Single scalar top production with polarized beams in ep collisions at HERA

From the point of view of the R-parity breaking supersymmetric model, we propose a scalar top (stop) search with longitudinally polarized electron (e-) and positron(e+) beams which will soon be available at the upgraded HERA. Fully polarized e- or e+ beams could produce the stop two times as much as unpolarized beams, while they increase background events due to the process of the standard model by about 30% in comparison with unpolarized ones. We show that right-handed e+ beams at HERA is efficient to produce the stop in the model. With 1 fb**(-1) of integrated luminosity we estimate reach in the coupling constant lambda'(131) for masses of the stop in the range 160-400 GeV. We can set a 95% confidence-level exclusion limit for lambda'(131) > 0.01-0.05 in the stop mass range of 240-280 GeV if no singal of the stop is observed. We also point out that y(=Q**2/sx) distributions of e+ coming from the stop shows the different behavior from those of the standard model.Comment: 12 pages, 6 eps figure

Neo-liberalism: Employability, and the Labor Market Mobility among Racialized Migrants- Canada's Study

The paper discusses the effect of political paradigm on the path of career development and the predicament of employment outcomes among racialized migrants in Canada. The study highlights challenge of retraining, skills development and access to Canadian work experience that meets neo-labor market demands. The study also examines how neoliberals’ interventions in market place, elimination of social services, and employment support programs have deterred labor force integration of the racialized migrants’ job seekers. In this Grounded Theory study (GT), participants have shared their experiences and challenges they have encountered form own perspectives. They shared stories about difficulties of finding suitable training and employment support programs within the current neo-liberalized labor market in Canada. The outcomes suggested that the rise of neoliberalism as noted in policies of social and employment services cuts, coupled with employment standard Acts reforms (ESA), have given employers more powers over hiring process which in many cases has nothing to do with candidate’s skills or qualifications. In this neo-political paradigm, the racialized migrants felt they have wasted most of their productive years searching for (1) training, mentorship or employment support programs that can facilitate effective transition to the labor force, and (2) dealing with challenges of improving unrecognized skills and qualification attained from countries of origin

Robust and real-time control of magnetic bearings for space engines

Currently, NASA Lewis Research Center is developing magnetic bearings for Space Shuttle Main Engine (SSME) turbopumps. The control algorithms which have been used are based on either the proportional-intergral-derivative control (PID) approach or the linear quadratic (LQ) state space approach. These approaches lead to an acceptable performance only when the system model is accurately known, which is seldom true in practice. For example, the rotor eccentricity, which is a major source of vibration at high speeds, cannot be predicted accurately. Furthermore, the dynamics of a rotor shaft, which must be treated as a flexible system to model the elastic rotor shaft, is infinite dimensional in theory and the controller can only be developed on the basis of a finite number of modes. Therefore, the development of the control system is further complicated by the possibility of closed loop system instability because of residual or uncontrolled modes, the so called spillover problem. Consequently, novel control algorithms for magnetic bearings are being developed to be robust to inevitable parametric uncertainties, external disturbances, spillover phenomenon and noise. Also, as pointed out earlier, magnetic bearings must exhibit good performance at a speed over 30,000 rpm. This implies that the sampling period available for the design of a digital control system has to be of the order of 0.5 milli-seconds. Therefore, feedback coefficients and other required controller parameters have to be computed off-line so that the on-line computational burden is extremely small. The development of the robust and real-time control algorithms is based on the sliding mode control theory. In this method, a dynamic system is made to move along a manifold of sliding hyperplanes to the origin of the state space. The number of sliding hyperplanes equals that of actuators. The sliding mode controller has two parts; linear state feedback and nonlinear terms. The nonlinear terms guarantee that the systems would reach the intersection of all sliding hyperplanes and remain on it when bounds on the errors in the system parameters and external disturbances are known. The linear part of the control drives the system to the origin of state space. Another important feature is that the controller parameter can be computed off-line. Consequently, on-line computational burden is small

GRACE/SUSY Automatic Generation of Tree Amplitudes in the Minimal Supersymmetric Standard Model

GRACE/SUSY is a program package for generating the tree-level amplitude and evaluating the corresponding cross section of processes of the minimal supersymmetric extension of the standard model (MSSM). The Higgs potential adopted in the system, however, is assumed to have a more general form indicated by the two-Higgs-doublet model. This system is an extension of GRACE for the standard model(SM) of the electroweak and strong interactions. For a given MSSM process the Feynman graphs and amplitudes at tree-level are automatically created. The Monte-Carlo phase space integration by means of BASES gives the total and differential cross sections. When combined with SPRING, an event generator, the program package provides us with the simulation of the SUSY particle productions.Comment: 39 page, 1 figur