Measuring Physical Properties of the W Boson in 7 TeV Proton-proton Collisions
Measuring Physical Properties of the W Boson in 7 TeV Proton-proton Collisions

Author: Phillip Killewald

Publisher:

Published: 2010

Total Pages: 144

ISBN-13:

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Abstract: The Large Hadron Collider (LHC) is a recently-activated proton-proton collider operating at a center-of-mass energy of 7 TeV. The Compact Muon Solenoid (CMS) is one of two general-purpose collider-detectors centered at one of the interaction points of the LHC. A measurement of the PW boson production cross-section and mass is presented to test the performance of the CMS detector in early (70 nb^-1) LHC data and to test theoretical predictions at this never-before-experienced energy regime. The cross-section measurement uses standard event counting techniques, while the mass measurement is performed using fitting of the analytical differential cross-section formula to the transverse mass spectrum from selected W to muon and muon neutrino events. The W production cross-section is measured to be [9,013 +/- 540 (stat.) +/- 552 (sys.) +/- 991 (lumi.)] pb, consistent with theoretical predictions at next-to-leading order in the strong coupling constant. The mass of the W is measured to be [80.07 +/- 0.64 (stat.) +/- 0.48 (sys.)] GeV/c^2, consistent with previous experimental measurements.

Measurements of Higgs Boson Properties in Proton-Proton Collisions at √s =7, 8 and 13 TeV at the CERN Large Hadron Collider
Measurements of Higgs Boson Properties in Proton-Proton Collisions at √s =7, 8 and 13 TeV at the CERN Large Hadron Collider

Author: Ulascan Sarica

Publisher: Springer Nature

Published: 2019-09-26

Total Pages: 103

ISBN-13: 3030254747

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This thesis documents the measurement of lifetime, width, mass, and couplings to two electroweak bosons of the recently-discovered Higgs boson using data from the CMS experiment at the Large Hadron Collider. Both on-shell (at the mass of around 125 GeV) and off-shell (above 200 GeV) Higgs boson production is studied and an excess of off-shell production with significance above two standard deviations is observed for the first time. The latter is a qualitative new way to study the Higgs field, responsible for generation of mass of all the known elementary particles. In addition, phenomenological tools have been developed with the Monte Carlo event generator and matrix element techniques for an optional analysis of LHC data. Optimization of the CMS data with careful alignment of the silicon tracker is also presented.

Inclusive b Jet Production in Proton-Proton Collisions
Inclusive b Jet Production in Proton-Proton Collisions

Author: Patrick L.S. Connor

Publisher: Springer Nature

Published: 2019-11-29

Total Pages: 325

ISBN-13: 3030343839

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^ 74 GeV and |y| 2.4; the b jets must contain a B hadron. The measurement has significant statistics up to p T ∼ O(TeV). Advanced methods of unfolding are performed to extract the signal. It is found that fixed-order calculations with underlying event describe the measurement well.

Search for New Heavy Charged Bosons and Measurement of High-Mass Drell-Yan Production in Proton—Proton Collisions
Search for New Heavy Charged Bosons and Measurement of High-Mass Drell-Yan Production in Proton—Proton Collisions

Author: Markus Zinser

Publisher: Springer

Published: 2018-09-25

Total Pages: 386

ISBN-13: 3030006506

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This book presents two analyses, the first of which involves the search for a new heavy charged gauge boson, a so-called W' boson. This new gauge boson is predicted by some theories extending the Standard Model gauge group to solve some of its conceptual problems. Decays of the W' boson in final states with a lepton (l± = e± , μ±) and the corresponding (anti-)neutrino are considered. Data collected by the ATLAS experiment in 2015 at a center of mass energy of √s =13 TeV is used for the analysis. In turn, the second analysis presents a measurement of the double-differential cross section of the process pp->Z/gamma^* + X -> l^+l^- + X, including a gamma gamma induced contribution, at a center of mass energy of sqrt{s} = 8 TeV. The measurement is performed in an invariant mass region of 116 GeV to 1500 GeV as a function of invariant mass and absolute rapidity of the l^+l^-- pair, and as a function of invariant mass and pseudorapidity separation of the l^+l^-- pair. The data analyzed was recorded by the ATLAS experiment in 2012 and corresponds to an integrated luminosity of 20.3/fb. It is expected that the measured cross sections are sensitive to the PDFs at very high values of the Bjorken-x scaling variable, and to the photon structure of the proton.

Study of Double Parton Scattering Using Four-Jet Scenarios
Study of Double Parton Scattering Using Four-Jet Scenarios

Author: Paolo Gunnellini

Publisher: Springer

Published: 2015-08-24

Total Pages: 290

ISBN-13: 3319222139

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This thesis addresses in a very new and elegant way several measurements and the extraction of so-called double parton scattering. The new and elegant way lies in the combination of measurements and a very smart extraction of double parton scattering results, which is easy to apply and overcomes many of the technical difficulties of older methods. Many new phenomena in particle physics can be observed when particles are collided at the highest energies; one of the highlights in recent years was the discovery of the Higgs boson at the Large Hadron Collider at CERN. Understanding the production mechanism of the Higgs boson at the LHC requires detailed knowledge of the physics of proton-proton collisions. When the density of partons in the protons becomes large, there is a non-negligible probability that more than one parton participates in the interaction and the so-called double parton scattering becomes important. In some cases very particular final state signatures can be observed, which can be regarded as an indication of such double partonic scattering and where the different interactions can be separated. Such multiple partonic interactions play an important role when precise predictions from known processes are required.

Precise Determination of the Mass of the Higgs Boson and Tests of Compatibility of Its Couplings with the Standard Model Predictions Using Proton Collisions at 7 and 8 TeV.
Precise Determination of the Mass of the Higgs Boson and Tests of Compatibility of Its Couplings with the Standard Model Predictions Using Proton Collisions at 7 and 8 TeV.

Author:

Publisher:

Published: 2015

Total Pages: 75

ISBN-13:

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Properties of the Higgs boson with mass near 125 GeV are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. The decay channels include [gamma][gamma], ZZ, WW, [tau][tau], bb, and [mu][mu] pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1 fb−1 at 7 TeV and up to 19.7 fb−1 at 8 TeV. From the high-resolution [gamma][gamma] and ZZ channels, the mass of the Higgs boson is determined to be 125.02\, +0.26-0.27(stat)+0.14-0.15(syst) GeV. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is 1.00 " 0.09 (stat), +0.08 -0.07 (theo) " 0.07 (syst) at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.

Associated Production of W + Charm in 13 TeV Proton-Proton Collisions Measured with CMS and Determination of the Strange Quark Content of the Proton
Associated Production of W + Charm in 13 TeV Proton-Proton Collisions Measured with CMS and Determination of the Strange Quark Content of the Proton

Author: Svenja Karen Pflitsch

Publisher: Springer Nature

Published: 2020-08-18

Total Pages: 148

ISBN-13: 303052762X

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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.