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Measurements Of Ttu00af Spin Correlations And Top Quark Polarization Using Dilepton Final States In Pp Collisions At S
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Book Synopsis Spin Correlations in Tt Events from Pp Collisions by : Boris Lemmer
Download or read book Spin Correlations in Tt Events from Pp Collisions written by Boris Lemmer and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis introduces readers to the Standard Model, the top quark and its properties, before explaining the concept of spin correlation measurement. The first measurement of top quark spin correlations at the LHC in the lepton+jets decay channel is presented. As the heaviest elementary particle, the top quark plays an essential role in the Standard Model of elementary particle physics. In the case of top quarks being produced in pairs at hadron colliders, the Standard Model predicts their spins to be correlated. The degree of correlation depends on both the production mechanism and properties of the top quark. Any deviation from the Standard Model prediction can be an indicator for new physics phenomena. The thesis employs an advanced top quark reconstruction algorithm including dedicated identification of the up- and down-type quarks from the W boson decay.
Book Synopsis Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method by : Alexander Grohsjean
Download or read book Measurement of the Top Quark Mass in the Dilepton Final State Using the Matrix Element Method written by Alexander Grohsjean and published by Springer Science & Business Media. This book was released on 2010-10-01 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main pacemakers of scienti?c research are curiosity, ingenuity, and a pinch of persistence. Equipped with these characteristics a young researcher will be s- cessful in pushing scienti?c discoveries. And there is still a lot to discover and to understand. In the course of understanding the origin and structure of matter it is now known that all matter is made up of six types of quarks. Each of these carry a different mass. But neither are the particular mass values understood nor is it known why elementary particles carry mass at all. One could perhaps accept some small generic mass value for every quark, but nature has decided differently. Two quarks are extremely light, three more have a somewhat typical mass value, but one quark is extremely massive. It is the top quark, the heaviest quark and even the heaviest elementary particle that we know, carrying a mass as large as the mass of three iron nuclei. Even though there exists no explanation of why different particle types carry certain masses, the internal consistency of the currently best theory—the standard model of particle physics—yields a relation between the masses of the top quark, the so-called W boson, and the yet unobserved Higgs particle. Therefore, when one assumes validity of the model, it is even possible to take precise measurements of the top quark mass to predict the mass of the Higgs (and potentially other yet unobserved) particles.
Book Synopsis QCD Radiation in Top-Antitop and Z+Jets Final States by : Kiran Joshi
Download or read book QCD Radiation in Top-Antitop and Z+Jets Final States written by Kiran Joshi and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis contains new research in both experimental and theoretical particle physics, making important contributions in each. Two analyses of collision data from the ATLAS experiment at the LHC are presented, as well as two phenomenological studies of heavy coloured resonances that could be produced at the LHC. The first data analysis was the measurement of top quark-antiquark production with a veto on additional jet activity. As the first detector-corrected measurement of jet activity in top-antitop events it played an important role in constraining the theoretical modelling, and ultimately reduced these uncertainties for ATLAS's other top-quark measurements by a factor of two. The second data analysis was the measurement of Z+2jet production and the observation of the electroweak vector boson fusion (VBF) component. As the first observation of VBF at a hadron collider, this measurement demonstrated new techniques to reliably extract VBF processes and paved the way for future VBF Higgs measurements. The first phenomenological study developed a new technique for identifying the colour of heavy resonances produced in proton-proton collisions. As a by-product of this study an unexpected and previously unnoticed correlation was discovered between the probability of correctly identifying a high-energy top and the colour structure of the event it was produced in. The second phenomenological study explored this relationship in more detail, and could have important consequences for the identification of new particles that decay to top quarks.
Book Synopsis Top-Quark Pair Production Cross Sections and Calibration of the Top-Quark Monte-Carlo Mass by : Jan Kieseler
Download or read book Top-Quark Pair Production Cross Sections and Calibration of the Top-Quark Monte-Carlo Mass written by Jan Kieseler and published by Springer. This book was released on 2016-06-15 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the first experimental calibration of the top-quark Monte-Carlo mass. It also provides the top-quark mass-independent and most precise top-quark pair production cross-section measurement to date. The most precise measurements of the top-quark mass obtain the top-quark mass parameter (Monte-Carlo mass) used in simulations, which are partially based on heuristic models. Its interpretation in terms of mass parameters used in theoretical calculations, e.g. a running or a pole mass, has been a long-standing open problem with far-reaching implications beyond particle physics, even affecting conclusions on the stability of the vacuum state of our universe. In this thesis, this problem is solved experimentally in three steps using data obtained with the compact muon solenoid (CMS) detector. The most precise top-quark pair production cross-section measurements to date are performed. The Monte-Carlo mass is determined and a new method for extracting the top-quark mass from theoretical calculations is presented. Lastly, the top-quark production cross-sections are obtained – for the first time – without residual dependence on the top-quark mass, are interpreted using theoretical calculations to determine the top-quark running- and pole mass with unprecedented precision, and are fully consistently compared with the simultaneously obtained top-quark Monte-Carlo mass.
Book Synopsis Measurement of the TtH Production Cross-section with a Collimated H -> Bb Decay in Pp Collisions at Sqrt(s) by : Eftychia Tzovara
Download or read book Measurement of the TtH Production Cross-section with a Collimated H -> Bb Decay in Pp Collisions at Sqrt(s) written by Eftychia Tzovara and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The predictions of the Standard Model (SM) of particle physics have been probed with remarkable accuracy, so far. The Large Hadron Collider (LHC) at CERN has significantly contributed to this quest. A remarkable achievement of the ATLAS and CMS experiments at the LHC was the discovery of the Higgs boson in 2012, the last missing piece of the SM. With the increasing amount of proton-proton collisions delivered by the LHC, more precise measurements of the Higgs boson are now possible, while rare processes are accessible as well. A property of the Higgs boson that is of particular importance is its coupling to the top quark, which is expected to be the strongest in the SM due to the high mass of the top quark. Therefore, its precise measurement is a stringent test of the SM. A direct measurement of the top-quark Yukawa coupling can be assessed through the Higgs-boson production in association with a pair of top quarks (ttH). This thesis presents the measurement of the ttH process with a subsequent Higgs-boson decay to a pair of b-quarks (H -> bb), the decay mode with the largest branching ratio. The measurement is performed with data collected by the ATLAS detector, corresponding to an integrated luminosity of 139 fb^-1 at a center-of-mass energy of 13 TeV. Events with one or two charged leptons from the tt decay in the final state are considered to the measurement. The main challenge of the ttH(H -> bb) channel emerges from the large SM backgrounds from the production of top-quark pairs with additional jets (tt+jets). Also the many jets coming from b-hadrons (b-jets) in the final state cause combinatorial ambiguities. Thus, the identification of such jets is decisive in order to determine the signal and reject many background processes. The ttH events are split into exclusive analysis regions, based on the number of leptons, jets, and jets tagged as b-jets, providing regions enhanced in signal, or in the main background components. Specifically in the single-lepton channel, a boosted category is defined by selecting events in which the Higgs boson and possibly also the hadronically decaying top quark are produced with high transverse momentum (pT), with their decay products being collimated in large-radius jets. The single-lepton boosted channel targets events with Higgs-boson candidate pT >= 300 GeV and is the main scope of this thesis. To identify the reconstructed objects with the underlying particles and to maximise the discrimination of the ttH signal from the overwhelming tt+jets background events in the signal-enriched regions, machine-learning algorithms are employed. The background is dominated by a tt process with an additional gluon in the final state which further splits into a pair of b-quarks (tt+bb). Besides, a large number of heavy-flavour jets in the final state is not well modelled, thus many systematic uncertainties have to be considered, decreasing the sensitivity of the measurement. All the defined analysis regions are analysed together in a combined profile likelihood fit to test for the presence of signal. The fit simultaneously determines the event yields for the signal and the most important background component, while constraining the overall background model within the assigned systematic uncertainties. Eventually, the ratio of the measured ttH cross section to the SM expectation in the inclusive cross-section measurement is found to be 0.35 +0.36,-0.34}, corresponding to an observed (expected) significance of 1.0 (2.7) standard deviations. A ttH signal strength larger than the SM prediction is excluded at 95% confidence level. The measurement uncertainty is dominated by systematic uncertainties, mainly regarding the theoretical knowledge of the tt +>= 1b background process. Finally, to further test the SM, the cross-section is measured differentially as a function of the generator-level Higgs-boson pT, taking advantage of the reconstruction of the Higgs-boson kinematics.
Book Synopsis Measurements of the X c and X b Quarkonium States in pp Collisions with the ATLAS Experiment by : Andrew Chisholm
Download or read book Measurements of the X c and X b Quarkonium States in pp Collisions with the ATLAS Experiment written by Andrew Chisholm and published by Springer. This book was released on 2015-09-14 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis, which won one of the six 2015 ATLAS Thesis Awards, concerns the study of the charmonium and bottomonium bound heavy quark bound states. The first section of the thesis describes the observation of a candidate for the chi_b(3P) bottomonium states. This represented the first observation of a new particle at the LHC and its existence was subsequently confirmed by D0 and LHCb experiments. The second part of the thesis presents measurements of the prompt and non-prompt production of the chi_c1 and chi_c2 charmonium states in proton-proton collisions. These measurements are compared to several theoretical predictions and can be used to inform the development of theoretical models of quarkonium production.
Book Synopsis Search for Heavy Resonances in Four-top-quark Final States in Pp Collisions at √s by : Alicia Wongel
Download or read book Search for Heavy Resonances in Four-top-quark Final States in Pp Collisions at √s written by Alicia Wongel and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Top Quark Spin Correlations with the CMS Detector by : JASON R. THIEMAN
Download or read book Top Quark Spin Correlations with the CMS Detector written by JASON R. THIEMAN and published by Springer. This book was released on 2024-12-02 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Spin Structure of the Proton by : Steven D. Bass
Download or read book The Spin Structure of the Proton written by Steven D. Bass and published by World Scientific. This book was released on 2008 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main challenges in nuclear and particle physics in the last 20 years has been to understand how the proton''s spin is built up from its quark and gluon constituents. Quark models generally predict that about 60% of the proton''s spin should be carried by the spin of the quarks inside, whereas high energy scattering experiments have shown that the quark spin contribution is small OCo only about 30%. This result has been the underlying motivation for about 1000 theoretical papers and a global program of dedicated spin experiments at BNL, CERN, DESY and Jefferson Laboratory to map the individual quark and gluon angular momentum contributions to the proton''s spin, which are now yielding exciting results. This book gives an overview of the present status of the field: what is new in the data and what can be expected in the next few years. The emphasis is on the main physical ideas and the interpretation of spin data. The interface between QCD spin physics and the famous axial U(1) problem of QCD (eta and etaprime meson physics) is also highlighted. Sample Chapter(s). Chapter 1: Introduction (159 KB). Contents: Spin Experiments and Data; Dispersion Relations and Spin Sum Rules; g 1 Spin Sum Rules; Fixed Poles; The Axial Anomaly, Gluon topology and g (0) A; Chiral Symmetry and Axial U(1) Dynamics; QCD Inspired Models of the Proton Spin Problem; The Spin-Flavour Structure of the Proton; QCD Fits to g 1 Data; Polarized Quark Distributions; Polarized Glue o g(x, Q 2 ); Transversity; Deeply Virtual Compton Scattering and Exclusive Processes; Polarized Photon Structure Functions; Conclusions and Open Questions: How Does the Proton Spin?. Readership: Academics, as well as physicists working on particle and nuclear physics at the interface of theory and experiment.
Book Synopsis Measurement of Quarkonium Polarization to Probe QCD at the LHC by : Valentin Knünz
Download or read book Measurement of Quarkonium Polarization to Probe QCD at the LHC written by Valentin Knünz and published by Springer. This book was released on 2017-01-07 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis discusses in detail the measurement of the polarizations of all S-wave vector quarkonium states in LHC proton-proton collisions with the CMS detector. Heavy quarkonium states constitute an ideal laboratory to study non-perturbative effects of quantum chromodynamics and to understand how quarks bind into hadrons. The experimental results are interpreted through an original phenomenological approach, which leads to a coherent picture of quarkonium production cross sections and polarizations within a simple model, dominated by one single color-octet production mechanism. These findings provide new insights into the dynamics of heavy quarkonium production at the LHC, an important step towards a satisfactory understanding of hadron formation within the standard model of particle physics.
Book Synopsis Combination of the W Boson Polarization Measurements in Top Quark Decays Using ATLAS and CMS Data at √s by : Georges Aad
Download or read book Combination of the W Boson Polarization Measurements in Top Quark Decays Using ATLAS and CMS Data at √s written by Georges Aad and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamental Interactions by : A. Astbury
Download or read book Fundamental Interactions written by A. Astbury and published by World Scientific Publishing Company Incorporated. This book was released on 2005 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: I. Nuclear astrophysics / C.R. Brune -- II. Relativistic heavy ion physics in the new millennium / J.L. Nagle -- III. B physics and CP violation / H. Quinn -- Measurements of the CKM angle [symbol] at Belle / K. Abe -- New phenomena at DØ / T. Adams -- Lepton flavour violating Tau decays / S. Banerjee -- Collision dynamics at RHIC / O. Barannikova -- Hadron spectroscopy at HERA / M. Barbi -- Search for extra dimensions with ATLAS at LHC / K. Benslama -- Higgs physics with CMS / T. Boccali -- Searches for new physics at HERA / N. Brümmer -- Electroweak penguin and leptonic decays at BaBar / F. Bucci -- A first measurement of the helicity asymmetries for polarized proton collisions at SQRT(S)=200GeV / G. Bunce -- Final results from the Muon G-2 experiment / G. Bunce -- Cosmic ray astrophysics with AMS-02 / D. Casadei -- Properties of the X(3872) / S.-K. Choi -- Recent results in diffraction at HERA / J.E. Cole -- Recent results in heavy flavour production at HERA / J.E. Cole -- Top quark physics results from DØ / J. Ellison -- Search for the radion decay [symbol] final states in CMS / L. Fanò -- Status of parity violation in cesium / J. Ginges -- Measurements of the KM angle at [symbol], at Belle / N.C. Hastings -- Observation of the [symbol] pentaquark at HERMES / B. Hommez -- Constraining low scale gravity with ultrahigh energy neutrinos / S. Hussain -- Simulation of the radio signal from ultrahigh energy neutrino-initiated showers / S. Hussain -- Status of the TWIST measurement of P[symbol] / B.A. Jamieson -- Neutrino physics in the seesaw model / E. Jenkins -- Measurement of heavy flavour production in P-P and D-Au collisions at RHIC by the detection of the inclusive muons / J.H. Kang -- Superallowed fermi [symbol]-decay studies with SCEPTAR and the 8[symbol] gamma-ray spectrometer / K.A. Koopmans -- Recent QCD results from CDF / S. Lami -- [symbol] production and nuclear effects for D+Au and P+P collisions in PHENIX at RHIC / M.J. Leitch -- Precision measurement of the muon decay spectrum / R.P. MacDonald -- See-Saw induced CMSSM lepton-flavour violation post-WMAP / D. Maybury -- Measurement of electroweak gauge boson self-couplings at LEP / W. Menges -- Neutron stars as type I superconductors / M.A. Metlitski -- Differentiating solutions to the gauge hierarchy problem through rare muon decays / B. Murakami -- Top quark physics at CDF / J. Nielsen -- Anisotropic flow in ultra-relativistic heavy-ion collisions / M.D. Oldenburg -- Measurements related to the CKM angle gamma from BaBar / T.C. Petersen -- Measurements related to the CKM matrix at Belle / L.E. Piilonen -- Jets in deep-inelastic scattering at HERA and determinations of [symbol] / R. Pöschl -- Semileptonic B Decays from BaBar : |V[symbol]| and |V[symbol]| / M. Rotondo -- Spin and chiral properties of high-energy neutrinos in Schwarzchild space-time / D. Singh -- Two-loop QCD corrections to top quark decay / M. Ślusarczyk -- W mass and width measurement at LEP / F. Spano -- Rare decays at Belle / R. Stamen -- [symbol] measurement at Belle (observation of CP violation in B[symbol] decay) / K. Sumisawa -- Electroweak physics results from DØ / T. Toole -- Search for a single t quark production via contact interactions with Delphi at LEP2 / F. Veloso -- Recent beauty physics results at CDF / I. Vila -- Fermion pair and photo pair production at LEP2 / H. Wahlen -- Electroweak results from CDF / D.S. Waters -- HyperCP, a search for CP violation in hyperon decay / C. White -- Main injector neutrino oscillation experiment, MINOS / C. White -- Status report on the ANTARES project / J.D. Zornoza
Book Synopsis Precision Measurements and Search for Axion-like Particles in Final States with a Z Boson and a Photon in Pp Collisions at √s by : Vincent Goumarre
Download or read book Precision Measurements and Search for Axion-like Particles in Final States with a Z Boson and a Photon in Pp Collisions at √s written by Vincent Goumarre and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
