A Search For Toverlinet Resonances Using Lepton Plus Jets Events In Proton Proton Collisions At Sqrts PDF Download

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A Search for \(t\overline{t} \) Resonances Using Lepton-plus-jets Events in Proton-proton Collisions at \(\sqrt{s}

A Search for \(t\overline{t} \) Resonances Using Lepton-plus-jets Events in Proton-proton Collisions at \(\sqrt{s}
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Release: 2015
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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 $\mathrm{ T \bar{t} }$ Resonances in Highly-boosted Lepton+jets and Fully Hadronic Final States in Proton-proton Collisions at $ \sqrt{s}

Search for $\mathrm{ T \bar{t} }$ Resonances in Highly-boosted Lepton+jets and Fully Hadronic Final States in Proton-proton Collisions at $ \sqrt{s}
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Release: 2017
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A search for the production of heavy resonances decaying into top quark-antiquark pairs is presented. The analysis is performed in the lepton+jets and fully hadronic channels using data collected in proton-proton collisions at $\sqrt{s}$ =13 TeV using the CMS detector at the LHC, corresponding to an integrated luminosity of 2.6 inverse femtobarns. The selection is optimized for massive resonances, where the top quarks have large Lorentz boosts. No evidence for resonant ttbar production is found in the data, and upper limits on the production cross section of heavy resonances are set. The exclusion limits for resonances with masses above 2 TeV are significantly improved compared to those of previous analyses at $\sqrt{s}$ = 8 TeV.


Search for Heavy Resonances Decaying to Tau Lepton Pairs in Proton-proton Collisions at $\sqrt{s}$

Search for Heavy Resonances Decaying to Tau Lepton Pairs in Proton-proton Collisions at $\sqrt{s}$
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Release: 2016
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A search for heavy resonances that decay to tau lepton pairs is performed using proton-proton collisions at \sqrt{s}$ = 13 TeV. The data were collected with the CMS detector at the CERN LHC and correspond to an integrated luminosity of 2.2 inverse femtobarns. The observations are in agreement with standard model predictions. An upper limit at 95% confidence level on the product of the production cross section and branching fraction into tau lepton pairs is calculated as a function of the resonance mass. For the sequential standard model, the presence of Z' bosons decaying into tau lepton pairs is excluded for Z' masses below 2.1 TeV, extending previous limits for this final state. For the topcolor-assisted technicolor model, which predicts Z' bosons that preferentially couple to third-generation fermions, Z' masses below 1.7 TeV are excluded, representing the most stringent limit to date.


A Search for Tt Resonances in the Single Lepton Final State with the ATLAS Experiment

A Search for Tt Resonances in the Single Lepton Final State with the ATLAS Experiment
Author: Andrew David Altheimer
Publisher:
Total Pages:
Release: 2014
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ISBN:

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A search for undiscovered particles decaying into top-antitop quark pairs produced in proton-proton collisions with the ATLAS experiment at the Large Hadron Collider utilizing 20.3 fb$^-1$ of data collected at $\sqrt{s}=8$ \tev\ center-of-mass energy during the 2012 data taking period is presented. The invariant mass spectrum of events containing multiple jets, exactly one lepton, and missing transverse energy and which are consistent with the decay of a top-antitop quark pair is studied and found to be consistent with that predicted by the Standard Model. Upper limits on the production cross section times branching ratio of several benchmark signal models are set at a 95\% confidence level.


Searches for Dijet Resonances

Searches for Dijet Resonances
Author: Lydia Audrey Beresford
Publisher: Springer
Total Pages: 175
Release: 2018-09-04
Genre: Science
ISBN: 331997520X

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This book addresses one of the most intriguing mysteries of our universe: the nature of dark matter. The results presented here mark a significant and substantial contribution to the search for new physics, in particular for new particles that couple to dark matter. The first analysis presented is a search for heavy new particles that decay into pairs of hadronic jets (dijets). This pioneering analysis explores unprecedented dijet invariant masses, reaching nearly 7 TeV, and sets constraints on several important new physics models. The two subsequent analyses focus on the difficult low dijet mass region, down to 200 GeV, and employ a novel technique to efficiently gather low-mass dijet events. The results of these analyses transcend the long-standing constraints on dark matter mediator particles set by several existing experiments.


Searches for Light- and Heavy-flavor Three-jet Resonances in Proton-proton Collisions with the CMS Detector at $\sqrt{s}$

Searches for Light- and Heavy-flavor Three-jet Resonances in Proton-proton Collisions with the CMS Detector at $\sqrt{s}$
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Total Pages: 173
Release: 2014
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ISBN:

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A search for three-jet hadronic resonance production in proton-proton collisions at 8 TeV center-of-mass energy has been conducted by the CMS Collaboration at the LHC. The data set corresponds to an integrated luminosity of 19.4 fb-1. The search method is modelindependent. Events are selected that contain a large number of jets with high transverse momentum. An ensemble of jets is used to extract a new possible signal from copious QCD background. Event selection is optimized using a benchmark model where supersymmetric gluinos are pair-produced and each of the gluinos decays exclusively into three jets. Two scenarios of this decay are considered denoted by the RPV couplings [lambda]'' 112 and [lambda]'' 113 or [lambda]'' 223. The first coupling allows for gluinos to decay into only light-flavor jets, while the latter two allow decays into one heavy-flavor and two light-flavor jets. No significant deviation is found between the selected events and the expected standard model multijet and t$\bar{t}$ background. For gluinos decaying through 00 112, masses below 650 GeV are excluded at the 95% confidence level. The search including heavy-flavor jets in the final state with the couplings [lambda]'' 113 or [lambda]'' 223 is the first of its kind. Gluinos decaying into one heavy-flavor and two light-flavor jets are excluded for masses between 200 and 835 GeV.


Search for Pair-produced Resonances Decaying to Jet Pairs in Proton{u2013}proton Collisions at $\sqrt{s}$

Search for Pair-produced Resonances Decaying to Jet Pairs in Proton{u2013}proton Collisions at $\sqrt{s}$
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Total Pages: 22
Release: 2015
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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

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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Total Pages: 25
Release: 2016
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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.