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Volume 3 (1953)
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Volume 2 (1953)
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Volume 1 (1952)
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Volume 0 (1932)