22 research outputs found
Top Quark Charge Asymmetry: Searching for Light Axigluons in top pair + jet Production at the LHC
We investigate the discovery potential of light color-octet bosons in the
mass range of 100 - 400 GeV in exclusive top-pair plus jet production at the
LHC. We study the impact of such bosons on the incline, the energy and the
rapidity asymmetries. We show that light axigluons with large couplings to
quarks can be discovered at the LHC with a luminosity of a few inverse fb.
Almost all of the considered axigluon parameter space can be probed using the
already available 2011/2012 LHC data. In a small-coupling scenario, axigluons
could be discovered using the charge asymmetry with 65 inverse fb at the LHC
and a center of mass energy of 14 TeV. We furthermore show that top pair+jet
production could reveal the existence of scenarios where axigluons couple with
a different strength to up- and down-type quarks.Comment: 25 pages, 11 figures, 1 tabl
Effective Theory for a Heavy Scalar Coupled to the SM via Vector-Like Quarks
We illustrate the application of the recently developed SCET
framework in the context of a specific model, in which the Standard Model (SM)
is supplemented by a heavy scalar and three generations of heavy,
vector-like quarks . We construct the appropriate effective field theory
for two-body decays of into SM particles. We explicitly compute the Wilson
coefficients of the SCET operators appearing at leading and
next-to-leading order (NLO) in an expansion in powers of , as well as
for a subset of operators arising at NNLO, retaining the full dependence on the
ratio . For the phenomenologically most relevant decay channels of
the heavy scalar, we study the impact of resummation effects of Sudakov
logarithms on the decay rates.Comment: 11 pages, 6 figure
Consistent Searches for SMEFT Effects in Non-Resonant Dijet Events
We investigate the bounds which can be placed on generic new-physics
contributions to dijet production at the LHC using the framework of the
Standard Model Effective Field Theory, deriving the first consistently-treated
EFT bounds from non-resonant high-energy data. We recast an analysis searching
for quark compositeness, equivalent to treating the SM with one
higher-dimensional operator as a complete UV model. In order to reach
consistent, model-independent EFT conclusions, it is necessary to truncate the
EFT effects consistently at order and to include the possibility
of multiple operators simultaneously contributing to the observables, neither
of which has been done in previous searches of this nature. Furthermore, it is
important to give consistent error estimates for the theoretical predictions of
the signal model, particularly in the region of phase space where the probed
energy is approaching the cutoff scale of the EFT. There are two linear
combinations of operators which contribute to dijet production in the SMEFT
with distinct angular behavior; we identify those linear combinations and
determine the ability of LHC searches to constrain them simultaneously.
Consistently treating the EFT generically leads to weakened bounds on
new-physics parameters. These constraints will be a useful input to future
global analyses in the SMEFT framework, and the techniques used here to
consistently search for EFT effects are directly applicable to other
off-resonance signals.Comment: v1: 23 pages, 9 figures, 3 tables; v2: references added, typos
corrected, matches version published in JHE
Exclusive Radiative Decays of Z Bosons in QCD Factorization
We discuss the very rare, exclusive hadronic decays of a Z boson into a meson
and a photon. The QCD factorization approach allows to organize the decay
amplitude as an expansion in powers of , where the
leading terms contain convolutions of perturbatively calculable hard functions
with the leading-twist light-cone distribution amplitudes of the meson. We find
that power corrections to these leading terms are negligible since they are
suppressed by the small ratio .
Renormalization-group effects play a crucial role as they render our
theoretical predictions less sensitive to the hadronic input parameters which
are currently not known very precisely. Thus, measurements of the decays at the LHC or a future lepton collider provide a theoretically very
clean way to test the QCD factorization approach. The special case where
is complicated by the fact that the decay amplitude receives
an additional contribution where the meson is formed from a two-gluon state.
The corresponding branching ratios are very sensitive to the hadronic
parameters describing the system. Future measurements of these
decays could yield interesting information about these parameters and the gluon
distribution amplitude.Comment: 6 pages, 3 figures, 1 table, contribution to the proceedings of the
38th International Conference on High Energy Physics, 3-10 August 2016,
Chicago, US
Consistent Searches for SMEFT Effects in Non-Resonant Dilepton Events
Employing the framework of the Standard Model Effective Field Theory, we
perform a detailed reinterpretation of measurements of the Weinberg angle in
dilepton production as a search for new-physics effects. We truncate our signal
prediction at order , where denotes the new-physics mass
scale, and introduce a theory error to account for unknown contributions of
order . Two linear combinations of four-fermion operators with
distinct angular behavior contribute to dilepton production with growing impact
at high energies. We define suitable angular observables and derive bounds on
those two linear combinations using data from the Tevatron and the LHC. We find
that the current data is able to constrain interesting regions of parameter
space, with important contributions at lower cutoff scales from the Tevatron,
and that the future LHC data will eventually be able to simultaneously
constrain both independent linear combinations which contribute to dilepton
production.Comment: 11 pages, 4 figures v2: updated to match version accepted for
publicatio
The Role of Macrophytes in Constructed Surface-flow Wetlands for Mine Water Treatment : A Review
<jats:title>Abstract</jats:title><jats:p>Constructed wetlands are a standard sustainable technology in waste and mine water treatment. Whereas macrophytes actively contribute to decomposition and/or removal of wastewater’s organic pollutants, removal of hydrolysable metals from mine water is not attributable to direct metabolic, but rather various indirect macrophyte-related mechanisms. These mechanisms result in higher treatment efficiency of (vegetated) wetlands relative to (unvegetated) settling ponds. Contribution of macrophytes to treatment predominantly includes: enhanced biogeochemical oxidation and precipitation of hydrolysable metals due to catalytic reactions and bacterial activity, particularly on immersed macrophyte surfaces; physical filtration of suspended hydrous ferric oxides by dense wetland vegetation down to colloids that are unlikely to gravitationally settle efficiently; scavenging and heteroaggregation of dissolved and colloidal iron, respectively, by plant-derived natural organic matter; and improved hydrodynamics and hydraulic efficiency, considerably augmenting retention and exposure time. The review shows that constructed surface-flow wetlands have considerable advantages that are often underestimated. In addition to treatment enhancement, there are socio-environmental benefits such as aesthetic appearance, biotope/habitat value, and landscape diversity that need to be considered. However, there is currently no quantitative, transferrable approach to adequately describe the effect and magnitude of macrophyte-related benefits on mine water amelioration, let alone clearly assign optimal operational deployment of either settling ponds or wetlands. A better (quantitative) understanding of underlying processes and kinetics is needed to optimise assembly and sizing of settling ponds and wetlands in composite passive mine water treatment systems.</jats:p>
Overweight, physical activity, tobacco and alcohol consumption in a cross-sectional random sample of German adults
BACKGROUND: There is a current paucity of data on the health behaviour of non-selected populations in Central Europe. Data on health behaviour were collected as part of the EMIL study which investigated the prevalence of infection with Echinococcus multilocularis and other medical conditions in an urban German population. METHODS: Participating in the present study were 2,187 adults (1,138 females [52.0%]; 1,049 males [48.0%], age: 18–65 years) taken from a sample of 4,000 persons randomly chosen from an urban population. Data on health behaviour like physical activity, tobacco and alcohol consumption were obtained by means of a questionnaire, documentation of anthropometric data, abdominal ultrasound and blood specimens for assessment of chemical parameters. RESULTS: The overall rate of participation was 62.8%. Of these, 50.3% of the adults were overweight or obese. The proportion of active tobacco smokers stood at 30.1%. Of those surveyed 38.9% did not participate in any physical activity. Less than 2 hours of leisure time physical activity per week was associated with female sex, higher BMI (Body Mass Index), smoking and no alcohol consumption. Participants consumed on average 12 grams of alcohol per day. Total cholesterol was in 62.0% (>5.2 mmol/l) and triglycerides were elevated in 20.5% (≥ 2.3 mmol/l) of subjects studied. Hepatic steatosis was identified in 27.4% of subjects and showed an association with male sex, higher BMI, higher age, higher total blood cholesterol, lower HDL, higher triglycerides and higher ALT. CONCLUSION: This random sample of German urban adults was characterised by a high prevalence of overweight and obesity. This and the pattern of alcohol consumption, smoking and physical activity can be considered to put this group at high risk for associated morbidity and underscore the urgent need for preventive measures aimed at reducing the significantly increased health risk