Search for sterile neutrinos at the DANSS experiment

DANSS is a highly segmented 1~m${}^3$ plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1~$\mathrm{GW_{th}}$ reactor of the Kalinin Nuclear Power Plant 350~km NW from Moscow. The distance to the core is varied on-line from 10.7~m to 12.7~m. The reactor building provides about 50~m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 $\widetilde\nu_e$ per day at the closest position with the cosmic background less than 3$\%$. The inverse beta decay process is used to detect $\widetilde\nu_e$. Sterile neutrinos are searched for assuming the $4\nu$ model (3 active and 1 sterile $\nu$). The exclusion area in the $\Delta m_{14}^2,\sin^22\theta_{14}$ plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor $\widetilde\nu_e$ spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at 3 distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to $\sin^22\theta_{14}<0.01$ in the most sensitive region.Comment: 10 pages, 13 figures, version accepted for publicatio

Measurements of the νμ\nu_{\mu} and νˉμ\bar{\nu}_{\mu}-induced Coherent Charged Pion Production Cross Sections on 12C^{12}C by the T2K experiment

We report an updated measurement of the $\nu_{\mu}$-induced, and the first measurement of the $\bar{\nu}_{\mu}$-induced coherent charged pion production cross section on $^{12}C$ nuclei in the T2K experiment. This is measured in a restricted region of the final-state phase space for which $p_{\mu,\pi} > 0.2$ GeV, $\cos(\theta_{\mu}) > 0.8$ and $\cos(\theta_{\pi}) > 0.6$, and at a mean (anti)neutrino energy of 0.85 GeV using the T2K near detector. The measured $\nu_{\mu}$ CC coherent pion production flux-averaged cross section on $^{12}C$ is $(2.98 \pm 0.37 (stat.) \pm 0.31 (syst.) \substack{ +0.49 \\ -0.00 } \mathrm{ (Q^2\,model)}) \times 10^{-40}~\mathrm{cm}^{2}$. The new measurement of the $\bar{\nu}_{\mu}$-induced cross section on $^{12}{C}$ is $(3.05 \pm 0.71 (stat.) \pm 0.39 (syst.) \substack{ +0.74 \\ -0.00 } \mathrm{(Q^2\,model)}) \times 10^{-40}~\mathrm{cm}^{2}$. The results are compatible with both the NEUT 5.4.0 Berger-Sehgal (2009) and GENIE 2.8.0 Rein-Sehgal (2007) model predictions

Supernova Model Discrimination with Hyper-Kamiokande

Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants—neutron stars and black holes—are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokande's response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations toward a precise reproduction of the explosion mechanism observed in nature

First measurement of the electron-neutrino charged-current pion production cross section on carbon with the T2K near detector

The T2K Collaboration presents the first measurement of electron neutrino-induced charged-current pion production on a predominantly carbon target in a restricted kinematical phase space. This is performed using data from the 2.5° off-axis near detector, ND280. The differential cross sections with respect to the outgoing electron and pion kinematics, in addition to the total flux-integrated cross section, are obtained. Comparisons between the measured and predicted cross-section results using the eut, enie, and uro Monte Carlo event generators are presented. The measured total flux-integrated cross section is [ 2.52 ± 0.52 ( stat ) ± 0.30 ( syst ) ] × 10 − 39 cm 2 nucleon − 1 , which is lower than the event generator predictions

Signal selection and model-independent extraction of the neutrino neutral-current single π + cross section with the T2K experiment

This article presents a study of single π + production in neutrino neutral-current interactions (NC1π +) using the FGD1 hydrocarbon target of the ND280 detector of the T2K experiment. We report the largest sample of such events selected by any experiment, providing the first new data for this channel in over four decades and the first using a sub-GeV neutrino flux. The signal selection strategy and its performance are detailed together with validations of a robust cross section extraction methodology. The measured flux-averaged integrated cross-section is σ = (6.07 ± 1.22) × 10−41 cm2 /nucleon, 1.3 σ above the NEUT v5.4.0 expectation

First differential measurement of the single π+ production cross section in neutrino neutral-current scattering

Since its first observation in the 1970s, neutrino-induced neutral-current single positive pion production (NC1π +) has remained an elusive and poorly understood interaction channel. This process is a significant background in neutrino oscillation experiments and studying it further is critical for the physics program of next-generation accelerator-based neutrino oscillation experiments. In this Letter we present the first double-differential cross-section measurement of NC1π + interactions using data from the ND280 detector of the T2K experiment collected in ν-beam mode. The measured flux-averaged integrated cross-section is σ = (6.07±1.22)×10−41 cm2 /nucleon. We compare the results on a hydrocarbon target to the predictions of several neutrino interaction generators and final-state interaction models. While model predictions agree with the differential results, the data shows a weak preference for a cross-section normalization approximately 30% higher than predicted by most models studied in this Letter

Measurements of the νμ and ν¯μ -induced coherent charged pion production cross sections on C12 by the T2K experiment

We report an updated measurement of the ν μ -induced, and the first measurement of the ¯ ν μ -induced coherent charged pion production cross section on 12 C nuclei in the Tokai-to-Kamioka experiment. This is measured in a restricted region of the final-state phase space for which p μ , π &gt; 0.2     GeV , cos ( θ μ ) &gt; 0.8 and cos ( θ π ) &gt; 0.6 , and at a mean (anti)neutrino energy of 0.85 GeV using the T2K near detector. The measured ν μ charged current coherent pion production flux-averaged cross section on 12 C is ( 2.98 ± 0.37 ( stat ) ± 0.31 ( syst ) + 0.49 − 0.00 ( Q 2   model ) ) × 10 − 40     cm 2 . The new measurement of the ¯ ν μ -induced cross section on 12 C is ( 3.05 ± 0.71 ( stat ) ± 0.39 ( syst ) + 0.74 − 0.00 ( Q 2   model ) ) × 10 − 40     cm 2 . The results are compatible with both the NEUT 5.4.0 Berger-Sehgal (2009) and GENIE 2.8.0 Rein-Sehgal (2007) model predictions