Search Results (34)

There is evidence that the properties of hadrons are modified in a nuclear medium. Information about the medium modifications of the internal structure of hadrons is fundamental for the study of dense nuclear matter and high-energy processes, including heavy-ion and nucleus–nucleus collisions. At the moment, however, empirical information about medium modifications of hadrons is limited; therefore, theoretical studies are essential for progress in the field. In the present work, we review theoretical studies of the electromagnetic and axial form factors of octet baryons in symmetric nuclear matter. The calculations are based on a model that takes into account the degrees of freedom revealed in experimental studies of low and intermediate square transfer momentum $q^2=-Q^2$: valence quarks and meson cloud excitations of baryon cores. The formalism combines a covariant constituent quark model, developed for a free space (vacuum) with the quark–meson coupling model for extension to the nuclear medium. We conclude that the nuclear medium modifies the baryon properties differently according to the flavor content of the baryons and the medium density. The effects of the medium increase with density and are stronger (quenched or enhanced) for light baryons than for heavy baryons. In particular, the in-medium neutrino–nucleon and antineutrino–nucleon cross-sections are reduced compared to the values in free space. The proposed formalism can be extended to densities above the normal nuclear density and applied to neutrino–hyperon and antineutrino–hyperon scattering in dense nuclear matter. Full article

We investigate quasielastic (anti)neutrino scattering on the ¹²C nucleus utilizing a novel scaling variable, ${\psi }^{*}$. This variable is derived from the interacting relativistic Fermi gas model, which incorporates both scalar and vector interactions, leading to a relativistic effective mass for the interacting nucleons. For inclusive lepton scattering from nuclei, we develop a new scaling function, denoted as $f^{\mathrm{QE}}\left({\psi }^{*}\right)$, based on the coherent density fluctuation model (CDFM). This model serves as a natural extension of the relativistic Fermi gas (RFG) model applicable to finite nuclei. In this study, we compute theoretical predictions and compare them with experimental data from Miner$\nu$a and T2K for inclusive (anti)neutrino cross-sections. The scaling function is derived within the CDFM framework, employing a relativistic effective mass of $m_N^{*}=0.8m_N$. The findings demonstrate a high degree of consistency with experimental data across all (anti)neutrino energy ranges. Full article

Reactor-emitted electron antineutrinos can be detected via the inverse beta decay reaction, which produces a characteristic signal: a two-fold coincidence between a prompt positron event and a delayed neutron capture event within a specific time frame. While liquid scintillators are widely used for detecting neutrinos reacting with matter, detection is difficult because of the low interaction of neutrinos. In particular, it is important to distinguish between neutron (n) and gamma (γ) signals. The principle of the interaction of neutrons with matter differs from that of gamma rays with matter, and hence the detection signal’s waveform is different. Conventionally, pulse shape discrimination (PSD) is used for n/γ separation. This study developed a machine learning method to see if it is more efficient than the traditional PSD method. The possibility of n/γ discrimination in the region beyond the linear response limits was also examined, by using 10- and 2-inch photomultiplier tubes (PMTs) simultaneously. To the best of our knowledge, no study has attempted PSD in a PMT nonlinear region using artificial neural networks. Our results indicate that the proposed method has the potential to distinguish between n and γ signals in a nonlinear region. Full article

This paper presents a combined analysis of muon neutrino and antineutrino charged-current cross sections at kinematics of relevance for the T2K, MINERvA and MicroBooNE experiments. We analyze the sum, difference and asymmetry of neutrino versus antineutrino cross sections in order to get a better understanding of the nuclear effects involved in these processes. Nuclear models based on the superscaling behavior and the relativistic mean field theory are applied, covering a wide range of kinematics, from hundreds of MeV to several GeV, and the relevant nuclear regimes, i.e., from quasileastic reactions to deep inelastic scattering processes. The NEUT neutrino-interaction event generator, used in neutrino oscillation experiments, is also applied to the analysis of the quasielastic channel via local Fermi gas and spectral function approaches. Full article

At least two relics of the Big Bang have survived: the cosmological microwave background (CMB) and the cosmological neutrino background (C$\nu$B). Being the second most abundant particle in the universe, the neutrino has a significant impact on its evolution from the Big Bang to the present day. Neutrinos affect the following cosmological processes: the expansion rate of the universe, its chemical and isotopic composition, the CMB anisotropy and the formation of the large-scale structure of the universe. Another relic neutrino background is theoretically predicted, it consists of non-equilibrium antineutrinos of Primordial Nucleosynthesis arising as a result of the decay of neutrons and tritium nuclei. Such antineutrinos are an indicator of the baryon asymmetry of the universe. In addition to experimentally detectable active neutrinos, the existence of sterile neutrinos is theoretically predicted to generate neutrino masses and explain their oscillations. Sterile neutrinos can also solve such cosmological problems as the baryonic asymmetry of the universe and the nature of dark matter. The recent results of several independent experiments point to the possibility of the existence of a light sterile neutrino. However, the existence of such a neutrino is inconsistent with the predictions of the Standard Cosmological Model. The inclusion of a non-zero lepton asymmetry of the universe and/or increasing the energy density of active neutrinos can eliminate these contradictions and reconcile the possible existence of sterile neutrinos with Primordial Nucleosynthesis, the CMB anisotropy, and also reduce the H₀-tension. In this brief review, we discuss the influence of the physical properties of active and sterile neutrinos on the evolution of the universe from the Big Bang to the present day. Full article

The semi-inclusive cross-section of two-nucleon emission induced by neutrinos and antineutrinos is computed by employing the relativistic mean field model of nuclear matter and the dynamics of meson-exchange currents. Within this model, we explore a factorization approximation based on the product of an integrated two-hole spectral function and a two-nucleon cross-section averaged over hole pairs. We demonstrate that the integrated spectral function of the uncorrelated Fermi gas can be analytically computed, and we derive a simple, fully relativistic formula for this function, showcasing its dependency solely on both missing momentum and missing energy. A prescription for the average momenta of the two holes in the factorized two-nucleon cross-section is provided, assuming that these momenta are perpendicular to the missing momentum in the center-of-mass system. The validity of the factorized approach is assessed by comparing it with the unfactorized calculation. Our investigation includes the study of the semi-inclusive cross-section integrated over the energy of one of the emitted nucleons and the cross-section integrated over the emission angles of the two nucleons and the outgoing muon kinematics. A comparison is made with the pure phase-space model and other models from the literature. The results of this analysis offer valuable insights into the influence of the semi-inclusive hadronic tensor on the cross-section, providing a deeper understanding of the underlying nuclear processes. Full article

Core-collapse supernovae (SNe) are one of the most powerful cosmic sources of neutrinos, with energies of several MeV. The emission of neutrinos and antineutrinos of all flavors carries away the gravitational binding energy of the compact remnant and drives its evolution from the hot initial to the cold final states. Detecting these neutrinos from Earth and analyzing the emitted signals present a unique opportunity to explore the neutrino mass ordering problem. This research outlines the detection of neutrinos from SNe and their relevance in understanding the neutrino mass ordering. The focus is on developing a model-independent analysis strategy, achieved by comparing distinct detection channels in large underground detectors. The objective is to identify potential indicators of mass ordering within the neutrino sector. Additionally, a thorough statistical analysis is performed on the anticipated neutrino signals for both mass orderings. Despite uncertainties in supernova explosion parameters, an exploration of the parameter space reveals an extensive array of models with significant sensitivity to differentiate between mass orderings. The assessment of various observables and their combinations underscores the potential of forthcoming supernova observations in addressing the neutrino mass ordering problem. Full article

T2K (Tokai to Kamioka) is a long baseline neutrino experiment that exploits a neutrino and antineutrino beam produced at the Japan Particle Accelerator Research Centre (J-PARC) to provide world-leading measurements of the parameters governing neutrino oscillation. Neutrino oscillations are analyzed by tuning the neutrino rates and spectra at a near detector complex, located at J-PARC, and extrapolating them to the water Cherenkov far detector, Super-Kamiokande, located 295 km away, where oscillations are observed. The latest T2K results include multiple analysis improvements, in particular, a new sample is added for the far detector analysis, requiring the presence of a pion in muon-neutrino interactions. This is the first time that a pion sample has been included in the study of neutrino disappearance at T2K and the first time a sample with more than one Cherenkov ring has been included in the T2K oscillation analysis, opening a road for further samples with charged and neutral pion tagging. The inclusion of such a sample enables proper control of the oscillated spectrum in a larger neutrino energy range and on subleading neutrino interaction processes. Finally, T2K is engaged with the Super-Kamiokande collaboration to combine T2K neutrino beam data and Super-Kamiokande atmospheric data to perform a joint fit of the oscillation parameters. Such a combination allows the degeneracies between the measurement of the CP-violating phase ${\delta }_{\mathrm{CP}}$ and the measurement of the ordering of the neutrino mass eigenstates to be lifted. A precise evaluation of the enhanced sensitivity of this joint fit will be presented. Full article

The Jiangmen Underground Neutrino Observatory (JUNO) is a neutrino experiment under construction in an underground laboratory with a 650 m rock overburden near Jiangmen in southern China. The detector’s main component will be 20 kton of liquid scintillator held in a spherical acrylic vessel. The experiment is designed for the determination of neutrino mass ordering, one of the key open questions in neutrino physics. This measurement will be based on observations of the vacuum oscillation pattern of antineutrinos from two nuclear power plants at a baseline of 53 km. The estimated sensitivity is 3$\sigma$ in about six years with 26.6 GW${}_{\mathrm{th}}$ of reactor power. A key ingredient for the success is an excellent and extremely challenging energy resolution of 3% at 1 MeV. The light produced by the scintillator will be seen by 17,612 large twenty-inch PMTs and 25,600 small three-inch PMTs. The OSIRIS detector will monitor the radio purity of the liquid scintillator during the months-long filling process of the main detector. The unoscillated antineutrino spectrum from one reactor core will be measured with unprecedented precision by the Taishan Antineutrino Observatory (TAO), located at a baseline of about 30 m. JUNO is expected to substantially improve the precision of ${sin}^{2}2{\theta }_{12}$, $\Delta m_{21}^2$, and $\Delta m_{31}^2$ neutrino oscillation parameters. Astrophysical measurements of solar, geo-, supernova, DSNB, and atmospheric neutrinos, as well as searching for proton decay and dark matter, are integral parts of the vast JUNO physics program. This contribution reviews the physics goals and current status of the JUNO project. Full article

The Scintillating Bubble Chamber (SBC) collaboration is developing liquid-noble bubble chambers for the detection of sub-keV nuclear recoils. These detectors benefit from the electron recoil rejection inherent in moderately-superheated bubble chambers with the addition of energy reconstruction provided from the scintillation signal. The ability to measure low-energy nuclear recoils allows the search for GeV-scale dark matter and the measurement of coherent elastic neutrino-nucleus scattering on argon from MeV-scale reactor antineutrinos. The first physics-scale detector, SBC-LAr10, is in the commissioning phase at Fermilab, where extensive engineering and calibration studies will be performed. In parallel, a functionally identical low-background version, SBC-SNOLAB, is being built for a dark matter search underground at SNOLAB. SBC-SNOLAB, with a 10 kg-yr exposure, will have sensitivity to a dark matter–nucleon cross section of $2\times {10}^{-42}$ cm${}^2$ at 1 GeV/$c^2$ dark matter mass, and future detectors could reach the boundary of the argon neutrino fog with a tonne-yr exposure. In addition, the deployment of an SBC detector at a nuclear reactor could enable neutrino physics investigations including measurements of the weak mixing angle and searches for sterile neutrinos, the neutrino magnetic moment, and the light Z’ gauge boson. Full article

The latest direct measurements of the germanium quenching factor deviate significantly from the standard Lindhard model for nuclear recoil energies at the sub keV region. Here, we show that the recently measured coherent elastic neutrino–nucleus scattering (CE$\nu$NS) data from reactor antineutrinos can be used to probe the quenching factor model, and a 2$\sigma$ improvement can be achieved in the fit to the measured CE$\nu$NS data if the quenching factor is described by a modified Lindhard model with a negative value of q, which is also consistent with the direct quenching factor measurement. Constraints on the parameter space of a light vector or scalar mediator that couples to neutrinos and quarks, and on a neutrino magnetic moment, are also placed by using the measured CE$\nu$NS data, and we find that they are quite sensitive to the quenching factor model at low recoil energies. Full article

The MicroBooNE detector is a liquid argon time projection chamber (LArTPC) with an 85 ton active mass that receives flux from the Booster Neutrino and the Nutrinos from the Main Injector (NuMI) beams, providing excellent spatial resolution of the reconstructed final-state particles. Since 2015, MicroBooNE has accumulated many neutrino and anti-neutrino scattering events with argon nuclei enabling searches for rare interaction channels. The Cabibbo-suppressed production of hyperons in anti-neutrino–nucleus interactions provides sensitivity to a range of effects, including second-class currents, SU(3) symmetry violations and reinteractions between the hyperon and the nuclear remnant. This channel exclusively involves anti-neutrinos, offering an unambiguous constraint on wrong-sign contamination. The effects of nucleon structure and final state interactions are distinct from those affecting the quasielastic channel and modify the $\Lambda$ and $\Sigma$ production cross sections in different ways, providing new information that could help to break their degeneracy. Few measurements of this channel have been made, primarily in older experiments such as Gargamelle. We present the sensitivity of the MicroBooNE experiment to the cross section for direct (Cabibbo-suppressed) $\Lambda$ production in muon anti-neutrino interactions, using anti-neutrinos from the off-axis NuMI beam. Full article

A detailed understanding of neutrino–nucleus interactions is essential for the precise measurement of neutrino oscillations at long baseline experiments, such as T2K. The T2K near detector complex, designed to constrain the T2K flux and cross-section models, also provides a complementary program of neutrino interaction cross-section measurements. Through the use of multiple target materials (carbon, water, lead, iron), and the ability to sample different neutrino spectra (with detectors located on- and off-axis with respect to the beam direction), T2K is able to investigate atomic number and energy dependence of interaction cross-sections in a single experiment. In particular, T2K has recently performed the first joint on-/off-axis measurement of the charged current channel without pion in the final state. Furthermore, dedicated efforts are devoted to investigating rare or poorly studied interaction channels. Indeed, an improved analysis of the coherent pion production cross-section was recently accomplished, including an anti-neutrino sample for the first time. Those results, together with an overview of the T2K measurement strategy, adopted to reduce the model dependence, will be presented in these proceedings. Full article

Applying TQRPA calculations of Gamow–Teller strength functions in hot nuclei, we compute the (anti)neutrino spectra and energy loss rates arising from weak processes on hot ${}^{56}$Fe under pre-supernova conditions. We use a realistic pre-supernova model calculated by the stellar evolution code MESA. Taking into account both charged and neutral current processes, we demonstrate that weak reactions with hot nuclei can produce high-energy (anti)neutrinos. We also show that, for hot nuclei, the energy loss via (anti)neutrino emission is significantly larger than that for nuclei in their ground state. It is found that the neutral current de-excitation via the $\nu \overline{\nu }$-pair emission is presumably a dominant source of antineutrinos. In accordance with other studies, we confirm that the so-called single-state approximation for neutrino spectra might fail under certain pre-supernova conditions. Full article

We analyze the expected arrival time spectrum of supernova neutrinos using simulated luminosity and compute the expected number of events in future detectors such as the DUNE Far Detector and Hyper-Kamiokande. We develop a general method using minimum square statistics that can compute the sensitivity to any variable affecting neutrino time of flight. We apply this method in two different situations: First, we compare the time spectrum changes due to different neutrino mass values to put limits on electron (anti)neutrino effective mass. Second, we constrain Lorentz invariance violation through the mass scale, $M_{QG}$, at which it would occur. We consider two main neutrino detection techniques: 1. DUNE-like liquid argon TPC, for which the main detection channel is ${\nu }_e+{}^{40}\mathrm{Ar}\to e^{-}+{}^{40}{\mathrm{K}}^{\ast }$, related to the supernova neutronization burst; and 2. HyperK-like water Cherenkov detector, for which ${\overline{\nu }}_e+p\to e^{+}+n$ is the main detection channel. We consider a fixed supernova distance of 10 kpc and two different masses of the progenitor star: (i) 15 $M_{\odot }$ with neutrino emission time up to 0.3 s and (ii) 11.2 $M_{\odot }$ with neutrino emission time up to 10 s. The best mass limits at 3$\sigma$ are for $\mathcal{O}\left(1\right)$ eV. For ${\nu }_e$, the best limit comes from a DUNE-like detector if the mass ordering happens to be inverted. For ${\overline{\nu }}_e$, the best limit comes from a HyperK-like detector. The best limit for the Lorentz invariance violation mass scale at the 3$\sigma$ level considering a superluminal or subluminal effect is $M_{QG}\gtrsim {10}^{13}$ GeV ($M_{QG}\gtrsim 5\times {10}^5$ GeV) for linear (quadratic) energy dependence. Full article