72 Works

New physics in top pair production.

Roman Lysak
We present the latest results about the searches for a new physics in top quark pair production. The ATLAS and CMS collaborations results are presented using the data collected at LHC in 2012 at the energy of interactions of 8 TeV. The most of such searches look for vector-like quarks. No presence of excess is found and the $95\% $ C.L. lower limits on vector-like quark masses are set between about 600 -- 850 $\GeVcc$...

From the LHC to a future lepton collider.

Kirill Melnikov
I discuss the complementarity of top quark physics that can be studied at the LHC and at a future lepton collider.

Measurement of jet multiplicity distributions insemi-leptonic top quark pair events.

Shawn Williamson
The normalized differential cross section of $t\bar{t}$ events in the semileptonic decay channel in jet multiplicity bins is presented, measured in proton-proton collisions using $5.0\,\text{fb}^{-1}$ of data collected at $\sqrt{s} = 7\,\text{TeV}$. Additionally, the normalized differential cross section of top quark pair production in bins of the number of radiated additional hard partons is measured. These measurements are sensitive to additional radiation at the top quark scale. Comparisons of data with predictions from different Monte...

Helicity Amplitudes and Angular Decay Distributions.

J. G. Koerner
I discuss how to obtain angular decay distributions for sequential cascade decays using helicity methods. The angular decay distributions follow from a reasonably simple master formula involving bilinear forms of helicity amplitudes and Wigner's $d$ functions. I discuss in some detail the issue of gauge invariance for off-shell gauge bosons. As a technical exercise I calculate the linear relation between the helicity amplitudes and the invariant amplitudes of semileptonic and rare baryon decays. I discuss...

Technical Design Report: Scientific Instrument High Energy Density Physics (HED)

Motoaki Nakatsutsumi, Karen Appel, Gerd Priebe, Ian Thorpe, Alexander Pelka, Bruno Muller & Thomas Tschentscher
This technical design report (TDR) of the High Energy Density Physics scientific instrument (HED instrument) at the European XFEL outlines the scientific and technological requirements for the various subsystems and describes the technical realization of the instrument chosen to match these requirements.The scientific requirements have been extracted from a range of proposed scientific applications at HED. Most of these applications had been discussed in the past years as the core of the scientific activity at...

V+jets background and systematic uncertainties in top quark analyses.

Stefanie Adomeit & Reinhild Yvonne Peters
Vector boson production in association with jets is an important process to test perturbative quantum chromodynamics and also a background process in top quark analyses. Measurements on vector boson production in association with light and heavy flavour jets are presented, performed by the D0 and CDF collaborations at the Tevatron as well as the ATLAS and CMS experiments at LHC. Techniques applied in top quark analyses to estimate the vector boson+jets background are also discussed.

Search for rare top quark decays.

Bruno Galhardo
Contribution to Proceedings

Alternative methods for top-quark mass determination at the Tevatron and LHC.

Frederic Deliot
I am summarizing here the determination of the top-quark mass from the CDF and D0 Collaborations at the Tevatron and the ATLAS and CMS Collaborations at the LHC using non-conventional methods. I am concentrating on the extraction of the top-quark mass from the top-antitop cross-section, on the mass measurement using the so-called endpoint method and on the top-quark mass determination from the $b$-lifetime.

Particle physics 2013 - Highlights and Annual Report

Thomas Schoerner-Sadenius, Manfred Fleischer, Michael Medinnis & Ilka Flegel

Small-$x$ behavior of deep-inelastic structure functions F$_2$ and F$^{cc}_2$.

Anatoly Kotikov
It is shown that in the leading twist approximation of the Wilson operator product expansion with ``frozen'' and analytic strong coupling constants, Bessel-inspired behavior of the structure functions $F_2$ and $F_2^{cc}$ at small $x$ values, obtained for a flat initial condition in the DGLAP evolution equations, leads to good agreement with the deep inelastic scattering experimental data from HERA.

The scalar mesons in multi-channel $\pi\pi$ scattering and decays of the $\psi$ and $\Upsilon$ families.

Yurii S. Surovtsev, Petr Bydzovsky, Thomas Gutsche, Robert Kaminski, Valery E. Lyubovitskij & Miroslav Nagy
The $f_0$ mesons are studied in a combined analysis of data on isoscalar S-wave processes $\pi\pi\to\pi\pi,K\overline{K},\eta\eta$ and on decays $J/\psi\to\phi(\pi\pi, K\overline{K})$, $\psi(2S)\to J/\psi(\pi\pi)$ and $\Upsilon(2S)\to\Upsilon(1S)\pi\pi$ from the Argus, Crystal Ball, CLEO, CUSB, DM2, Mark~II, Mark~III, and BESIII Collaborations. The method of analysis, based on analyticity and unitarity and using an uniformization procedure, is set forth with some details. Some spectroscopic implications from results of the analysis are discussed.

Lectures on new physics searches in $B\to D^{(*)}\tau\nu_\tau$.

Svjetlana Fajfer & Ivan Nisandzic
The Standard model's predictions for the rates for $B\to D^{*} \tau \nu_\tau$ and $B\to D\tau\nu_\tau$ differ from the experimental results. The difference might be accounted by the presence of new physics. The understanding of the non-perturbative QCD dynamics in the meson transitions is crucial in order to refine the searches for new physics effects. We give short introduction to heavy quark effective theory (HQET) and then investigate the most general set of lowest dimensional effective...

Flavor changing neutral currents in top quark production and decay

Efe Yazgan
6th International Workshop on Top Quark Physics, TOP2013, Durbach, Germany, 14 Sep 2013 - 19 Sep 2013; 285-294 (2014). doi:10.3204/DESY-PROC-2014-02/34

Proceedings of the 6th International Workshop on Top-Quark Physics (TOP 2013).

Ulrich Husemann, Hannes Mildner & Frank Roscher
Proc. of TOP 2013; DESY-PROC-2014-02; ISSN 1435-8077

Top charge asymmetry -- theory status fall 2013.

Susanne Westhoff
I review the current status of the charge asymmetry in hadronic top-quark pair production from a theory perspective. The standard-model predictions for the observables at the Tevatron and LHC are being discussed, as well as possible explanations of the Tevatron excess in terms of new physics. I give an outlook for future investigations of the top-quark charge asymmetry, focussing on novel observables at the LHC.

Leptons: $\mathbf{e}$, $\boldsymbol{\mu}$, $\boldsymbol{\tau}$ + systematic uncertainties.

Timothee Theveneaux-Pelzer & Javier Fernandez Menendez
An overview of the charged lepton performance in the ATLAS and CMS experiments at the LHC and in the CDF and D0 experiments at the Tevatron is given, in the specific context of physics analyses requiring the selection of leptons from top-quark decays. The trigger and reconstruction algorithms are presented, as well as the identification and isolation criteria, pointing out the specificities of top-quark analysis selections. The impact of the lepton-related experimental systematic uncertainties are...

Unfolding in particle physics: a window on solving inverse problems.

Francesco Spano
A pedagogical exposition of unfolding techniques in particle physics is presented. Building on example analyses about top quark physics, the origin, the main building blocks and the crucial challenges of inverse, ill-posed problems in particle physics are discussed.

Separating single top quark signal from background using distribution mixture model.

Jiri Franc, Michal Stepanek, Vaclav Krus & Vladislav Simak
A very common situation in experimental high energy physics is signal which cannot be separated from background by use of any cut. Application of the distribution mixtures, a modified iterative Expectation-Maximization algorithm for weighted data, and taking advantage of Bayesian statistics represents promising multivariate technique in this area. The paper presents statistical theory, computational aspects of the algorithm, and working results of signal from background separation obtained by application of the proposed method to a...

Experimental status of top charge asymmetry measurements.

Viatcheslav Sharyy
The latest measurements of the asymmetry in the angular distributions of the \ttbar\ events are reviewed. The measurements of the forward-backward asymmetry \Afb\ in the \ppbar\ 1.98 TeV collisions at the Tevatron show some tension with the Standard Model calculation, while results of the measurements of the charge asymmetry \Ac\ in $pp$ collisions at 7 TeV and 8 TeV at the LHC are compatible with Standard Model predictions.

The top quark and the SM stability.

Mikhail Shaposhnikov
I will discuss the significance of precise knowledge of the top quark and Higgs boson masses for physics beyond the Standard Model and cosmology.

Measurement of the charge asymmetry in top quark pair production at CMS.

Frank Roscher
The $\mathrm{t\bar{t}}$ charge asymmetry is measured in the lepton$+$jets decay channel using a dataset of 19.7$\mathrm{fb^{-1}}$ collected with the CMS detector at the LHC. We present an inclusive measurement as well as three differential measurements as functions of rapidity, transverse momentum, and invariant mass of the $\mathrm{t\bar{t}}$ system. The measured inclusive $\mathrm{t\bar{t}}$ charge asymmetry is $ 0.005 \pm 0.007~(\rm{stat.})\,\pm 0.006 ~(\rm{syst.})$; both this result and the differential measurements are consistent with the predictions of the...

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  • 2014

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