Secondary particles spectra in the decay of a polarized top quark with anomalous tWbtWb coupling

Analytic expression for energy and angular dependence of a secondary charged lepton in the decay of a polarized top quark with anomalous $tWb$ couplings in the presence of all anomalous couplings are derived. The angular distribution of the b-quark is derived as well. It is presented that the charged lepton spin correlation coefficient is not very sensitive to the anomalous couplings. However, the b-quark spin correlation coefficient is sensitive to anomalous couplings and could be used as a powerful tool for searching of non-SM coupling.Comment: 9 pages, 5 figure

Probing the Anomalous Couplings of the Top Quark with Gluon at the LHC and Tevatron

In this paper, we study the sensitivity of the fraction of $t\bar{t}$ events arising from gluon-gluon fusion to the chromoelectric and chromomagnetic dipole moments (CEDM and CMDM) as well as the total and differential $t\bar{t}$ cross sections at the LHC and Tevatron. The sensitivity of measured charged asymmetry at the LHC to CEDM and CMDM is also studied. We find that at the Tevatron and the LHC, non-zero values of CMDM could suppress the $t\bar{t}$ production rate. It is shown that the ratio of $\sigma(gg\rightarrow t\bar{t})/\sigma(p\bar{p}\rightarrow t\bar{t})$ at the Tevatron is more sensitive to CEDM and CMDM than the LHC case. The presence of CEDM always increases the contribution of gluon-gluon fusion process in top pair rate at the Tevatron and LHC. Except for a small range of CMDM, the presence of CEDM and CMDM can increase the fraction of gluon-gluon fusion at the Tevatron and LHC. The measured ratio of $\sigma(gg\rightarrow t\bar{t})/\sigma(p\bar{p}\rightarrow t\bar{t})$ at the Tevatron is used to derive bounds on the chromoelectric and chromomagnetic dipole moments as well as the total and differential ($d\sigma/dm_{t\bar{t}}$) cross sections at the LHC and Tevatron, and the measured charged asymmetry at the LHC. The combination of $d\sigma_{TeV}/dm_{t\bar{t}}$ and $\sigma_{LHC}$ provides stringent limits on CMDM and CEDM.Comment: 11 pages,6 figures,2 table

Impact of Torsion Space-Time on ttˉt\bar{t} observables at Hadron Colliders

Starting from the effective torsion space-time model, we study its effects on the top pair production cross section at hadron colliders. We also study the effect of this model on top pair asymmetries at the Tevatron and the LHC. We find that torsion space-time can explain forward-backward asymmetry according to measured anomaly at Tevatron. We find an allowed region in the parameters space which can satisfy simultaneously all $t\bar{t}$ observables measured at Tevatron and LHC.Comment: 17 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1207.064

Longitudinal analysis of crash frequency data

This study comprises mainly of three papers. First, a systematic evaluation of the effects of Missouri\u27s Strategic Highway Safety Plan between 2004 and 2007 is presented. Negative binomial regression models were developed for the before-through-change conditions for the various collision types and crash severities. The models were used to predict the expected number of crashes assuming with and without the implementation of MSHSP. This procedure estimated significant reductions of 10% in crashes frequency and a 30% reduction for fatal crashes. Reductions in the number of different collision types were estimated to be 18-37%. The results suggest that the MSHSP was successful in decreasing fatalities. Second, ten years (2002 - 2011) of Missouri Interstate highway crash data was utilized to develop a longitudinal negative binomial model using generalized estimating equation (GEE) procedure. This model incorporated the temporal correlations in crash frequency data was compared to the more traditional NB model and was found to be superior. The GEE model does not underestimate the variance in the coefficient estimates, and provides more accurate and less biased estimates. Furthermore, the autoregressive correlation structure used for the temporal correlation of the data was found to be an appropriate structure for longitudinal type of data used in this study. Third, this study developed another longitudinal negative binomial model that takes into account the seasonal effects of crash causality factors using Missouri crash data. A GEE with autoregressive correlation structure was used again for model estimation. The results improves the understanding of seasonality and whether the magnitude and/or type of various effects are different according to climatic changes. It was found that the traffic volume has a higher effect in increasing the crash occurrence in spring and lower effect in winter, compared to fall season. The crash reducing effect of better pavements was found to be highest in spring season followed by summer and winter, compared to the fall season. The results suggest that winter season has the highest effect in increasing crash occurrences followed by summer and spring --Abstract, page v