ABSTRACT
High-energy jets recoiling against missing transverse energy (MET) are powerful probes of dark matter at the LHC. Searches based on large MET signatures require a precise control of the Z ( ν ν ¯ ) + jet background in the signal region. This can be achieved by taking accurate data in control regions dominated by Z ( â + â - ) + jet, W ( â ν ) + jet and γ + jet production, and extrapolating to the Z ( ν ν ¯ ) + jet background by means of precise theoretical predictions. In this context, recent advances in perturbative calculations open the door to significant sensitivity improvements in dark matter searches. In this spirit, we present a combination of state-of-the-art calculations for all relevant V + jets processes, including throughout NNLO QCD corrections and NLO electroweak corrections supplemented by Sudakov logarithms at two loops. Predictions at parton level are provided together with detailed recommendations for their usage in experimental analyses based on the reweighting of Monte Carlo samples. Particular attention is devoted to the estimate of theoretical uncertainties in the framework of dark matter searches, where subtle aspects such as correlations across different V + jet processes play a key role. The anticipated theoretical uncertainty in the Z ( ν ν ¯ ) + jet background is at the few percent level up to the TeV range.
ABSTRACT
BACKGROUND: Tooth extractions lead to morphological changes of the alveolar ridge. For oral rehabilitation sufficient bone volume of the alveolar ridge is required. This clinical study compared the ability of Bio-Oss® Collagen to autogenous bone to preserve bone volume after tooth extraction. METHODS: A total of 17 patients with 20 extraction sites were examined. After extraction, 10 sockets were each filled with either autogenous bone or Bio-Oss® Collagen and covered with a resorbable membrane. The width of the alveolar ridge was measured postoperatively, and after 4 and 6 months respectively. Prior to implant insertion, a bone biopsy was taken from the grafted sites and evaluated histologically. RESULTS: The width of the alveolar ridge in the Bio-Oss® Collagen group decreased about 5.33 ± 6.62% after 4 months and 9.45 ± 10.51% after 6 months. The reduction in the group augmented with autogenous bone was 14.31 ± 21.41% after 4 months and 19.17 ± 8.38% after 6 months. No statistically significant differences were observed. The histological examination showed comparable area fractions of total bone in both groups (Bio-Oss® Collagen: 59.99 ± 24.23%; autogenous bone: 61.55 ± 25.13%; p = 1.0). CONCLUSIONS: The present study demonstrated that autogenous bone and Bio-Oss® Collagen are suitable for ridge preservation. However, both techniques could not entirely prevent tissue volume loss.
ABSTRACT
Charged gauge boson pair production at the Large Hadron Collider allows detailed probes of the fundamental structure of electroweak interactions. We present precise theoretical predictions for on-shell W+ W- production that include, for the first time, QCD effects up to next to next to leading order in perturbation theory. As compared to next to leading order, the inclusive W+ W- cross section is enhanced by 9% at 7 TeV and 12% at 14 TeV. The residual perturbative uncertainty is at the 3% level. The severe contamination of the W+ W- cross section due to top-quark resonances is discussed in detail. Comparing different definitions of top-free W+ W- production in the four and five flavor number schemes, we demonstrate that top-quark resonances can be separated from the inclusive W+ W- cross section without a significant loss of theoretical precision.
ABSTRACT
Top-antitop quark pairs belong to the most abundantly produced and precisely measurable heavy-particle signatures at hadron colliders and allow for crucial tests of the standard model and new physics searches. Here we report on the calculation of the next-to-leading order (NLO) QCD corrections to hadronic W(+)W(-)bb production, which provides a complete NLO description of the production of top-antitop pairs and their subsequent decay into W bosons and bottom quarks, including interferences, off-shell effects, and nonresonant backgrounds. Numerical predictions for the Tevatron and the LHC are presented.
ABSTRACT
We report on the calculation of the next-to-leading-order QCD corrections to the production of W-boson pairs in association with a hard jet at the Fermilab Tevatron and CERN Large Hadron Collider, which is an important source of background for Higgs boson and new-physics searches. The corrections stabilize the leading-order prediction for the cross section considerably, in particular, if a veto against the emission of a second hard jet is applied.
