TOP 2014: Experimental Summary

A summary of the experimental results of the TOP2014 International Workshop in Cannes, France, is presented. This inspiring conference clearly showed the richness and diversity of top-quark physics research. Results cover a very broad spectrum of analyses involving studies of the strong and electroweak interactions of the top quark, high-precision measurements of intrinsic top-quark properties, developments of new tools in top-quark analyses, observations of new Standard Model processes, the interaction between the top quark and the Higgs boson and sensitive searches for new physics beyond the Standard Model.Comment: 8 pages, 3 figures, presentation given at 7th International Workshop on Top Quark Physics (TOP 2014), 29 September - 03 October 2014, Cannes, France, to appear in the proceeding

Top Quark Highlights

Highlights of top quark physics presented at the 2009 Europhysics Conference on High Energy Physics from 16-22 July 2009 in Krakow, Poland, are reviewed.Comment: Talk given at the 2009 Europhysics Conference on High Energy Physics, Krakow, Poland, 21/07/2009. 15 pages, 6 figures

The Jet Calibration in the H1 Liquid Argon Calorimeter

The jet calibration of the Liquid-Argon-Calorimeter of the H1 Detector at HERA is described. In the measurement of high jet transverse energies systematic uncertainties as low as 2% can be reached in deep inelastic scattering with a high photon virtuality (Q^2) and in photoproduction. Furthermore, the concept of a new energy weighting scheme of H1 is presented. First applications with a high Q^2 neutral current deep inelastic scattering sample show that the resolution of the balance in transverse momentum between the hadronic system and the electron is improved.Comment: 6 pages, talk given at International Conference on Calorimetry in High Energy Physics, Pasadena, California, USA, March 2002, to appear in the proceeding

Search for a new Resonance decaying into Top-Antitop at Tevatron

In this report a new search for a narrow-width heavy resonance decaying into top quark pairs (X -> ttbar) in ppbar collisions at sqrt(s)=1.96 TeV has been performed using data collected by the D0 detector at the Fermilab Tevatron collider. The analysis considers ttbar candidate events in the lepton+jets channel using a lifetime tag to identify b-jets and the ttbar invariant mass distribution to search for evidence of resonant production. The analyzed dataset corresponds to an integrated luminosity of approximately 370 pb^-1. Since no evidence for a ttbar resonance X is found, upper limits on sigma(X) x B(X -> ttbar) for different hypothesized resonance masses using a Bayesian approach are set. Within a topcolor-assisted technicolor model, the existence of a leptophobic Z' boson with M(Z') < 680 GeV and width Gamma(Z') = 0.012 M(Z') can be excluded at 95% C.L..Comment: Talk given at the "International Europhysics Conference on High Energy Physics", July 21st - 27th 2005, Lisboa, Portuga

Photoproduction of W Bosons at HERA: Reweighting Method for implementing QCD Corrections in Monte Carlo Programs

A procedure of implementing QCD corrections in Monte Carlo programs by a reweighting method is described for the photoproduction of W bosons at HERA. Tables for W boson production in LO and NLO are given in bins of the transverse momentum of the W boson and its rapidity.Comment: 39 pages, latex, 5 figure

A new LHC search for dark matter produced via heavy Higgs bosons using simplified models

Searches for dark matter produced via scalar resonances in final states consisting of Standard Model (SM) particles and missing transverse momentum are of high relevance at the LHC. Motivated by dark-matter portal models, most existing searches are optimized for unbalanced decay topologies for which the missing momentum recoils against the visible SM particles. In this work, we show that existing searches are also sensitive to a wider class of models, which we characterize by a recently presented simplified model framework. We point out that searches for models with a balanced decay topology can be further improved with more dedicated analysis strategies. For this study, we investigate the feasibility of a new search for bottom-quark associated neutral Higgs production with a $b \bar b Z + p_\text{T}^\text{miss}$ final state and perform a detailed collider analysis. Our projected results in the different simplified model topologies investigated here can be easily reinterpreted in a wide range of models of physics beyond the SM, which we explicitly demonstrate for the example of the Two-Higgs-Doublet model with an additional pseudoscalar Higgs boson.Comment: 27 pages, 8 figures, 4 table

ALP-ine quests at the LHC: hunting axion-like particles via peaks and dips in ttˉt \bar{t} production

We present an analysis of the sensitivity of current and future LHC searches for new spin-0 particles in top-anti-top-quark ($t\bar{t}$) final states, focusing on generic axion-like particles (ALPs) that are coupled to top quarks and gluons. As a first step, we derive new limits on the effective ALP Lagrangian in terms of the Wilson coefficients $c_t$ and $c_{\tilde{G}}$ based on the results of the CMS search using $35.9$ fb$^{-1}$ of data, collected at $\sqrt{s} = 13$ TeV. We then investigate how the production of an ALP with generic couplings to gluons and top quarks can be distinguished from the production of a pseudoscalar which couples to gluons exclusively via a top-quark loop. To this end, we make use of the invariant $t\bar{t}$ mass distribution and angular correlations that are sensitive to the $t\bar{t}$ spin correlation. Using a mass of 400 GeV as an example, we find that already the data collected during Run 2 and Run 3 of the LHC provides an interesting sensitivity to the underlying nature of a possible new particle. We also analyze the prospects for data anticipated to be collected during the high-luminosity phase of the LHC. Finally, we compare the limits obtained from the $t \bar t$ searches to existing experimental bounds from LHC searches for narrow di-photon resonances, from measurements of the production of four top quarks, and from global analyses of ALP-SMEFT interference effects.Comment: 28 pages, 9 figure

Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA

Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Comment: 27 pages, 8 figures and 3 table