New limits on top squark NLSP from ATLAS 4.7 fb−1fb^{-1} data

Using the ATLAS 4.7 $fb^{-1}$ data on new physics search in the jets + \met channel, we obtain new limits on the lighter top squark ($\tilde t_1$) considering all its decay modes assuming that it is the next to lightest supersymmetric particle (NLSP). If the decay \lstop \ra c \lspone dominates and the production of dark matter relic density is due to NLSP - LSP co-annihilation then the lower limit on \mlstop is 240 GeV. The limit changes to 200 GeV if the decay \lstop \ra b W \lspone dominates. Combining these results it follows that \lstop NLSP induced baryogenesis is now constrained more tightly.Comment: 9 pages, 2 figures, published in MPL

Structure, strength and defect characterisation of cement based materials.

In cement based systems, the residual stresses are created by internal expansion. This provides toughening by the release of the residual stresses as the macro-crack propagates. While circumstantial evidence of the residual stresses exist (e.g. micro-crack formation leading to permanent deformation in flexural tests), it is very difficult to observe the mechanism in action. The quantitative estimate of the changes occurring in such cement-based systems is challenging due to the anisotropy and complexity of the material. Non-Destructive Testing (NDT) techniques were used in this research to observe the mechanism in action. An ultrasound technique is used to examine strength development and an acoustic emission (AE) technique is used to examine micro-structural changes, micro-cracks, crack initiation, crack propagation, crack arrests and crack bridging in plain concrete samples including samples containing admixtures and waste materials. The NDT techniques were found to be accurate in being able to measure compressive strength, with good correlation between both standard mechanical testing and NDT techniques. It was shown that admixtures could be effectively used to alter the properties of a curing cement mortar. This work has also demonstrated that ultrasound can be successfully used to determine the compressive strength of concrete from an early age. The ability to pre-determine the strength of concrete through correlation with NDT test parameters may reduce the time spent waiting on concrete to set and to obtain results using standard mechanical testing methods. The findings in this research present the effect admixtures had on the curing process of the cement based material. The introduction of certain additives into mortars have demonstrated an increase in both the rate of initial hardening and the magnitude of the compressive strength attained over the curing period depending on the mixture specification. The additives considered have been shown to actively alter and enhance the chemical process of curing from the start of hydration. Some additives that accelerate the curing process (accelerators) were found to lower the compressive strength of concrete using the ultrasound technique. Additives that caused an increase in the final strength of mortar also increased its toughness. The significant contributions in this research enabled observation of micro-structural changes and failure behaviour under compressive and flexural loading conditions on an on-line basis. The results obtained are encouraging and lead to increased understanding of cracking mechanisms in concrete containing various types of additives and aggregates. The application of the AE technique allowed the failure of interfacial bonding to be observed. The variation of the aggregate size and its effect on the monitored waveforms was established and the parameters in the AE signals are directly related to crack propagation (grain bridging/micro-mechanism) and strength of interfacial bonding. These findings have greatly contributed to the understanding of the concrete behaviour under complex conditions where no other technique could provide such valuable information on an online basis

Examining the Utility of Hope Interventions to Mitigate the Effect of Discrimination on Distress in African Americans

Hope is a positive psychology resource that utilizes one’s perceptions of strengths to create clear goals, produce multiple pathways to reach goals, overcome barriers, and generate the energy needed to pursue goals by increasing positive affect and satisfaction, while reducing negative problem orientations (Magyar-Moe, 2014). Hope interventions also significantly reduce psychological distress (Rustøen, Cooper, & Miaskowski, 2011). Discrimination is a significant barrier to quality of life for African Americans (Bilkins, Allen, Davey, & Davey, 2016). Discriminatory experiences increase levels of distress (Brown, et al., 2000). However, it is unknown if hope interventions can protect African Americans against distress caused by microaggressions. Thus, the current study studied the utility of different hope interventions in buffering the effects of microaggressions on distress (i.e., anxiety, anger, depression). One hundred and three African American undergraduate students participated in an experimental study. Participants were randomly assigned to one of two induction tasks (neutral or microaggression stress) and one of four interventions (basic hope, hope savoring, integrated hope, or control). Multiple measures of state-based anxiety, anger, and depression were administered three times during the experiment. First, the microaggression task was effective in inducing higher levels of stress and increased participants’ scores of state-based anxiety, anger, and depression. In addition, a 2 (induction) x 4 (intervention) x 3 (time) mixed ANOVA was used to determine the buffering effects of different hope interventions. Results revealed a non-significant 3-way interaction effect, suggesting that hope interventions do not moderate the causal relationship between microaggression stress and distress, especially for anxiety and anger. However, there was a significant induction*intervention effect for depression scores at Time 3, which suggests that certain hope interventions are effective in reducing depression for participants who did not experience the microaggression stress induction task. Results from these analyses are complicated. They suggest that hope interventions are effective in working with African American college students under specific conditions and only with specific distress indices

Probing large distance higher dimensional gravity from lensing data

The modifications induced in the standard weak-lensing formula if Newtonian gravity differs from inverse square law at large distances are studied. The possibility of putting bounds on the mass of gravitons from lensing data is explored. A bound on graviton mass, esitmated to be about 100 Mpc$^{-1}$ is obtained from analysis of some recent data on gravitational lensing.Comment: 6 pages, 1 figure, added reference

Little Higgs model effects in γγ→γγ\gamma \gamma \to \gamma \gamma

Though the predictions of the Standard Model (SM) are in excellent agreement with experiments there are still several theoretical problems associated with the Higgs sector of the SM, where it is widely believed that some ``{\it new physics}'' will take over at the TeV scale. One beyond the SM theory which resolves these problems is the Little Higgs (LH) model. In this work we have investigated the effects of the LH model on \gggg scattering \cite{Choudhury:2006xa}.Comment: Talk given at LCWS06, Bangalore, 4 pages (style files included

Unitarity constraints on the stabilized Randall-Sundrum scenario

Recently proposed stabilization mechanism of the Randall-Sundrum metric gives rise to a scalar radion, which couples universally to matter with a weak interaction ($\simeq 1$ TeV) scale. Demanding that gauge boson scattering as described by the effective low enerrgy theory be unitary upto a given scale leads to significant constraints on the mass of such a radion.Comment: 10 page Latex 2e file including 4 postscript figures. Accepted in Journal of Physics

Analysis of the B→K2∗(→Kπ)l+l−B \to K^*_{2} (\to K \pi) l^+ l^- decay

In this paper we study the angular distribution of the rare B decay $B \to K^*_2 (\to K \pi) l^+ l^-$, which is expected to be observed soon. We use the standard effective Hamiltonian approach, and use the form factors that have already been estimated for the corresponding radiative decay $B \to K^*_2 \gamma$. The additional form factors that come into play for the dileptonic channel are estimated using the large energy effective theory (LEET), which enables one to relate the additional form factors to the form factors for the radiative mode. Our results provide, just like in the case of the $K^*(892)$ resonance, an opportunity for a straightforward comparison of the basic theory with experimental results which may be expected in the near future for this channel.Comment: 14 pages, 5 figures; as accepted for Phys. Rev.