Download or read book First Differential Measurements of tZq Production and Luminosity Determination Using Z Boson Rates at the LHC written by David Walter and published by Springer. This book was released on 2024-03-05 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes two groundbreaking measurements in the precision frontier at the LHC: the first ever differential measurement of the Z-associated single top quark (tZq) production, and the luminosity measurement using Z boson production rate for the first time in CMS. Observed only in 2018, the tZq process is of great importance in probing top quark electroweak couplings. These couplings are natural places for new phenomena to happen in the top quark sector of the standard model. Yet, they are the least explored directly. One has to obtain a firm understanding of the modeling of sensitive distributions to new top-Z interactions. The present analysis marks a major milestone in this long-term effort. All distributions relevant for new phenomena, and/or modeling of tZq, are studied in full depth using advanced Machine Learning techniques.The luminosity and its uncertainty contributes to every physics result of the experiment. The method minutely developed in this thesis provides a complementary measurement that results in a significant overall reduction of uncertainties.
Download or read book First Simultaneous Measurement of Single and Pair Production of Top Quarks in Association with a Z Boson at the LHC written by Federica Cecilia Colombina and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photon Physics at the LHC written by Michael Hance and published by Springer Science & Business Media. This book was released on 2012-11-08 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis reports on the first studies of Standard Model photon production at the Large Hadron Collider (LHC) using the ATLAS detector. Standard Model photon production is a large background in the search for Higgs bosons decaying into photon pairs, and is thus critical to understand. The thesis explains the techniques used to reconstruct and identify photon candidates using the ATLAS detector, and describes a measurement of the production cross section for isolated prompt photons. The thesis also describes a search for the Higgs boson in which the analysis techniques used in the measurement are exploited to reduce and estimate non-prompt backgrounds in diphoton events.
Download or read book Determination of the Absolute Luminosity at the LHC written by Simon White and published by . This book was released on 2010 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: For particle colliders, the most important performance parameters are the beam energy and the luminosity. High energies allow the particle physics experiments to study and observe new effects. The luminosity describes the ability of the collider to produce the required number of useful interactions or events. The Large Hadron Collider (LHC) was designed to produce proton proton collisions at a center of mass energy of 14 TeV. This energy is the highest ever reached in a particle accelerator. The knowledge and understanding of particIe physics at such high energy is based on simulations and theoretical predictions. As opposed to electron positron colliders, for which the Bhabba scattering cross section can be accurately calculated and used for luminosity calibration, there are no processes with well known cross section and sufficiently high production rate to be directly used for the purpose of luminosity calibration in the early operation of the LHC. The luminosity can also be expressed as a function of the numbers of charges per beam and the beam sizes at the interaction point. Using this relation the absolute luminosity can be determined from machine parameters. The determination of the absolute luminosity from machine parameters is an alternative to the cross section based calibration and provides complementary information to the fragmentation model. ln the LHC, it was proposed to use the method developed by S. Van Der Meer at the ISR to provide a luminosity calibration based on machine parameters to the physics experiments during the first year of operation. This thesis presents how this method was implemented and performed for the first time in the LHC to optimize and calibrate the luminosity. Additional beam dynamics and optics studies and measurements performed at the RHIC collider will also be presented.
Download or read book Forward Physics And Luminosity Determination At Lhc written by Katri Huitu and published by World Scientific. This book was released on 2001-08-30 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently there has been much interest in studying events with tagged forward protons at the existing and forthcoming hadronic colliders, the Tevatron and the LHC. These studies not only allow one to monitor the luminosity of the colliding protons with high accuracy but also provide new ways of investigating the subtle issues of QCD dynamics and searches for the manifestations of new physics.This book reviews the state of the art of forward physics measurements and the theoretical development. It will catalyze many new approaches within the framework of the extensive physics programme of the LHC. This in turn will stimulate closer contact between the LHC experiments as well as between the experimentalists and the theorists to maximize the potenntial of LHC physics.
Download or read book Measurement of the Inclusive Z to Ee Production Cross Section in Proton Proton Collisions at sqrt s written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis comprises a precision measurement of the inclusive \Zee production cross section in proton-proton collisions provided by the Large Hadron Collider (LHC) at a center-of-mass energy of $\sqrt{s}=7$~TeV and the absolute luminosity based on \Zee decays. The data was collected by the Compact Muon Solenoid (CMS) detector near Geneva, Switzerland during the year of 2010 and corresponds to an integrated luminosity of $\int\mathcal{L}dt = 35.9\pm 1.4$~pb$^{-1}$. Electronic decays of $Z$ bosons allow one of the first electroweak measurements at the LHC, making the cross section measurement a benchmark of physics performance after the first year of CMS detector and LHC machine operations. It is the first systematic uncertainty limited \Zee cross section measurement performed at $\sqrt{s}=7$~TeV. The measured cross section pertaining to the invariant mass window $M_{ee}\in (60,120)$~GeV is reported as: $\sigma(pp\to Z+X) \times \mathcal{B}(Z\to ee) = 997 \pm 11 \mathrm{(sta t)} \pm 19 \mathrm{(syst)} \pm 40 \mathrm{(lumi)} \textrm{ pb}$, which agrees with the theoretical prediction calculated to NNLO in QCD. Leveraging \Zee decays as ``standard candles'' for measuring the absolute luminosity at the LHC is examined; they are produced copiously, are well understood, and have clean detector signatures. Thus the consistency of the inclusive \Zee production cross section measurement with the theoretical prediction motivates inverting the measurement to instead use the \Zee signal yield to measure the luminosity. The result, which agrees with the primary relative CMS luminosity measurement calibrated using Van der Meer separation scans, is not only the most precise absolute luminosity measurement performed to date at a hadron collider, but also the first one based on a physics signal at the LHC.
Download or read book Measurement of Z Boson Production with the ATLAS Experiment at the LHC written by James Dassoulas and published by . This book was released on 2014 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inclusive Electroweak Measurements in the Muon Channel with Pp Collisions at the Square Root Of S written by Philip Coleman Harris and published by . This book was released on 2011 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we perform the measurement of the production of W and Z bosons in proton-proton collisions at [the square root of]s = 7 TeV with the Large Hadron Collider (LHC). In the LHC, W and Z bosons are produced at a high rate, providing for large yields, which along with the clean signature of W boson decay into a muon and neutrino and the Z boson decay into two muons, allow for precision measurement of their production within the first year of operation. Deviation of these values from standard model predictions gives a clear indication of new physics interactions occurring at the LHC. We present the measurement of the inclusive W--> [mu] [epsilon] and Z --> [mu]+ [mu]- cross sections along with the W boson charge ratio (W+/W-) and the W/Z production ratio in the muon channel using the first data corresponding to 35.9 pb-1 of proton proton collisions at [the square root of]s = 7 TeV. Measured values of ... are in agreement with the most advanced NNLO predictions. These are currently the most precise Electroweak measurements at the LHC.
Download or read book Measurement of the Z Boson Production with the ATLAS Experiment at the LHC written by Mikhail Karnevskiy and published by . This book was released on 2012 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book First Measurement of Z Bosons with the ATLAS Detector at the LHC and Its Implications for New Physics Beyond the Standard Model written by Pai-hsien Jennifer Hsu and published by . This book was released on 2011 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Z Boson Production in Heavy ion Collisions with the CMS Detector at the LHC written by Zsigmond Anna Júlia and published by . This book was released on 2015 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Luminosity Measurement at the Compact Muon Solenoid Experiment of the LHC written by Olena Karacheban and published by Springer. This book was released on 2018-06-22 with total page 153 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the application of a novel technology for beam instrumentation and luminosity measurement and first results on a cutting edge technology potentially to be used after the upgrade of the Large Hadron Collider to higher luminosity. It presents a unique diamond-based luminometer with a detailed performance study. The online bunch-by-bunch luminosity measurements provide an invaluable feedback to the Collider for beam optimisation and for the understanding of beam dynamics. The precision of the luminosity measurement is crucial for all physics analyses. This book highlights the Van der Meer method, which is used for the calibration of the luminometers of the CMS (Compact Muon Solenoid) experiment, and describes the estimate of systematic uncertainties, e.g. due to radiation damage of sensors and electronics and uncertainties of beam parameters. For the future high-luminosity upgrade of the collider, sapphire sensors are investigated in a test beam. It is demonstrated for the first time that sapphire sensors can be used as single particle detectors. A model for the charge transport in sapphire is developed and successfully applied.
Download or read book Erratum to written by and published by . This book was released on 2015 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study top quark pair production in association with a Z boson at the Large Hadron Collider (LHC) and investigate the prospects of measuring the couplings of top quarks to the Z boson. To date these couplings have not been constrained in direct measurements. Such a determination will be possible for the first time at the LHC. Our calculation improves previous coupling studies through the inclusion of next-to-leading order (NLO) QCD corrections in production and decays of all unstable particles. We treat top quarks in the narrow-width approximation and retain all NLO spin correlations. To determine the sensitivity of a coupling measurement we perform a binned log-likelihood ratio test based on normalization and shape information of the angle between the leptons from the Z boson decay. The obtained limits account for statistical uncertainties as well as leading theoretical systematics from residual scale dependence and parton distribution functions. We use current CMS data to place the first direct constraints on the ttbZ couplings. We also consider the upcoming high-energy LHC run and find that with 300 inverse fb of data at an energy of 13 TeV the vector and axial ttbZ couplings can be constrained at the 95% confidence level to C_V=0.24^{+0.39}_{-0.85} and C_A=-0.60^{+0.14}_{-0.18}, where the central values are the Standard Model predictions. This is a reduction of uncertainties by 25% and 42%, respectively, compared to an analysis based on leading-order predictions. We also translate these results into limits on dimension-six operators contributing to the ttbZ interactions beyond the Standard Model.
Download or read book A Comprehensive Study of Perturbative and Non perturbative Quantum Chromodynamics in Measurements of the Underlying Event and the Transverse Momentum of the Z Boson with the CMS Detector at the LHC written by Khristian Kotov and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Also we present a first measurement of the multiplicity and transverse momentum flow in the first LHC collision data at 900 GeV center-of-mass energy recorded in December 2009. The systematic bias to the measurement due to the event selection and track reconstruction are estimated using the full CMS simulation. The results are compared to the predictions of one of the soft QCD models, previously studied by CDF collaboration at the Tevatron.
Download or read book W and Z Bosons at the LHC written by Ann-Karin Sanchez and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2013-01 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Processes involving W and Z bosons decaying leptonically are among the best understood at hadron colliders. This and their copious production allow for a wide range of studies. The study of hard-diffractive event observables, such as a large rapidity gap in W or Z boson events, is strongly influenced by the underlying multiparton interactions. At present, the description of these processes relies largely on the generator specific tuning of data. Therefore, the measurement and extensive study of such events can be used in the understanding and implementation of detailed simulations of diffraction. Moreover, the measurements of single pomeron exchange are sensitive to the structure of the pomeron and the dynamics of diffraction. A detailed overview towards the observation of a diffractive signal with improvements of Monte Carlo simulations containing multiparton interactions is given. Finally, a precise measurement of the W and Z transverse momenta is presented. The distributions can potentially be used to constrain the gluon distribution function to high precision at LHC energies.
Download or read book Measurement of the Single Top TW Associated Production Cross Section at 7 TeV with 4 9 Fb 1 of Data in the Dilepton Decay Channel at the LHC Using the CMS Detector written by William Patrick Martin and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first measurement of the production cross section for a single top quark in association with a W boson with the CMS experiment at the Large Hadron Collider is presented. The analysed data is from proton-proton collisions at a centre-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.9 fb-1. The analysis focuses on the leptonic final states of the process and implements a cut-based method. The final state consists of two leptons, two neutrinos and a jet from the fragmentation of a b-quark. The primary source of background events arises from tt(overbar) production, followed by Z/gamma* processes. The observed signal has a significance of 3:5sigma and corresponds to a cross section measurement of 14:9+5:0 -5:1 (stat + syst) pb, in agreement with the Standard Model expectations.
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.
