1,720,989 research outputs found
Structure Formation Limits on Axion-Like Dark Matter
No full textWe derive structure formation limits on dark matter (DM) composed of keV-scaleaxion-like particles (ALPs), produced via freeze-in through the interactions with photonsand Standard Model (SM) fermions. We employ Lyman-alpha (Ly-α) forest data sets aswell as the observed number of Milky Way (MW) subhalos. We compare results obtainedusing Maxwell-Boltzmann and quantum statistics for describing the SM bath. It should beemphasized that the presence of logarithmic divergences complicates the calculation of theproduction rate, which can not be parameterized with a simple power law behaviour. Theobtained results, in combination with X-ray bounds, exclude the possibility for a photophilic“frozen-in” ALP DM with mass below∼19 keV. For the photophobic ALP scenario, inwhich DM couples primarily to SM fermions, the ALP DM distribution function is peaked atsomewhat lower momentum and hence for such realization we find weaker limits on DM mass.Future facilities, such as the upcoming Vera C. Rubin observatory, will provide measurementswith which the current bounds can be significantly improved to∼80 keV
The Neutrino Magnetic Moment Portal: Cosmology, Astrophysics, and Direct Detection
Get PDFWe revisit the physics of neutrino magnetic moments, focusing in particular on the case where the right-handed, or sterile, neutrinos are heavier (up to several MeV) than the left-handed Standard Model neutrinos. The discussion is centered around the idea of detecting an upscattering event mediated by a transition magnetic moment in a neutrino or dark matter experiment. Considering neutrinos from all known sources, as well as including all available data from XENON1T and Borexino, we derive the strongest up-to-date exclusion limits on the active-to-sterile neutrino transition magnetic moment. We then study complementary constraints from astrophysics and cosmology, performing, in particular, a thorough analysis of BBN . We find that these data sets scrutinize most of the relevant parameter space. Explaining the XENON1T excess with transition magnetic moments is marginally possible if very conservative assumptions are adopted regarding the supernova 1987 A and CMB constraints. Finally, we discuss model-building challenges that arise in scenarios that feature large magnetic moments while keeping neutrino masses well below 1 eV. We present a successful ultraviolet-complete model of this type based on TeV-scale leptoquarks, establishing links with muon magnetic moment, B physics anomalies, and collider searches at the LHC.We revisit the physics of neutrino magnetic moments, focusing in particular on the case where the right-handed, or sterile, neutrinos are heavier (up to several MeV) than the left-handed Standard Model neutrinos. The discussion is centered around the idea of detecting an upscattering event mediated by a transition magnetic moment in a neutrino or dark matter experiment. Considering neutrinos from all known sources, as well as including all available data from XENON1T and Borexino, we derive the strongest up-to-date exclusion limits on the active-to-sterile neutrino transition magnetic moment. We then study complementary constraints from astrophysics and cosmology, performing, in particular, a thorough analysis of BBN. We find that these data sets scrutinize most of the relevant parameter space. Explaining the XENON1T excess with transition magnetic moments is marginally possible if conservative assumptions are adopted regarding the supernova 1987A and CMB constraints. Finally, we discuss model-building challenges that arise in scenarios that feature large magnetic moments while keeping neutrino masses well below 1 eV. We present a successful ultraviolet-complete model of this type based on TeV-scale leptoquarks, establishing links with muon magnetic moment, B physics anomalies, and collider searches at the LHC
BSM Explanation of the 5 MeV Bump in the Reactor Antineutrino Spectrum
No full textWe address the 5 MeV event excess in the measured antineutrino spectrum from nuclear reactors in a beyond the Standard model framework, a challenge which has not been met to date. We employ nonstandard neutrino interactions with baryons that can induce the reaction 13C(\overline{\nu}, \overline{\nu}^\prime n)12C in organic scintillator detectors. The de-excitation of 12C yields a prompt 4.4 MeV photon, while the thermalization of the product neutron causes proton recoils, which in turn yield an additional prompt energy contribution with finite width such that this process can mimic neutrinos at around 5 MeV energy. We find that the minimal viable model that could induce this reaction involves a sterile neutrino charged under an Abelian symmetry group. Such sterile neutrinos can simultaneously explain the discrepancy between the measured and predicted antineutrino fluxes at short-baseline reactor experiments
Short Baseline Oscillations and the Gallium Mystery
No full textData from several neutrino experiments suggest an anomalous neutrino flavor transition across relatively short baselines which is in conflict with the three-flavor neutrino oscillation paradigm. In particular, MiniBooNE and BEST collaborations have reported anomalous findings at . In this contribution, such measurements and their possible explanations within and beyond the Standard Model are discussed
Seeking New Physics at Neutrino Oscillation Experiments
No full textOne of the most important achievements in the field of particle physics was the discovery of neutrino oscillations. Neutrino oscillation experiments still have a lot to offer, primarily the discovery of CP violation in the lepton sector is anticipated. In addition to solving the remaining puzzles in the standard three-neutrino framework, neutrino experiments are also sensitive to new physics effects that could appear in the process of neutrino production, propagation and/or detection. We discuss a novel class of new physics realizations, testable already at present-day acceleration based experiments such as NOvA and T2K. The idea is based on the fact that neutrino mixing parameters at the scale of neutrino production and neutrino detection do not necessarily need to coincide given that they are subject to renormalization group effects. This mismatch between the leptonic mixing matrix at different scales changes the neutrino oscillation phenomenology by inducing a number of new signatures, some of which are discussed here
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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