New Strong Interactons at the Tevatron ?

Recent results from CDF indicate that the inclusive cross section for jets with $E_T > 200$ GeV is significantly higher than that predicted by QCD. We describe here a simple flavor-universal variant of the ``coloron" model of Hill and Parke that can accommodate such a jet excess, and which is not in contradiction with other experimental data. As such, the model serves as a useful baseline with which to compare both the data and other models proposed to describe the jet excess. An interesting theoretical feature of the model is that if the global chiral symmetries of the quarks remain unbroken in the confining phase of the coloron interaction, it realizes the possibility that the ordinary quarks are composite particles.Comment: added $1/Lambda^4$ contributions to scattering cross-sections; 10 pages, LaTeX, includes 1 figure. Full postscript version at http://smyrd.bu.edu/htfigs/htfigs.htm

Limits on the Ununified Standard Model

The ununified standard model is an extension of the standard model that contains separate electroweak gauge groups for quarks and leptons. When it was originally proposed, data allowed the new gauge bosons to be quite light. We use recent data from precision electroweak measurements to put stringent bounds on the ununified standard model. In particular, at the 95% confidence level, we find that the ununified gauge bosons must have masses above about 2 TeV.Comment: 14 pages, plain TeX, 2 postscript figures, figures also available at http://smyrd.bu.edu/htfigs/figure.htm

Effects of R-parity violating supersymmetry in top pair production at linear colliders with polarized beams

In the minimal supersymmetric standard model with R-parity violation, the lepton number violating top quark interactions can contribute to the top pair production at a linear collider via tree-level u-channel squark exchange diagrams. We calculate such contributions and find that in the allowed range of these R-violating couplings, the top pair production rate as well as the top quark polarization and the forward-backward asymmetry can be significantly altered. By comparing the unpolarized beams with the polarized beams, we find that the polarized beams are more powerful in probing such new physics.Comment: 10 pages, 6 fig

Mixing of Newtonian and viscoelastic fluids using “butterfly” impellers

AbstractThe mixing of high viscosity and viscoelastic fluids may be performed in industry using a “butterfly” impeller, which has received scant attention. This paper describes the characterisation of these impellers using both Newtonian and viscoelastic (Boger) fluids with an identical base viscosity under laminar flow conditions in batch tanks without baffles. Measurements are made using two rotational speeds (N=30 or 60rpm) over a wide range of impeller to tank diameter ratios from 0.53 to 0.98. Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) have been used to determine local velocity fields, shear rates, flow numbers and mixing times, with impeller power number Po obtained from torque measurements. A down-pumping flow pattern is observed, with maximum normalised velocities of 25% of the impeller tip speed observed in the axial plane, increasing to 60% in the rotational plane due to solid body rotation. Angle resolved measurements found these to be slightly increased as the impeller passes the image plane, with viscoelastic fluids displaying a greater uniformity of velocity across the image planes due to elastic energy storage. Maximum shear rates are greatest between the impeller and the wall, yet remain low i.e. O(10)s−1. Mixing times obtained from PLIF show that mixing times in viscoelastic fluids show a slight reduction compared to the Newtonian equivalent. The impeller power number was determined as Po=0.6 in the turbulent regime, while the laminar constant Kp and the Metzner–Otto constant ks were equal to 122 and 16.0 respectively

Assessment of different methods of analysis to characterise the mixing of shear-thinning fluids in a Kenics KM static mixer using PLIF

AbstractThe performance of Kenics KM static mixers has been determined for the blending of two shear-thinning fluid streams with identical or different rheology. Planar Laser Induced Fluorescence (PLIF) has been used to obtain the concentration distribution at the mixer outlet by doping one fluid stream with fluorescent dye upstream of the mixer inlet. The effect of scale of the static mixer, total flow rate, flow ratio between the fluid streams and inlet configuration have been investigated. The applicability of different methods to characterise mixing performance is examined by comparing conventional mixing measures such as coefficient of variation and maximum striation area against recent alternative methods presented in the literature, such as the areal distribution method developed by Alberini et al. (2014). A method of characterising individual striations by determining their distribution as a function of size and concentration is also presented. These findings illustrate the complexity of information-rich PLIF images, and highlight how different methods of analysis may be appropriate given the dependencies of the downstream process

Interface charged impurity scattering in semiconductor MOSFETs and MODFETs: temperature dependent resistivity and 2D "metallic" behavior

We present the results on the anomalous 2D transport behavior by employing Drude-Boltzmann transport theory and taking into account the realistic charge impurity scattering effects. Our results show quantitative agreement with the existing experimental data in several different systems and address the origin of the strong and non-monotonic temperature dependent resistivity.Comment: Presented at SIMD, Dec. 1999 in Hawaii. To be published in Superlattices and Microstructures, May 2000 issu

Spin-2 Kaluza-Klein scattering in a stabilized warped background

Scattering amplitudes involving massive spin-2 particles typically grow rapidly with energy. In this paper we demonstrate that the anomalous high-energy growth of the scattering amplitudes cancel for the massive spin-2 Kaluza-Klein modes arising from compactified five-dimensional gravity in a stabilized warped geometry. Generalizing previous work, we show that the two sum rules which enforce the cancellations between the contributions to the scattering amplitudes coming from the exchange of the (massive) radion and those from the exchange of the tower of Goldberger-Wise scalar states (admixtures of the original gravitational and scalar fields of the theory) still persist in the case of the warping which would be required to produce the hierarchy between the weak and Planck scales in a Randall-Sundrum model. We provide an analytic proof of one combination of these generalized scalar sum rules and show how the sum rule depends on the Einstein equations determining the background geometry and the mode-equations and normalization of the tower of physical scalar states. Finally, we provide a consistent and self-contained derivation of the equations governing the physical scalar modes, and we list, in appendixes, the full set of sum rules ensuring proper high-energy growth of all 2 → 2 massive spin-2 scattering amplitudes.R. Sekhar Chivukula, Dennis Foren, Kirtimaan A. Mohan, Dipan Sengupta, and Elizabeth H. Simmon

Walking Technicolor And The ZbbˉZb\bar b Vertex

A slowly running technicolor coupling will affect the size of non-oblique corrections to the $Zb\bar b$ vertex from extended technicolor dynamics. We show that while ``walking technicolor'' reduces the magnitude of the corrections, they generally remain large enough to be seen at LEP.Comment: LaTeX, 11 pages, 3 figure

Top quark associated production of topcolor pions at hadron colliders

We investigate the associated production of a neutral physical pion with top quarks in the context of topcolor assisted technicolor. We find that single-top associated production does not yield viable rates at either the Tevatron or LHC. tt-associated production at the Tevatron is suppressed relative to Standard Model ttH, but at the LHC is strongly enhanced and would allow for easy observation of the main decay channels to bottom quarks, and possible observation of the decay to gluons.Comment: 13 pages, 4 figures, submitted to PR