Download or read book Next to Leading Order Corrections to Weak Boson Production with a Massive Quark Jet Pair at Hadron Colliders written by Fernando Febres Cordero and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: We present the calculation of Next-to-Leading-Order Quantum Chromo Dynamics corrections for the production of W or Z weak bosons associated with a bottom anti-bottom quark pair at hadron colliders (ppbar, pp to W/Z bbbar), including the effects of a non-zero bottom-quark mass. We find a considerable reduction of the renormalization and factorization scale dependence of our results with respect to Leading-Order calculations. In particular, we study the impact of the corrections on the total cross section and invariant mass distributions of the bottom anti-bottom quark pair at the Fermilab Tevatron ppbar collider. We perform a detailed comparison with a calculation that considers massless bottom quarks and find significant deviations in regions of phase space with small invariant mass of the bottom anti-bottom quark pair. Our results will be relevant to ongoing and future searches at hadron colliders, as the W/Z bbbar production mode is the main background to important signals, such as light Standard Model Higgs boson production or single top-quark production.
Download or read book Jet Physics at the LHC written by Klaus Rabbertz and published by Springer. This book was released on 2016-10-11 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews the latest experimental results on jet physics from proton-proton collisons at the LHC. Jets allow to determine the strong coupling constant over a wide range of energies up the highest ones possible so far, and to constrain the gluon parton distribution of the proton, both of which are important uncertainties on theory predictions in general and for the Higgs boson in particular.A novel approach in this book is to categorize the examined quantities according to the types of absolute, ratio, or shape measurements and to explain in detail the advantages and differences. Including numerous illustrations and tables the physics message and impact of each observable is clearly elaborated.
Download or read book NLO Vector Boson Production With Light Jets written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this contribution we present recent progress in the computation of next-to-leading order (NLO) QCD corrections for the production of an electroweak vector boson in association with jets at hadron colliders. We focus on results obtained using the virtual matrix element library BlackHat in conjunction with SHERPA, focusing on results relevant to understanding the background to top production. The production of a vector boson in association with several jets at the Large Hadron Collider (LHC) is an important background for other Standard Model processes as well as new physics signals. In particular, the production of a W boson in association with many jets is an important background for processes involving one or more top quarks. Precise predictions for the backgrounds are crucial to measurement of top-quark processes. Vector boson production in association with multiple jets is also a very important background for many SUSY searches, as it mimics the signatures of many typical decay chains. Here we will discuss how polarization information can be used as an additional handle to differentiate top pair production from 'prompt' W-boson production. More generally, ratios of observables, for example for events containing a W boson versus those containing a Z boson, are expected to be better-behaved as many uncertainties cancel in such ratios. Precise calculation of ratios, along with measurement of one of the two processes in the ratio, can be used in data-driven techniques for estimating backgrounds.
Download or read book Associated Production of W Charm in 13 TeV Proton Proton Collisions Measured with CMS and Determination of the Strange Quark Content of the Proton written by Svenja Karen Pflitsch and published by Springer Nature. This book was released on 2020-08-18 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: The associated production of a W boson and a single charm quark (W+c) is the only process in proton-proton collisions that directly probes the strange quark content of the proton. In this thesis, W+charm production is measured in proton-proton collisions at the LHC at 13 TeV, as recorded by the Compact Muon Solenoid (CMS) experiment. The analysis focuses on the identification of W bosons in their leptonic decay to a muon and a neutrino and charm quarks are tagged via the full reconstruction of D*-Mesons. The measured cross sections of W+c production are used, in combination with other relevant CMS results and the most precise HERA DIS data, in a QCD analysis to determine the strange quark content of the proton. The resulting strange quark distribution and suppression, with respect to the other light sea quarks, are in good agreement with those obtained in neutrino scattering experiments and extend their kinematic reach.
Download or read book Search for New Phenomena in Top Antitop Quarks Final States with Additional Heavy Flavour Jets with the ATLAS Detector written by Daiki Yamaguchi and published by Springer Nature. This book was released on 2019-10-30 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reports on the search for a new heavy particle, the Vector-Like Top quark (VLT), in the Large Hadron Collider (LHC) at CERN. The signal process is the pair production of VLT decaying into a Higgs boson and top quark (TT→Ht+X, X=Ht, Wb, Zt). The signal events result in top–antitop quarks final states with additional heavy flavour jets. The book summarises the analysis of the data collected with the ATLAS detector in 2015 and 2016. In order to better differentiate between signals and backgrounds, exclusive taggers of top quark and Higgs boson were developed and optimised for VLT signals. These efforts improved the sensitivity by roughly 30%, compared to the previous analysis. The analysis outcomes yield the strongest constraints on parameter space in various BSM theoretical models. In addition, the book addresses detector operation and the evaluation of tracking performance. These efforts are essential to properly collecting dense events and improving the accuracy of the reconstructed objects that are used for particle identification. As such, they represent a valuable contribution to data analysis in extremely dense environments.
Download or read book Perspectives on LHC Physics written by Aaron Pierce and published by World Scientific. This book was released on 2008 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Large Hadron Collider (LHC), located at CERN, Geneva, Switzerland, is the world's largest and highest energy and highest intensity particle accelerator. This book provides an overview on the techniques that will be crucial for finding new physics at the LHC, as well as perspectives on the importance and implications of the discoveries. Among the contributors to this book are leaders and visionaries in the field of particle physics beyond the Standard Model, including two Nobel Laureates (Steven Weinberg and Frank Wilczek), and presumably some future Nobel Laureates, plus top younger theorists and experimenters.
Download or read book Measurement of the W Boson Helicity in Top antitop Quark Events with the CDF II Experiment written by Thorsten Chwalek and published by . This book was released on 2006 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1995 the top quark was discovered at the Tevatron proton-antiproton collider at Fermilab by the CDF and D0 collaborations [1, 2]. It is the most massive known elementary particle and its mass is currently measured with a precision of about 1.3% [3, 4]. However, the measurements of several other top quark properties are still statistically limited, so the question remains whether the Standard Model of elementary particle physics successfully predicts these properties. This thesis addresses one interesting aspect of top quark decay, the helicity of the produced W boson. Until the start of the Large Hadron Collider (LHC) at CERN, the Tevatron with a center-of-mass energy of {radical}s = 1.96 TeV is the only collider, where top quarks can be produced. In the Standard Model the top quark decays predominantly into a W boson and a b quark, with a branching ratio close to 100%. The V-A structure of the weak interaction of the Standard Model predicts that the W{sup +} bosons from the top quark decay t {yields} W{sup +}b are dominantly either longitudinally polarized or left handed, while right handed W bosons are heavily suppressed and even forbidden in the limit of a massless b quark. Under the assumption of a massless b quark, for a top quark mass of 173 GeV/c{sup 2} the Standard Model predicts the fraction F0 of longitudinally polarized W bosons to be 0.7 and 0.3 for the fraction F{_} of left handed W bosons, while the fraction F{sub +} of right handed W bosons is predicted to be zero. Since next-to-leading order corrections change these fractions only slightly, a significant deviation from the predicted value for F{sub 0} or a nonzero value for F{sub +} could indicate new physics. Left-right symmetric models [5], for example, lead to a significant right handed fraction of W bosons in top decays. Such a right handed component (V+A coupling) would lead to a smaller left handed fraction, while F{sub 0} would remain unchanged. Since the decay rate to longitudinal W bosons depends on the Yukawa coupling of the top quarks, the measurement of F{sub 0} is sensitive to the mechanism of electroweak symmetry breaking. Alternative models can lead to an altered F{sub 0} fraction. In this analysis the W helicity fractions are measured in a selected sample rich in t{bar B} events where one lepton, at least four jets, and missing transverse energy are required. All kinematic quantities describing the t{bar t} decay are determined. As a sensitive observable, we use the cosine of the decay angle {theta}*, which is defined as the angle between the momentum of the charged lepton in the W boson rest frame and the W boson momentum in the top quark rest frame. The data used in this analysis were taken with the Collider Detector at Fermilab (CDF II) in the years 2002-2006 and correspond to an integrated luminosity of about 955 pb{sup -1}. Previous CDF measurements of the W boson helicity fractions in top quark decays used either the square of the invariant mass of the charged lepton and the b quark jet, M{sub {ell}b}{sup 2}, or the lepton p{sub T} distribution as a discriminant. The D0 collaboration used a matrix-element method to extract a value of F{sub 0}; in a second analysis the reconstructed distribution of cos {theta}* was utilized to measure F{sub +}. CDF gives the latest value of F{sub 0} = 0.74{sub -0.34}{sup +0.22}, while D measured F{sub 0} = 0.56 {+-} 0.31. The CDF collaboration also gives the current upper limit of F{sub +}
Download or read book Towards Global Interpretation of LHC Data written by Toni Mäkelä and published by Springer Nature. This book was released on 2023-05-16 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the first global interpretation of measurements of jet and top quark production at the Large Hadron Collider, including a simultaneous extraction of the standard model parameters together with constraints on new physics, unbiased from the assumptions on the standard model parameters. As a long-standing problem, any hadron collider search for new physics depends on parton distribution functions, which cannot be predicted but are extracted experimentally. However, performing the extraction in the same kinematic region where physics beyond the standard model is expected to manifest causes the risk of absorbing the new physics effects into the parton distributions. In this book, the issue is addressed by extending the standard model by effective contributions from quark contact interactions describing new physics and extracting the parton distributions and standard model parameters simultaneously with setting limits on the contact interactions. In the process, the most precise single measurement of the strong coupling constant at the LHC is performed, to date. Furthermore, the book details the first investigation of the mass renormalization scale dependence of the top quark mass, highlighting the importance of a proper scale choice for obtaining robust predictions and improving the precision of experimental analyses. The initial chapters provide the reader with a succinct yet accessible introduction to the relevant theoretical and experimental topics. The presented investigations are at the edge of precision in the phenomenology of high-energy physics and serve to pave the road toward a global interpretation of LHC data.
Download or read book Elliptic Integrals Elliptic Functions and Modular Forms in Quantum Field Theory written by Johannes Blümlein and published by Springer. This book was released on 2019-01-30 with total page 509 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book includes review articles in the field of elliptic integrals, elliptic functions and modular forms intending to foster the discussion between theoretical physicists working on higher loop calculations and mathematicians working in the field of modular forms and functions and analytic solutions of higher order differential and difference equations.
Download or read book Top Quark Physics at Hadron Colliders written by Arnulf Quadt and published by Springer Science & Business Media. This book was released on 2007-08-16 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: This will be a required acquisition text for academic libraries. More than ten years after its discovery, still relatively little is known about the top quark, the heaviest known elementary particle. This extensive survey summarizes and reviews top-quark physics based on the precision measurements at the Fermilab Tevatron Collider, as well as examining in detail the sensitivity of these experiments to new physics. Finally, the author provides an overview of top quark physics at the Large Hadron Collider.
Download or read book QCD Higher Order Effects and Search for New Physics written by Jian Wang and published by Springer. This book was released on 2015-10-28 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book mainly investigates the precision predictions on the signal of new physics at the Large Hadron Collider (LHC) in the perturbative Quantum Chromodynamics (QCD) scheme. The potential of the LHC to discover the signal of dark matter associated production with a photon is studied after including next-to-leading order QCD corrections. The factorization and resummation of t-channel top quark transverse momentum distribution in the standard model at both the Tevatron and the LHC with soft-collinear effective theory are presented. The potential of the early LHC to discover the signal of monotops is discussed. These examples illustrate the method of searching for new physics beyond what is known today with high precision.
Download or read book Hadron Collider Physics 2002 written by Martin Erdmann and published by Springer Science & Business Media. This book was released on 2003 with total page 572 pages. Available in PDF, EPUB and Kindle. Book excerpt: I Opening Review on Hadron-Collider Physics.- Hadron Colliders, the Standard Model, and Beyond.- 1 What is the Standard Model?.- 2 Hadron Colliders and the Standard Model.- 2.1 Precision electroweak.- 2.2 CKM.- 2.3 Top quark.- 2.4 Higgs boson.- 2.5 QCD.- 3 Beyond the Standard Model.- 3.1 Direct evidence.- 3.2 Indirect evidence.- References.- II Status of the Accelerators and Detectors.- Tevatron Collider Run II Status.- 1 Introduction.- 2 Overview.- 3 Run II Milestones.- 4 Parameters.- 5 Performance to Date.- 6 Accomplishments.- 6.1 Accomplishments: Helix Adjustments.- 6.2 Accomplishments: Antiproton Emittance.- 6.3 Accomplishments: Tevatron Injection Closure.- 7 Outstanding Issues.- 8 Future Prospects.- 9 Reliability.- 10 Summary.- 11 Acknowledgements.- Status of CDF II and Prospects for Run II.- 1 Introduction.- 2 The CDF II Detector and Trigger Upgrades.- 3 Physics Results and Prospects.- 4 Conclusions.- References.- Status of the D Detector.- 1 Introduction.- 2 Overview.- 3 Silicon Vertex Detector.- 4 Central Fiber Tracker.- 5 Calorimeters.- 6 Muon Detectors.- 7 Forward Proton Detectors.- 8 Trigger and Data Acquisition.- 9 Conclusions.- References.- III Standard Model Processes: Parton Luminosities, QCD Evolution.- The Proton Structure as Measured at HERA.- 1 Introduction.- 2 NC Cross Sections in the Complete Kinematic Plane.- 3 High-Q2 Measurements.- 4 Charged Current Measurements.- 5 Summary and Outlook.- References.- Global Fits of Parton Distributions.- 1 Introduction.- 2 Parton Uncertainties.- 2.1 Hessian (Error Matrix) approach.- 2.2 Offset method.- 2.3 Statistical approach.- 2.4 Lagrange multiplier method.- 2.5 Results.- 3 Theoretical Errors.- 3.1 Problems in the fit.- 3.2 Types of Theoretical Error, NNLO.- 3.3 Empirical approach.- 4 Conclusions.- References.- Low x Physics at HERA.- 1 Introduction.- 2 Formalism and Theory.- 3 Results.- 3.1 Inclusive measurements.- 3.2 Exclusive results.- 4 Summary.- References.- Saturation Effects in Hadronic Cross Sections.- 1 Introduction.- 2 The Loop-Loop Correlation Model.- 3 Saturation in Proton-Proton Scattering.- 4 Gluon Saturation.- 5 Conclusion.- References.- IV Standard Model Processes: QCD at High pt.- Progress in NNLO Calculations for Scattering Processes.- 1 Why NNLO Calculations are Important.- 1.1 Renormalisation scale uncertainty.- 1.2 Factorisation scale dependence.- 1.3 Jet algorithms.- 1.4 Transverse momentum of the incoming partons.- 1.5 Power corrections.- 1.6 The shape of the prediction.- 1.7 Parton densities at NNLO.- 2 Recent Progress in the Field.- 3 What Remains to be Done.- References.- Heavy Flavour Production at D .- 1 Introduction.- 2 b-production Cross-section.- 2.1 Muon and Jet Cross-section.- 2.2 b-tagging.- 3 J/? Cross-section.- 4 Other Measurements.- References.- Heavy Quark Production at CDF.- 1 Introduction.- 2 Beauty Production at CDF.- 2.1 CDF Run I results.- 2.2 Preliminary results from CDF Run II.- 3 Quarkonia Production at CDF.- 4 Charm Production at CDF.- 4.1 Run I results.- 4.2 Run II charm production cross-sections.- 5 Conclusion.- References.- Heavy Quark Production at HERA.- 1 Introduction.- 2 Open Charm Production.- 3 Charmonium.- 4 Beauty Production.- 5 Summary.- References.- Theoretical Developments on Hard QCD Processes at Colliders.- 1 Introduction.- 2 Heavy Quarks.- 2.1 Total Cross Sections.- 2.2 Transverse Momentum Distributions.- 2.3 Top Quark Spin Correlations.- 3 Jets.- 3.1 Jet Definitions.- 3.2 Precision Jet Physics.- 3.3 Multiparton Processes.- 4 Photons and Massive Gauge Bosons.- 4.1 Isolated Photons.- 4.2 Photon Pairs.- 4.3 Vector Boson and Higgs Production.- 4.4 Transverse Momentum Distributions.- 5 Conclusions and Outlook.- References.- Jet Production at CDF.- 1 Introduction.- 2 Inclusive Jet Production.- 3 Three-jet Production.- 4 Study of Jet Shapes in Run 2.- 5 Study of the Underlying Event.- 6 Study of W+Njet Production.- References.- Jet Algorithms at D .- 1 Introduction.- 2 The Measurement of Jets.- 3 Run I Co
Download or read book Testing The Standard Model Tasi 1990 Proceedings Of The 1990 Theoretical Advanced Study Institute In Elementary Particle Physics written by Mirjam Cvetic and published by World Scientific. This book was released on 1991-06-18 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Theoretical Advanced Study Institute (TASI) has become the major summer school for advanced students in elementary particle theory in the United States, offering courses in particle theory, phenomenology, and mathematical physics. The theme of the 1990 school, 'Testing the Standard Model', was chosen because of the many new high precision results that had recently become available from the TEVATRON, SLC, and LEP. The goal was to explore the theoretical background and implications of experiments at these and future facilities, both in and beyond the standard model.
Download or read book A Study of Weak Corrections to Drell Yan Top quark Pair and Di jet Production at High Energies with MCFM written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Electroweak (EW) corrections can be enhanced at high energies due to the soft or collinear radiation of virtual and real $W$ and $Z$ bosons that result in Sudakov-like corrections of the form $\alpha_W^l\log^n(Q^2/M_{W, Z}^2)$, where $\alpha_W =\alpha/(4\pi\sin^2\theta_W)$ and $n\le 2l-1$. The inclusion of EW corrections in predictions for hadron colliders is therefore especially important when searching for signals of possible new physics in distributions probing the kinematic regime $Q^2 \gg M_V^2$. Next-to-leading order (NLO) EW corrections should also be taken into account when their size ($\mathcal{O}(\alpha)$) is comparable to that of QCD corrections at next-to-next-to-leading order (NNLO) ($\mathcal{O}(\alpha_s^2)$). To this end we have implemented the NLO weak corrections to the Neutral-Current Drell-Yan process, top-quark pair production and di-jet production in the parton-level Monte-Carlo program MCFM. This enables a combined study with the corresponding QCD corrections at NLO and NNLO. We provide both the full NLO weak corrections and their Sudakov approximation since the latter is often used for a fast evaluation of weak effects at high energies and can be extended to higher orders. With both the exact and approximate results at hand, the validity of the Sudakov approximation can be readily quantified.
Download or read book Theoretical Studies on Extended Higgs Sectors Towards Future Precision Measurements written by Masashi Aiko and published by Springer Nature. This book was released on 2023-05-20 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book investigates the physics of the discovered Higgs boson and additional Higgs bosons in the extended Higgs models which includes higher-order quantum corrections. While the 125 GeV Higgs boson was discovered, the structure of the Higgs sector is still a mystery. Since the Higgs sector determines the concrete realization of the Higgs mechanism, the study of its nature is one of the central interests in current and future high-energy physics. The book begins with a review of the standard model and the two-Higgs doublet model, which is one of the representatives of the extended Higgs models. Subsequently, we discuss the studies of the two-Higgs doublet model at the lowest order of perturbation. Following the lowest-order analysis, we study the higher-order electroweak corrections in Higgs physics. After reviewing the renormalization procedure and the higher-order corrections in the decays of the discovered Higgs boson, we discuss the higher-order corrections in the Higgs strahlung process from an electron-positron collision, the decays of the additional charged and CP-odd Higgs bosons in the two-Higgs doublet model. From the series of these studies, it is found that the nature of the Higgs sector can be widely investigated by future collider experiments.
Download or read book The Higgs Boson Discovery at the Large Hadron Collider written by Roger Wolf and published by Springer. This book was released on 2015-05-18 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the field of Higgs boson physics. It offers the first in-depth review of the complete results in connection with the discovery of the Higgs boson at CERN’s Large Hadron Collider and based on the full dataset for the years 2011 to 2012. The fundamental concepts and principles of Higgs physics are introduced and the important searches prior to the advent of the Large Hadron Collider are briefly summarized. Lastly, the discovery and first mensuration of the observed particle in the course of the CMS experiment are discussed in detail and compared to the results obtained in the ATLAS experiment.
Download or read book Search for New Physics in tt Final States with Additional Heavy Flavor Jets with the ATLAS Detector written by Javier Montejo Berlingen and published by Springer. This book was released on 2016-07-20 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: This doctoral thesis focuses on the search for new phenomena in top-antitop quark (tt) final states with additional b-quark jets at the LHC. It uses the full Run 1 dataset collected by the ATLAS experiment in proton-proton collisions at √s=8 TeV. The final state of interest consists of an isolated lepton, a neutrino and at least six jets with at least four b-tagged jets, a challenging experimental signature owing to the large background from tt+heavy-flavor production. This final state is characteristic of ttH production, with the Higgs boson decaying into bb, a process that allows direct probing of the top-Higgs Yukawa coupling. This signature is also present in many extensions of the Standard Model that have been proposed as solutions to the hierarchy problem, such as supersymmetry or composite Higgs models, which predict the pair production of bosonic or fermionic top quark partners, or the anomalous production of four-top-quark events. All these physics processes have been searched for using an ambitious search strategy that has been developed on the basis of a combination of state-of-art theoretical predictions and a sophisticated statistical analysis to constrain in-situ the large background uncertainties. As a result, the most restrictive bounds to date on the above physics processes have been obtained.
