Author: Sarah SchlobohmPublisher:
ISBN:
Category : Higgs bosons
Languages : en
Pages : 192
Book Description
A Search for the Minimally Supersymmetric Higgs Boson in B-quark and Tau-lepton Final States Using Proton-antiproton Collisions at 1.96 TeV
Author: Sarah SchlobohmPublisher:
ISBN:
Category : Higgs bosons
Languages : en
Pages : 192
Book Description
Search for Higgs Bosons and Supersymmetric Particles in Tau Final States in Proton-antiproton Collisions at 1.96 TeV
Author: Ingo TorchianiSearch for New Physics in Electron-tau Final States in Proton - Antiproton Collisions at 1.96 TeV.
Author: Carsten NoedingPublisher:
ISBN:
Category :
Languages : en
Pages : 190
Book Description
During the last decades, particle physicists have studied the tiniest building blocks of matter--the quarks and the leptons--and the forces between them in great detail. From these experiments, a theoretical framework has been built that describes the observed results with high precision. The achievement of this theory, which is referred to as the Standard Model of elementary particle physics, was the elaboration of a unified description of the strong, weak and electromagnetic forces in the framework of quantum gauge-field theories. Moreover, the Standard Model combines the weak and electromagnetic forces in a single electroweak gauge theory. The fourth force which is realized in nature, gravity, is too weak to be observable in laboratory experiments carried out in high-energy particle physics and is not part of the Standard Model. Although the Standard Model has proven highly successful in correlating a huge amount of experimental results, a key ingredient is as yet untested: the origin of electroweak symmetry breaking. Currently, the only viable ansatz that is compatible with observation is the Higgs mechanism. It predicts the existence of a scalar particle, called the Higgs boson, and the couplings to the fundamental Standard Model particles, however not its mass. An upper limit on the mass of the Higgs boson of {approx} 1 TeV can be inferred from unitarity arguments. One of the key tasks of particle physics in the next years will be to verify the existence of this particle. The introduction of an elementary scalar particle in a quantum field theory is highly problematic. The Higgs boson mass is subject to large quantum corrections, which makes it difficult to understand how its mass can be less than a TeV as required by theory. In addition, the Standard Model does not provide an answer to fundamental questions like the values of free parameters of the model, the pending integration of gravity or the evolution of the coupling constants of the fundamental forces at large energy regimes. Hence there are strong reasons to believe that the Standard Model is only a low-energy approximation to a more fundamental theory. One of the best studied candidates for an extension of the Standard Model is supersymmetry, which predicts the existence of a supersymmetric partner for each fundamental particle that differs only in spin. To allow different masses for Standard Model particles and their corresponding supersymmetric partners, supersymmetry must be broken. The mechanism behind supersymmetry breaking is currently unknown, however, various hypotheses exist. Supersymmetric models do not only solve the problem of the large quantum corrections to the Higgs boson mass, but they also allow the unification of the coupling constants at a common scale. In addition, certain supersymmetric models provide a suitable candidate for cold dark matter, which represents a large fraction of mass in our universe. Searches for supersymmetric particles have been performed by the four LEP experiments (ALEPH, DELPHI, L3, OPAL) up to the kinematic limit. Since no evidence for supersymmetric particles has been found, lower limits on their masses have been derived. The search for supersymmetry is now continuing at the Tevatron collider, located at the Fermi National Accelerator Laboratory in Batavia, Illinois. Two dedicated detector systems, CDF and D0, are installed at the Tevatron to analyze proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. A particular promising discovery channel for supersymmetry within the Tevatron energy range is the trilepton channel. In this channel, the lighter supersymmetric partners of the Higgs and gauge bosons, the charginos and neutralinos, decay into final states with leptons or hadrons and missing energy. Using the leptonic final states, the signal can be separated from the large Standard Model background. Supersymmetry requires an extension of the Standard Model Higgs sector, leading to more than one neutral Higgs boson. Enhanced couplings result in sizable cross sections for Higgs boson production, and the decay into a tau pair becomes an important Higgs boson discovery channel. Within the present thesis, a search for new physics predicted by constrained supersymmetric models is performed in final states consisting of an electron and a tau using data collected with the D0 detector from April 2002 to July 2004. The first analysis searches for the associated production of the lightest chargino and the second lightest neutralino in final states with an electron, a hadronically decaying tau, an additional lepton and missing transverse energy: e + {tau}{sub h} + {ell} + E{sub T}. The second analysis searches for neutral supersymmetric Higgs bosons in the decay mode {phi} {yields} {tau}{tau} {yields} e + {tau}{sub h} + E{sub T}. To improve the sensitivity, the results are interpreted in combination with other channels.
A Search for the Charged Higgs Boson Decays of the Top Quark Using Hadronic Decays of the Tau Lepton in Proton-antiproton Collisions at [square Root]s
![A Search for the Charged Higgs Boson Decays of the Top Quark Using Hadronic Decays of the Tau Lepton in Proton-antiproton Collisions at [square Root]s PDF](https://books.google.com/books/content/images/frontcover/K29BtwAACAAJ?fife=w80-h100)
Author: Leslie Stevan GroerSearch for Higgs Bosons and Supersymmetric Particles in Tau Final States
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 215
Book Description
Elementary particle physics tries to find an answer to no minor question: What is our universe made of? To our current knowledge, the elementary constituents of matter are quarks and leptons, which interact via four elementary forces: electromagnetism, strong force, weak force and gravity. All forces, except gravity, can be described in one framework, the Standard Model of particle physics. The model's name reflects its exceptional success in describing all available experimental high energy physics data to high precision up to energies of about 100 GeV. An exception is given by the neutrino masses but even these can be integrated into the model. The Standard Model is based on the requirement of invariance of all physics processes under certain fundamental symmetry transformations. The consideration of these symmetries leads naturally to the correct description of the electromagnetic, weak and strong forces as the exchange of interaction particles, the gauge bosons. However, this formalism has the weakness that it only allows for massless particles. In order to obey the symmetries, a way to introduce the particle masses is given by the Higgs mechanism, which predicts the existence of the only particle of the Standard Model which has yet to be observed: the Higgs boson. In spite of the success of the Standard Model, it has to be considered as a low energy approximation of a more profound theory for various reasons. For example, the underlying theory is expected to allow for an integration of gravity into the framework and to provide a valid particle candidate for the dark matter in our universe. Furthermore, a solution has to be found to the problem that the Higgs boson as a fundamental scalar is sensitive to large radiative corrections driving its mass to the Planck scale of 1019 GeV. Several models have been proposed to address the remaining open questions of the Standard Model. Currently, the most promising extension of the Standard Model is Supersymmetry, which provides elegant solutions to the named problems by introducing a supersymmetric partner to each Standard Model particle. The superpartners of the matter particles are called squarks and sleptons, while the superpartners of the interaction particles are called gauginos. The mass eigenstates of the gauginos are referred to as charginos and neutralinos, according to their electric charge. Since the predicted supersymmetric particles have not yet been observed, Supersymmetry, if it exists in nature, has to be broken in such a way that the masses of Standard Model particles and of their superpartners differ. During the last decades, the energies accessible to experiments has steadily increased. The Tevatron Accelerator at the Fermi National Accelerator Laboratory, with the two multipurpose experiments D0 and CDF, provides currently the highest center-of-mass energy ever reached in experiments using collisions of protons and antiprotons ((square root)s = 1.96 TeV). The study of the particle collisions allows probing of predictions of the Standard Model and its extensions, e.g. Supersymmetry.
Discovering the Higgs Bosons of Minimal Supersymmetry with Tau Leptons and a Bottom Quark
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 14
Book Description
We investigate the prospects for the discovery at the CERN Large Hadron Collider or at the Fermilab Tevatron of neutral Higgs bosons through the channel where the Higgs are produced together with a single bottom quark and the Higgs decays into a pair of tau leptons, bg → b?° → b??−,?° = h°, H°, A°. We work within the framework of the minimal supersymmetric model. The dominant physics background from the production of b?+?−, j?+?− (j = g, u, d, s, c), b{bar b}W+W−, W +2j and Wbj is calculated with realistic acceptance cuts and efficiencies. Promising results are found for the CP-odd pseudoscalar (A°) and the heavier CP-even scalar (H°) Higgs bosons with masses up to one TeV.
Search for the Standard Model Higgs Boson in Missing Transverse Energy and B-quark Final States Using Proton-antiproton Collisions at 1.96 TeV
Author: Tyler McMillan DorlandPublisher:
ISBN:
Category : Higgs bosons
Languages : en
Pages : 192
Book Description
High Energy Physics Index
Author: Search for the Higgs Boson Decaying to Two Tau Leptons in Proton-antiproton Collisions at a Center of Mass Energy of 1.96 TeV
Author: Andrey ElaginPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A search for the Higgs boson decaying to tau tau using 7.8 fb^-1 of pp collisions at 1.96 TeV collected with CDF II detector is presented. The search is sensitive to four production mechanisms of the Higgs boson: ggH, WH, ZH and VBF. Modes where one tau decay leptonically, and another decay, hadronically, are considered. Two novel techniques are developed and used in the search. A Probabilistic Particle Flow Algorithm is used for energy measurements of the hadronic tau candidates. The signal is discriminated from backgrounds by the Missing Mass Calculator, which allows for full invariant mass reconstruction of tau tau pair. The data are found to be consistent with the background only hypothesis. Therefore a 95% confidence level upper limit on the Standard Model Higgs boson cross section was set. At M_H=120 GeV/c^2 observed limit is 14.9 x sigma_SM x Br(H -> tau tau).
Search for Lepton Flavour Violating Decays of the Higgs Boson to E Tau and E Mu in Proton-proton Collisions at Sqrt(s)
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A direct search for lepton flavour violating decays of the Higgs boson (H) in the H to e tau and H to e mu channels is described. The data sample used in the search was collected in proton-proton collisions at sqrt(s)=8 TeV with the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7 inverse femtobarns. No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H to e tau)