Digital halftoning using fibonacci-like sequence pertubation and using vision-models in different color spaces

A disadvantage in error diffusion is that it creates objectionable texture patterns at certain gray levels. An approach, threshold perturbation by Fibonacci-like sequences, was studied. This process is simpler than applying a vision model and it also decreases the visible patterns in error diffusion. Vector error diffusion guarantees minimum color distance in binarization provided that a uniform color space is used. Four color spaces were studied in this research. It was found that vector error diffusion in two linear color spaces made no reduction in the quality of halftoning compared with that in CIEL*a*b* or CIEL*u*v* color spaces. A luminance vision MTF and a chroma vision MTF were used in model-based error diffusion to further improve the halftone image quality

Preferred skin colour reproduction

The memory colour reproduction is an important factor in judging image quality of photographic images of real life scenes. As the most important memory colour category, skin tone was extensively studied for preferred colour reproduction in this research. The methodology to study skin colour preference was then applied to study the colour preference of two other important colour categories: green foliage and blue sky. There are three essential parts for preferred skin colour enhancement: 1) building a skin colour model to detect skin colours or skin pixels; 2) finding a preferred skin colour region or a preferred skin colour centre; and 3) developing an algorithm to morph skin colours toward the preferred skin colour region. This study for skin colour enhancement started with the mathematical modelling of the skin colour region for skin colour detection. The modelling of skin colours was then applied to adjust skin colours of test images for psychophysical experiments that were to determine a preferred skin colour region. Finally, the skin colour modelling and the preferred skin colour centres were applied to adjust skin colours of digital photographic images for preferred colour reproduction. Two approaches were developed to model the skin colour distribution for skin colour detection. The first approach was to model a local colour region for general applications. A convex hull is constructed to fit the geometrical shape of a local region, and then the convex hull is approximated with mathematical formulae. The formulations and data fitting are adjusted with interactive 3-D visualization. The approach is flexible for fitting data gamut with various mathematical forms for different purposes. The other approach was to model skin colours with elliptical shapes. Three elliptical skin colour models were developed for skin colour detection. The first one is to model the skin colour cluster using a single ellipse ignoring the lightness (or luminance) dependency. It is simple and efficient, and the skin colour detection accuracy may be adequate for many applications. In the second model, the skin colour ellipse is adapted to different lightness so that the shape of the ellipse fits the skin colour cluster more accurately. The model is more complex to train and is less efficient in computation, but it is more accurate in skin colour detection. In the third method, an ellipsoid is trained to fit the skin colour cluster. It is almost as simple to train as the first model, but the skin colour detection accuracy is improved. Finally, these models were applied to train mixed skin colours, African skin colours, Caucasian skin colours, and Asian skin colours

Higgs Boson Studies at the Tevatron

We combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90--200 GeV$/c^2$ produced in the gluon-gluon fusion, $WH$, $ZH$, $t{\bar{t}}H$, and vector boson fusion processes, and decaying in the $H\rightarrow b{\bar{b}}$, $H\rightarrow W^+W^-$, $H\rightarrow ZZ$, $H\rightarrow\tau^+\tau^-$, and $H\rightarrow \gamma\gamma$ modes. The data correspond to integrated luminosities of up to 10 fb$^{-1}$ and were collected at the Fermilab Tevatron in $p{\bar{p}}$ collisions at $\sqrt{s}=1.96$ TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/$c^2$. The local significance corresponds to 3.0 standard deviations at $m_H=125$ GeV/$c^2$, consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for $H \to b\bar{b}$, $H \to W^+W^-$, $H\rightarrow\tau^+\tau^-$, and $H\rightarrow\gamma\gamma$. The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/$c^2$

Evidence for a Particle Produced in Association with Weak Bosons and Decaying to a Bottom-Antibottom Quark Pair in Higgs Boson Searches at the Tevatron

We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron p[bar over p] collisions at √s=1.96  TeV, correspond to integrated luminosities of up to 9.7  fb[superscript -1]. The searches are conducted for a Higgs boson with mass in the range 100–150  GeV/c[superscript 2]. We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135  GeV/c[superscript 2]. The largest local significance is 3.3 standard deviations, corresponding to a global significance of 3.1 standard deviations. We interpret this as evidence for the presence of a new particle consistent with the standard model Higgs boson, which is produced in association with a weak vector boson and decays to a bottom-antibottom quark pair

Tevatron Run II combination of the effective leptonic electroweak mixing angle

International audienceDrell-Yan lepton pairs produced in the process pp¯→ℓ+ℓ-+X through an intermediate γ*/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin2θefflept using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9–10  fb-1 of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin2θefflept=0.23148±0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin2θW, or equivalently the W-boson mass MW, using the zfitter software package yields sin2θW=0.22324±0.00033 or equivalently, MW=80.367±0.017  GeV/c2

Tevatron Combination of Single-Top-Quark Cross Sections and Determination of the Magnitude of the Cabibbo-Kobayashi-Maskawa Matrix Element Vtb\bf V_{tb}

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb$^{−1}$ per experiment. The t-channel cross section is measured to be σ$_t$=2.25$_{-0.31}^{+0.29}$ pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ$_{s+t}$=3.30$_{-0.40}^{+0.52}$ pb, without assuming the standard model value for the ratio σ$_s$/σ$_t$. The resulting value of the magnitude of the top-to-bottom quark coupling is |V$_{tb}$|=1.02$_{-0.05}^{+0.06}$, corresponding to |V$_{tb}$|>0.92 at the 95% C.L