A Search For Resonant Production Of T Bar T Pairs In 4 8 Rm Fb 1 Of Integrated Luminosity Of P Bar P Collisions At Sqrt S
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A Search For Resonant Production Of Tt Pairs In 4 8 Fb 1 Of Integrated Luminosity Of Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2011
A Search For Resonant Production Of Tt Pairs In 4 8 Fb 1 Of Integrated Luminosity Of Pp Collisions At U221a S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
We search for resonant production of tt pairs in 4.8 fb-1 integrated luminosity of pp collision data at √s = 1.96 TeV in the lepton+jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix element reconstruction technique is used; for each event a probability density function (pdf) of the tt candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant tt production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of tt pairs. A benchmark model of leptophobic Z' → tt is excluded with mZ'
Search For Anomalous T T Bar Production In The Highly Boosted All Hadronic Final State
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Author :
language : en
Publisher:
Release Date : 2012
Search For Anomalous T T Bar Production In The Highly Boosted All Hadronic Final State written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.
Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At S 1 2
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Author :
language : en
Publisher:
Release Date : 2007
Measurement Of The Relative Fraction Of Ttbar Events Produced Via Gluon Fusion In Ppbar Collision At S 1 2 written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
In this thesis we present a measurement of the relative fraction of t{bar t} events produced via gluon-fusion to the total number of t{bar t} events. Using the kinematics of the production and decay of the top and antitop quark pair, we trained a Neural Network to discriminate the gluon-fusion events. The Neural Network was then used as a template to fit for the gluon-fusion fraction in data. Using a total integrated luminosity of 955 pb−1 we find [sigma](gg2!{bar t})/[sigma](p{bar p}2!{bar t})
Evidence For T Bar T Production At The Tevatron
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Author :
language : en
Publisher:
Release Date : 1994
Evidence For T Bar T Production At The Tevatron written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with categories.
We summarize here the results of the ''counting experiments'' by the CDF Collaboration in the search of t{bar t} production in p{bar p} collisions at (square root)s = 1800 TeV at the Tevatron. We analyze their statistical significance by calculating the probability that the observed excess is a fluctuation of the expected backgrounds, and assuming the excess is from top events, extract a measurement of the t{bar t} production cross-section.
Measurement Of The T Tbar Cross Section At The Run Ii Tevatron Using Support Vector Machines
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Author :
language : en
Publisher:
Release Date : 2010
Measurement Of The T Tbar Cross Section At The Run Ii Tevatron Using Support Vector Machines written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
This dissertation measures the t{bar t} production cross section at the Run II CDF detector using data from early 2001 through March 2007. The Tevatron at Fermilab is a p{bar p} collider with center of mass energy √s = 1.96 TeV. This data composes a sample with a time-integrated luminosity measured at 2.2 ± 0.1 fb−1. A system of learning machines is developed to recognize t{bar t} events in the 'lepton plus jets' decay channel. Support Vector Machines are described, and their ability to cope with a multi-class discrimination problem is provided. The t{bar t} production cross section is then measured in this framework, and found to be [sigma]{sub t{bar t}} = 7.14 ± 0.25 (stat){sub -0.86}{sup +0.61}(sys) pb.
Zhongguo Di Shao Shu Min Zu He Min Zu Qu Yu Zi Zhi
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Author : Zhengxiang Chen
language : en
Publisher:
Release Date : 1972
Zhongguo Di Shao Shu Min Zu He Min Zu Qu Yu Zi Zhi written by Zhengxiang Chen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1972 with China categories.
Measurement Of The T Tbar Production Cross Section In The Cdf Detector
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Author : Jose Enrique Palencia Cortezón
language : en
Publisher:
Release Date : 2013-11-16
Measurement Of The T Tbar Production Cross Section In The Cdf Detector written by Jose Enrique Palencia Cortezón and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-11-16 with categories.
Measurement Of The T Bar T Production Cross Section In The Dilepton Channel In Pp Collisions At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2013
Measurement Of The T Bar T Production Cross Section In The Dilepton Channel In Pp Collisions At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Measurement Of The Tt Bar Production Cross Section In The Dilepton Channel At Cdf
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Author : Reda Tafirout
language : en
Publisher:
Release Date : 2004
Measurement Of The Tt Bar Production Cross Section In The Dilepton Channel At Cdf written by Reda Tafirout and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with categories.
We report a measurement of the t{bar t} production cross section using dilepton events with jets and missing transverse energy in p{bar p}collisions at {radical}s = 1.96 TeV. Using 197 pb{sup -1} of data recorded by the upgraded Collider Detector at Fermilab (CDF II), we use two complementary techniques to select candidate events. The combined result yields a t{bar t} production cross section of 7.0{sub -2.1}{sup +2.4}(stat){sub -1.1}{sup +1.6}(syst) {+-} 0.4(luminosity)pb which is consistent with the Standard Model.
Resonance Searches With The T Overline T Invariant Mass Distribution Measured With The D O Experiment At Sqrt S
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Author :
language : en
Publisher:
Release Date : 2010
Resonance Searches With The T Overline T Invariant Mass Distribution Measured With The D O Experiment At Sqrt S written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Understanding the universe, its birth and its future is one of the biggest motivations in physics. In order to understand the cosmos, the fundamental particles forming the universe, the components our matter is built of need to be known and understood. Over time physicists have built a theory which describes the physics of the known fundamental particles very well: the Standard Model (SM) of particle physics. The SM describes the particles, their interactions and phenomena with high precision. So far no proven deviations from the SM have been found, though recently evidence for possible physics beyond the SM has been observed. The SM is not describing the mass of the elementary particles however and even with the addition of the Higgs mechanism giving mass to the particles, we have no full theory for all four fundamental forces. We know the model needs to be extended or replaced by another one, as gravitation is not included in the SM. Having a theory which describes all fundamental particles found so far and all but one fundamental interaction is a great success. However, all this describes about 4% of the universe we live in. 23% is dark matter and 73% is dark energy. Dark matter is believed to interact only through gravity and maybe the weak force, which makes it hardly observable. Dark energy is even more elusive. Among other theories the cosmologic constant and scalar fields are discussed to describe it. One should also note that other models exist which for example modify the Newtonian law of gravity. The Higgs mechanism has become the most popular model for mass generation. Alternative theories like Super Symmetry (SUSY), large Extra Dimensions, Technicolor, String Theory, to name just a few, have spread to describe the necessary mass generation or new particles. As proof for new physics beyond the SM has not been found yet, one assumes that new physics will manifest itself at a larger energy scale and therefore a higher particle mass. Particles with high masses are therefore presumed to be a window to test the SM for deviations caused by new physics. The heaviest fundamental particle which is in our reach is the top quark. Its mass is almost as large as that of a complete tungsten atom. It is so heavy, that it decays faster than it can hadronize. It seems the perfect probe to study new physics at the moment. In this analysis the top quark is used as a probe to search for a new resonance, whose properties are similar to a SM Z boson but is much more massive. This analysis will study t{bar t} decays to search for an excess in the invariant mass distribution of the t{bar t} pairs. Resonant states are suggested for massive Z-like bosons in extended gauge theories, Kaluza Klein states of the gluon or Z, axigluons, topcolor, and other beyond the Standard Model theories. Independent of the exact model a resonant production mechanism should be visible in the t{bar t} invariant mass distribution. In this thesis a model-independent search for a narrow-width heavy resonance X decaying into t{bar t} is performed. In the SM, the top quark decays into a W boson and a b quark nearly 100% of the time, which has been proven experimentally, too. The t{bar t} event signature is fully determined by the W boson decay modes. In this analysis, only the lepton+jets final state, which results from the leptonic decay of one of the W bosons and the hadronic decay of the other, is considered. The event signature is an isolated electron or muon with high transverse momentum, large transverse energy imbalance due to the undetected neutrino, and at least three jets, two of which result from the hadronization of b quarks.