Testing for Multiple Bubbles 2: Limit Theory of Real Time Detectors

Singapore MOE Academic Research Tier 2Published in International Economic Review, https://doi.org/10.1111/iere.12131</p

Absorption Systems In Radio-Selected QSO Surveys

Radio-selected samples of quasars with complete optical identifications offer an ideal dataset with which to investigate dust bias associated with intervening absorption systems. Here, we review our work on the Complete Optical and Radio Absorption Line System (CORALS) survey whose aim is to quantify this bias and assess the impact of dust on absorber statistics. First, we review previously published results on the number density and gas content of high column density absorbers over the redshift range 0.6 < z < 3.5. We then present the latest results from CORALS which focus on measuring the metal content of our unbiased absorber sample and an investigation of their optical--IR colours. Overall we find that although dust is unarguably present in absorption galaxies, the level appears to be low enough that the statistics of previous magnitude limited samples have not been severely affected and that the subsequent reddening of background QSOs is small.Comment: Proceedings of IAUC199, Probing Galaxies through Quasar Absorption Lines, P. R. Williams, C. Shu, and B. Menard, ed

The b' search at the LHC

We consider the production and detection of a sequential, down type quark via the mode $p p \to b' {\bar b}' \to W^+ W^- t {\bar t} \to \ell \nu_{\ell} 8 j$ at the LHC, with the collision energy $\sqrt{s}=10$ TeV and the total integrated luminosity around 1 fb$^{-1}$. We assume $m_{b'}=m_{t'}=600$ GeV. A full reconstruction is employed and the signal and background discrimination is studied within a neural network approach. Our results show that this mode can make a useful contribution to the $b'$ search.Comment: 13 pages, 1 figure, published versio

Efficient fluorescence collection from trapped ions with an integrated spherical mirror

Efficient collection of fluorescence from trapped ions is crucial for quantum optics and quantum computing applications, specifically, for qubit state detection and in generating single photons for ion-photon and remote ion entanglement. In a typical setup, only a few per cent of ion fluorescence is intercepted by the aperture of the imaging optics. We employ a simple metallic spherical mirror integrated with a linear Paul ion trap to achieve photon collection efficiency of at least 10% from a single Ba$^+$ ion. An aspheric corrector is used to reduce the aberrations caused by the mirror and achieve high image quality.Comment: 5 pages and 4 figure

Two-Fluid MHD Simulations of Converging HI Flows in the Interstellar Medium. I: Methodology and Basic Results

We develop an unconditionally stable numerical method for solving the coupling between two fluids (frictional forces/heatings, ionization, and recombination), and investigate the dynamical condensation process of thermally unstable gas that is provided by the shock waves in a weakly ionized and magnetized interstellar medium by using two-dimensional two-fluid magnetohydrodynamical simulations. If we neglect the effect of magnetic field, it is known that condensation driven by thermal instability can generate high density clouds whose physical condition corresponds to molecular clouds (precursor of molecular clouds). In this paper, we study the effect of magnetic field on the evolution of supersonic converging HI flows and focus on the case in which the orientation of magnetic field to converging flows is orthogonal. We show that the magnetic pressure gradient parallel to the flows prevents the formation of high density and high column density clouds, but instead generates fragmented, filamentary HI clouds. With this restricted geometry, magnetic field drastically diminishes the opportunity of fast molecular cloud formation directly from the warm neutral medium, in contrast to the case without magnetic field.Comment: ApJ accepte

The Mid-Infrared Extinction Law and its Variation in the Coalsack Nebula

In recent years the wavelength dependence of interstellar extinction from the ultraviolet (UV), optical, through the near- and mid-infrared (IR) has been studied extensively. Although it is well established that the UV/optical extinction law varies significantly among the different lines of sight, it is not clear how the IR extinction varies among various environments. In this work, using the color-excess method and taking red giants as the extinction tracer, we determine the interstellar extinction Alambda in the four Spitzer/IRAC bands of the Coalsack nebula, a nearby starless dark cloud, based on the data obtained from the 2MASS and Spitzer/GLIMPSE surveys. We select five individual regions across the nebula that span a wide variety of physical conditions, ranging from diffuse, translucent to dense environments, as traced by the visual extinction, the Spitzer/MIPS 24micron emission, and CO emission. We find that Alambda/AKs, the mid-IR extinction relative to AKs, decreases from diffuse to dense environments, which may be explained in terms of ineffective dust growth in dense regions. The mean extinction (relative to AKs) is calculated for the four IRAC bands as well, which exhibits a flat mid-IR extinction law, consistent with previous determinations for other regions. The extinction in the IRAC 4.5micron band is anomalously high, much higher than that of the other three IRAC bands. It cannot be explained in terms of CO and CO2 ices. The mid-IR extinction in the four IRAC bands have also been derived for four representative regions in the Coalsack Globule 2 which respectively exhibit strong ice absorption, moderate or weak ice absorption, and very weak or no ice absorption. The derived mid-IR extinction curves are all flat, with Alambda/AKs increasing with the decrease of the H2O ice absorption optical depth.Comment: 39 pages, 13 figures, accepted by Ap

Relating Neutrino Masses by dilepton modes of Doubly Charged Scalars

We study a model with Majorana neutrino masses generated through doubly charged scalars at two-loop level. We give explicit relationships between the neutrino masses and the same sign dilepton decays of the doubly charged scalars. In particular, we demonstrate that at the tribimaximal limit of the neutrino mixings, the absolute neutrino masses and Majorana phases can be extracted through the measurements of the dilepton modes at colliders.Comment: 14 pages, 8 figures, references added, version to be published in PR