Numerical Computation of p-values with myFitter

Likelihood ratio tests are a widely used method in global analyses in particle physics. The computation of the statistical significance (p-value) of these tests is usually done with a simple formula that relies on Wilks' theorem. There are, however, many realistic situations where Wilks' theorem does not apply. In particular, no simple formula exists for the comparison of models that are not nested, in the sense that one model can be obtained from the other by fixing some of its parameters. In this paper I present methods for efficient numerical computations of p-values, which work for both nested and non-nested models and do not rely on additional approximations. These methods have been implemented in a publicly available C++ framework for maximum likelihood fits called myFitter and have recently been applied in a global analysis of the Standard Model with a fourth generation of fermions

Multi-Higgs boson production in the Standard Model and beyond

We present a calculation of the loop-induced processes gg -> HH and gg -> HHH, and investigate the observability of multi-Higgs boson production at the CERN Large Hadron Collider (LHC) in the Standard Model (SM) and beyond. While the SM cross sections are too small to allow observation at the LHC, we demonstrate that physics beyond the SM can lead to amplified, observable cross sections. Furthermore, the applicability of the heavy top quark approximation in two- and three-Higgs boson production is investigated. We conclude that multi-Higgs boson production at the SuperLHC is an interesting probe of Higgs sectors beyond the SM and warrants further study.Comment: 17 pages, 17 figure

Normalizing Weak Boson Pair Production at the Large Hadron Collider

The production of two weak bosons at the Large Hadron Collider will be one of the most important sources of SM backgrounds for final states with multiple leptons. In this paper we consider several quantities that can help normalize the production of weak boson pairs. Ratios of inclusive cross-sections for production of two weak bosons and Drell-Yan are investigated and the corresponding theoretical errors are evaluated. The possibility of predicting the jet veto survival probability of VV production from Drell-Yan data is also considered. Overall, the theoretical errors on all quantities remain less than 5-20%. The dependence of these quantities on the center of mass energy of the proton-proton collision is also studied.Comment: 11 pages; added references, minor text revisions, version to appear in Phys. Rev.

Gluon-induced WW background to Higgs boson searches at the LHC

Vector-boson pair production is an important background for Higgs boson and new physics searches at the Large Hadron Collider LHC. We have calculated the loop-induced gluon-fusion process gg -> WW -> leptons, allowing for arbitrary invariant masses of the intermediate W bosons. This process contributes at O(alpha_s^2) relative to quark-antiquark annihilation, but its importance is enhanced by the large gluon flux at the LHC and by experimental cuts employed in Higgs boson searches. We find that gg -> WW provides only a moderate correction (ca. 5%) to the inclusive W-pair production cross section at the LHC. However, after taking into account realistic experimental cuts, the gluon-fusion process becomes significant and increases the theoretical WW background estimate for Higgs searches in the pp -> H -> WW -> leptons channel by approximately 30%

Top Background Extrapolation for H -> WW Searches at the LHC

A leading order (LO) analysis is presented that demonstrates that key top backgrounds to H -> W^+W^- -> l^\pm l^\mp \sla{p}_T decays in weak boson fusion (WBF) and gluon fusion (GF) at the CERN Large Hadron Collider can be extrapolated from experimental data with an accuracy of order 5% to 10%. If LO scale variation is accepted as proxy for the theoretical error, parton level results indicate that the tt~j background to the H -> WW search in WBF can be determined with a theoretical error of about 5%, while the tt~ background to the H -> WW search in GF can be determined with a theoretical error of better than 1%. Uncertainties in the parton distribution functions contribute an estimated 3% to 10% to the total error.Comment: 17 pages, 9 tables, 4 figures; LO caveat emphasized, version to be published in Phys. Rev.

Robust LHC Higgs Search in Weak Boson Fusion

We demonstrate that an LHC Higgs search in weak boson fusion production with subsequent decay to weak boson pairs is robust against extensions of the Standard Model or MSSM involving a large number of Higgs doublets. We also show that the transverse mass distribution provides unambiguous discrimination of a continuum Higgs signal from the Standard Model.Comment: 12p, 2 figs., additional comments on backgrounds, version to appear in PR

Ökologischer Weinbau in Deutschland - Feldversuche und praktische Erfahrungen zur Kupferreduzierung

Ableitend aus dem aktuellen Kenntnisstand, den vorgestellten Ergebnissen und vielfältigen Erfahrungen aus der Praxis muss festgestellt werden, dass derzeit keine praxisreifen Kupferersatzstoffe aus den Bereichen anorganische Salze, Pflanzenextrakte und biologische Antagonisten zur Verfügung stehen. Die im Rahmen der vorgestellten Versuche mit einem unformulierten Präparat des biologischen Antagonisten von Plasmopara viticola, Erwinia herbicola, erzielten Ergebnisse machen den Forschungsbedarf in diesem Sektor deutlich. Die Wirkungspotentiale von Erwinia herbicola konnten mit dem unformulierten Versuchsprodukt bei gleichzeitig starkem Infektionsdruck und den realisierten Applikationsintervallen nicht ausgeschöpft werden. Gute Ergebnisse beim Einsatz von Erwinia herbicola Anfang der 90er Jahre belegen die Wirksamkeit dieses Antagonisten, wobei besonders durch entsprechende Formulierung Wirkungssteigerungen erreicht wurden. Um die Existenz des europäischen Bioweinbaus sicherzustellen ist der Erhalt bestimmter Kupferverbindungen im Anhang II der EU-VO 2092/91 derzeit unverzichtbar. Weiterhin ist aufgrund der klimatisch bedingten, an Stärke zunehmenden Infektionsereignisse durch Plasmopara viticola eine Reduzierung der Aufwandmengen unter 3 kg/ha und Jahr in der Praxis nicht vorstellbar. Möglichkeiten zu einer weiteren nationalen Reduzierung des Kupfereinsatzes (< 3 kg/ha) bei hohem Befallsdruck wären derzeit nur nach einer Wiederzulassung von phosphithaltigen Präparaten durch die BBA (Ökofluid-P und Robus sind derzeit nicht als Pflanzenstärkungsmittel registriert) gegeben und im Sinne der Praxis verantwortbar, wobei die Akzeptanz dieser Präparate durch die Bioanbauverbände gegeben sein müsste. Bei einer Eingruppierung als Pflanzenschutzmittel wäre eine Aufnahme in den Anhang II der EU Verordnung zu beantragen. Bereits bekannte Ergebnisse aus den 90er Jahren und aktuelle Untersuchungen zu Phosphonatrückständen in den Weinen aus den vorgestellten Versuchen sowie weiteren Proben aus der Praxis belegen die bestehende Rückstandsproblematik. Aktuell laufende Untersuchungen weisen jedoch darauf hin, dass dieser Problematik durch eine Begrenzung des Einsatzes bis in den Bereich des Entwicklungsstadiums „Erbsengröße“ (BBCH 75) sowie den Einsatz von Präparaten mit geringerer Phosphonatkonzentration deutlich entgegengewirkt werden kann. Die Untersuchungen hierzu sind noch nicht abgeschlossen und werden fortgesetzt

Next-to-leading order multi-leg processes for the Large Hadron Collider

In this talk we discuss recent progress concerning precise predictions for the LHC. We give a status report of three applications of our method to deal with multi-leg one-loop amplitudes: The interference term of Higgs production by gluon- and weak boson fusion to order O(alpha^2 alpha_s^3) and the next-to-leading order corrections to the two processes pp -> ZZ jet and u ubar -> d dbar s sbar. The latter is a subprocess of the four jet cross section at the LHC.Comment: 6 pages, 5 figures. Talk given at the 8th international Symposium on Radiative Corrections (RADCOR), October 1-5 2007, Florence, Ital

Towards pair production near threshold with unstable particle effective theory

We illustrate the use of effective theory techniques to describe processes involving unstable particles close to resonance. First, we present the main ideas in the context of a scalar resonance in an Abelian gauge-Yukawa model. We then outline the necessary modifications to describe W-pair production close to threshold in electron-positron collisions.Comment: Invited talk given at the 11th International Conference on QCD, Montpellier, France (5--10th July 2004