Search for Boosted Dark Matter Interacting with Electrons in Super-Kamiokande.

A search for boosted dark matter using 161.9 kt yr of Super-Kamiokande IV data is presented. We search for an excess of elastically scattered electrons above the atmospheric neutrino background, with a visible energy between 100 MeV and 1 TeV, pointing back to the Galactic center or the Sun. No such excess is observed. Limits on boosted dark matter event rates in multiple angular cones around the Galactic center and Sun are calculated. Limits are also calculated for a baseline model of boosted dark matter produced from cold dark matter annihilation or decay. This is the first experimental search for boosted dark matter from the Galactic center or the Sun interacting in a terrestrial detector.

The interacting roles of climate, soils, and plant production on soil microbial communities at a continental scale.

Soil microbial communities control critical ecosystem processes such as decomposition, nutrient cycling, and soil organic matter formation. Continental scale patterns in the composition and functioning of microbial communities are related to climatic, biotic, and edaphic factors such as temperature and precipitation, plant community composition, and soil carbon, nitrogen, and pH. Although these relationships have been well explored individually, the examination of the factors that may act directly on microbial communities vs. those that may act indirectly through other ecosystem properties has not been well developed. To further such understanding, we utilized structural equation modeling (SEM) to evaluate a set of hypotheses about the direct and indirect effects of climatic, biotic, and edaphic variables on microbial communities across the continental United States. The primary goals of this work were to test our current understanding of the interactions among climate, soils, and plants in affecting microbial community composition, and to examine whether variation in the composition of the microbial community affects potential rates of soil enzymatic activities. A model of interacting factors created through SEM shows several expected patterns. Distal factors such as climate had indirect effects on microbial communities by influencing plant productivity, soil mineralogy, and soil pH, but factors related to soil organic matter chemistry had the most direct influence on community composition. We observed that both plant productivity and soil mineral composition were important indirect influences on community composition at the continental scale, both interacting to affect organic matter content and microbial biomass and ultimately community composition. Although soil hydrolytic enzymes were related to the moisture regime and soil carbon, oxidative enzymes were also affected by community composition, reflected in the abundance of soil fungi. These results highlight that soil microbial communities can be modeled within the context of multiple interacting ecosystem properties acting both directly and indirectly on their composition and function, and this provides a rich and informative context with which to examine communities. This work also highlights that variation in climate, microbial biomass, and microbial community composition can affect maximum rates of soil enzyme activities, potentially influencing rates of decomposition and nutrient mineralization in soils.

Search for Nucleon and Dinucleon Decays with an Invisible Particle and a Charged Lepton in the Final State at the Super-Kamiokande Experiment.

Search results for nucleon decays p→e^{+}X, p→µ^{+}X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e^{+}ν, np→µ^{+}ν, and np→τ^{+}ν in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}X}>7.9×10^{32} yr, τ_{p→µ^{+}X}>4.1×10^{32} yr, τ_{n→νγ}>5.5×10^{32} yr, τ_{np→e^{+}ν}>2.6×10^{32} yr, τ_{np→µ^{+}ν}>2.2×10^{32} yr, and τ_{np→τ^{+}ν}>2.9×10^{31} yr at a 90% confidence level are obtained. Some of these searches are novel.

Search for neutrinos from annihilation of captured low-mass dark matter particles in the sun by super-kamiokande.

Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c^{2}-200-GeV/c^{2}) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c^{2} (at 10 GeV/c^{2}, 1.49×10^{-39} cm^{2} for χχ→bb[over ¯] and 1.31×10^{-40} cm^{2} for χχ→τ^{+}τ^{-} annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c^{2} mass range.

Search for trilepton nucleon decay via p→e+νν and p→µ+νν in the Super-Kamiokande experiment.

The trilepton nucleon decay modes p→e+νν and p→µ+νν violate |Δ(B-L)| by two units. Using data from a 273.4 kt yr exposure of Super-Kamiokande a search for these decays yields a fit consistent with no signal. Accordingly, lower limits on the partial lifetimes of τp→e+νν>1.7×10(32) years and τp→µ+νν>2.2×10(32) years at a 90% confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.

Search for nucleon decay via n→ν[over ¯]π0 and p→ν[over ¯]π+ in Super-Kamiokande.

We present the results of searches for nucleon decay via n→ν[over ¯]π0 and p→ν[over ¯]π+ using data from a combined 172.8 kt·yr exposure of Super-Kamiokande-I,-II, and-III. We set lower limits on the partial lifetime for each of these modes: τn→ν[over ¯]π0>1.1×10(33) years and τp→ν[over ¯]π+>3.9×10(32) years at a 90% confidence level.

Search for dinucleon decay into kaons in Super-Kamiokande.

A search for the dinucleon decay pp → K+ K+ has been performed using 91.6 kton·yr data from Super-Kamiokande-I. This decay provides a sensitive probe of the R-parity-violating parameter λ112''. A boosted decision tree analysis found no signal candidates in the data. The expected background was 0.28±0.19 atmospheric neutrino induced events and the estimated signal detection efficiency was 12.6%±3.2%. A lower limit of 1.7×10(32) years has been placed on the partial lifetime of the decay O16 → C14K+ K+ at 90% C.L. A corresponding upper limit of 7.8×10(-9) has been placed on the parameter λ112''.

Evidence for the appearance of atmospheric tau neutrinos in super-Kamiokande.

Super-Kamiokande atmospheric neutrino data were fit with an unbinned maximum likelihood method to search for the appearance of tau leptons resulting from the interactions of oscillation-generated tau neutrinos in the detector. Relative to the expectation of unity, the tau normalization is found to be 1.42 ± 0.35(stat)(-0.12)(+0.14)(syst) excluding the no-tau-appearance hypothesis, for which the normalization would be zero, at the 3.8σ level. We estimate that 180.1 ± 44.3(stat)(-15.2)(+17.8) (syst) tau leptons were produced in the 22.5 kton fiducial volume of the detector by tau neutrinos during the 2806 day running period. In future analyses, this large sample of selected tau events will allow the study of charged current tau neutrino interaction physics with oscillation produced tau neutrinos.

Search for differences in oscillation parameters for atmospheric neutrinos and antineutrinos at Super-Kamiokande.

We present a search for differences in the oscillations of antineutrinos and neutrinos in the Super-Kamiokande-I, -II, and -III atmospheric neutrino sample. Under a two-flavor disappearance model with separate mixing parameters between neutrinos and antineutrinos, we find no evidence for a difference in oscillation parameters. Best-fit antineutrino mixing is found to be at (Δm2,sin2 2θ)=(2.0×10(-3) eV2, 1.0) and is consistent with the overall Super-K measurement.

Is the proton stable.

For nearly 50 years there has been a strong belief that the proton is absolutely stable. The current experimental upper bound on its decay rate is less than one proton decay per 3 tons of matter per year, which corresponds to a mean lifetime of more than 10(30) years. Even more sensitive searches for proton decay are now in progress. These are partially motivated by the development of a class of models that combine the presently accepted theories of electromagnetic, weak, and strong inter-actions into an elegant unified form. Some of these theories predict a proton lifetime short enough for the decays to be detectable by the proposed experiments. If the proton is unstable, a plausible explanation can be given for the apparent excess of matter over antimatter in the universe.

Exposure to barbiturates in utero and during childhood risk of intracranial and spinal cord tumors.

Barbiturate exposure during childhood was assessed from medical records of 237 children with intracranial and spinal cord tumors and 474 matched controls in a prepaid health plan. In utero exposure was also examined in a subset of 86 "cases" and 172 controls whose mothers were health plan members during pregnancy. No association of in utero exposure to barbiturates was found [odds ratio (O.R.) = 0.96, 95% confidence interval (C.I.) = 0.47, 1.94]. An association was noted for barbiturate use during childhood (O.R. = 1.80, 95% C.I. = 1.18, 2.74) but was reduced (O.R. = 1.41, 95% C.I. = 0.89, 2.21) when history of epilepsy was taken into account and was no longer significant. An apparent dose-response effect disappeared after adjustment for a history of epilepsy. Although barbiturate use for epilepsy due to preexisting brain tumors clearly explains some of the observed association, the small, residual risk prevents us from ruling out a possible carcinogenic effect of barbiturates. Further study of cohorts of adult as well as childhood users of barbiturates and other anticonvulsants is recommended.

Monoclonal anti-gamma interferon antibodies enhance experimental allergic encephalomyelitis.

Interferon-gamma (IFN-gamma) is a cytokine with multiple activities on a variety of cells. Under various circumstances, IFN-gamma can exhibit either pro-inflammatory or inhibitory actions. Treatment of SJL/J mice with a monoclonal antibody (Mab) to IFN-gamma during the afferent limb of the immune response to myelin protein produced an enhancement of acute experimental allergic encephalomyelitis (EAE), with increased morbidity, mortality and earlier onset of disease. Systemic administration of IFN-gamma did not improve or worsen clinical outcome, but delayed disease onset. Passive transfer of immune lymph node cells co-activated with MBP and anti-IFN-gamma Mab resulted in more sever disease than that induced by MBP stimulated cells or MBP and IFN-gamma co-stimulated cells. However, in vitro proliferation of an MBP specific T cell line was not influenced by IFN-gamma nor anti-IFN-gamma treatment. Mab to IFN-gamma inhibited suppressor function, in a non-specific assay. These in vivo and in vitro results suggest that systemic IFN-gamma serves as a physiological regulator of a suppressor mechanism in EAE. The abrogation of this regulatory mechanism by anti-IFN-gamma administration contributes to a more severe form of experimental allergic encephalomyelitis.

A method for the determination of vanadium and iron oxidation states in naturally occurring oxides and silicates.

A valence-specific analytical method for determining V(3+) in ore minerals has been developed that involves two steps: dissolution of a mineral sample without disturbing the V(3+)/V(tot) ratio, followed by determination of V(3+) in the presence of V(4+). The samples are dissolved in a mixture of hydrofluoric and sulphuric acids at 100 degrees in Teflon-lined reaction vessels. Tervalent vanadium is then determined colorimetrically by formation of a V(3+)-thiocyanate complex in aqueous-acetone medium. Fe(3+) is measured semi-quantitatively in the same solution. The method has been tested with two naturally occurring samples containing vanadium and iron. The results obtained were supported by those obtained by other methods, including electron spin resonance spectroscopy, thermogravimetric analysis, and Mössbauer spectroscopy.

An analytical scheme for determining forms of sulphur in oil shales and associated rocks.

An analytical scheme for determining various forms of sulphur in oil shales and associated rocks is presented. Acid-soluble sulphate, sulphur contained in monosulphide and in disulphide minerals, and organically-bound sulphur are all quantitatively recovered as separate fractions. Finely-ground oil-shale samples are treated in an inert atmosphere with 6M hydrochloric acid to dissolve the acid-soluble sulphate minerals and form H(2)S from the decomposition of monosulphide minerals. The acid-soluble sulphate is precipitated as barium sulphate and the H(2)S is collected and weighed as silver sulphide. Disulphide minerals in the solid residue from the acid treatment are reduced by an acidified Cr(II) solution in an inert atmosphere, releasing the sulphide as H(2)S. The H(2)S is collected as silver sulphide. An Eschka fusion oxidizes and solubilizes all sulphur remaining within the Cr(II)-treated residue. This sulphate represents organically-bound sulphur and is collected as barium sulphate. The analytical procedures have been verified by using (57)Fe Mössbauer spectroscopy. Good agreement between the chemical and Mössbauer data substantiated the sequential removal of the forms of sulphur and also demonstrated the ability of Mössbauer spectroscopy to determine the absolute quantities of iron present in specific minerals.

The Three Mile Island Population Registry.

Shortly after the March 28, 1979, accident at the Three Mile Island (TMI) nuclear plant outside Harrisburg, Pa., the Pennsylvania Department of Health, in conjunction with the Centers for Disease Control and the U.S. Bureau of the Census, conducted a census of the 35,930 persons residing within 5 miles of the plant. With the help of 150 enumerators, demographic and health-related information was collected on each person to provide baseline data for future short- and long-term epidemiologic studies of the effects of the accident. Individual radiation doses were estimated on the basis of residential location and the amount of time each person spent in the 5-mile area during the 10 days after the accident. Health and behavioral resurveys of the population will be conducted approximately every 5 years. Population-mobility, morbidity, and mortality will be studied yearly by matching the TMI Population Registry with postal records, cancer registry records, and death certificate data. Because the radiation dose from TMI was extremely small, any increase in morbidity or mortality attributable to the accident would be so small as not to be measurable by present methods; however, adverse health effects as a result of psychological stress may occur. Also, a temporary increase in reporting of disease could occur because of increased surveillance and attention to health.