Progress in Particle and Nuclear Physics最新文献

{"title":"Shear viscosity of nucleonic matter","authors":"Xian-Gai Deng,&nbsp;De-Qing Fang,&nbsp;Yu-Gang Ma","doi":"10.1016/j.ppnp.2023.104095","DOIUrl":"10.1016/j.ppnp.2023.104095","url":null,"abstract":"<div><p><span>The research status of the shear viscosity of nucleonic matter is reviewed. Some methods to calculate the shear viscosity of nucleonic matter are introduced, including mean free path, Green–Kubo, shear </span>strain rate, Chapman–Enskog and relaxation time approximation. Based on these methods, results for infinite and finite nucleonic matter are discussed, which are attempts to investigate the universality of the ratio of shear viscosity over entropy density and transport characteristics like the liquid–gas phase transition in nucleonic matter. In addition, shear viscosity is also briefly discussed for the quantum chrodynamical matter produced in relativistic heavy-ion collisions.</p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139047626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Electromagnetic transition form factors of baryon resonances","authors":"G. Ramalho ,&nbsp;M.T. Peña","doi":"10.1016/j.ppnp.2024.104097","DOIUrl":"10.1016/j.ppnp.2024.104097","url":null,"abstract":"<div><p><span>Recent experimental and theoretical advancements have led to significant progress in our understanding of the electromagnetic<span> structure of nucleons (</span></span><span><math><mi>N</mi></math></span>), nucleon excitations (<span><math><msup><mrow><mi>N</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span><span>), and other baryons. These breakthroughs have been made possible by the capabilities of modern facilities, enabling the induction of photo- and electro-excitation of nucleon resonances. These experiments have specifically probed the evolution of their electromagnetic structure across a range of squared momentum transfer scales, from </span><span><math><mrow><msup><mrow><mi>Q</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>0</mn><mo>−</mo><mn>0</mn><mo>.</mo><mn>01</mn><mspace></mspace><msup><mrow><mi>GeV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span> up to <span><math><mrow><msup><mrow><mi>Q</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>=</mo><mn>5</mn></mrow></math></span> or <span><math><mrow><mn>8</mn><mspace></mspace><msup><mrow><mi>GeV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span><span>. These experimental advances have sparked notable developments in theoretical approaches. New theoretical methods have been tested and proven to be robust, marking the beginning of a new era in our understanding on baryons. This includes the study of newly discovered exotic hadrons with various multiquark components. We present a comprehensive review of progress in experimental data on </span><span><math><mrow><msup><mrow><mi>γ</mi></mrow><mrow><mo>∗</mo></mrow></msup><mi>N</mi><mo>→</mo><msup><mrow><mi>N</mi></mrow><mrow><mo>∗</mo></mrow></msup></mrow></math></span><span><span> reactions. Additionally, we discuss various analyses and theoretical results, such as quark models in combination (or not) with meson cloud excitations of the baryon quark cores, lattice </span>QCD<span>, Dyson–Schwinger equations, chiral effective field theory, the large </span></span><span><math><msub><mrow><mi>N</mi></mrow><mrow><mi>c</mi></mrow></msub></math></span> limit, and AdS/CFT correspondence, among others. Some of these methods have matured in their predictive power, offering new perspectives on exotic hadrons with multiquark components. We place special emphasis on both the low-<span><math><msup><mrow><mi>Q</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span> and large-<span><math><msup><mrow><mi>Q</mi></mrow><mrow><mn>2</mn></mrow></msup></math></span><span> regions to reinforce crucial physical constraints on observables that hold in these limits. Furthermore, we illustrate that the combination of lattice QCD with chiral effective field theory and quark models, respectively, proves beneficial in interpreting data and applying constraints within those different regimes. As a practical contribution and for future reference, we review the formulas for helicity amplitudes, multipole form factors and the ","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139468887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neutrinos and nucleosynthesis of elements","authors":"Tobias Fischer ,&nbsp;Gang Guo ,&nbsp;Karlheinz Langanke ,&nbsp;Gabriel Martínez-Pinedo ,&nbsp;Yong-Zhong Qian ,&nbsp;Meng-Ru Wu","doi":"10.1016/j.ppnp.2024.104107","DOIUrl":"https://doi.org/10.1016/j.ppnp.2024.104107","url":null,"abstract":"<div><p>Neutrinos are known to play important roles in many astrophysical scenarios from the early period of the big bang to current stellar evolution being a unique messenger of the fusion reactions occurring in the center of our sun. In particular, neutrinos are crucial in determining the dynamics and the composition evolution in explosive events such as core-collapse supernovae and the merger of two neutron stars. In this paper, we review the current understanding of supernovae and binary neutron star mergers by focusing on the role of neutrinos therein. Several recent improvements on the theoretical modeling of neutrino interaction rates in nuclear matter as well as their impact on the heavy element nucleosynthesis in the supernova neutrino-driven wind are discussed, including the neutrino–nucleon opacity at the mean field level taking into account the relativistic kinematics of nucleons, the effect due to the nucleon–nucleon correlation, and the nucleon–nucleon bremsstrahlung. We also review the framework used to compute the neutrino–nucleus interactions and the up-to-date yield prediction for isotopes from neutrino nucleosynthesis occurring in the outer envelope of the supernova progenitor star during the explosion. Here improved predictions of energy spectra of supernova neutrinos of all flavors have had significant impact on the nucleosynthesis yields. Rapid progresses in modeling the flavor oscillations of neutrinos in these environments, including several novel mechanisms for collective neutrino oscillations and their potential impacts on various nucleosynthesis processes are summarized.</p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2024-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140024411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reactor antineutrino flux and anomaly","authors":"Chao Zhang ,&nbsp;Xin Qian ,&nbsp;Muriel Fallot","doi":"10.1016/j.ppnp.2024.104106","DOIUrl":"https://doi.org/10.1016/j.ppnp.2024.104106","url":null,"abstract":"<div><p>Reactor antineutrinos have played a significant role in establishing the standard model of particle physics and the theory of neutrino oscillations. In this article, we review the reactor antineutrino flux and in particular the reactor antineutrino anomaly (RAA) coined over a decade ago. RAA refers to a deficit of the measured antineutrino inverse beta decay rates at very short-baseline reactor experiments compared to the theoretically improved predictions (i.e. the Huber–Mueller model). Since the resolution of several previous experimental anomalies have led to the discovery of non-zero neutrino mass and mixing, many efforts have been invested to study the origin of RAA both experimentally and theoretically. The progress includes the observation of discrepancies in antineutrino energy spectrum between data and the Huber–Mueller model, the re-evaluation of the Huber–Mueller model uncertainties, the potential isotope-dependent rate deficits, and the better agreement between data and new model predictions using the improved summation method. These developments disfavor the hypothesis of a light sterile neutrino as the explanation of RAA and supports the deficiencies of Huber–Mueller model as the origin. Looking forward, more effort from both the theoretical and experimental sides is needed to fully understand the root of RAA and to make accurate predictions of reactor antineutrino flux and energy spectrum for future discoveries.</p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139944977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cosmological phase transitions: From perturbative particle physics to gravitational waves","authors":"Peter Athron ,&nbsp;Csaba Balázs ,&nbsp;Andrew Fowlie ,&nbsp;Lachlan Morris ,&nbsp;Lei Wu","doi":"10.1016/j.ppnp.2023.104094","DOIUrl":"10.1016/j.ppnp.2023.104094","url":null,"abstract":"<div><p><span><span>Gravitational waves (GWs) were recently detected for the first time. This revolutionary discovery opens a new way of learning about </span>particle physics<span><span> through GWs from first-order phase transitions (FOPTs) in the early Universe. FOPTs could occur when new fundamental symmetries are spontaneously broken down to the </span>Standard Model and are a vital ingredient in solutions of the matter anti-matter asymmetry problem. The purpose of our work is to review the path from a particle physics model to GWs, which contains many specialized parts, so here we provide a timely review of all the required steps, including: </span></span><em>(i)</em> building a finite-temperature effective potential in a particle physics model and checking for FOPTs; <em>(ii)</em> computing transition rates; <em>(iii)</em><span> analyzing the dynamics of bubbles of true vacuum expanding in a thermal plasma; </span><em>(iv)</em> characterizing a transition using thermal parameters; and, finally, <em>(v)</em><span> making predictions for GW spectra using the latest simulations and theoretical results and considering the detectability of predicted spectra at future GW detectors. For each step we emphasize the subtleties, advantages and drawbacks of different methods, discuss open questions and review the state-of-art approaches available in the literature. This provides everything a particle physicist needs to begin exploring GW phenomenology.</span></p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138469422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hot QCD phase diagram from holographic Einstein–Maxwell–Dilaton models","authors":"Romulo Rougemont ,&nbsp;Joaquin Grefa ,&nbsp;Mauricio Hippert ,&nbsp;Jorge Noronha ,&nbsp;Jacquelyn Noronha-Hostler ,&nbsp;Israel Portillo ,&nbsp;Claudia Ratti","doi":"10.1016/j.ppnp.2023.104093","DOIUrl":"10.1016/j.ppnp.2023.104093","url":null,"abstract":"<div><p><span><span>In this review, we provide an up-to-date account of quantitative bottom-up holographic descriptions of the strongly coupled quark–gluon plasma (QGP) produced in relativistic heavy-ion collisions, based on the class of gauge-gravity Einstein–Maxwell–Dilaton (EMD) effective models. The holographic approach is employed to tentatively map the QCD<span> phase diagram at finite temperature onto a dual theory of charged, asymptotically Anti-de Sitter (AdS) black holes living in five dimensions. With a quantitative focus on the hot QCD phase diagram, the nonconformal holographic EMD models reviewed here are adjusted to describe first-principles lattice results for the finite-temperature QCD </span></span>equation of state, with </span><span><math><mrow><mn>2</mn><mo>+</mo><mn>1</mn></mrow></math></span><span> flavors and physical quark masses, at zero chemical potential and vanishing electromagnetic fields<span>. We review the evolution of such effective models and the corresponding improvements produced in quantitative holographic descriptions of the deconfined hot QGP phase of QCD. The predictive power of holographic EMD models is tested by quantitatively comparing their predictions for the hot QCD equation of state at nonzero baryon density and the corresponding state-of-the-art lattice QCD results. Hydrodynamic transport coefficients such as the shear and bulk viscosities predicted by these EMD constructions are also compared to the corresponding profiles favored by the latest phenomenological multistage models simultaneously describing different types of heavy-ion data. We briefly report preliminary results from a Bayesian analysis using EMD models, which provide systematic evidence that lattice QCD results at finite temperature and </span></span><em>zero</em> baryon density strongly constrains the free parameters of such bottom-up holographic constructions. Remarkably, the set of parameters constrained by lattice results at vanishing chemical potential turns out to produce EMD models in quantitative agreement with lattice QCD results also at finite baryon density. We also review results for equilibrium and transport properties from magnetic EMD models, which effectively describe the hot and magnetized QGP at finite temperatures and magnetic fields with zero chemical potentials. Finally, we provide a critical assessment of the main limitations and drawbacks of the holographic models reviewed in the present work, and point out some perspectives we believe are of fundamental importance for future developments.</p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2023-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138481482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High precision tests of QCD without scale or scheme ambiguities","authors":"Leonardo Di Giustino ,&nbsp;Stanley J. Brodsky ,&nbsp;Philip G. Ratcliffe ,&nbsp;Xing-Gang Wu ,&nbsp;Sheng-Quan Wang","doi":"10.1016/j.ppnp.2023.104092","DOIUrl":"10.1016/j.ppnp.2023.104092","url":null,"abstract":"<div><p><span>A key issue in making precise predictions in QCD is the uncertainty in setting the renormalization scale </span><span><math><msub><mrow><mi>μ</mi></mrow><mrow><mi>r</mi></mrow></msub></math></span> and thus determining the correct values of the QCD running coupling <span><math><mrow><msub><mrow><mi>α</mi></mrow><mrow><mi>s</mi></mrow></msub><mrow><mo>(</mo><msub><mrow><mi>μ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span> at each order in the perturbative expansion of a QCD observable. It has often been conventional to simply set the renormalization scale to the typical scale of the process <span><math><mi>Q</mi></math></span> and vary it in the range <span><math><mrow><msub><mrow><mi>μ</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>∈</mo><mrow><mo>[</mo><mi>Q</mi><mo>/</mo><mn>2</mn><mo>,</mo><mn>2</mn><mi>Q</mi><mo>]</mo></mrow></mrow></math></span> in order to estimate the theoretical error. This is the practice of Conventional Scale Setting (CSS). The resulting CSS prediction will however depend on the theorist’s choice of renormalization scheme and the resulting pQCD series will diverge factorially. It will also disagree with renormalization scale setting used in QED and electroweak theory thus precluding grand unification. A solution to the renormalization scale-setting problem is offered by the Principle of Maximum Conformality (PMC), which provides a systematic way to eliminate the renormalization scale-and-scheme dependence in perturbative calculations. The PMC method has rigorous theoretical foundations, it satisfies Renormalization Group Invariance (RGI) and preserves all self-consistency conditions derived from the renormalization group. The PMC cancels the renormalon growth, reduces to the Gell-Mann–Low scheme in the <span><math><mrow><msub><mrow><mi>N</mi></mrow><mrow><mi>c</mi></mrow></msub><mo>→</mo><mn>0</mn></mrow></math></span> Abelian limit and leads to scale- and scheme-invariant results. The PMC has now been successfully applied to many high-energy processes. In this article we summarize recent developments and results in solving the renormalization scale and scheme ambiguities in perturbative QCD. In particular, we present a recently developed method the PMC<span><math><msub><mrow></mrow><mrow><mi>∞</mi></mrow></msub></math></span> and its applications, comparing the results with CSS. The method preserves the property of renormalizable SU(N)/U(1) gauge theories defined as <em>Intrinsic Conformality</em> (<em>iCF</em>).</p><p>This property underlies the scale invariance of physical observables and leads to a remarkably efficient method to solve the conventional renormalization scale ambiguity at every order in pQCD.</p><p>This new method reflects the underlying conformal properties displayed by pQCD at NNLO, eliminates the scheme dependence of pQCD predictions and is consistent with the general properties of the PMC. A new method to identify conformal and <span><math><mi>β</mi></mat","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2023-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138438416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring QCD matter in extreme conditions with Machine Learning","authors":"Kai Zhou ,&nbsp;Lingxiao Wang ,&nbsp;Long-Gang Pang ,&nbsp;Shuzhe Shi","doi":"10.1016/j.ppnp.2023.104084","DOIUrl":"10.1016/j.ppnp.2023.104084","url":null,"abstract":"<div><p>In recent years, machine learning has emerged as a powerful computational tool and novel problem-solving perspective for physics, offering new avenues for studying strongly interacting QCD matter properties under extreme conditions. This review article aims to provide an overview of the current state of this intersection of fields, focusing on the application of machine learning to theoretical studies in high energy nuclear physics. It covers diverse aspects, including heavy ion collisions, lattice field theory, and neutron stars, and discuss how machine learning can be used to explore and facilitate the physics goals of understanding QCD matter. The review also provides a commonality overview from a methodology perspective, from data-driven perspective to physics-driven perspective. We conclude by discussing the challenges and future prospects of machine learning applications in high energy nuclear physics, also underscoring the importance of incorporating physics priors into the purely data-driven learning toolbox. This review highlights the critical role of machine learning as a valuable computational paradigm for advancing physics exploration in high energy nuclear physics.</p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138293236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Binary stars in the new millennium","authors":"Xuefei Chen,&nbsp;Zhengwei Liu,&nbsp;Zhanwen Han","doi":"10.1016/j.ppnp.2023.104083","DOIUrl":"10.1016/j.ppnp.2023.104083","url":null,"abstract":"<div><p>Binary stars are as common as single stars. Binary stars are of immense importance to astrophysicists because that they allow us to determine the masses of the stars independent of their distances. They are the cornerstone of the understanding of stellar evolutionary theory and play an essential role in cosmic distance measurement, galactic evolution, nucleosynthesis and the formation of important objects such as cataclysmic variable stars, X-ray binaries, Type Ia supernovae, and gravitational wave-producing double compact objects. In this article, we review the significant theoretical and observational progresses in addressing binary stars in the new millennium. Increasing large survey projects have led to the discovery of enormous numbers of binary stars, which enables us to conduct statistical studies of binary populations, and therefore provide unprecedented insight into the stellar and binary evolution physics. Meanwhile, the rapid development of theoretical concepts and numerical approaches for binary evolution have made a substantial progress on the alleviation of some long-standing binary-related problems such as the stability of mass transfer and common envelope evolution. Nevertheless, it remains a challenge to have a full understanding of fundamental problems of stellar and binary astrophysics. The upcoming massive survey projects and increasingly sophisticated computational methods will lead to future progress.</p></div>","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146641023000649/pdfft?md5=aff98a5df6b4d91a26d359a2563e7dba&pid=1-s2.0-S0146641023000649-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71506513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The gallium anomaly","authors":"S.R. Elliott ,&nbsp;V.N. Gavrin ,&nbsp;W.C. Haxton","doi":"10.1016/j.ppnp.2023.104082","DOIUrl":"10.1016/j.ppnp.2023.104082","url":null,"abstract":"<div><p>In order to test the end-to-end operations of gallium solar neutrino experiments, intense electron-capture sources were fabricated to measure the responses of the radiochemical SAGE and GALLEX/GNO detectors to known fluxes of low-energy neutrinos. Such tests were viewed at the time as a cross-check, given the many tests of ⁷¹Ge recovery and counting that had been routinely performed, with excellent results. However, the four ⁵¹Cr and ³⁷Ar source experiments yielded rates below expectations, a result commonly known as the Ga anomaly. As the intensity of the electron-capture sources can be measured to high precision, the neutrino lines they produce are fixed by known atomic and nuclear rates, and the neutrino absorption cross section on ⁷¹Ga is tightly constrained by the lifetime of ⁷¹Ge, no simple explanation for the anomaly has been found. To check these calibration experiments, a dedicated experiment BEST was performed, utilizing a neutrino source of unprecedented intensity and a detector optimized to increase statistics while providing some information on counting rate as a function of distance from the source. The results BEST obtained are consistent with the earlier solar neutrino calibration experiments, and when combined with those measurements, yield a Ga anomaly with a significance of approximately 4<span><math><mi>σ</mi></math></span>, under conservative assumptions. But BEST found no evidence of distance dependence and thus no explicit indication of new physics. In this review we describe the extensive campaigns carried out by SAGE, GALLEX/GNO, and BEST to demonstrate the reliability and precision of their experimental procedures, including ⁷¹Ge recovery, counting, and analysis. We also describe efforts to define uncertainties in the neutrino capture cross section, which now include estimates of effects at the <span><math><mrow><mo>≲</mo><mn>0</mn><mo>.</mo><mn>5</mn></mrow></math></span>% level such as radiative corrections and weak magnetism. With the results from BEST, an anomaly remains even if one retains only the transition to the ⁷¹Ge ground state, whose strength is fixed by the known lifetime of ⁷¹Ge. We then consider the new-physics solution most commonly suggested to resolve the Ga anomaly, oscillations into a sterile fourth neutrino, <span><math><mrow><msub><mrow><mi>ν</mi></mrow><mrow><mi>e</mi></mrow></msub><mo>→</mo><msub><mrow><mi>ν</mi></mrow><mrow><mi>s</mi></mrow></msub></mrow></math></span>. We find such a solution generates substantial tension with several null experiments, owing to the large mixing angle required. While this does not exclude such solutions – the sterile sector might include multiple neutrinos as well as new interactions – it shows the need for more experimental constraints, if we are to make progress in resolving the Ga and other low-energy neutrino anomalies. We conclude by consider the role future low-e","PeriodicalId":412,"journal":{"name":"Progress in Particle and Nuclear Physics","volume":null,"pages":null},"PeriodicalIF":9.6,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0146641023000637/pdfft?md5=6095ff5f92e1bbbd29a5ca4f20f766c0&pid=1-s2.0-S0146641023000637-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71506507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}