Cosmogenic neutron production at the Sudbury Neutrino Observatory

Neutrons produced in nuclear interactions initiated by cosmic-ray muons present an irreducible background to many rare-event searches, even in detectors located deep underground. Models for the production of these neutrons have been tested against previous experimental data, but the extrapolation to deeper sites is not well understood. Here we report results from an analysis of cosmogenically produced neutrons at the Sudbury Neutrino Observatory. A specific set of observables are presented, which can be used to benchmark the validity of geant4 physics models. In addition, the cosmogenic neutron yield, in units of 10-4 cm2/(g·μ), is measured to be 7.28±0.09(stat)-1.12+1.59(syst) in pure heavy water and 7.30±0.07(stat)-1.02+1.40(syst) in NaCl-loaded heavy water. These results provide unique insights into this potential background source for experiments at SNOLAB

Measurement of neutron production in atmospheric neutrino interactions at the Sudbury Neutrino Observatory

Neutron production in GeV-scale neutrino interactions is a poorly studied process. We have measured the neutron multiplicities in atmospheric neutrino interactions in the Sudbury Neutrino Observatory experiment and compared them to the prediction of a Monte Carlo simulation using GENIE and a minimally modified version of GEANT4. We analyzed 837 days of exposure corresponding to Phase I, using pure heavy water, and Phase II, using a mixture of Cl in heavy water. Neutrons produced in atmospheric neutrino interactions were identified with an efficiency of $15.3\%$ and $44.3\%$, for Phase I and II respectively. The neutron production is measured as a function of the visible energy of the neutrino interaction and, for charged current quasi-elastic interaction candidates, also as a function of the neutrino energy. This study is also performed classifying the complete sample into two pairs of event categories: charged current quasi-elastic and non charged current quasi-elastic, and $\nu_{\mu}$ and $\nu_e$. Results show good overall agreement between data and Monte Carlo for both phases, with some small tension with a statistical significance below $2\sigma$ for some intermediate energies

Measurement of the nu(e) and total B-8 solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set

This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of He-3 proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active B-8 solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54(-0.31)(+0.33)(stat.)(-0.34)(+0.36)(syst.) x 10(6) cm(-2) s(-1), consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Delta m(2) = 7.59(-0.21)(+0.19) x 10(-5) eV(2) and theta = 34.4(-1.2)(+1.3) degrees. DOI: 10.1103/PhysRevC.87.01550

Tests of Lorentz invariance at the Sudbury Neutrino Observatory

Experimental tests of Lorentz symmetry in systems of all types are critical for ensuring that the basic assumptions of physics are well-founded. Data from all phases of the Sudbury Neutrino Observatory, a kiloton-scale heavy water Cherenkov detector, are analyzed for possible violations of Lorentz symmetry in the neutrino sector. Such violations would appear as one of eight possible signal types in the detector: six seasonal variations in the solar electron neutrino survival probability differing in energy and time dependence, and two shape changes to the oscillated solar neutrino energy spectrum. No evidence for such signals is observed, and limits on the size of such effects are established in the framework of the Standard Model Extension, including 40 limits on perviously unconstrained operators and improved limits on 15 additional operators. This makes limits on all minimal, Dirac-type Lorentz violating operators in the neutrino sector available for the first time

Design research and innovation framework for transformative practices

In this chapter, the concept of Transformative Practices is introduced, i.e. shared relative steady ways of living and working with others (Wittgenstein, 1993), including specific configurations of actions, norms and knowledge (Freeman et al., 2011) and related tools and environments, focused at addressing our societal challenges, by transforming (elevating) our personal and social ethics and related behaviour through designing new ways of interaction with each other and the world. Through design research and innovation within these practices, we work together towards social-cul- turally, environmentally and economically sustainable communities

Recent results from SNO

The SNO project has now completed two of its three major phases of operation. The no-oscillation hypothesis has been ruled out at 5σ in the pure heavy water phase and 8σ in the salt phase. Discussion in terms of the SeeSaw model is presented. © 2004 Published by Elsevier B.V

Search for hep solar neutrinos and the diffuse supernova neutrino background using all three phases of the Sudbury Neutrino Observatory

A search has been performed for neutrinos from two sources, the hep reaction in the solar pp fusion chain and the νe component of the diffuse supernova neutrino background (DSNB), using the full dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47 kton-years after fiducialization. The hep search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of φhep<30×103 cm-2 s-1 [90% credible interval (CI)]. No events are observed in the DSNB search region, and we set an improved upper bound on the νe component of the DSNB flux of φνeDSNB<19 cm-2 s-1 (90% CI) in the energy range 22.