Squarks in Tevatron Dilepton Events ?

We consider unusual events in the CDF and D0 dilepton+jets sample with very high ET(lepton) and ET(missing). It is possible, but very unlikely, that these events originate from top quark pair production; however, they have characteristics that are better accounted for by decays of supersymmetric quarks with mass in the region of 300 GeV.Comment: 5 pages, 2 postscript (eps) figures, uses sprocl.sty (included

An Analysis of U.S. Postwar Consumption and Saving: Part II -- Empirical Results

A new empirical analysis of aggregate United States consumption and saving for the period 1947-80 is presented. The model is based on the theory of exact aggregation. It recognizes explicitly that households with different characteristics may be heterogeneous in their behavior and that aggregate behavior may depend on the changing composition of households by characteristics and therefore may not be adequately portrayed by a representative consumer, but otherwise it imposes minimal assumptions on household behavior. The model integrates longitudinal and cross-sectional microeconomic data on household characteristics with the traditional aggregate time-series data. Various hypotheses on consumption, such as age independence, proportionality to wealth, and price independence, are tested , and rejected. Strong evidence of relative price effects and a systematic variation of aggregate consumption with changing age distribution of wealth in the economy is found. Especially important is the substantial estimated difference in the shares of wealth consumed between households headed by persons born prior to and those born after 1939. One important lesson from this study is that modeling the aggregate U.S. economy as a representative consumer may give rise to misleading results.

Post-War Economic Growth in the Group-of-Five Countries: A New Analysis

An inter-country aggregate production function is estimated using annual data for the post-war period drawn from the Group-of-Five (G-5) countries: France, West Germany, Japan, United Kingdom and United states. It is assumed that all countries have the same underlying production function, not in terms of the measured outputs and inputs, but in terms of efficiency equivalent units of outputs and inputs. The measured quantities of outputs and inputs of each country may be converted into efficiency-equivalent quantities of outputs and inputs by the multiplication of country and commodity-specific and time-varying augmentation factors. These augmentation factors are estimated simultaneously with the parameters of the aggregate production function. Within this framework, the traditional assumptions for the measurement of productivity--constant returns to scale, neutrality of technical progress and profit maximization--are tested and all are rejected. Additional hypotheses about the nature of technical progress are also tested. It is found that technical progress may be represented as purely capital augmenting. In particular, the rate of augmentation is estimated at between 14 and 16 percent per annum for France, West Germany and Japan, and between 8 and 10 percent per annum for the U.K. and the U.S. for the period under study. It is also found that technical progress is capital-saving rather than labor-saving and is therefore unlikely to be a cause of structural unemployment. Using the estimated production function parameters, a growth-accounting exercise is carried out and the results are compared with those obtained from the conventional approach. Technical progress is found to be the most important source of growth, accounting for more than 50 percent, followed by the growth of capital input. Together they account for more than 75 percent of the growth of real output in the Group-of-Five (G-5) countries in the period under study. An international and intertemporal comparison of the productive efficiencies is also undertaken. It is found that the United States had the highest level of overall productive efficiency for the whole period under study. However, the productive efficiencies of France, West Germany and Japan rose rapidly from less than 40 percent of the U.S. level in 1949 to two-thirds of the U.S. level in 1985. There is thus some evidence of convergence.

An Analysis of Postwar U.S. Consumption and Saving: Part I -- The Model and Aggregation

A new empirical analysis of aggregate United States consumption and saving for the period 1947-80 is presented. The model is based on the theory of exact aggregation. It recognizes explicitly that households with different characteristics may be heterogeneous in their behavior and that aggregate behavior may depend on the changing composition of households by characteristics and therefore may not be adequately portrayed by a representative consumer, but otherwise it imposes minimal assumptions on household behavior. The model integrates longitudinal and cross-sectional microeconomic data on household characteristics with the traditional aggregate time-series data. Various hypotheses on consumption, such as age independence, proportionality to wealth, and price independence, are tested and rejected. Strong evidence of relative price effects and a systematic variation of aggregate consumption with changing age distribution of wealth in the economy is found. Especially important is the substantial estimated difference in the shares of wealth consumed between households headed by persons born prior to and those born after 1939. One important lesson from this study is that modeling the aggregate U. S. economy as a representative consumer may give rise to misleading results.

How and why do student teachers use ICT?

This paper examines how and why student teachers made use of information and communication technology (ICT) during a 1-year initial teacher education programme from 2008 to 2009. This is a mixed methods study involving a survey (N = 340) of the entire cohort and a series of semi-structured interviews with a sample of student teachers within the cohort (N = 21). The study explored several themes, including the nature of student teachers' use of ICT; variation in the use of ICT; support for, and constraints on, using ICT; attitudes to ICT and to teaching and learning more generally. It was found that nearly all teachers were receptive to using ICT – more so than their in-service counterparts – and made frequent use of it during their placement (internship) experience. The Interactive Whiteboard (IWB) was central to nearly all student teachers' use of ICT, in good part, because it was already used by their mentors and was widely accessible. Student teachers' use of ICT was categorized in three levels. Routine users focused mostly on the use of the IWB for whole class teaching; extended users gave greater opportunities for pupils to use ICT for themselves; innovative student teachers used ICT in a greater range of contexts and made more effort to overcome barriers such as access. ICT use was seen as emerging from a mix of factors: chiefly student teachers' access to ICT; their feeling of ‘self-efficacy’ when using ICT; and their belief that ICT had a positive impact on learning – in particular, the impact on pupils' behavioural and affective engagement. Factors which influenced ICT use included mentoring, training and support. Limitations on student teachers' use of ICT are explored and it is suggested that new teachers need to be supported in developing a more discerning use as they begin their teaching careers

Statistical Understanding of Quark and Lepton Masses in Gaussian Landscapes

The fundamental theory of nature may allow a large landscape of vacua. Even if the theory contains a unified gauge symmetry, the 22 flavor parameters of the Standard Model, including neutrino masses, may be largely determined by the statistics of this landscape, and not by any symmetry. Then the measured values of the flavor parameters do not lead to any fundamental symmetries, but are statistical accidents; their precise values do not provide any insights into the fundamental theory, rather the overall pattern of flavor reflects the underlying landscape. We investigate whether random selection from the statistics of a simple landscape can explain the broad patterns of quark, charged lepton, and neutrino masses and mixings. We propose Gaussian landscapes as simplified models of landscapes where Yukawa couplings result from overlap integrals of zero-mode wavefunctions in higher-dimensional supersymmetric gauge theories. In terms of just five free parameters, such landscapes can account for all gross features of flavor, including: the hierarchy of quark and charged lepton masses; small quark mixing angles, with 13 mixing less than 12 and 23 mixing; very light Majorana neutrino masses, with the solar to atmospheric neutrino mass ratio consistent with data; distributions for leptonic 12 and 23 mixings that are peaked at large values, while the distribution for 13 mixing is peaked at low values; and order unity CP violating phases in both the quark and lepton sectors. While the statistical distributions for flavor parameters are broad, the distributions are robust to changes in the geometry of the extra dimensions. Constraining the distributions by loose cuts about observed values leads to narrower distributions for neutrino measurements of 13 mixing, CP violation, and neutrinoless double beta decay.Comment: 86 pages, 26 figures, 2 tables, and table of content

Neutrino mixing and mass hierarchy in Gaussian landscapes

The flavor structure of the Standard Model may arise from random selection on a landscape. In a class of simple models, called "Gaussian landscapes," Yukawa couplings derive from overlap integrals of Gaussian zero-mode wavefunctions on an extra-dimensional space. Statistics of vacua are generated by scanning the peak positions of these wavefunctions, giving probability distributions for all flavor observables. Gaussian landscapes can account for all of the major features of flavor, including both the small electroweak mixing in the quark sector and the large mixing observed in the lepton sector. We find that large lepton mixing stems directly from lepton doublets having broad wavefunctions on the internal manifold. Assuming the seesaw mechanism, we find the mass hierarchy among neutrinos is sensitive to the number of right-handed neutrinos, and can provide a good fit to neutrino oscillation measurements.Comment: 11 pages, 2 figure