The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is a pulsed source of neutrons and, as a byproduct of this operation, an intense source of pulsed neutrinos via stopped-pion ...decay. The COHERENT collaboration uses this source to investigate coherent elastic neutrino-nucleus scattering and other physics with a suite of detectors. This work includes a description of our Geant4 simulation of neutrino production at the SNS and the flux calculation which informs the COHERENT studies. We estimate the uncertainty of this calculation at about 10% based on validation against available low-energy pion production data.
We report on the technical design and expected performance of a 592 kg heavy-water-Cherenkov detector to measure the absolute neutrino flux from the pion-decay-at-rest neutrino source at the ...Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The detector will be located roughly 20 m from the SNS target and will measure the neutrino flux with better than 5% statistical uncertainty in 2 years. This heavy-water detector will serve as the first module of a two-module detector system to ultimately measure the neutrino flux to 2-3% at both the First Target Station and the planned Second Target Station of the SNS. This detector will significantly reduce a dominant systematic uncertainty for neutrino cross-section measurements at the SNS, increasing the sensitivity of searches for new physics.
We report the first measurement of coherent elastic neutrino-nucleus scattering (\cevns) on argon using a liquid argon detector at the Oak Ridge National Laboratory Spallation Neutron Source. Two ...independent analyses prefer \cevns over the background-only null hypothesis with greater than \(3\sigma\) significance. The measured cross section, averaged over the incident neutrino flux, is (2.2 \(\pm\) 0.7) \(\times\)10\(^{-39}\) cm\(^2\) -- consistent with the standard model prediction. The neutron-number dependence of this result, together with that from our previous measurement on CsI, confirms the existence of the \cevns process and provides improved constraints on non-standard neutrino interactions.
We report on the preparation of and calibration measurements with a \(^{83\mathrm{m}}\)Kr source for the CENNS-10 liquid argon detector. \(^{83\mathrm{m}}\)Kr atoms generated in the decay of a ...\(^{83}\)Rb source were introduced into the detector via injection into the Ar circulation loop. Scintillation light arising from the 9.4 keV and 32.1 keV conversion electrons in the decay of \(^{83\mathrm{m}}\)Kr in the detector volume were then observed. This calibration source allows the characterization of the low-energy response of the CENNS-10 detector and is applicable to other low-energy-threshold detectors. The energy resolution of the detector was measured to be 9\(\%\) at the total \(^{83\mathrm{m}}\)Kr decay energy of 41.5 keV. We performed an analysis to separately calibrate the detector using the two conversion electrons at 9.4 keV and 32.1 keV
Using an 185-kg NaITl array, COHERENT has measured the inclusive electron-neutrino charged-current cross section on \({}^{127}\)I with pion decay-at-rest neutrinos produced by the Spallation Neutron ...Source at Oak Ridge National Laboratory. Iodine is one the heaviest targets for which low-energy (\(\leq\) 50 MeV) inelastic neutrino-nucleus processes have been measured, and this is the first measurement of its inclusive cross section. After a five-year detector exposure, COHERENT reports a flux-averaged cross section for electron neutrinos of \(9.2^{+2.1}_{-1.8} \times 10^{-40}\) cm\(^2\). This corresponds to a value that is \(\sim\)41% lower than predicted using the MARLEY event generator with a measured Gamow-Teller strength distribution. In addition, the observed visible spectrum from charged-current scattering on \(^{127}\)I has been measured between 10 and 55 MeV, and the exclusive zero-neutron and one-or-more-neutron emission cross sections are measured to be \(5.2^{+3.4}_{-3.1} \times 10^{-40}\) and \(2.2^{+3.5}_{-2.2} \times 10^{-40}\) cm\(^2\), respectively.
The COHERENT experiment is well poised to test sub-GeV dark matter models using low-energy recoil detectors sensitive to coherent elastic neutrino-nucleus scattering (CEvNS) in the \(\pi\)-DAR ...neutrino beam produced by the Spallation Neutron Source. We show how a planned 750-kg liquid argon scintillation detector would place leading limits on scalar light dark matter models, over two orders of magnitude of dark matter mass, for dark matter particles produced through vector and leptophobic portals in the absence of other effects beyond the standard model. The characteristic timing structure of a \(\pi\)-DAR beam allows a unique opportunity for constraining systematic uncertainties on the standard model background in a time window where signal is not expected, enhancing expected sensitivity. Additionally, we discuss future prospects, further increasing the discovery potential of CEvNS detectors. Such methods would test the calculated thermal dark matter abundance for all couplings \(\alpha'\leq1\) within the vector portal model over an order of magnitude of dark matter masses.
Using neutrinos produced at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL), the COHERENT collaboration has studied the Pb(\(\nu_e\),X\(n\)) process with a lead ...neutrino-induced-neutron (NIN) detector. Data from this detector are fit jointly with previously collected COHERENT data on this process. A combined analysis of the two datasets yields a cross section that is \(0.29^{+0.17}_{-0.16}\) times that predicted by the MARLEY event generator using experimentally-measured Gamow-Teller strength distributions, consistent with no NIN events at 1.8\(\sigma\). This is the first inelastic neutrino-nucleus process COHERENT has studied, among several planned exploiting the high flux of low-energy neutrinos produced at the SNS.
Coherent elastic neutrino-nucleus scattering (CEvNS) is the dominant neutrino scattering channel for neutrinos of energy \(E_\nu < 100\) MeV. We report a limit for this process using data collected ...in an engineering run of the 29 kg CENNS-10 liquid argon detector located 27.5 m from the Oak Ridge National Laboratory Spallation Neutron Source (SNS) Hg target with \(4.2\times 10^{22}\) protons on target. The dataset yielded \(< 7.4\) observed CEvNS events implying a cross section for the process, averaged over the SNS pion decay-at-rest flux, of \(<3.4 \times 10^{-39}\) cm\(^{2}\), a limit within twice the Standard Model prediction. This is the first limit on CEvNS from an argon nucleus and confirms the earlier CsI non-standard neutrino interaction constraints from the collaboration. This run demonstrated the feasibility of the ongoing experimental effort to detect CEvNS with liquid argon.
We present updated results from the NOvA experiment for \(\nu_\mu\rightarrow\nu_\mu\) and \(\nu_\mu\rightarrow\nu_e\) oscillations from an exposure of \(8.85\times10^{20}\) protons on target, which ...represents an increase of 46% compared to our previous publication. The results utilize significant improvements in both the simulations and analysis of the data. A joint fit to the data for \(\nu_\mu\) disappearance and \(\nu_e\) appearance gives the best fit point as normal mass hierarchy, \(\Delta m^2_{32} = 2.44\times 10^{-3}{{\rm eV}^2}/c^4\), \(\sin^2\theta_{23} = 0.56\), and \(\delta_{CP} = 1.21\pi\). The 68.3% confidence intervals in the normal mass hierarchy are \(\Delta m^2_{32} \in 2.37,2.52\times 10^{-3}{{\rm eV}^2}/c^4\), \(\sin^2\theta_{23} \in 0.43,0.51 \cup 0.52,0.60\), and \(\delta_{CP} \in 0,0.12\pi \cup 0.91\pi,2\pi\). The inverted mass hierarchy is disfavored at the 95% confidence level for all choices of the other oscillation parameters.
We report on the preparation of and calibration measurements with a 83mKr source for the CENNS-10 liquid argon detector. 83mKr atoms generated in the decay of a 83Rb source were introduced into the ...detector via injection into the Ar circulation loop. Scintillation light arising from the 9.4 keV and 32.1 keV conversion electrons in the decay of 83mKr in the detector volume were then observed. This calibration source allows the characterization of the low-energy response of the CENNS-10 detector and is applicable to other low-energy-threshold detectors. The energy resolution of the detector was measured to be 9% at the total 83mKr decay energy of 41.5 keV. We performed an analysis to separately calibrate the detector using the two conversion electrons at 9.4 keV and 32.1 keV.
PDF