Search

The search for neutrino events in correlation with gravitational wave (GW) events for three observing runs (O1, O2 and O3) from 09/2015 to 03/2020 has been performed using the Borexino data-set of the same period. We have searched for signals of neutrino-electron scattering with visible energies above 250 keV within a time window of 1000 s centered at the detection moment of a particular GW event. The search was done with three visible energy thresholds of 0.25, 0.8 and 3.0 MeV.Two types of incoming neutrino spectra were considered: the mono-energetic line and the spectrum expected from supernovae. The same spectra were considered for electron antineutrinos detected through inverse beta-decay (IBD) reaction. GW candidates originated by merging binaries of black holes (BHBH), neutron stars (NSNS) and neutron star and black hole (NSBH) were analysed separately. Additionally, the subset of most intensive BHBH mergers at closer distances and with larger radiative mass than the rest was considered. In total, follow-ups of 74 out of 93 gravitational waves reported in the GWTC-3 catalog were analyzed and no statistically significant excess over the background was observed. As a result, the strongest upper limits on GW-associated neutrino and antineutrino fluences for all flavors (\nu_e, \nu_\mu, \nu_\tau) have been obtained in the (0.5 - 5.0) MeV neutrino energy range., Comment: 13 pages, 8 figures

International audience; The Jiangmen Underground Neutrino Observatory (JUNO), the first multi-kton liquid scintillator detector, which is under construction in China, will have a unique potential to perform a real-time measurement of solar neutrinos well below the few MeV threshold typical for Water Cherenkov detectors. JUNO's large target mass and excellent energy resolution are prerequisites for reaching unprecedented levels of precision. In this paper, we provide estimation of the JUNO sensitivity to 7Be, pep, and CNO solar neutrinos that can be obtained via a spectral analysis above the 0.45 MeV threshold. This study is performed assuming different scenarios of the liquid scintillator radiopurity, ranging from the most opti mistic one corresponding to the radiopurity levels obtained by the Borexino experiment, up to the minimum requirements needed to perform the neutrino mass ordering determination with reactor antineutrinos - the main goal of JUNO. Our study shows that in most scenarios, JUNO will be able to improve the current best measurements on 7Be, pep, and CNO solar neutrino fluxes. We also perform a study on the JUNO capability to detect periodical time variations in the solar neutrino flux, such as the day-night modulation induced by neutrino flavor regeneration in Earth, and the modulations induced by temperature changes driven by helioseismic waves.

Since the beginning of 2012, the Borexino collaboration has been reporting precision measurements of the solar neutrino fluxes, emitted in the proton-proton chain and in the Carbon-Nitrogen-Oxygen cycle. The experimental sensitivity achieved in Phase-II and Phase-III of the Borexino data taking made it possible to detect the annual modulation of the solar neutrino interaction rate due to the eccentricity of Earth's orbit, with a statistical significance greater than 5$\sigma$. This is the first precise measurement of the Earth's orbital parameters based solely on solar neutrinos and an additional signature of the solar origin of the Borexino signal. The complete periodogram of the time series of the Borexino solar neutrino detection rate is also reported, exploring frequencies between one cycle/year and one cycle/day. No other significant modulation frequencies are found. The present results were uniquely made possible by Borexino's decade-long high-precision solar neutrino detection., Comment: 12 pages, 10 figures

The study of very low energy neutrinos requires a suppression of the natural radioactivity up to ultra-traces level. This is what the Borexino experiment succeeded to achieve with the development of technologies for liquid purification and non-standard approaches in constructing and assembling the detector, allowing a threshold down to 50 keV. Thanks to these measures, the entire solar neutrino spectrum has been detected, neglecting the hep neutrinos which account for less than 10 − 5 of the total flux, together with a small, but clean and robust geoneutrino signal; they represent new achievements in the physics of the Sun, the stars and neutrinos, and they open new horizons in the study of the Earth’s interior too. This report describes the technology employed to achieve these goals and the results obtained throughout more than 10 years of data collection. Among the results, actual breakthroughs can be counted: the identification of the nuclear reactions which produce 99% of solar energy and consequently solar luminosity, combined with the demonstration of the solar stability on a 105 years scale; the confirmation of the Standard Solar Model predictions through the measured neutrino fluxes, leading the way for a significant indication in favor of the high metallicity composition of the Sun; the independent demonstration of the validity of the MSW neutrino oscillation solution, through the determination in a single experiment of the distinctive transition of the electron neutrino survival probability from the matter to the vacuum regime; and finally the achievement of the first experimental evidence of the CNO cycle, which dominates in the stars. To this date BOREXINO is a unique experiment with its unprecedented radiopurity level, achieved by means of innovative techniques, which have now become a standard reference for the whole physics field of rare events search.

The European physical journal / C 82(3), 278 (2022). doi:10.1140/epjc/s10052-022-10197-0, The search for neutrino events in correlation with 42 most intense fast radio bursts (FRBs) has been performed using the Borexino dataset from 05/2007 to 06/2021. We have searched for signals with visible energies above 250 keV within a time window of ±1000 s corresponding to detection time of a particular FRB. We also applied an alternative approach based on searching for specific shapes of neutrino-electron scattering spectra in the full exposure data of the Borexino detector. In particular, two incoming neutrino spectra were considered: the monoenergetic line and the spectrum expected from supernovae. The same spectra were considered for electron antineutrinos detected through inverse beta-decay reaction. No statistically significant excess over the background was observed. As a result, the strongest upper limits on FRB-associated neutrino fluences of all flavors have been obtained in the 0.5–50 MeV neutrino energy range., Published by Springer, Heidelberg

Proceedings of 37th International Cosmic Ray Conference - Sissa Medialab Trieste, Italy, 2021 37th International Cosmic Ray Conference, PoS(ICRC2021), Berlin, Germany - Online, 12 Jul 2021 - 23 Jul 2021; Sissa Medialab Trieste, Italy (2021). doi:10.22323/1.395.1109, The Borexino experiment has recently provided the first direct experimental evidence of the sub-dominant CNO-cycle in the Sun, which is assumed to be the main energy production mechanism in heavier stars. Borexino is a liquid scintillator detector located at the Laboratori Nazionali del Gran Sasso, Italy with the main goal to measure solar neutrinos. The extreme radiopurity of the scintillator and the successful thermal stabilisation of the detector have proven to be valuable assets in the quest for CNO neutrinos.The low abundance of CNO neutrinos and the similarity of its spectral shape to that of \emph{pep} solar neutrinos and the intrinsic 210Bi background, make CNO neutrino detection challenging. Therefore, it is necessary to constrain these backgrounds independently. The energy and radial distribution of the events can then be exploited to perform a multivariate fit, which requires a careful evaluation of the systematic uncertainty associated with the Monte-Carlo spectral shapes used. Borexino has successfully rejected the null hypothesis of CNO-cycle neutrinos in the Sun with greater than 5.0σ significance with 99% C.L. This article will present the overview of the strategy and methods used to achieve this result and the consequence of this result for solar and stellar physics., Published by Sissa Medialab Trieste, Italy

Dissertation, RWTH Aachen University, 2022; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2022). = Dissertation, RWTH Aachen University, 2022, The work presented in this dissertation is centered around the recent geoneutrino and solar neutrino measurements carried out with the Borexino experiment at the Laboratori Nazionali del Gran Sasso. The improved geoneutrino measurement includes a substantial increase in the precision and the rejection of the no-mantle signal with a very high significance. These results have been achieved through my different contributions, such as the optimisation of the event selection cuts, evaluation of the several non-antineutrino backgrounds, estimation of the systematic uncertainties, as well as the refinement and execution of the final spectral fits. The results have been also validated using sensitivity studies. A comprehensive overview of this analysis and the final results have been published by the Borexino collaboration in Physical Review D and this article has been co-written by me. The latest solar neutrino measurements of Borexino include the first experimental evidence of the Carbon-Nitrogen-Oxygen (CNO) cycle in the Sun and the first directional measurement of sub-MeV solar neutrinos. For the analysis of CNO neutrinos, the primary contribution presented in this thesis is the estimation of the upper limit on the Bi-210 background rate, which is crucial for the observation of the rare CNO solar neutrinos. Furthermore, the CNO rate has been obtained through a multivariate spectral fit, along with an assessment of the systematic uncertainty arising from the fit parameters. These results containing my contributions have been published by the Borexino collaboration in Nature. This dissertation also presents the upgraded Bi-210 upper limit, as well as the multivariate fit results using the newly acquired, highly stable, and final data set of Borexino. Finally, I present my work regarding the directional measurement which comprises calibration of the Cherenkov light in Borexino Monte-Carlo utilising gamma sources, optimisation of the event selection, validation and improvement of the analysis strategy, estimation of the systematic uncertainties, as well as the execution of the final fits to obtain the solar neutrino signal and the Be-7 solar neutrino rate. This measurement by the Borexino collaboration has been accepted for a joint-publication in Physical Review Letters and Physical Review D and these articles have been co-written by me., Published by RWTH Aachen University, Aachen

Dissertation, RWTH Aachen University, 2022; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2023). = Dissertation, RWTH Aachen University, 2022, The Sun is powered through different fusion processes that can be grouped in two categories: the \textit{pp}-chain and the CNO cycle. Building a theory of the balance between gravitational and radiation forces is difficult, not least because almost all of the information about the Sun can only be gathered at a surface level. Particle physics however predicts that the two aforementioned processes emit different kinds of neutrinos: \textit{solar neutrinos}. While their elusive nature makes them extremely difficult to detect, the same property allows them to escape from the solar core. They are the only direct probe of the solar core's internal processes and their measurement on Earth represents a tremendous experimental and theoretical success. This thesis explores methods related to the experimental challenges of measuring CNO neutrinos. These neutrinos constitute less than one percent of the Sun's neutrino output but their generating process is thought to be the main source of stellar energy in our universe. The findings in this thesis led in part to the first experimental evidence for CNO neutrinos with the Borexino detector, which was published in Nature. Another part of this thesis focuses on JUNO's expected sensitivity to solar neutrinos. JUNO is a very large liquid scintillator currently under construction in south China and is shown in this thesis to have the potential for unprecedentedly precise solar neutrino measurements. These sensitivity studies are also currently under preparation for publication. Finally, this thesis encompasses work with the OSIRIS detector, a pre-detector for JUNO which will make sure its liquid scintillator doesn't exceed certain levels of contamination - which could dismantle its sensitivity not only to its main goal of measuring the neutrino mass hierarchy with $3\sigma$ in six years, but also severely hinder its solar neutrino measurements. The first part of this section is about developing a source calibration program which will perform all of OSIRIS's calibration needs: energy reconstruction, vertex reconstruction, charge reconstruction, and inter-PMT time offsets on a sub-nano-second scale. It will also be used to monitor OSIRIS's scintillator for time-dependent changes thus providing fast feedback. The results presented in this thesis are also currently being implemented in a paper which is planned to be published once the first calibration data has been measured. In the second part of this section, OSIRIS's sensitivity to its main goal of measuring $^{238}$U and $^{232}$Th in the liquid scintillator is calculated with an improved analysis compared to existing ones. The results on OSIRIS's sensitivity to its main goal and to $^{85}$Kr were already published in the European Physical Journal C as part of an overall design and sensitivity review., Published by RWTH Aachen University, Aachen

Physical review / D 105(5), 052002 (2022). doi:10.1103/PhysRevD.105.052002, Liquid scintillator detectors play a central role in the detection of neutrinos from various sources. In particular, it is the only technique used so far for the precision spectroscopy of sub-MeV solar neutrinos, as demonstrated by the Borexino experiment at the Gran Sasso National Laboratory in Italy. The benefit of a high light yield, and thus a low energy threshold and a good energy resolution, comes at the cost of the directional information featured by water Cherenkov detectors, measuring 8B solar neutrinos above a few MeV. In this paper we provide the first directionality measurement of sub-MeV solar neutrinos which exploits the correlation between the first few detected photons in each event and the known position of the Sun for each event. This is also the first signature of directionality in neutrinos elastically scattering off electrons in a liquid scintillator target. This measurement exploits the subdominant, fast Cherenkov light emission that precedes the dominant yet slower scintillation light signal. Through this measurement, we have also been able to extract the rate of 7Be solar neutrinos in Borexino. The demonstration of directional sensitivity in a traditional liquid scintillator target paves the way for the possible exploitation of the Cherenkov light signal in future kton-scale experiments using liquid scintillator targets. Directionality is important for background suppression as well as the disentanglement of signals from various sources., Published by Inst., Melville, NY

We present an improved measurement of the CNO solar neutrino interaction rate at Earth obtained with the complete Borexino Phase-III dataset. The measured rate R$_{\rm CNO}$ = $6.7^{+2.0}_{-0.8}$ counts/(day$ \cdot$ 100 tonnes), allows us to exclude the absence of the CNO signal with about 7$\sigma$ C.L. The correspondent CNO neutrino flux is $6.6^{+2.0}_{-0.9} \times 10^8$ cm$^{-2}$ s$^{-1}$, taking into account the neutrino flavor conversion. We use the new CNO measurement to evaluate the C and N abundances in the Sun with respect to the H abundance for the first time with solar neutrinos. Our result of $N_{\rm CN}$ = $(5.78^{+1.86}_{-1.00})\times10^{-4}$ displays a $\sim$2$\sigma$ tension with the "low metallicity" spectroscopic photospheric measurements. On the other hand, our result used together with the $^7$Be and $^8$B solar neutrino fluxes, also measured by Borexino, permits to disfavour at 3.1$\sigma$ C.L. the "low metallicity" SSM B16-AGSS09met as an alternative to the "high metallicity" SSM B16-GS98., Comment: 8 pages, 6 figures

The Borexino collaboration observed an excess of the counting rate over the expected counting rate of events from CNO-ν. This result is consistent with the prediction of the Hydridic Earth Model on the contribution of 40K geo-antineutrino scattering on electrons to single Borexino events. The proportion of potassium in the Earth 1.5 ± 1.0% of the Earth’s mass is the most likely value that provides the observed excess of the counting rate.

The European physical journal / C 81(12), 1075 (2021). doi:10.1140/epjc/s10052-021-09799-x, Cosmogenic radio-nuclei are an important source of background for low-energy neutrino experiments. In Borexino, cosmogenic 11C decays outnumber solar pep and CNO neutrino events by about ten to one. In order to extract the flux of these two neutrino species, a highly efficient identification of this background is mandatory. We present here the details of the most consolidated strategy, used throughout Borexino solar neutrino measurements. It hinges upon finding the space-time correlations between 11C decays, the preceding parent muons and the accompanying neutrons. This article describes the working principles and evaluates the performance of this Three-Fold Coincidence (TFC) technique in its two current implementations: a hard-cut and a likelihood-based approach. Both show stable performances throughout Borexino Phases II (2012���2016) and III (2016���2020) data sets, with a 11C tagging efficiency of ���90 % and ��� 63���66 % of the exposure surviving the tagging. We present also a novel technique that targets specifically 11C produced in high-multiplicity during major spallation events. Such 11C appear as a burst of events, whose space-time correlation can be exploited. Burst identification can be combined with the TFC to obtain about the same tagging efficiency of ���90% but with a higher fraction of the exposure surviving, in the range of ��� 66���68 %., Published by Springer, Heidelberg

The cycle’s catalytic reactions account for just 1% of the Sun’s energy, but they are the dominant energy producers in heavier stars.

Context: The Sun is by far a privileged target for testing stellar models with unique precision. A recent concern appeared with the progress in the solar surface abundances derivation that has led to a decrease of the solar metallicity. While the ancient high-metallicity models were in fair agreement with other solar observational indicators, it is no longer the case for low-metallicity models. Recent collection of data are however promising to shed a new light on it. For instance, the Borexino collaboration released in 2020 the first-ever complete estimate of neutrinos emitted in the CNO cycle. It has reaffirmed the role of the neutrino constraints in the solar modelling process and its associated issues. In parallel, newly claimed detection of solar gravity modes of oscillations offers another opportunity of probing the stratification in the Sun's central layers. Aims: We propose to combine the diagnoses from neutrinos and helioseismology, both from pressure and gravity modes, for assessing the predictions of solar models. We compare in detail the different physical prescriptions currently at disposal for stellar model computations. Results: The CNO neutrino flux confirms a preference for high-metallicity models. Nevertheless, we found that mild modification of the nuclear screening factors can re-match low-metallicity model predictions to observed fluxes, although it does not restore the agreement with the helioseismic frequency ratios. Neither the high-metallicity or low-metallicity models are able to reproduce the gravity-mode period spacing. The disagreement is huge, more than 100$\sigma$ to the reported value. Reversely, the family of standard models narrows the expected range of the Sun's period spacing: between $\sim$2150 to $\sim$2190~s. Moreover, we show this indicator can constrain the chemical mixture, opacity, and to a lower extent nuclear reactions in solar models., Comment: 18 pages, 10 figures, accepted for publications in Astronomy and Astrophysics

Reactor neutrino experiments provide a rich environment for the study of axionlike particles (ALPs). Using the intense photon flux produced in the nuclear reactor core, these experiments have the potential to probe ALPs with masses below 10 MeV. We explore the feasibility of these searches by considering ALPs produced through Primakoff and Compton-like processes as well as nuclear transitions. These particles can subsequently interact with the material of a nearby detector via inverse Primakoff and inverse Compton-like scatterings, via axio-electric absorption, or they can decay into photon or electron-positron pairs. We demonstrate that reactor-based neutrino experiments have a high potential to test ALP-photon couplings and masses, currently probed only by cosmological and astrophysical observations, thus providing complementary laboratory-based searches. We furthermore show how reactor facilities will be able to test previously unexplored regions in the $\sim$MeV ALP mass range and ALP-electron couplings of the order of $g_{aee} \sim 10^{-8}$ as well as ALP-nucleon couplings of the order of $g_{ann}^{(1)} \sim 10^{-9}$, testing regions beyond TEXONO and Borexino limits., 40 pages, 13 figures, 4 tables. SN1987A and Globular Cluster stars limits updated, references added

Liquid xenon is one of the leading targets to search for dark matter via its elastic scattering on nuclei or electrons. Due to their low-threshold and low-background capabilities, liquid xenon detectors can also detect coherent elastic neutrino–nucleus scattering (CEνNS) or neutrino–electron scattering. In this paper, we investigate the feasibility of a compact and movable liquid xenon detector with an active target mass of O(10∼100) kg and single-electron sensitivity to detect CEνNS from anti-neutrinos from a nuclear reactor. Assuming a single- and few-electron background rate at the level achieved by the XENON10/100 experiments, we expect a 5-σ detection of CEνNS with less than 400 kg-days of exposure. We further investigate the sensitivity of such a detector to neutrino magnetic moment with neutrino electron scattering. If an electronic recoil background rate of 0.01∼0.1 events/keV/kg/day above 1 keV can be achieved with adequate shielding, a liquid xenon detector can reach a neutrino magnetic moment sensitivity of 10−11μB, which would improve upon the current most-constraining laboratory limits from the GEMMA and Borexino experiments. Additionally, such a detector would be able to probe the region compatible with a magnetic moment interpretation of the low-energy excess electronic recoil events recently reported by XENON1T.

Time Laboratories are facilities typically hosted at National Metrology Institutes and Astronomical Observatories, aimed at developing and operating innovative methods and techniques for the generation and measurement of accurate time and time intervals. For Italy, this role is carried out by INRIM Time Laboratory, whose main tasks are related to the contribution to the realization of TAI/UTC international time scales by the BIPM, and to the generation of UTC(IT), the Italian Standard Time. Its dissemination to final users through NTP and White Rabbit technique, the regular provision of Certification Services for the Italian industries under the CIPM Mutual Recognition Agreement, together with the participation to the design and development of the timing aspects of the Galileo system, represent the main contributions provided by the Laboratory towards the national and international high-level production sectors. However, in such a context, also low-level research activities become crucial, aimed at improving Laboratory’s metrological capabilities, as well as supporting a wide-range of scientific experiments requiring accurate time. Concerning the latter aspect, INRIM Time Laboratory provided its support to important Particle Physics and Astrophysics experiments over the years, namely Borexino for the measurement of the neutrino velocity over the CERN-Gran Sasso baseline, in 2012, and EEE (Extreme Energy Events) for the detection of high-energy cosmic showers, in 2020. In this work, we present a general overview about the importance of timing in Particle Physics and Astrophysics communities, retracing the INRIM Time Laboratory experiences with Borexino, EEE, and the White Rabbit time dissemination. We will analyze the timing requirements of three representative experiments of both communities. ATLAS (A Toroidal LHC ApparatuS), one of the four LHC experiments at CERN, CTA (Cherenkov Telescope Array) for the study of high-energy gamma ray space sources, and the LIGO-VIRGO interferometers, for the detection of gravitational waves. The experiences gained by the Laboratory over the years, together with the studies conducted on the aforementioned experiments and possibly on others, would strengthen the relationships between the time community and the ones dealing with fundamental physics, relationships that could become even more synergistic, yielding to common benefits, also with the well-known interaction on the White Rabbit technique.

The couplings between the neutrinos and exotic fermion can be probed in both neutrino scattering experiments and dark matter direct detection experiments. We present a detailed analysis of the general neutrino interactions with an exotic fermion and electrons at neutrino-electron scattering experiments. We obtain the constraints on the coupling coefficients of the scalar, pseudoscalar, vector, axialvector, tensor and electromagnetic dipole interactions from the CHARM-II, TEXONO and Borexino experiments. For the flavor-universal interactions, we find that the Borexino experiment sets the strongest bounds in the low mass region for the electromagnetic dipole interactions, and the CHARM-II experiment dominates the bounds for other scenarios. If the interactions are flavor dependent, the bounds from the CHARM-II or TEXONO experiment can be avoided, and there are correlations between the flavored coupling coefficients for the Borexino experiment. We also discuss the detection of sub-MeV DM absorbed by bound electron targets and illustrate that the vector coefficients preferred by XENON1T data is allowed by the neutrino experiments., 18 pages, 5 figures, 1 table. Version published in JHEP

The fundamental processes by which nuclear energy is generated in the Sun have been known for many years. However, continuous progress in areas such as neutrino experiments, stellar spectroscopy and helioseismic data and techniques requires ever more accurate and precise determination of nuclear reaction cross sections, a fundamental physical input for solar models. In this work, we review the current status of (standard) solar models and present a detailed discussion on the relevance of nuclear reactions for detailed predictions of solar properties. In addition, we also provide an analytical model that helps understanding the relation between nuclear cross sections, neutrino fluxes and the possibility they offer for determining physical characteristics of the solar interior. The latter is of particular relevance in the context of the conundrum posed by the solar composition, the solar abundance problem, and in the light of the first ever direct detection of solar CN neutrinos recently obtained by the Borexino collaboration. Finally, we present a short list of wishes about the precision with which nuclear reaction rates should be determined to allow for further progress in our understanding of the Sun., Comment: 29 pages, Review article prepared for Research Topic "Nuclear reactions of astrophysical interest", Front. Astron. Space Sci

The review is conceived to help the reader to interpret present geoneutrino results in the framework of Earth's energetics and composition. Starting from the comprehension of antineutrino production, propagation, and detection, the status of the geoneutrino field is presented through the description of the experimental and technological features of the Borexino and KamLAND ongoing experiments. The current understanding of the energetical, geophysical and geochemical traits of our planet is examined in a critical analysis of the currently available models. By combining theoretical models and experimental results, the mantle geoneutrino signal extracted from the results of the two experiments demonstrates the effectiveness in investigating deep earth radioactivity through geoneutrinos from different sites. The obtained results are discussed and framed in the puzzle of the diverse classes of formulated Bulk Silicate Earth models, analyzing their implications on planetary heat budget and composition. As a final remark, we present the engaging technological challenges and the future experiments envisaged for the next decade in the geoneutrino field., Comment: Submitted to "La Rivista del Nuovo Cimento"

Constraints on the indirect detection of dark matter are usually obtained from observations of astrophysical objects -- the Galactic Center, dwarf galaxies, M31, etc. Here we propose instead to look for the annihilation or decay of dark matter particles taking place inside detectors searching \emph{directly} for dark matter or in large neutrino experiments. We show that the data from XENON1T and Borexino set limits on the annihilation and decay rate of dark matter particles with masses in the keV to few MeV range. All relevant final states are considered: annihilation into $\gamma\gamma$ and $e^-e^+$, and decays into $\gamma\gamma$, $\gamma\nu$ and $e^-e^+$. The expected sensitivities in XENONnT, DARWIN, JUNO and THEIA are also computed. Though weaker than current astrophysical bounds, the laboratory limits (and projections) obtained are free from the usual astrophysical uncertainties associated with $J$-factors and unknown backgrounds, and may thus offer a complementary probe of the dark matter properties. We point out that current and future (astro)particle physics detectors might also be used to set analogous limits for different decays and dark matter masses above a few MeV., Comment: 13 pages, 6 figures

With large active volume sizes dark matter direct detection experiments are sensitive to solar neutrino fluxes. Nuclear recoil signals are induced by $^8$B neutrinos, while electron recoils are mainly generated by the pp flux. Measurements of both processes offer an opportunity to test neutrino properties at low thresholds with fairly low backgrounds. In this paper we study the sensitivity of these experiments to neutrino magnetic dipole moments assuming 1, 10 and 40 tonne active volumes (representative of XENON1T, XENONnT and DARWIN), 0.3 keV and 1 keV thresholds. We show that with nuclear recoil measurements alone a 40 tonne detector could be as competitive as Borexino, TEXONO and GEMMA, with sensitivities of order $8.0\times 10^{-11}\,\mu_B$ at the $90\%$ CL after one year of data taking. Electron recoil measurements will increase sensitivities way below these values allowing to test regions not excluded by astrophysical arguments. Using electron recoil data and depending on performance, the same detector will be able to explore values down to $4.0\times 10^{-12}\mu_B$ at the $90\%$ CL in one year of data taking. By assuming a 200-tonne liquid xenon detector operating during 10 years, we conclude that sensitivities in this type of detectors will be of order $10^{-12}\,\mu_B$. Reducing statistical uncertainties may enable improving sensitivities below these values., Comment: 9 pages, 5 figures

Models of gauged $U(1)_{L_\mu-L_\tau}$ can provide a solution to the long-standing discrepancy between the theoretical prediction for the muon anomalous magnetic moment and its measured value. The extra contribution is due to a new light vector mediator, which also helps to alleviate an existing tension in the determination of the Hubble parameter. In this article, we explore ways to probe this solution via the scattering of solar neutrinos with electrons and nuclei in a range of experiments and considering high and low solar metallicity scenarios. In particular, we reevaluate Borexino constraints on neutrino-electron scattering, finding them to be more stringent than previously reported, and already excluding a part of the $(g-2)_\mu$ explanation with mediator masses smaller than $2\times10^{-2}$ GeV. We then show that future direct dark matter detectors will be able to probe most of the remaining solution. Due to its large exposure, LUX-ZEPLIN will explore regions with mediator masses up to $5\times10^{-2}$ GeV and DARWIN will be able to extend the search beyond $10^{-1}$ GeV, thereby covering most of the area compatible with $(g-2)_\mu$. For completeness, we have also computed the constraints derived from the recent XENON1T electron recoil search and from the CENNS-10 LAr detector, showing that none of them excludes new areas of the parameter space. Should the excess in the muon anomalous magnetic moment be confirmed, our work suggests that direct detection experiments could provide crucial information with which to test the $U(1)_{L_\mu-L_\tau}$ solution, complementary to efforts in neutrino experiments and accelerators., Comment: 21 pages + appendices and references, 8 figures; v2: added references, updated description of loop-induced kinetic mixing suitable for low-energy processes; v3: matches published version

Solar neutrino experiments are highly sensitive to sources of $\nu\to\overline{\nu}$ conversions in the $^8$B neutrino flux. In this work we adapt these searches to non-minimal sterile neutrino models recently proposed to explain the LSND, MiniBooNE, and reactor anomalies. The production of such sterile neutrinos in the Sun, followed the decay chain $\nu_4 \to \nu \phi \to \nu \nu \overline{\nu}$ with a new scalar $\phi$ results in upper limits for the neutrino mixing $|U_{e4}|^2$ at the per mille level. We conclude that a simultaneous explanations of all anomalies is in tension with KamLAND, Super-Kamiokande, and Borexino constraints on the flux of solar antineutrinos. We then present other minimal models that violate parity or lepton number, and discuss the applicability of our constraints in each case. Future improvements can be expected from existing Borexino data as well as from future searches at Super-Kamiokande with added Gd., Comment: 14 pages, 7 figures, 1 table. v2: included neutral-current matter potential, derived new constraints from recent KamLAND and Super-Kamiokande data, and added new plots. Conclusions unchanged. Accepted for publication in Phys.Rev.D

Recently the XENON1T collaboration has released new results on searches for new physics in low-energy electronic recoils. The data shows an excess over background in the low-energy tail, particularly pronounced at about $2-3$ keV. With an exposure of $0.65$ tonne-year, large detection efficiency and energy resolution, the detector is sensitive as well to solar neutrino backgrounds, with the most prominent contribution given by $pp$ neutrinos. We investigate whether such signal can be explained in terms of new neutrino interactions with leptons mediated by a light vector particle. We find that the excess is consistent with this interpretation for vector masses below $\lesssim 0.1$ MeV. The region of parameter space probed by the XENON1T data is competitive with constraints from laboratory experiments, in particular GEMMA, Borexino and TEXONO. However we point out a severe tension with astrophysical bounds and cosmological observations., 6 pages, 4 figures. V3: Few typos corrected and one reference added. Matches version published in PLB

The recent confirmation by FNAL of the $(g-2)_\mu$ muon anomaly gives strong evidence for the possible existence of new physics beyond the Standard Model in the muon sector. Thus it is worthy to revisit the existing experimental constraints on models suggesting theoretically consistent explanations of the anomaly. In this work, we point out that accounting for the loss of coherence between the wave packets(mass states) of solar neutrinos is important for setting limits on any model with new flavor-sensitive couplings in the neutrino sector. By taking into account this effect and considering more accurately the experimental constraints from the BOREXINO measurement of the $^7$Be solar neutrino interaction rate we corrected the limits previously placed on the coupling of the light $Z'$ to $L_\mu$-$L_\tau$ current in the parameter space relevant to the muon $(g-2)_\mu$., Comment: 6 pages, version accepted for publication in PLB

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., 18 pages, 4 figures, matches version published in JCAP; in v3 updated terrestrial constraints/sensitivities (Fig. 2); our calculations unchanged

We study a Dark Matter (DM) model in which the dominant coupling to the standard model occurs through a neutrino-DM-scalar coupling. The new singlet scalar will generically have couplings to nuclei/electrons arising from renormalizable Higgs portal interactions. As a result the DM particle $X$ can convert into a neutrino via scattering on a target nucleus $\mathcal{N}$: $ X + \mathcal{N} \rightarrow \nu + \mathcal{N}$, leading to striking signatures at direct detection experiments. Similarly, DM can be produced in neutrino scattering events at neutrino experiments: $ \nu + \mathcal{N} \rightarrow X + \mathcal{N}$, predicting spectral distortions at experiments such as COHERENT. Furthermore, the model allows for late kinetic decoupling of dark matter with implications for small-scale structure. At low masses, we find that COHERENT and late kinetic decoupling produce the strongest constraints on the model, while at high masses the leading constraints come from DM down-scattering at XENON1T and Borexino. Future improvement will come from CE$\nu$NS data, ultra-low threshold direct detection, and rare kaon decays., Comment: 7 pages, 5 figures

The heat flux from the Earth’s interior and its connection with the number of neutrinos recorded by detectors at the Earth’s surface are discussed. The values predicted for the geoneutrino fluxes may be matched with experimental data, but the observed flux of the Earth’s internal heat requires the presence of a larger amount of radioactive elements. The amount of uranium and thorium within the Earth is constrained by measurements performed with the aid of modern geoneutrino detectors. This makes it possible to explain completely a flux of 50 TW. There are indications that the flux from the Earth’s interior is 200 to 250 TW. Such a flux could be explained only by the presence of a substantially larger amount of potassium in the Earth. In order to determine precisely the heat flux from the Earth’s interior, it is necessary to measure completely the flux of antineutrinos from all heat-releasing isotopes, including the flux of neutrinos from 40K decay. Possibly, this flux has already been observed at the Borexino detector.