29 research outputs found
Predictions for Higgs production at the Tevatron and the associated uncertainties
We update the theoretical predictions for the production cross sections of
the Standard Model Higgs boson at the Fermilab Tevatron collider, focusing on
the two main search channels, the gluon-gluon fusion mechanism and
the Higgs-strahlung processes with , including all
relevant higher order QCD and electroweak corrections in perturbation theory.
We then estimate the various uncertainties affecting these predictions: the
scale uncertainties which are viewed as a measure of the unknown higher order
effects, the uncertainties from the parton distribution functions and the
related errors on the strong coupling constant, as well as the uncertainties
due to the use of an effective theory approach in the determination of the
radiative corrections in the process at next-to-next-to-leading
order. We find that while the cross sections are well under control in the
Higgs--strahlung processes, the theoretical uncertainties are rather large in
the case of the gluon-gluon fusion channel, possibly shifting the central
values of the next-to-next-to-leading order cross sections by more than
. These uncertainties are thus significantly larger than the
error assumed by the CDF and D0 experiments in their recent
analysis that has excluded the Higgs mass range 162-166 GeV at the 95%
confidence level. These exclusion limits should be, therefore, reconsidered in
the light of these large theoretical uncertainties.Comment: 40 pages, 12 figures. A few typos are corrected and some updated
numbers are provide
Composite Higgs Boson Pair Production at the LHC
The measurement of the trilinear and quartic Higgs self-couplings is
necessary for the reconstruction of the Higgs potential. This way the Higgs
mechanism as the origin of electroweak symmetry breaking can be tested. The
couplings are accessible in multi-Higgs production processes at the LHC. In
this paper we investigate the prospects of measuring the trilinear Higgs
coupling in composite Higgs models. In these models, the Higgs boson emerges as
a pseudo-Goldstone boson of a strongly interacting sector, and the Higgs
potential is generated by loops of the Standard Model (SM) gauge bosons and
fermions. The Higgs self-couplings are modified compared to the SM and
controlled by the compositeness parameter in addition to the Higgs boson
mass. We construct areas of sensitivity to the trilinear Higgs coupling in the
relevant parameter space for various final states
Intestinal parasitism among waste pickers in Mato Grosso do Sul, Midwest Brazil
ABSTRACT The purpose of this study was to estimate the prevalence of intestinal parasites in both cooperative-affiliated and independent waste pickers operating at the municipal sanitary landfill in Campo Grande, Mato Grosso do Sul, Brazil, and associate these findings with hemoglobin, eosinophils, vitamin A and C levels and interleukin 5 and 10 (IL-5 and IL-10) production. Biological samples were collected, in addition to clinical, epidemiological, and sociodemographic data. Stool analyzes were based on sedimentation by centrifugation and on spontaneous sedimentation. High-performance liquid chromatography was used to determine vitamin A and C levels. ELISA was employed to quantify interleukins. Intestinal parasites were found in 29 of the 66 subjects assessed (43.9%). Endolimax nana (22.7%), Entamoeba coli (21.1%), Giardia lamblia (6.1%), Entamoeba histolytica/E. dispar (4.5%), and Ascaris lumbricoides (4.5%) were the most prevalent species. Pathogenic parasites were detected in 11 individuals (16.7%). Hypovitaminoses A and C were detected in 19.6% (13/66) and 98.4% (65/66) of subjects, respectively. IL-5 and IL-10 production was observed in 21 (31.8%) and 32 (48.4%) subjects, respectively. Infection with pathogenic intestinal parasites was not a cause of vitamin A and C deficiency or IL-5 and IL-10 production among these workers
Interference effects for H → W W → ℓνqq¯′ and H → ZZ → ℓℓ¯qq¯ searches in gluon fusion at the LHC
Signal-background interference effects are studied for H → W W and H → ZZ searches in gluon fusion at the LHC. More specifically, the interference in the channels with semileptonic weak boson pair decay is analysed for light and heavy Higgs masses with minimal and realistic experimental selection cuts. In the semileptonic decay modes, the interference is affected by tree-level background contributions enhanced by 1/e2 relative to the gluon-fusion continuum background in the fully leptonic decay modes. We find that for both light and heavy Higgs masses the interference with the loop-induced weak-boson pair background dominates over the interference with the tree-level weak-boson plus jets background for a range of selection cuts. We therefore conclude that higher-order background contributions can induce leading interference effects. With appropriate background suppression cuts the interference can be reduced to the 10% level for heavy Higgs masses, and to the per mille level for the light SM Higgs. © 2015, The Author(s)