Research study of droplet sizing technology leading to the development of an advanced droplet sizing system

An instrument to measure the size and velocity of droplets was developed. The instrument uses one of two techniques, as appropriate. In the first technique two small laser beams of one color identify the center of a larger laser beam of a different color. This defines a region of almost uniform intensity where the light scattered by the individual droplets can be related to their size. The first technique uses the visibility of a Doppler burst and validates it against the peak intensity of the signal's pedestal. Results are presented for monodisperse, bimodal, trimodal, and polydisperse sprays produced by the Berglund-Liu droplet generator and a pressure nozzle. Size distributions of a given spray obtained using three different size ranges show excellent self-consistency in the overlapping region. Measurements of sprays of known characteristics exhibit errors in the order of 10%. The principles of operation and design criteria of the instrument are discussed in great detail

The Higgs mass in the MSSM infrared fixed point scenario

In the infrared fixed point (IFP) scenario of the minimal supersymmetric model (MSSM), the top-quark mass and other physical quantities of the low-energy theory are insensitive to the values of the parameters of the theory at some high energy scale. In this framework we evaluate the light CP-even Higgs mass, $m_h$, taking into account some important effects that had not been previously considered. In particular, the supersymmetric correction to the relation between the running and the physical top-quark masses lowers the value of $\tan\beta$, thereby implying a lower predicted value of $m_h$. Assuming a supersymmetric threshold of $M_S\leq 1$ TeV and $M_t=175$ GeV, we find an upper bound of $m_h\le 97\pm 2$ GeV; the most plausible value of $m_h$ lies somewhat below the upper bound. This places the Higgs boson in the IFP scenario well within the reach of the LEP-2 Higgs search.Comment: 18 pages, LaTeX, 5 ps figures, uses psfig.sty. Final version, some comments and a figure added, references correcte

Renormalization of dimension-six operators relevant for the Higgs decays h→γγ,γZh\rightarrow \gamma\gamma,\gamma Z

The discovery of the Higgs boson has opened a new window to test the SM through the measurements of its couplings. Of particular interest is the measured Higgs coupling to photons which arises in the SM at the one-loop level, and can then be significantly affected by new physics. We calculate the one-loop renormalization of the dimension-six operators relevant for $h\rightarrow \gamma\gamma, \gamma Z$, which can be potentially important since it could, in principle, give log-enhanced contributions from operator mixing. We find however that there is no mixing from any current-current operator that could lead to this log-enhanced effect. We show how the right choice of operator basis can make this calculation simple. We then conclude that $h\rightarrow \gamma\gamma, \gamma Z$ can only be affected by RG mixing from operators whose Wilson coefficients are expected to be of one-loop size, among them fermion dipole-moment operators which we have also included.Comment: 21 pages. Improved version with h -> gamma Z results added and structure of anomalous-dimension matrix determined further. Conclusions unchange

Self collimation of ultrasound in a 3D sonic crystal

We present the experimental demonstration of self-collimation (subdiffractive propagation) of an ultrasonic beam inside a three-dimensional sonic crystal. The crystal is formed by two crossed steel cylinders structures in a woodpile-like geometry disposed in water. Measurements of the 3D field distribution show that a narrow beam which diffractively spreads in the absence of the sonic crystal is strongly collimated in propagation inside the crystal, demonstrating the 3D self-collimation effect.Comment: 3 figures, submitted to Applied Physics Letter

The use of arc-erosion as a patterning technique for transparent conductive materials

Within the framework of cost-effective patterning processes a novel technique that saves photolithographic processing steps, easily scalable to wide area production, is proposed. It consists of a tip-probe, which is biased with respect to a conductive substrate and slides on it, keeping contact with the material. The sliding tip leaves an insulating path (which currently is as narrow as 30 μm) across the material, which enables the drawing of tracks and pads electrically insulated from the surroundings. This ablation method, called arc-erosion, requires an experimental set up that had to be customized for this purpose and is described. Upon instrumental monitoring, a brief proposal of the physics below this process is also presented. As a result an optimal control of the patterning process has been acquired. The system has been used on different substrates, including indium tin oxide either on glass or on polyethylene terephtalate, as well as alloys like Au/Cr, and Al. The influence of conditions such as tip speed and applied voltage is discusse