Phenomenological Constraints on Anomaly-Free Dark Matter Models

We study minimal benchmark models of dark matter with an extra anomaly-free U(1)' gauge boson Z'. We find model parameters that give rise to the correct cosmological dark matter density while evading the latest direct detection searches for dark matter scattering produced by the XENON1T experiment, including the effects of Z-Z' mixing. We also find regions of parameter space that evade the constraints from LHC measurements of dileptons and dijets, precision electroweak measurements, and LHC searches for monojet events with missing transverse energy. We study two benchmark Z' models with Y-sequential couplings to quarks and leptons, one with a vector-like coupling to the dark matter particle and one with an axial dark matter coupling. The vector-like model is extremely tightly constrained, with only a narrow allowed strip where $m_\chi \simeq M_{Z'}/2$, and the axial model is excluded within the parameter range studied. We also consider two leptophobic Z$^\prime$ benchmark models, finding again narrow allowed strips where $m_\chi \simeq M_{Z'}/2$ as well as more extended regions where $\log_{10} (m_\chi/ {\rm GeV}) \gtrsim 3.2$.Comment: 29 pages, 18 figures, 0 anomalie

Anomaly-Free Dark Matter Models are not so Simple

We explore the anomaly-cancellation constraints on simplified dark matter (DM) models with an extra U(1)$^\prime$ gauge boson $Z'$. We show that, if the Standard Model (SM) fermions are supplemented by a single DM fermion $\chi$ that is a singlet of the SM gauge group, and the SM quarks have non-zero U(1)$^\prime$ charges, the SM leptons must also have non-zero U(1)$^\prime$ charges, in which case LHC searches impose strong constraints on the $Z'$ mass. Moreover, the DM fermion $\chi$ must have a vector-like U(1)$^\prime$ coupling. If one requires the DM particle to have a purely axial U(1)$^\prime$ coupling, which would be the case if $\chi$ were a Majorana fermion and would reduce the impact of direct DM searches, the simplest possibility is that it is accompanied by one other new singlet fermion, but in this case the U(1)$^\prime$ charges of the SM leptons still do not vanish. This is also true in a range of models with multiple new singlet fermions with identical charges. Searching for a leptophobic model, we then introduce extra fermions that transform non-trivially under the SM gauge group. We find several such models if the DM fermion is accompanied by two or more other new fermions with non-identical charges, which may have interesting experimental signatures. We present benchmark representatives of the various model classes we discuss.Comment: 19 pages, 0 figures, this v2 matches version accepted for publicatio

The application of performance measures in the UK retail sector: an exploratory analysis

Abstract: An empirical investigation of the use of performance measurement by small and medium sized online retailers in the UK. The purpose of the study is to investigate type and range of performance measures applied and extent to which measures are likely to affect business performance and strategy development. The key findings are that whilst a good range of measures are applied, the measures are more likely to be used for checking strategy implementation rather than strategy formulation or for informing corrective action to ensure longer term strategic success. Further work is required to explore relationships between strategy and business performance

Modeling of Cane Sugar Colorant Removal in Packed-Bed Ion Exchange Columns and an Investigation into Pretreatment Methods

Cane sugar colorants have been extensively researched but still little is known about their exact compositions. Rather than distinct compounds, they are a mixture of many compounds. Some it is assumed can be classified into the pseudo components that have been defined using gel permeation chromatography, based on molecular weight. The defining of these components has allowed the colorants to be modeled independently, instead of as one lumped color parameter. The measured colored components were modeled using a linear driving force adsorption model, which could be applied in the design process for optimizing the decolorizing capacity of the resins. The majority of these colored compounds possess a charge allowing the removal by packed-bed ion exchangers and decolorizing processes such as the White Sugar Mill (WSM) process. The WSM process has the advantage of producing white sugar directly from sugar cane as opposed to producing raw sugar, which required refining to make white sugar. This is done by performing ultra-filtration on juice, before sending the permeate to a continuous ion exchange operation. One of the disadvantages of the WSM process is the high capital and associated running cost of ultra-filtration. As a result an alternative for this pretreatment has been investigated in the form of a packed carbon bed. Some advantages to a carbon bed pretreatment, followed by the ion exchange treatment, have been identified, namely the removal of colorants and their precursors as well as inorganic material. The removal by ion exchange of these inorganic materials, which can be deposited on the evaporator tubes reducing heat transfer coefficients, could have huge effects on cleaning costs and operability at the mill. It was found that carbon beds could increase the overall color removal, and prolong resin life, even without the removal of suspended solids by ultra-filtration. Preliminary testing was done using hydrogen peroxide as an oxidizing agent in conjunction with a carbon bed pretreatment. Results have shown that this form of treatment could extend the number of bed cycles before regeneration and improve overall colorant removal to the extent that white sugar can be produced directly

A Simple No-Scale Model of Modulus Fixing and Inflation

We construct a no-scale model of inflation with a single modulus whose real and imaginary parts are fixed by simple power-law corrections to the no-scale K{\" a}hler potential. Assuming an uplift of the minimum of the effective potential, the model yields a suitable number of e-folds of expansion and values of the tilt in the scalar cosmological density perturbations and of the ratio of tensor and scalar perturbations that are compatible with measurements of the cosmic microwave background radiation.Comment: 12 pages, 6 figures, revised statements about string motivatio

Detecting circular polarisation in the stochastic gravitational-wave background from a first-order cosmological phase transition

We discuss the observability of circular polarisation of the stochastic gravitational-wave background (SGWB) generated by helical turbulence following a first-order cosmological phase transition, using a model that incorporates the effects of both direct and inverse energy cascades. We explore the strength of the gravitational-wave signal and the dependence of its polarisation on the helicity fraction, $\zeta_*$, the strength of the transition, $\alpha$, the bubble size, $R_*$, and the temperature, $T_*$, at which the transition finishes. We calculate the prospective signal-to-noise ratios of the SGWB strength and polarisation signals in the LISA experiment, exploring the parameter space in a way that is minimally sensitive to the underlying particle physics model. We find that discovery of SGWB polarisation is generally more challenging than measuring the total SGWB signal, but would be possible for appropriately strong transitions with large bubble sizes and a substantial polarisation fraction.Comment: 31 pages, 8 Figure

The CTA Sensitivity to Lorentz-Violating Effects on the Gamma-Ray Horizon

The arrival of TeV-energy photons from distant galaxies is expected to be affected by their QED interaction with intergalactic radiation fields through electron-positron pair production. In theories where high-energy photons violate Lorentz symmetry, the kinematics of the process $\gamma + \gamma\rightarrow e^+ + e^-$ is altered and the cross-section suppressed. Consequently, one would expect more of the highest-energy photons to arrive if QED is modified by Lorentz violation than if it is not. We estimate the sensitivity of Cherenkov Telescope Array (CTA) to changes in the $\gamma$-ray horizon of the Universe due to Lorentz violation, and find that it should be competitive with other leading constraints.Comment: 13 pages, 4 figures, typos corrected + references added, results unchanged. Matches version accepted by JCA

Dark Matter Constraints from the Eccentric Supermassive Black Hole Binary OJ 287

OJ 287 is a blazar thought to be a binary system containing a ~ 18 billion solar mass primary black hole accompanied by a ~ 150 million solar mass secondary black hole in an eccentric orbit, which triggers electromagnetic flares twice in every ~ 12 year orbital period when it traverses the accretion disk of the primary. The times of these emissions are consistent with the predictions of general relativity calculated to the 4.5th post-Newtonian order. The orbit of the secondary black hole samples the gravitational field at distances between O(10) and O(50) Schwarzschild radii around the primary, and hence is sensitive to the possible presence of a dark matter spike around it. We find that the agreement of general-relativistic calculations with the measured timings of flares from OJ 287 constrains the mass of such a spike to < 3% of the primary mass.Comment: Matches version accepted for publicatio

THE ROLE OF PERFORMANCE MEASUREMENT ON BUSINESS PERFORMANCE: A COMPARATIVE STUDY OF SMALL AND MEDIUM-SIZED INTERNET RETAILERS BASED IN THE UNITED KINGDOM AND INDONESIAN

This study investigates the application of performance measurement and considers how its use might affect the business performance of small and medium-sized retail businesses in the United Kingdom and Indonesia, which are using the Internet a as channel to market. In both countries, retailers were surveyed and the study has produced some interesting results, which have theoretical, practical and managerial implications. At the outset of the study, little was known about the extent of Internet adoption by retail businesses in Indonesia and it was not surprising to find that in the United Kingdom, Internet retailing is well established but in Indonesia, it is in the early stages of development. Nevertheless, there was sufficient Internet activity by Indonesian retailers to enable comparison of the use of performance measures by retailers in a mature economy and its use in a developing economy. The findings revealed similarities and differences in the number and type of performance measures used by retailers but more interestingly found evidence of different strategic orientations, which suggested that certain types of organizational behavior could be used to predict the type of performance measures that might be applied by a retailer. More specifically, in both countries, retailers adopting a conservativeness-oriented strategy were more likely to make greater use of performance measurement than those classified as applying an aggressiveness-oriented strategy but level of aggressiveness, was found to be an indicator of financial performance. In the United Kingdom low aggressiveness was an indicator of better financial performance whereas in Indonesia high aggressiveness was an indicator of better financial performance. This study has explored complex issues, by investigating strategic orientation and performance measurement and made suggestions as to how these constructs might affect business performance in Internet retailing within developed and less-developed countries. The findings have important managerial implications for Internet retailers about how performance measures might be used effectively to enhance business performance

Categorisation and Detection of Dark Matter Candidates from String/M-theory Hidden Sectors

We study well-motivated dark matter candidates arising from weakly-coupled hidden sectors in compactified string/$M$-theory. Imposing generic top-down constraints greatly restricts allowed candidates. By considering the possible mechanisms for achieving the correct dark matter relic density, we compile categories of viable dark matter candidates and annihilation mediators. We consider the case where supersymmetry breaking occurs via moduli stabilisation and is gravitationally mediated to the visible and other hidden sectors, without assuming sequestering of the sector in which supersymmetry is broken. We find that in this case, weakly-coupled hidden sectors only allow for fermionic dark matter. Additionally, most of the mechanisms for obtaining the full relic density only allow for a gauge boson mediator, such as a dark $Z'$. Given these considerations, we study the potential for discovering or constraining the allowed parameter space given current and future direct detection experiments, and direct production at the LHC. We also present a model of a hidden sector which would contain a satisfactory dark matter candidate.Comment: 29 pages, 10 figure