How good are your fits? Unbinned multivariate goodness-of-fit tests in high energy physics

Multivariate analyses play an important role in high energy physics. Such analyses often involve performing an unbinned maximum likelihood fit of a probability density function (p.d.f.) to the data. This paper explores a variety of unbinned methods for determining the goodness of fit of the p.d.f. to the data. The application and performance of each method is discussed in the context of a real-life high energy physics analysis (a Dalitz-plot analysis). Several of the methods presented in this paper can also be used for the non-parametric determination of whether two samples originate from the same parent p.d.f. This can be used, e.g., to determine the quality of a detector Monte Carlo simulation without the need for a parametric expression of the efficiency.Comment: 32 pages, 12 figure

Structural neural networks subserving oculomotor function in first-episode schizophrenia

BACKGROUND: Smooth pursuit and antisaccade abnormalities are well documented in schizophrenia, but their neuropathological correlates remain unclear. METHODS: In this study, we used statistical parametric mapping to investigate the relationship between oculomotor abnormalities and brain structure in a sample of first-episode schizophrenia patients (n = 27). In addition to conventional volumetric magnetic resonance imaging, we also used magnetization transfer ratio, a technique that allows more precise tissue characterization. RESULTS: We found that smooth pursuit abnormalities were associated with reduced magnetization transfer ratio in several regions, predominantly in the right prefrontal cortex. Antisaccade errors correlated with gray matter volume in the right medial superior frontal cortex as measured by conventional magnetic resonance imaging but not with magnetization transfer ratio. CONCLUSIONS: These preliminary results demonstrate that specific structural abnormalities are associated with abnormal eye movements in schizophrenia

Nonperturbative Effects in Gluon Radiation and Photoproduction of Quark Pairs

We introduce a nonperturbative interaction for light-cone fluctuations containing quarks and gluons. The $\bar qq$ interaction squeezes the transverse size of these fluctuations in the photon and one does not need to simulate this effect via effective quark masses. The strength of this interaction is fixed by data. Data on diffractive dissociation of hadrons and photons show that the nonperturbative interaction of gluons is much stronger. We fix the parameters for the nonperturbative quark-gluon interaction by data for diffractive dissociation to large masses (triple-Pomeron regime). This allows us to predict nuclear shadowing for gluons which turns out to be not as strong as perturbative QCD predicts. We expect a delayed onset of gluon shadowing at $x \leq 10^{-2}$ shadowing of quarks. Gluon shadowing turns out to be nearly scale invariant up to virtualities $Q^2\sim 4 GeV^2$ due to presence of a semihard scale characterizing the strong nonperturbative interaction of gluons. We use the same concept to improve our description of gluon bremsstrahlung which is related to the distribution function for a quark-gluon fluctuation and the interaction cross section of a $\bar qqG$ fluctuation with a nucleon. We expect the nonperturbative interaction to suppress dramatically the gluon radiation at small transverse momenta compared to perturbative calculations.Comment: 58 pages of Latex including 11 figures. Shadowing for soft gluons and Fig. 6 are added as well as a few reference

The effect of autonomy, training opportunities, age and salaries on job satisfaction in the South East Asian retail petroleum industry

South East Asian petroleum retailers are under considerable pressure to improve service quality by reducing turnover. An empirical methodology from this industry determined the extent to which job characteristics, training opportunities, age and salary influenced the level of job satisfaction, an indicator of turnover. Responses are reported on a random sample of 165 site employees (a 68% response rate) of a Singaporean retail petroleum firm. A restricted multivariate regression model of autonomy and training opportunities explained the majority (35.4%) of the variability of job satisfaction. Age did not moderate these relationships, except for employees >21 years of age, who reported enhanced job satisfaction with additional salary. Human Capital theory, Life Cycle theory and Job Enrichment theory are invoked and explored in the context of these findings in the South East Asian retail petroleum industry. In the South East Asian retail petroleum industry, jobs providing employees with the opportunity to undertake a variety of tasks that enhanced the experienced meaningfulness of work are likely to promote job satisfaction, reduce turnover and increase the quality of service