3,813 research outputs found

    New limits for neutrinoless tau decays

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    Neutrinoless 3-prong tau lepton decays into a charged lepton and either two charged particles or one neutral meson have been searched for using 4.79fb^(-1) of data collected with the CLEO II detector at Cornell Electron Storage Ring. This analysis represents an update of a previous study and the addition of six decay channels. In all channels the numbers of events found are compatible with background estimates and branching fraction upper limits are set for 28 different decay modes. These limits are either more stringent than those set previously or represent the first attempt to find these decays

    Dissipation processes in the Tongue of the Ocean

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    Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 3159–3170, doi:10.1002/2015JC011165.The Tongue of the Ocean (TOTO) region located within the Bahamas archipelago is a relatively understudied region in terms of both its biological and physical oceanographic characteristics. A prey-field mapping cruise took place in the fall between 15 September 2008 and 1 October 2008, consisting of a series of transects and “clovers” to study the spatial and temporal variability. The region is characterized by a deep scattering layer (DSL), which is preyed on by nekton that serves as the food for beaked whale and other whale species. This study marks the first of its kind where concurrent measurements of acoustic backscatter and turbulence have been conducted for a nekton scattering layer well below the euphotic zone. Turbulence data collected from a Deep Microstructure Profiler are compared to biological and shear data collected by a 38 kHz Simrad EK 60 echo sounder and a hydrographic Doppler sonar system, respectively. From these measurements, the primary processes responsible for the turbulent production in the TOTO region are assessed. The DSL around 500 m and a surface scattering layer (SSL) are investigated for raised ε values. Strong correlation between turbulence levels and scattering intensity of prey is generally found in the SSL with dissipation levels as large as ∼10−7 W kg−1, 3 orders of magnitude above background levels. In the DSL and during the diel vertical migration, dissipation levels ∼10−8 W kg−1 were observed.U.S. Office of Naval Research Grant Number: N00014-08-1-1162-0

    Exclusive and inclusive semileptonic decays of B mesons to D mesons

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    This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.43.651

    What Caused the Significant Increase in Atlantic Ocean Heat Content Since the mid-20th Century?

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    As the upper layer of the world ocean warms gradually during the 20th century, the inter-ocean heat transport from the Indian to Atlantic basin should be enhanced, and the Atlantic Ocean should therefore gain extra heat due to the increased upper ocean temperature of the inflow via the Agulhas leakage. Consistent with this hypothesis, instrumental records indicate that the Atlantic Ocean has warmed substantially more than any other ocean basin since the mid-20th century. A surface-forced global ocean-ice coupled model is used to test this hypothesis and to find that the observed warming trend of the Atlantic Ocean since the 1950s is largely due to an increase in the inter-ocean heat transport from the Indian Ocean. Further analysis reveals that the increased inter-ocean heat transport is not only caused by the increased upper ocean temperature of the inflow but also, and more strongly, by the increased Agulhas Current leakage, which is augmented by the strengthening of the wind stress curl over the South Atlantic and Indian subtropical gyre

    A regional modeling study of the entraining Mediterranean outflow

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    Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C12005, doi:10.1029/2007JC004145.We have evaluated a regional-scale simulation of the Mediterranean outflow by comparison with field data obtained in the 1988 Gulf of Cádiz Expedition. Our ocean model is based upon the Hybrid Coordinate Ocean Model (HYCOM) and includes the Richardson number–dependent entrainment parameterization of Xu et al. (2006). Given realistic topography and sufficient resolution, the model reproduces naturally the major, observed features of the Mediterranean outflow in the Gulf of Cádiz: the downstream evolution of temperature, salinity, and velocity profiles, the mean path and the spreading of the outflow plume, and most importantly, the localized, strong entrainment that has been observed to occur just west of the Strait of Gibraltar. As in all numerical solutions, there is some sensitivity to horizontal and vertical resolution. When the resolution is made coarser, the simulated currents are less vigorous and there is consequently less entrainment. Our Richardson number–dependent entrainment parameterization is therefore not recommended for direct application in coarse-resolution climate models. We have used the high-resolution regional model to investigate the response of the Mediterranean outflow to a change in the freshwater balance over the Mediterranean basin. The results are found in close agreement with the marginal sea boundary condition (MSBC): A more saline and dense Mediterranean deep water generates a significantly greater volume transport of the Mediterranean product water having only very slightly greater salinity.National Science Foundation via grant OCE0336799 and the National Ocean Partnership Program (NOPP) via award N000140410676

    Search for associated Higgs boson production using like charge dilepton events in p(p)over-bar collisions at root s=1.96 TeV

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    We present a search for associated Higgs boson production in the process p (p) over bar -> W/ZH -> l(+/-)l'(+/-) + X in ee, e mu, and mu mu final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at root s = 1.96 TeV corresponding to 5.3 fb(-1) of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C. L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV

    Hadronic transitions Υ(2S)→Υ(1S)

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    This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.58.052004.Using a 73.6pb(-1) data sample of Υ(2S) events collected with the CLEO II detector at the Cornell Electron Storage Ring, we have investigated the hadronic transitions between the Υ(2S) and the Υ(1S). The dipion transition Υ(2S)→Υ(1S)π(+)π(-) was studied using two different analysis techniques. Selecting events in which Υ(1S)→e(+)e(-),μ(+)μ(-) (“exclusive” analysis), and using the Υ(1S) leptonic branching fractions world averages from the PDG review, we obtained B(Υ(2S)→Υ(1S)π(+)π(-))=0.189±0.004±0.010, while using a method allowing Υ(1S)→anything (“inclusive” analysis) we obtained B(Υ(2S)→Υ(1S)π(+)π(-))=0.196±0.002±0.010. The appropriate weighted average of the two measurements gives B(Υ(2S)→Υ(1S)π(+)π(-))=0.192±0.002±0.010. Combining the exclusive and inclusive results we derive the Υ(1S) leptonic branching fractions Bee=0.0229±0.0008±0.0011 and Bμμ=0.0249±0.0008±0.0013. We also studied Υ(2S)→Υ(1S)π(0)π(0) and obtained B(Υ(2S)→Υ(1S)π(0)π(0))=0.092±0.006±0.008. Parameters of the ππ system (dipion invariant mass spectra, angular distributions) were analyzed and found to be consistent with current theoretical models. Lastly, we searched for the η and single π(0) transitions and obtained the 90% confidence level upper limits B(Υ(2S)→Υ(1S)η)<0.0028 and B(Υ(2S)→Υ(1S)π(0))<0.0011
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