13,268 research outputs found
Free radical OH, a molecule of astrophysical and aeronomic interest
The chemistry and physics of the gaseous OH free radical as it applies to interstellar space, planetary atmospheres, and the sun is presented. Topics considered are: (1) rotational-vibrational transitions; (2) dissociation and ionization processes; (3) spectral characteristics
Tensile and creep rupture behavior of P/M processed Nb-base alloy, WC-3009
Due to its high strength at temperatures up to 1600 K, fabrication of niobium base alloy WC-3009 (Nb30Hf9W) by traditional methods is difficult. Powder metallurgy (P/M) processing offers an attractive fabrication alternative for this high strength alloy. Spherical powders of WC-3009 produced by electron beam atomizing (EBA) process were successfully consolidated into a one inch diameter rod by vacuum hot pressing and swaging techniques. Tensile strength of the fully dense P/M material at 300-1590 K were similar to the arc-melted material. Creep rupture tests in vacuum indicated that WC-3009 exhibits a class 1 solid solution (glide controlled) creep behavior in the 1480 to 1590 K temperature range and stress range of 14 to 70 MPa. The creep behavior was correlated with temperature and stress using a power law relationship. The calculated stress exponent n, was about 3.2 and the apparent activation energy, Q, was about 270 kJ/mol. The large creep ductility exhibited by WC-3009 was attributed to its high strain rate sensitivity
Criticality of tuning in athermal phase transitions
We experimentally address the importance of tuning in athermal phase
transitions, which are triggered only by a slowly varying external field acting
as tuning parameter. Using higher order statistics of fluctuations, a singular
critical instability is detected for the first time in spite of an apparent
universal self-similar kinetics over a broad range of driving force. The
results as well as the experimental technique are likely to be of significance
to many slowly driven non-equilibrium systems from geophysics to material
science which display avalanche dynamics.Comment: 5 pages, 4 figure
Diphoton Resonances in the Renormalizable Coloron Model
The renormalizable coloron model, which has previously been shown in the
literature to be consistent with a wide array of theoretical and precision
electroweak constraints, includes a pair of spinless bosons (one scalar, one
pseudoscalar). We show that either of them, or both together if they are
degenerate, could be responsible for the diphoton resonance signal for which
both CMS and ATLAS have seen evidence. Because either of these bosons would be
produced and decay through loops of spectator fermions, the absence of signals
in dijet, , and electroweak boson pair channels is not a surprise.Comment: 18 pages, 5 figures. (Modified to respond to referee comments,
discussion of Landau poles in scalar couplings added.
Color Discriminant Variable to Separate Dijet Resonances at the LHC
A narrow resonance decaying to dijets could be discovered at the 14 TeV run
of the LHC. To quickly identify its color structure in a model-independent
manner, we introduced a method based on a color discriminant variable,
determined from the measurements of the resonance's production cross section,
mass and width. This talk introduces a more transparent theoretical formulation
of the color discriminant variable that highlights its relationship to the
branching ratios of the resonance into incoming and outgoing partons and to the
properties of those partons. The formulation makes it easier to predict the
value of the variable for a given class of resonance. We show that this method
applies well to color-triplet and color-sextet scalar diquarks, distinguishing
them clearly from other candidate resonances.Comment: 9 pages, 3 figures. Presentation at the DPF 2015 Meeting of the
American Physical Society Division of Particles and Fields, Ann Arbor,
Michigan, August 4-8, 201
- …