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Distribution of logðL TFC Þ as a function of the N dt 1 p energy estimator. The plot is built using the entire set of data surviving the selection cuts described in Sec. II. The regions dominated by the abundant internal background of 14 C and 210 Po are indicated by the corresponding labels. The green-dashed horizontal line represents the L TFC -threshold, above/below which the events are assigned to the TFC-tagged/subtracted energy spectrum. It is clearly visible that the majority of the events of the 11 C energy decay spectrum lies above this threshold.
Source publication
We present the simultaneous measurement of the interaction rates Rpp, RBe, Rpep of pp, Be7, and pep solar neutrinos performed with a global fit to the Borexino data in an extended energy range (0.19–2.93) MeV with particular attention to details of the analysis methods. This result was obtained by analyzing 1291.51 days of Borexino Phase-II data, c...
Contexts in source publication
Context 1
... new TFC algorithm has (92 AE 4)% 11 C-tagging efficiency, while preserving (64.28 AE 0.01)% of the total exposure in the TFC-subtracted spectrum. Figure 1 shows the distribution of logðL TFC Þ of the present data set as a function of the N dt 1 p energy estimator and it demonstrates how 11 C decays can be identified by cutting the events on the basis of the value of L TFC . ...
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... recognize the pep ν contribution to the measured electron-recoil spectrum, the TFC-subtracted spectrum, zoomed into the highest energy region (between 800 and 2700 keV), is shown after applying stringent selection cuts on the radial distribution (R < 2.4 m) and on the pulse-shape variable distribution (PS-L PR < 4.8) (see Fig. 10): the CNO and pep neutrino interactions are clearly visible between 1250 and 1500 keV, and the spectrum is consistent with the Compton-like shoulder expected from the pep ...
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... Δχ 2 profile obtained by marginalizing the pep rate is shown in Fig. 11 (left) for both the HZ and LZ assumptions on CNO ν rate. Both curves are symmetric and allow us to establish, for the first time, that the absence of the pep reaction in the Sun is rejected at more than ...
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... 95% C.L. upper limit for R CNO to be ∼9 cpd=100 ton and 10 cpd=100 ton, for low and high metallicity, respectively. On data, we obtain the upper limit on R CNO ¼ 8.1 cpd=100 ton (95% C.L.) (see Table II), which is slightly stronger than the median limit expected from the MC based sensitivity study. The Δχ 2 profile for the CNO rate is shown in Fig. 11 (bottom). This result, using a weaker hypothesis on pep ν, confirms the current best limit on the flux of CNO νs previously obtained with Borexino Phase-I data ...
Citations
... In the long-term, future xenon experiments like XLZD [55][56][57][58] should be poised to set constraints on new physics manifesting in low-energy EνeS at an interesting level of sensitivity (given estimates for the sensitivity of the current generation like LZ, XENONnT and PandaX [34,46,[59][60][61][62]), but this will depend strongly on the level of electron recoil background that is achieved. At present, the best limits still come from Borexino [63][64][65][66][67][68][69][70], whose sensitivity mostly (but not entirely) supersedes [71] that of experiments using terrestrial neutrino sources like beam-dumps or reactors [72][73][74][75][76]. ...
Micro-pattern gaseous detectors (MPGDs) are a class of technologies that enable the full three-dimensional spatial reconstruction of ionisation tracks from nuclear and electron recoils in gas. Anticipating near-future 30 m-scale time projection chambers with MPGD-based readout, we forecast the sensitivity of such directionally-sensitive low-energy recoil detectors to neutrino interactions beyond the Standard Model. We work in the framework of neutrino non-standard interactions (NSIs), and calculate the combined recoil energy-angle distributions of the electron recoil signal generated by solar neutrinos in atmospheric-pressure He:CF gas. We estimate the expected exclusion limits that such an experiment could place on various NSI parameters, as well as the mass and coupling of a new light mediator that interacts with electrons and neutrinos. We find that with an achievable background reduction of around a factor of ten from current estimates for a 30 m optical-readout detector using this gas mixture, sensitivity to NSI parameters would already approach Borexino's sensitivity. Directionality also allows for event-by-event neutrino energy reconstruction, which would provide a means to resolve some parameter degeneracies present in the modified neutrino cross section in this formalism. Our results strongly motivate the development of small-scale directionally-sensitive gas detectors for neutrino physics.
... Over the past few decades, liquid scintillator based detectors have been widely employed in particle and astroparticle physics for rare event searches, aiming to detect dark matter [4] and neutrinos from natural [5] and artificial sources [6]. These experiments have been fundamental for the determination of the neutrino oscillation parameters [6,7] and solar neutrino spectroscopy [5,8,9]. ...
JUNO is a huge neutrino detector that will use 20 kton of organic liquid scintillator as its detection medium. The scintillator is a mixture of linear alkyl benzene (LAB), 2.5 g/L of 2,5-diphenyloxazole (PPO) and 3 mg/L of 1,4-Bis(2-methylstyryl)benzene (Bis-MSB). The main goal of JUNO is to determine the Neutrino Mass Ordering [1,2,3]. In order to achieve this purpose, good energy and position reconstruction is required, hence a complete understanding of the optical characteristics of the liquid scintillator is mandatory. In this paper we present the first measurements on the JUNO scintillator emission spectrum, absorption length and fluorescence time distribution performed respectively with a spectrofluorimeter, a spectrophotometer and a custom made setup of the liquid scintillator produced by the JUNO purification plants.
... In parallel the χ 2 value comes to the smaller value an satisfies better to the statistical behavior. The columns 5 and 6 labeled as HZ and LZ show the theoretical interaction rates predicted by the standard solar model under the high (HZ) and low (LZ) metallicity [5]. ...
... The column 4 shows the result with free parameter of R(40K). The columns 5 and 6 labeled as HZ and LZ show the theoretical interaction rates predicted by the standard solar model under the high (HZ) and low (LZ) metallicity [5]. ...
The Borexino Collaboration interprets its data within the framework of Bulk Silicate Earth model and the model of the Sun with high metallicity. Other authors have given a different interpretation of the same data within the framework of Hydridic Earth model and low-metallicity Sun model. In order to understand what occasion takes place in Nature, the Borexino single events energy spectrum was numerically simulated using the Monte Carlo method for various assumptions about the processes that could exist in Nature. The existence of large potassium geo-antineutrino flux and its absence were considered. At the same time, the high or low metallicity of the Sun were included in simulations. A comparison of counting rates reconstruction from simulated data with the reconstruction ones from Borexino single events spectrum demonstrates that large potassium geo-antineutrino flux with low metallicity of the Sun is preferable and is realized in Nature.
... The world's best LS radiopurity was achieved by Borexino [42,43], suppressing 238 U and 232 Th by ten orders of magnitude (less than 9.4 × 10 −20 g/g of 238 U and less than 5.7 × 10 −19 g/g of 232 Th at 95% C.L.). This level of radiopurity was fundamental for the successful detection of solar neutrinos via elastic scattering off electrons. ...
Large-scale organic liquid scintillator detectors are highly efficient in the detection of MeV-scale electron antineutrinos. These signal events can be detected through inverse beta decay on protons, which produce a positron accompanied by a neutron. A noteworthy background for antineutrinos coming from nuclear power reactors and from the depths of the Earth (geoneutrinos) is generated by () reactions. In organic liquid scintillator detectors, particles emitted from intrinsic contaminants such as U, Th, and Pb/Po, can be captured on C nuclei, followed by the emission of a MeV-scale neutron. Three distinct interaction mechanisms can produce prompt energy depositions preceding the delayed neutron capture, leading to a pair of events correlated in space and time within the detector. Thus, () reactions represent an indistinguishable background in liquid scintillator-based antineutrino detectors, where their expected rate and energy spectrum are typically evaluated via Monte Carlo simulations. This work presents results from the open-source SaG4n software, used to calculate the expected energy depositions from the neutron and any associated de-excitation products. Also simulated is a detailed detector response to these interactions, using a dedicated Geant4-based simulation software from the JUNO experiment. An expected measurable CO event rate and reconstructed prompt energy spectrum with associated uncertainties, are presented in the context of JUNO, however, the methods and results are applicable and relevant to other organic liquid scintillator neutrino detectors.
... What is more, neutrino experiments give us new clues to constrain the parameter space [81]. The Borexino data related to the scattering of low energy solar neutrinos [82,83] can provide the most stringent constraint on the low M Z p and low g p region. Another constraint is from CCFR collaboration [84], obtained via the neutrino trident production where a muon neutrino scattered off of a nucleus producing a μ þ μ − pair. ...
We discuss the possibility of light scalar dark matter generated by right-handed neutrino in a L μ − L τ model, in which the dark matter ϕ d m carries U ( 1 ) L μ − L τ charge but it is a singlet in the Standard Model. We discuss the case that dark matter production mainly comes from scattering associated with a pair of right-handed neutrinos non-thermally while other related processes are highly suppressed. A feasible parameter space is considered and we found the correct dark matter relic density can be obtained without influencing the result of leptogenesis result. The heavier right-handed neutrino will induce colder dark matter production and the allowed dark matter mass region is [ 10 − 5 GeV , 0.1 GeV ] .
Published by the American Physical Society 2025
... Over the past few decades, liquid scintillator based detectors have been widely employed in particle and astroparticle physics for rare event searches, aiming to detect dark matter [4] and neutrinos from natural [5] and artificial sources [6]. These experiments have been fundamental for the determination of the neutrino oscillation parameters [6,7] and solar neutrino spectroscopy [5,8,9]. ...
JUNO is a huge neutrino detector that will use 20 kton of organic liquid scintillator as its detection medium. The scintillator is a mixture of linear alkyl benzene (LAB), 2.5 g/L of 2,5-diphenyloxazole (PPO) and 3 mg/L of 1,4-Bis(2-methylstyryl)benzene (Bis-MSB). The main goal of JUNO is to determine the Neutrino Mass Ordering [1, 2, 3]. In order to achieve this purpose, good energy and position reconstruction is required, hence a complete understanding of the optical characteristics of the liquid scintillator is mandatory. In this paper we present the measurements on the JUNO scintillator emission spectrum, absorption length and fluorescence time distribution performed respectively with a spectrofluorimeter, a spectrophotometer and a custom made setup
... This paper is focused on establishing this sensitivity, and exploring implications for a precise measurements of the ν μ =ν τ scattering cross sections. We specifically focus on the 7 Be component of the flux as measured by Borexino [18], since this component is measured with high statistics, and in a region of the parameter space wellseparated from experimental backgrounds. In addition, since this is a mono-energetic flux, the neutrino survival probability is straightforward to implement and use to establish sensitivity to the scattering cross section. ...
We perform a detailed study of neutrino-electron elastic scattering using the monoenergetic Be 7 neutrinos in Borexino, with an emphasis on exploring the differences between the contributions of ν e , ν μ , and ν τ . We find that current data are capable of measuring these components such that the contributions from ν μ and ν τ cannot be zero, although distinguishing between them is challenging—the differences stemming from Standard Model radiative corrections are insufficient without significantly more precise measurements. In studying these components, we compare predicted neutrino-electron scattering event rates within the Standard Model (accounting for neutrino oscillations), as well as going beyond the Standard Model in two ways. We allow for nonunitary evolution to modify neutrino oscillations, and find that with a larger exposure ( ∼ 30 x ), Borexino may provide relevant information for constraining nonunitarity, and that JUNO may be able to accomplish this with its data collection of Be 7 neutrinos. We also consider novel ν μ - and ν τ -electron scattering from a gauged U ( 1 ) L μ − L τ model, showing consistency with previous analyses of Borexino and this scenario, but also demonstrating the impact of uncertainties on Standard Model mixing parameters on these results.
Published by the American Physical Society 2024
... In the analysis of solar neutrino experiments we include the total rates from the radiochemical experiments Chlorine [28] (1 data point), Gallex/GNO [4] (2 data points), and SAGE [29] (1 data point), the spectral and day-night data from phases I-IV of Super-Kamiokande [30][31][32][33] (44,33,42, and 46 data points, respectively), the results of the three phases of SNO in the form of the day-night spectrum data of SNO-I [34] and SNO-II [35] and the three total rates of SNO-III [36] (34,38, and 3 data points, respectively), 1 and the full spectra from Borexino Phase-I [39] (33 data points), Phase-II [40] (192 data points), and Phase-III [41] (120 data points), together with their latest results based on the Correlated Integrated Directionality method [42] (1 data point; see Refs. [27,43] for details of our analysis of Borexino II and III phases). ...
We perform a global analysis of most up-to-date solar neutrino data and KamLAND reactor antineutrino data in the framework of the 3+1 sterile neutrino mixing scenario (invoked to explain the results of the Gallium source experiments) with the aim of quantifying the dependence of the (in)compatibility of the required mixing with assumptions on the initial fluxes. The analysis of solar data is performed in two alternative ways: using the flux predicted by the latest standard solar models, and in a model independent approach where the solar fluxes are also determined by the fit. The dependence on the normalization of the capture rate in the solar Gallium experiments is also quantified. Similarly, in the KamLAND analysis we consider both the case where the reactor flux normalization is assumed to be known \textit{a priori}, as well as a normalization free case which relies solely on available neutrino data. Using a parameter goodness of fit test, we find that in most cases the compatibility between Gallium and solar+KamLAND data only occur at the level or higher. We also discuss the implications of enforcing better compatibility by tweaking the mechanism for the energy production in the Sun.
... The dominant channel of solar neutrino events in such experiments are electron recoils, where the large flux of pp neutrinos generates ∼400 electron elastic scattering events (νeES) per ton-year of exposure [11]. Because of this, experiments reaching O (10) ton-year exposures, like the next-generation dual-phase xenon experiment XLZD [32], are even expected to be competitive with Borexino [35][36][37][38][39][40][41][42][43], a 100-ton (fiducial mass) liquid scintillator that has led the measurement of solar neutrino fluxes for over a decade. Additionally, with low enough energy thresholds, nuclear recoils from coherent elastic neutrino-nucleus scattering (CEνNS) of 8 B neutrinos also constitute a background -as well as an additional signal -in direct detection exper-iments. ...
... We emphasise that our limit labelled 'Nondirectional' has exactly the same energy resolution and efficiency as the best directional limit shown, thereby proving the value of incorporating directional information. The horizontal line indicates the present 1σ measurement uncertainty from Borexino [40], while the vertical line indicates the current estimate of the worst-case scenario electron recoil background in an optical gas TPC from the simulation of Ref. [146] ing using just recoil energy information alone. We find that an atmospheric-pressure 1000 m 3 experiment can already constrain the CNO flux to within 20-30% whereas a nondirectional experiment cannot even distinguish it from zero at 1σ . ...
Cygnus is a proposed global network of large-scale gas time projection chambers (TPCs) with the capability of directionally detecting nuclear and electron recoils at ≳ keV energies. The primary focus of Cygnus so far has been the detection of dark matter, with directional sensitivity providing a means of circumventing the so-called “neutrino fog”. However, the excellent background rejection and electron/nuclear recoil discrimination provided by the 3-dimensional reconstruction of ionisation tracks could turn the solar neutrino background into an interesting signal in its own right. For example, directionality would facilitate the simultaneous spectroscopy of multiple different flux sources. Here, we evaluate the possibility of measuring solar neutrinos using the same network of gas TPCs built from 10 m 3 -scale modules operating under conditions that enable simultaneous sensitivity to both dark matter and neutrinos. We focus in particular on electron recoils, which provide access to low-energy neutrino fluxes like pp , pep , 7 Be, and CNO. An appreciable event rate is already detectable in experiments consisting of a single 10 m 3 module, assuming standard fill gases such as CF 4 mixed with helium at atmospheric pressure. With total volumes around 1000 m 3 or higher, the TPC network could be complementary to dedicated neutrino observatories, whilst entering the dark-matter neutrino fog via the nuclear recoil channel. We evaluate the required directional performance and background conditions to observe, discriminate, and perform spectroscopy on neutrino events. We find that, under reasonable projections for planned technology that will enable 10–30-degree angular resolution and ∼ 10 % fractional energy resolution, Cygnus could be a competitive directional neutrino experiment.
... In this effort, this work contains the latest analysis within the NuFIT program, Nu-FIT 6.0, which incorporates a number of changes and updates since our last published analysis in 2020 [4]. In the solar neutrino sector, the new generation of Standard Solar Models [10] are now used for the predictions, and the full day-night spectrum from the phase-IV of Super-Kamiokande [11] together with the final spectra from Borexino phases-II [12] and III [13] are included. For the long baseline (LBL) reactor data, we have updated the reactor antineutrino fluxes used for the predictions to the latest Daya-Bay measurements [14], and results from SNO+ [15][16][17] are included in the global analysis for the first time. ...
... In the solar neutrino sector, new data included since NuFIT 5.0 are the full day-night spectrum from the phase-IV of Super-Kamiokande [45], and the final spectra from Borexino phases-II [12] and III [13]. As for the predictions required for the solar neutrino analysis, the main update is that we have employed the new generation of Standard Solar Models [10]. ...
We present an updated global analysis of neutrino oscillation data as of September 2024. The parameters , , , and () are well-determined with relative precision at of about 13\%, 8\%, 15\%, and 6\%, respectively. The third mixing angle still suffers from the octant ambiguity, with no clear indication of whether it is larger or smaller than . The determination of the leptonic CP phase depends on the neutrino mass ordering: for normal ordering the global fit is consistent with CP conservation within , whereas for inverted ordering CP-violating values of around are favored against CP conservation at more than . While the present data has in principle 2.5-- sensitivity to the neutrino mass ordering, there are different tendencies in the global data that reduce the discrimination power: T2K and NOvA appearance data individually favor normal ordering, but they are more consistent with each other for inverted ordering. Conversely, the joint determination of from global disappearance data prefers normal ordering. Altogether, the global fit including long-baseline, reactor and IceCube atmospheric data results into an almost equally good fit for both orderings. Only when the table for atmospheric neutrino data from Super-Kamiokande is added to our , the global fit prefers normal ordering with . We provide also updated ranges and correlations for the effective parameters sensitive to the absolute neutrino mass from -decay, neutrinoless double-beta decay, and cosmology.
