Experimental & Theoretical Aspects of the Electroweak Sector

The electroweak sector of the Standard Model (SM) has been extremely successful in predicting and matching observations. The basic form of it was sketched out some fifty years ago with the elucidation of the Higgs mechanism in a non-Abelian Yang-Mills gauge theory, yet the existence of a central player in the story, the (or a) Higgs boson, was confirmed only in 2012. In the intervening years, a great deal of experimental research was done to measure parameters of the model and confirm other predictions. In this sense, it has been an extremely fruitful theory in addition to being robust. But questions regarding the origin of the values of certain parameters in the theory, and especially regarding obvious but unexplained hierarchies between them, beg to be answered. The question of the technical naturalness of the Higgs mass has been one of the most significant motivating factors behind theories of beyond-the-Standard-Model (BSM) physics, though other striking features (for instance, the large discrepancy between quark masses) have also motivated theories (for instance, 2-Higgs-doublet models and models with Yukawa unification). Thus the electroweak sector has also proven fruitful for BSM theorists. The present paper may be divided into two parts: a description and characterization of the electroweak sector as it exists in the Standard Model on the one hand (a SM part), and an exploration of what may lie beyond it on the other (a BSM part). In the SM part, we first review the conceptual development of the electroweak model of Glashow, Weinberg, and Salam (touching on Yang-Mills theory and the Higgs mechanism), then present the key phenomenology of the electroweak theory. This leads into a presentation of this author's work in studying nal-state radiation (FSR) uncertainties in a measurement of sin2 W, with W being the weak mixing angle, done by the Compact Muon Solenoid (CMS) group at the Large Hadron Collider (LHC) in 2011. The framework necessary to understand the analysis is laid out in the text but this author played only the small role described in the section on FSR. The full analysis was presented in the papers by N. Tran and the CMS Collaboration, referenced in the text. The BSM part begins with an interlude that includes a review one of the most discussed puzzles of the SM and a discussion of "naturalness." We then present some of the basics of supersymmetry, including its history, the SUSY algebra, and the MSSM. SUSY is probably the leading contender for an explanation of seemingly "unnatural" parameters. In the next chapter, we present a supersymmetric model in which a new generation of \vector-like" quarks (as opposed to chiral) mixes with the third generation. Such a mixing raises the value of the top Yukawa yt necessary to give a top quark of the observed mass, mt = 173 GeV. Since the one-loop quantum corrections to the Higgs mass scale as yt to the fourth power , even a minor increase in yt can have a large effect. With current experimental bounds, yt may increase by as much as 6%, which implies the top's contribution to the Higgs mass increases by up to 26%. The model preserves gauge unification and gives a Higgs mass mh ~ 125.5 GeV without requiring soft supersymmetry-breaking masses above 1 TeV while satisfying all experimental constraints and predicting new quarks around the TeV scale, discoverable at the LHC. We conclude with a summary of the model and remarks on future prospects

Strong, recent selective sweeps reshape genetic diversity in freshwater bivalve Megalonaias nervosa

Freshwater Unionid bivalves have recently faced ecological upheaval through pollution, barriers to dispersal, human harvesting, and changes in fish-host prevalence. Currently, over 70% of species are threatened, endangered or extinct. To characterize the genetic response to these recent selective pressures, we collected population genetic data for one successful bivalve species, Megalonaias nervosa. We identify megabase sized regions that are nearly monomorphic across the population, a signal of strong, recent selection reshaping genetic diversity. These signatures of selection encompass a total of 73Mb, greater response to selection than is commonly seen in population genetic models. We observe 102 duplicate genes with high dN/dS on terminal branches among regions with sweeps, suggesting that gene duplication is a causative mechanism of recent adaptation in M. nervosa. Genes in sweeps reflect functional classes known to be important for Unionid survival, including anticoagulation genes important for fish host parasitization, detox genes, mitochondria management, and shell formation. We identify selective sweeps in regions with no known functional impacts, suggesting mechanisms of adaptation that deserve greater attention in future work on species survival. In contrast, polymorphic transposable element insertions appear to be detrimental and underrepresented among regions with sweeps. TE site frequency spectra are skewed toward singleton variants, and TEs among regions with sweeps are present only at low frequency. Our work suggests that duplicate genes are an essential source of genetic novelty that has helped this successful species succeed in environments where others have struggled. These results suggest that gene duplications deserve greater attention in non-model population genomics, especially in species that have recently faced sudden environmental challenges.Comment: 6 figures, 4 supplementary tables, 31 pages tota

Strong, Recent Selective Sweeps Reshape Genetic Diversity in Freshwater Bivalve \u3ci\u3eMegalonaias nervosa\u3c/i\u3e

Freshwater Unionid bivalves have recently faced ecological upheaval through pollution, barriers to dispersal, harvesting, and changes in fish–host prevalence. Currently, over 70% of species in North America are threatened, endangered or extinct. To characterize the genetic response to recent selective pressures, we collected population genetic data for one successful bivalve species, Megalonaias nervosa. We identify megabase-sized regions that are nearly monomorphic across the population, signals of strong, recent selection reshaping diversity across 73 Mb total. These signatures of selection are greater than is commonly seen in population genetic models. We observe 102 duplicate genes with high dN/dS on terminal branches among regions with sweeps, suggesting that gene duplication is a causative mechanism of recent adaptation in M. nervosa. Genes in sweeps reflect functional classes important for Unionid survival, including anticoagulation genes important for fish host parasitization, detox genes, mitochondria management, and shell formation. We identify sweeps in regions with no known functional impacts, suggesting mechanisms of adaptation that deserve greater attention in future work on species survival. In contrast, polymorphic transposable elements (TEs) appear to be detrimental and underrepresented among regions with sweeps. TE site frequency spectra are skewed toward singleton variants, and TEs among regions with sweeps are present at low frequency. Our work suggests that duplicate genes are an essential source of genetic novelty that has helped this species succeed in environments where others have struggled. These results suggest that gene duplications deserve greater attention in non-model population genomics, especially in species that have recently faced sudden environmental challenges

Wind Signatures In The X-Ray Emission-Line Profiles Of The Late-O Supergiant Zeta Orionis

X-ray line-profile analysis has proved to be the most direct diagnostic of the kinematics and spatial distribution of the very hot plasma around O stars. The Doppler-broadened line profiles provide information about the velocity distribution of the hot plasma, while the wavelength-dependent attenuation across a line profile provides information about the absorption to the hot plasma, thus providing a strong constraint on its physical location. In this paper, we apply several analysis techniques to the emission lines in the Chandra High Energy Transmission Grating Spectrometer (HETGS) spectrum of the late-O supergiant zeta Ori (O9.7 Ib), including the fitting of a simple line-profile model. We show that there is distinct evidence for blueshifts and profile asymmetry, as well as broadening in the X-ray emission lines of zeta Ori. These are the observational hallmarks of a wind-shock X-ray source, and the results for zeta Ori are very similar to those for the earlier O star, zeta Pup, which we have previously shown to be well fit by the same wind-shock line-profile model. The more subtle effects on the line-profile morphologies in zeta Ori, as compared to zeta Pup, are consistent with the somewhat lower density wind in this later O supergiant. In both stars, the wind optical depths required to explain the mildly asymmetric X-ray line profiles imply reductions in the effective opacity of nearly an order of magnitude, which may be explained by some combination of mass-loss rate reduction and large-scale clumping, with its associated porosity-based effects on radiation transfer. In the context of the recent reanalysis of the helium-like line intensity ratios in both zeta Ori and zeta Pup, and also in light of recent work questioning the published mass-loss rates in OB stars, these new results indicate that the X-ray emission from zeta Ori can be understood within the framework of the standard wind-shock scenario for hot stars

Complete Genome Sequence of \u3ci\u3eRickettsia parkeri\u3c/i\u3e Strain Black Gap

A unique genotype of Rickettsia parkeri, designated R. parkeri strain Black Gap, has thus far been associated exclusively with the North American tick, Dermacentor parumapertus. The compete genome consists of a single circular chromosome with 1,329,522 bp and a G+C content of 32.5%

Wind signatures in the X-ray emission line profiles of the late O supergiant ζ\zeta Orionis

X-ray line profile analysis has proved to be the most direct diagnostic of the kinematics and spatial distribution of the very hot plasma around O stars. In this paper we apply several analysis techniques to the emission lines in the Chandra HETGS spectrum of the late-O supergiant zeta Ori (O9.7 Ib), including the fitting of a simple line-profile model. We show that there is distinct evidence for blue shifts and profile asymmetry, as well as broadening in the X-ray emission lines of zeta Ori. These are the observational hallmarks of a wind-shock X-ray source, and the results for zeta Ori are very similar to those for the earlier O star, zeta Pup, which we have previously shown to be well-fit by the same wind-shock line-profile model. The more subtle effects on the line-profile morphologies in zeta Ori, as compared to zeta Pup, are consistent with the somewhat lower density wind in this later O supergiant. In both stars, the wind optical depths required to explain the mildly asymmetric X-ray line profiles imply reductions in the effective opacity of nearly an order of magnitude, which may be explained by some combination of mass-loss rate reduction and large-scale clumping, with its associated porosity-based effects on radiation transfer. In the context of the recent reanalysis of the helium-like line intensity ratios in both zeta Ori and zeta Pup, and also in light of recent work questioning the published mass-loss rates in OB stars, these new results indicate that the X-ray emission from zeta Ori can be understood within the framework of the standard wind-shock scenario for hot stars.Comment: MNRAS, accepted; 16 pages, 5 figure

Inter-arrival times of message propagation on directed networks

One of the challenges in fighting cybercrime is to understand the dynamics of message propagation on botnets, networks of infected computers used to send viruses, unsolicited commercial emails (SPAM) or denial of service attacks. We map this problem to the propagation of multiple random walkers on directed networks and we evaluate the inter-arrival time distribution between successive walkers arriving at a target. We show that the temporal organization of this process, which models information propagation on unstructured peer to peer networks, has the same features as SPAM arriving to a single user. We study the behavior of the message inter-arrival time distribution on three different network topologies using two different rules for sending messages. In all networks the propagation is not a pure Poisson process. It shows universal features on Poissonian networks and a more complex behavior on scale free networks. Results open the possibility to indirectly learn about the process of sending messages on networks with unknown topologies, by studying inter-arrival times at any node of the network.Comment: 9 pages, 12 figure

Influence of intense multidisciplinary follow-up and orlistat on weight reduction in a primary care setting

BACKGROUND: Obesity is the most common health problem in developed countries. Recently, several physicians' organizations have issued recommendations for treating obesity to family physicians, including instructions in nutrition, physical activity and medications. The aim of this study was to examine if effective weight-reducing treatment can be given by a family physician. It compares regular treatment with intensive treatment that include close follow-up and orlistat treatment. METHODS: The study was conducted in three primary care clinics. 225 patients were divided into three groups according to their choice. Group A received a personal diet with fortnightly meetings with the family physician and dietitian and orlistat treatment. Group B received a general diet, monthly meetings with the family physician only and orlistat treatment. Group C received a personal diet, monthly meetings with the dietitian only and no drug treatment. The primary endpoint was reduction of at least 5% of the initial weight during the study period. RESULTS: A greater percentage of patients in group A achieved their weight reduction goals than in other groups (51%, 13% and 9% in groups A, B and C, respectively, p < 0.001). There was a significant reduction in triglycerides in all groups, a significant reduction of low density lipids (LDL) in groups A and B and no significant difference in high density lipids (HDL) in any group. CONCLUSIONS: Significant weight reduction was obtained in a family physician setting. Further research is needed to evaluate if, by providing the family physician with the proper tools, similar success can be achieved in more clinics