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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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 Resonant T Bar T Production In Proton Proton Collisions At U221a S
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language : en
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Release Date : 2016
Search For Resonant T Bar T Production In Proton Proton 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 2016 with categories.
A search is performed for the production of heavy resonances decaying into top-antitop quark pairs in proton-proton collisions at √s = 8 TeV. Data used for the analyses were collected with the CMS detector and correspond to an integrated luminosity of 19.7 fb–1. The search is performed using events with three different final states, defined by the number of leptons (electrons and muons) from the tt¯ → WbWb decay. The analyses are optimized for reconstruction of top quarks with high Lorentz boosts, where jet substructure techniques are used to enhance the sensitivity. Results are presented for all channels and a combination is performed. Furthermore, no significant excess of events relative to the expected yield from standard model processes is observed.
Search For Resonant Production Of Tt Decaying To Jets In Pp Collisions At U221a S
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Author :
language : en
Publisher:
Release Date : 2011
Search For Resonant Production Of Tt Decaying To Jets In 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.
This Letter reports a search for non-standard model topquark resonances, Z', decaying to ttMs; →W+bW-b , where both W decay to quarks. We examine the top-antitop quark invariant mass spectrum for the presence of narrow resonant states. The search uses a data sample of p{bar p} collisions at a center of mass energy of 1.96 TeV collected by the CDF II detector at the Fermilab Tevatron, with an integrated luminosity of 2.8 fb-1. No evidence for top-antitop quark resonant production is found. We place upper limits on the production cross section times branching ratio for a specific topcolor assisted technicolor model with width of ?Z' = 0.012 MZ'. Within this model, we exclude Z' boson with masses below 805 GeV/c2 at the 95% confidence level.
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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Author :
language : en
Publisher:
Release Date : 2011
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 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 t{bar t} pairs in 4.8 fb−1 integrated luminosity of p{bar p} 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 t{bar t} candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant t{bar t} production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of t{bar t} pairs. A benchmark model of leptophobic Z' → t{bar t} is excluded with m{sub Z'}
Observation Of Top Quark Pair Production In Association With A Photon And Measurement Of The Tt U00af Production Cross Section In Pp Collisions At U221a S
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language : en
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Release Date : 2015
Observation Of Top Quark Pair Production In Association With A Photon And Measurement Of The Tt U00af Production Cross Section In 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 2015 with categories.
A search is performed for top-quark pairs (tt¯) produced together with a photon (?) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 tt¯? candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 ± 26 and 120 ± 39 non-tt¯? background events, respectively. The production of tt¯? events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯? production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is ?fidtt¯? × BR = 63 ± 8(stat)+17–13(syst) ± 1(lumi) fb per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48 ± 10 fb.
Search For Pair Produced Resonances Decaying To Jet Pairs In Proton U2013 Proton Collisions At Sqrt S
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language : en
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Release Date : 2015
Search For Pair Produced Resonances Decaying To Jet Pairs In Proton U2013 Proton 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 2015 with categories.
Results are reported of a general search for pair production of heavy resonances decaying to pairs of hadronic jets in events with at least four jets. The study is based on up to 19.4 fb–1 of integrated luminosity from proton–proton collisions at a center-of-mass energy of 8 TeV, recorded with the CMS detector at the LHC. Limits are determined on the production of scalar top quarks (top squarks) in the framework of R-parity violating supersymmetry and on the production of color-octet vector bosons (colorons). First limits at the LHC are placed on top squark production for two scenarios. The first assumes decay to a bottom quark and a light-flavor quark and is excluded for masses between 200 and 385 GeV, and the second assumes decay to a pair of light-flavor quarks and is excluded for masses between 200 and 350 GeV at 95% confidence level. Furthermore, previous limits on colorons decaying to light-flavor quarks are extended to exclude masses from 200 to 835 GeV.
Search For Lepton Flavour Violating Decays Of Heavy Resonances And Quantum Black Holes To An E Pair In Proton Proton Collisions At U221a S
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language : en
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Release Date : 2016
Search For Lepton Flavour Violating Decays Of Heavy Resonances And Quantum Black Holes To An E Pair In Proton Proton 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 2016 with categories.
A search for narrow resonances decaying to an electron and a muon is presented. The $mathrm {e}$ ${mu }$ mass spectrum is also investigated for non-resonant contributions from the production of quantum black holes (QBHs). The analysis is performed using data corresponding to an integrated luminosity of 19.7 $̃text {fb}̂text {-1}$ collected in proton-proton collisions at a centre-of-mass energy of 8 $̃text {TeV}$ with the CMS detector at the LHC. With no evidence for physics beyond the standard model in the invariant mass spectrum of selected $mathrm {e}mu $ pairs, upper limits are set at 95 $%$ confidence level on the product of cross section and branching fraction for signals arising in theories with charged lepton flavour violation. In the search for narrow resonances, the resonant production of a $mathrm { au }$ sneutrino in R-parity violating supersymmetry is considered. The $mathrm { au }$ sneutrino is excluded for masses below 1.28 $̃text {TeV}$ for couplings $lambda _=lambda _ç=lambda '_ķ=0.01$ , and below 2.30 $̃text {TeV}$ for $lambda _=lambda _ç=0.07$ and $lambda '_ķ=0.11$ . These are the most stringent limits to date from direct searches at high-energy colliders. In addition, the resonance searches are interpreted in terms of a model with heavy partners of the ${mathrm {Z}} $ boson and the photon. In a framework of TeV-scale quantum gravity based on a renormalization of Newton’s constant, the search for non-resonant contributions to the $mathrm {e}$ ${mu }$ mass spectrum excludes QBH production below a threshold mass $M_{mathrm {th}}$ of 1.99 $̃text {TeV}$ . In models that invoke extra dimensions, the bounds range from 2.36 $̃text {TeV}$ for one extra dimension to 3.63 $̃text {TeV}$ for six extra dimensions. Furthermore, this is the first search for QBHs decaying into the $mathrm {e}$ ${mu }$ final state.
Search For New T Particles In Final States With Large Jet Multiplicities And Missing Transverse Energy In Pp Collisions At U221a S
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language : en
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Release Date : 2011
Search For New T Particles In Final States With Large Jet Multiplicities And Missing Transverse Energy In 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 present a search for a new particle T decaying to a top quark via T = t + X, where X goes undetected. We use a data sample corresponding to 5.7 fb-1 of integrated luminosity of pp collisions with √s = 1.96 TeV, collected at Fermilab Tevatron by the CDF II detector. Our search for pair production of T' is focused on the hadronic decay channel, pp = TT= tt+XX=bqqbqq + XX. We interpret our results in terms of a model where T is an exotic fourth generation quark and X is a dark matter particle. The data are consistent with standard model expectations. We set a limit on the generic production of TT = tt =+ XX, excluding the fourth generation exotic quarks T at 95% confidence level up to mT = 400 GeV/c2 for mX ≤ 70 GeV/c2.
A Search For T Overline T Resonances Using Lepton Plus Jets Events In Proton Proton Collisions At Sqrt S
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language : en
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Release Date : 2015
A Search For T Overline T Resonances Using Lepton Plus Jets Events In Proton Proton 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 2015 with categories.
A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb-1 of proton-proton collision data collected at a centre-of-mass energy of \(\sqrt{s}=8 \) TeV. The lepton-plus-jets final state is used, where the top pair decays to \({W}^{+}b{W}^{-}\overline{b} \), with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with [Gamma]/m = 15% decaying to \(t\overline{t} \). These range from 4.8 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV.
Search For High Mass Diphoton Resonances In Pp Collisions At U221a S
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language : en
Publisher:
Release Date : 2015
Search For High Mass Diphoton Resonances In 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 2015 with categories.
This article describes a search for high-mass resonances decaying to a pair of photons using a sample of 20.3 fb-1 of pp collisions at √s = 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data are found to be in agreement with the Standard Model prediction, and limits are reported in the framework of the Randall-Sundrum model. This theory leads to the prediction of graviton states, the lightest of which could be observed at the Large Hadron Collider. A lower limit of 2.66 (1.41) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/M¯Pl = 0.1 (0.01).