2,860 research outputs found
The effect of cyclic martensitic transformations on diffusion of cobalt atoms in Fe-18wt.%Mn-2wt.%Si alloy
The Formation of Crystal Defects in a Fe-Mn-Si Alloy Under Cyclic Martensitic Transformations
Genome-wide identification and Phylogenic analysis of kelch motif containing ACBP in Brassica napus
Nightside Pi2 Wave Properties During an Extended Period With Stable Plasmapause Location and Variable Geomagnetic Activity
The frequencies and amplitudes of inner magnetosphere Pi2 waves are affected by the radial plasma density profile. Variable geomagnetic activity and external driving conditions can affect both wave properties and density profiles simultaneously. When interpreting observations, this can lead to ambiguity about whether changing wave properties are due to changing external conditions, density profiles, or a combination of factors. We present a case study using multipoint ground‐based and in situ measurements to examine Pi2 wave properties during a period of variable geomagnetic activity. Multiple satellite passes demonstrate the density profile and plasmapause location are stable for at least 2 h over a wide range of magnetic local time. This stability allows us to examine how factors besides the radial density profile affect Pi2 wave properties. We find evidence for Pi2 waves with a broadband frequency spectrum as well as a discrete frequency plasmaspheric virtual resonance (PVR) that is observed at low, middle, and high latitudes and both inside and outside the plasmapause. The PVR is excited in repeated bursts before, during, and after (1) the development of a substorm, (2) several auroral intensifications, (3) the development of Subauroral Polarization Stream flows/electric fields/conductivities, and (4) variable interplanetary magnetic field conditions. Through all these changes the PVR frequency remains remarkably stable (8.2 ± 0.53 mHz, based on low‐latitude ground magnetometer observations), suggesting that these variations have little effect on the frequency. This is consistent with PVR model predictions for a stationary plasmapause.Key PointsPlasmapause location is stable before, during, and after this substorm over wide range of MLTThere are multiple intensifications of a plasmaspheric virtual resonance (PVR) with spatially varying amplitudePVR wave frequency remains stable at 8.2 ± 0.53 mHz during 2 h period despite changing magnetospheric and ionospheric conditionsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142250/1/jgra53953_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142250/2/jgra53953.pd
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Control of ULF wave accessibility to the inner magnetosphere by the convection of plasma density
During periods of storm activity and enhanced convection, the plasma density in theafternoon sector of the magnetosphere is highly dynamic due to the development of plasmasphericdrainage plume (PDP) structure. This significantly affects the local Alfvén speed and alters the propagationof ULF waves launched from the magnetopause. Therefore, it can be expected that the accessibility of ULFwave power for radiation belt energization is sensitively dependent on the recent history of magnetosphericconvection and the stage of development of the PDP. This is investigated using a 3-D model for ULF waveswithin the magnetosphere in which the plasma density distribution is evolved using an advection model forcold plasma, driven by a (VollandStern) convection electrostatic field (resulting in PDP structure). The wavemodel includes magnetic field day/night asymmetry and extends to a paraboloid dayside magnetopause,from which ULF waves are launched at various stages during the PDP development. We find that the plumestructure significantly alters the field line resonance location, and the turning point for MHD fast waves,introducing strong asymmetry in the ULF wave distribution across the noon meridian. Moreover, thedensity enhancement within the PDP creates a waveguide or local cavity for MHD fast waves, such thateigenmodes formed allow the penetration of ULF wave power to much lower L within the plume thanoutside, providing an avenue for electron energization
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Observation of the Baryonic Flavor-Changing Neutral Current Decay Lambda_b -> Lambda mu+ mu-
We report the first observation of the baryonic flavor-changing neutral
current decay Lambda_b -> Lambda mu+ mu- with 24 signal events and a
statistical significance of 5.8 Gaussian standard deviations. This measurement
uses ppbar collisions data sample corresponding to 6.8fb-1 at sqrt{s}=1.96TeV
collected by the CDF II detector at the Tevatron collider. The total and
differential branching ratios for Lambda_b -> Lambda mu+ mu- are measured. We
find B(Lambda_b -> Lambda mu+ mu-) = [1.73+-0.42(stat)+-0.55(syst)] x 10^{-6}.
We also report the first measurement of the differential branching ratio of B_s
-> phi mu+ mu- using 49 signal events. In addition, we report branching ratios
for B+ -> K+ mu+ mu-, B0 -> K0 mu+ mu-, and B -> K*(892) mu+ mu- decays.Comment: 8 pages, 2 figures, 4 tables. Submitted to Phys. Rev. Let
Search for Neutral Higgs Bosons in Events with Multiple Bottom Quarks at the Tevatron
The combination of searches performed by the CDF and D0 collaborations at the
Fermilab Tevatron Collider for neutral Higgs bosons produced in association
with b quarks is reported. The data, corresponding to 2.6 fb-1 of integrated
luminosity at CDF and 5.2 fb-1 at D0, have been collected in final states
containing three or more b jets. Upper limits are set on the cross section
multiplied by the branching ratio varying between 44 pb and 0.7 pb in the Higgs
boson mass range 90 to 300 GeV, assuming production of a narrow scalar boson.
Significant enhancements to the production of Higgs bosons can be found in
theories beyond the standard model, for example in supersymmetry. The results
are interpreted as upper limits in the parameter space of the minimal
supersymmetric standard model in a benchmark scenario favoring this decay mode.Comment: 10 pages, 2 figure
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
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