Strong Interaction Effects in Stop Pair Production at e+e−e^+ e^- Colliders

We discuss perturbative and non-perturbative strong interaction effects in the pair production of stop squarks ($\tilde{t}_1$) at $e^+ e^-$ colliders. Events with an additional hard gluon allow to detect or exclude stop pair production even in scenarios with very small mass splitting between $\tilde{t}_1$ and an invisible lightest supersymmetric particle (LSP). Such events can also help to establish that $\tilde{t}_1$ transforms as a triplet under $SU(3)_C$. We also carefully study non-perturbative $\tilde{t}_1$ fragmentation, which is currently not well understood: not only is the $\tilde{t}_1$ fragmentation function not known very well, but also there are ambiguities in the algorithm employed to model fragmentation. We present numerical results both for CERN LEP-183 and for a proposed future $e^+ e^-$ collider operating at center-of-mass energy $\sqrt{s}=500$ GeV.Comment: 16 pages and 4 figure

The Higgs Legacy of the LHC Run I

Based on Run I data we present a comprehensive analysis of Higgs couplings. For the first time this SFitter analysis includes independent tests of the Higgs-gluon and top Yukawa couplings, Higgs decays to invisible particles, and off-shell Higgs measurements. The observed Higgs boson is fully consistent with the Standard Model, both in terms of coupling modifications and effective field theory. Based only on Higgs total rates the results using both approaches are essentially equivalent, with the exception of strong correlations in the parameter space induced by effective operators. These correlations can be controlled through additional experimental input, namely kinematic distributions. Including kinematic distributions the typical Run I reach for weakly interacting new physics now reaches 300 to 500 GeV.Comment: 29 pages, 15 figure

Probing the Standard Model with Higgs signal rates from the Tevatron, the LHC and a future ILC

We explore the room for possible deviations from the Standard Model (SM) Higgs boson coupling structure in a systematic study of Higgs coupling scale factor benchmark scenarios using the latest signal rate measurements from the Tevatron and LHC experiments. We employ chi-squared fits performed with HiggsSignals, which takes into account detailed information on signal efficiencies and major correlations of theoretical and experimental uncertainties. All considered scenarios allow for additional non-standard Higgs boson decay modes, and various assumptions for constraining the total decay width are discussed. No significant deviations from the SM Higgs boson coupling structure are found in any of the investigated benchmark scenarios. We derive upper limits on an additional (undetectable) Higgs decay mode under the assumption that the Higgs couplings to weak gauge bosons do not exceed the SM prediction. We furthermore discuss the capabilities of future facilities for probing deviations from the SM Higgs couplings, comparing the high luminosity upgrade of the LHC with a future International Linear Collider (ILC), where for the latter various energy and luminosity scenarios are considered. At the ILC model-independent measurements of the coupling structure can be performed, and we provide estimates of the precision that can be achieved.Comment: 64 pages, 25 figures, 17 tables; v2: minor corrections in the text, references added. Matches published version on JHE