Challenges in New Physics searches in top-like events at the LHC

The prospects of exploring physics beyond the standard model involving top quarks and top-like signals at the LHC based on Monte Carlo simulations at √s = 14 and 10TeV are reviewed. A special attention is given to results that can be expected for the early LHC running in 2010-2011. Consequently, the first section deals with the implications of having a center-of-mass energy lower than what was simulated, √s = 7TeV, for the first years of the LHC running. This will be done qualitatively by discussing the impact on the cross section of various production processes. Following this discussion, several searches for physics Beyond the standard model that are related to the top quark are described: top-antitop resonances, 4th generation of quarks, top charge, W polarization, anomalous Wtb vertex coupling, top-antitop spin correlation, and flavor changing neutral current. Their order of appearance goes from lower to higher integrated luminosity needed to obtain meaningful results out of each analysis

The ttH analyses at the LHC

Detecting the presence of a light Higgs boson at the LHC is very difficult. For this reason, different experimental signatures will have to be combined to ensure its discovery. Among them we study the associate production with a pair of top quarks and the subsequent Higgs boson decay into b quark pairs, the dominant decay mode for m_H bb) channel with the ATLAS and the CMS detectors. In addition, the decay modes H -> WW and H -> gamma gamma in ttH processes have been investigated and are briefly reported at the end of this paper

Automated Reconstruction of Particle Cascades in High Energy Physics Experiments

We present a procedure for reconstructing particle cascades from event data measured in a high energy physics experiment. For evaluating the hypothesis of a specific physics process causing the observed data, all possible reconstruction versions of the scattering process are constructed from the final state objects. We describe the procedure as well as examples of physics processes of different complexity studied at hadron-hadron colliders. We estimate the performance by 20 microseconds per reconstructed decay vertex, and 0.6 kByte per reconstructed particle in the decay trees.Comment: 8 pages, 2 figures. Submitted to Computational Science & Discover

М. Ф. ФОН ДІТМАР – ЯСКРАВИЙПРЕДСТАВНИК ГІРНИЧОПРОМИСЛОВОЇ БУРЖУАЗІЇ ПІВДНЯ УКРАЇНИ(ОСТАННЯ ЧВЕРТЬ ХІХ– ПОЧАТОК ХХ СТ.)

В статті розглянуто постать відомого підприємця, науковця і суспільного діячаМ. Ф. фон Дітмара, визначено основні напрями його діяльності наПівдні Українив останній чверті ХІХ – на початку ХХ ст.The article considers the person of famous businessman, scientist and social activistM. F. von Ditmar, determines themain directions of his activity in SouthernUkraine in the last quarter ofXIX – the beginning ofXXcenturies

The ttH Physics Channel at the LHC

The global fit of Higgs boson contributions to the electroweak experimental observables, computed within the Standard Model, favors a light Higgs with a mass of m_H=76+33-25 GeV/c2, on the edge of the 95\% Confidence Level region excluded at LEP. Finding a light Higgs boson at LHC is experimentally difficult and several channels with various signatures will be sought for. The associate production of the Higgs boson with a pair of top quarks, with the subsequent decay of the Higgs boson into b-quark pairs (dominant for m_H<135 GeV/c2) , is one of the channels considered. This channel also gives a unique access to the top Yukawa coupling. The potential of the ATLAS and CMS detectors to observe this channel will be described. Several ingredients are crucial: reconstruction of the top-antitop system with a high-purity, excellent b-tagging capabilities and good knowledge of the ttbar+jets background. The decay of H to WW and to gamma gamma in ttH processes has been also studied and it is briefly reported

Visual Physics Analysis (VISPA) - Concepts and First Applications

VISPA is a novel development environment for high energy physics analyses, based on a combination of graphical and textual steering. The primary aim of VISPA is to support physicists in prototyping, performing, and verifying a data analysis of any complexity. We present example screenshots, and describe the underlying software concepts.Comment: Parallel talk at ICHEP08, Philadelphia, USA, July 2008. 4 pages, 2 figure

A Development Environment for Visual Physics Analysis

The Visual Physics Analysis (VISPA) project integrates different aspects of physics analyses into a graphical development environment. It addresses the typical development cycle of (re-)designing, executing and verifying an analysis. The project provides an extendable plug-in mechanism and includes plug-ins for designing the analysis flow, for running the analysis on batch systems, and for browsing the data content. The corresponding plug-ins are based on an object-oriented toolkit for modular data analysis. We introduce the main concepts of the project, describe the technical realization and demonstrate the functionality in example applications

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV

A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 inverse picobarns collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu