Searches for Supersymmetry Based on Events with B Jets and Four W Bosons in Pp Collisions at 8 TeV.
Searches for Supersymmetry Based on Events with B Jets and Four W Bosons in Pp Collisions at 8 TeV.

Author:

Publisher:

Published: 2015

Total Pages: 35

ISBN-13:

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Five mutually exclusive searches for supersymmetry are presented based on events in which b jets and four W bosons are produced in proton-proton collisions at √ = 8 TeV. The data, corresponding to an integrated luminosity of 19.5 inverse femtobarns, were collected with the CMS experiment at the CERN LHC in 2012. The five studies differ in the leptonic signature from the W boson decays, and correspond to all-hadronic, single-lepton, opposite-sign dilepton, same-sign dilepton, and ≥3 lepton final states. The results of the five studies are combined to yield 95% confidence level exclusions of 1280 and 570 GeV for the gluino and bottom-squark masses in the context of gluino and bottom-squark pair production, respectively. These limits are around 50 GeV more stringent than are obtained from any of the individual channels.

Search for Supersymmetry at CMS in Events with B-tagged Jets and Missing Transverse Energy at 8 TeV
Search for Supersymmetry at CMS in Events with B-tagged Jets and Missing Transverse Energy at 8 TeV

Author: Kristen Flowers (Physicist)

Publisher:

Published: 2015

Total Pages: 334

ISBN-13: 9781321696004

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This dissertation presents results from a search for physics beyond the Standard Model, using 19.39 pb-1 of data collected by the CMS detector at the Large Hadron Collider, during its 2012 operation at √ s=8 TeV. It focuses on models of supersymmetry that lead to final states with multiple jets, especially those from b-quark decay, and a large amount of missing transverse momentum. The amounts of background from top-quark, W+jets, Z → nu[special character omitted], and multi-jet production are determined from data-driven techniques. In particular, this includes a novel estimation of the ETmiss spectrum from semi-leptonic tt ̄ decay, which takes advantage of the precise knowledge of the W boson polarization. Predicted yields are consistent with simulated Standard Model processes and the observed data. Since no evidence of new physics is observed, limits are placed on the rate of gluino pair production to a final state with four b-quarks and two neutralinos. This process is excluded at 95% CL for a gluino with mass 1225 GeV and a neutralino with mass up to 350 GeV.

Search for Supersymmetry in Hadronic Final States
Search for Supersymmetry in Hadronic Final States

Author: Hannsjörg Artur Weber

Publisher: Springer

Published: 2015-06-11

Total Pages: 217

ISBN-13: 3319199560

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The project reported here was a search for new super symmetric particles in proton-proton collisions at the LHC. It has produced some of the world’s best exclusion limits on such new particles. Furthermore, dedicated simulation studies and data analyses have also yielded essential input to the upgrade activities of the CMS collaboration, both for the Phase-1 pixel detector upgrade and for the R&D studies in pursuit of a Phase-2 end cap calorimeter upgrade.

Search for Supersymmetry in Proton-proton Collisions at 8 TeV in Events with a Single Lepton, Large Jet Multiplicity, and Multiple B Jets
Search for Supersymmetry in Proton-proton Collisions at 8 TeV in Events with a Single Lepton, Large Jet Multiplicity, and Multiple B Jets

Author: Paul B. Geffert

Publisher:

Published: 2014

Total Pages: 257

ISBN-13: 9781321349412

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This thesis describes a search for supersymmetry in events with a single lepton, large jet multiplicity, multiple b jets, and significant transverse momentum imbalance in 19.3 fb-1 of pp collisions at center of mass energy of 8 TeV recorded in 2012 by the Compact Muon Solenoid experiment at the Large Hadron Collider. This signature targets strongly produced massive gluinos which decay through top squarks. The observed yields in the signal regions, spanning a broad range of event kinematics, agree with the Standard Model background predictions, which are obtained with a heavy reliance on data control samples. The results of this search are interpreted as cross section limits in the context of simplified supersymmetric scenarios in which gluinos are pair produced and cascade decay to a four top quark, two lightest neutralino final state. By comparing these limits with gluino pair production cross sections, gluinos with mass less than 1 TeV are excluded for low lightest neutralino masses, largely independent of top squark mass.

Search for New Physics in tt ̅ Final States with Additional Heavy-Flavor Jets with the ATLAS Detector
Search for New Physics in tt ̅ Final States with Additional Heavy-Flavor Jets with the ATLAS Detector

Author: Javier Montejo Berlingen

Publisher: Springer

Published: 2016-07-20

Total Pages: 288

ISBN-13: 3319410512

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This doctoral thesis focuses on the search for new phenomena in top-antitop quark (tt) final states with additional b-quark jets at the LHC. It uses the full Run 1 dataset collected by the ATLAS experiment in proton-proton collisions at √s=8 TeV. The final state of interest consists of an isolated lepton, a neutrino and at least six jets with at least four b-tagged jets, a challenging experimental signature owing to the large background from tt+heavy-flavor production. This final state is characteristic of ttH production, with the Higgs boson decaying into bb, a process that allows direct probing of the top-Higgs Yukawa coupling. This signature is also present in many extensions of the Standard Model that have been proposed as solutions to the hierarchy problem, such as supersymmetry or composite Higgs models, which predict the pair production of bosonic or fermionic top quark partners, or the anomalous production of four-top-quark events. All these physics processes have been searched for using an ambitious search strategy that has been developed on the basis of a combination of state-of-art theoretical predictions and a sophisticated statistical analysis to constrain in-situ the large background uncertainties. As a result, the most restrictive bounds to date on the above physics processes have been obtained.

Search for Supersymmetry in Pp Collisions at $\sqrt{s}$
Search for Supersymmetry in Pp Collisions at $\sqrt{s}$

Author:

Publisher:

Published: 2016

Total Pages:

ISBN-13:

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A search for supersymmetry in hadronic final states with highly boosted W bosons and b jets is presented, focusing on compressed scenarios. The search is performed using proton-proton collision data at a center-of-mass energy of 8 TeV, collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.7 fb$^{-1}$. Events containing candidates for hadronic decays of boosted W bosons are identified using jet substructure techniques, and are analyzed using the razor variables $M_\mathrm{R}$ and $R^2$, which characterize a possible signal as a peak on a smoothly falling background. The observed event yields in the signal regions are found to be consistent with the expected contributions from standard model processes, which are predicted using control samples in the data. The results are interpreted in terms of gluino pair production followed by their exclusive decay into top squarks and top quarks. The analysis excludes gluino masses up to 1.1 TeV for light top squarks decaying solely to a charm quark and a neutralino, and up to 700 GeV for heavier top squarks decaying solely to a top quark and a neutralino.

Searches for Supersymmetry Using the M$_{T2}$ Variable in Hadronic Events Produced in Pp Collisions at 8 TeV.
Searches for Supersymmetry Using the M$_{T2}$ Variable in Hadronic Events Produced in Pp Collisions at 8 TeV.

Author:

Publisher:

Published: 2015

Total Pages: 51

ISBN-13:

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Searches for supersymmetry (SUSY) are performed using a sample of hadronic events produced in 8 TeV pp collisions at the CERN LHC. The searches are based on the M$_{T2}$ variable, which is a measure of the transverse momentum imbalance in an event. The data were collected with the CMS detector and correspond to an integrated luminosity of 19.5 fb1. Two related searches are performed. The first is an inclusive search based on signal regions defined by the value of the M$_{T2}$ variable, the hadronic energy in the event, the jet multiplicity, and the number of jets identified as originating from bottom quarks. The second is a search for a mass peak corresponding to a Higgs boson decaying to a bottom quark-antiquark pair, where the Higgs boson is produced as a decay product of a SUSY particle. For both searches, the principal backgrounds are evaluated with data control samples. No significant excess over the expected number of background events is observed, and exclusion limits on various SUSY models are derived.

Phenomena Beyond the Standard Model: What Do We Expect for New Physics to Look Like?
Phenomena Beyond the Standard Model: What Do We Expect for New Physics to Look Like?

Author: Roman Pasechnik

Publisher: Frontiers Media SA

Published: 2020-09-03

Total Pages: 180

ISBN-13: 2889639908

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This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.

A Search for Supersymmetry in Events with a Z Boson, Jets, and Missing Transverse Energy in Pp Collisions with Sqrt(s)
A Search for Supersymmetry in Events with a Z Boson, Jets, and Missing Transverse Energy in Pp Collisions with Sqrt(s)

Author: Tova Ray Holmes

Publisher:

Published: 2016

Total Pages: 191

ISBN-13:

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A search for new phenomena in final states containing a Z boson decaying to electrons or muons, jets, and large missing transverse momentum is presented. This search uses proton--proton collision data collected during 2015 and 2016 at a center of mass energy sqrt(s)=13 TeV by the ATLAS detector at the Large Hadron Collider, which correspond to an integrated luminosity of 14.7 fb-1. The search targets the pair production of supersymmetric particles, squarks or gluinos, which decay via jets and a Z boson to the lightest Supersymmetric particle, which does not interact with the ATLAS detector. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.3 (1.0) TeV.

Searches for Supersymmetry Using the MT2 Variable in Hadronic Events Produced in Pp Collisions at 8 TeV.
Searches for Supersymmetry Using the MT2 Variable in Hadronic Events Produced in Pp Collisions at 8 TeV.

Author:

Publisher:

Published: 2015

Total Pages: 52

ISBN-13:

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Searches for supersymmetry (SUSY) are performed using a sample of hadronic events produced in 8 TeV pp collisions at the CERN LHC. The searches are based on the MT2 variable, which is a measure of the transverse momentum imbalance in an event. The data were collected with the CMS detector and correspond to an integrated luminosity of 19.5 fb−1. Two related searches are performed. The first is an inclusive search based on signal regions defined by the value of the MT2 variable, the hadronic energy in the event, the jet multiplicity, and the number of jets identified as originating from bottom quarks. The second is a search for a mass peak corresponding to a Higgs boson decaying to a bottom quark-antiquark pair, where the Higgs boson is produced as a decay product of a SUSY particle. For both searches, the principal backgrounds are evaluated with data control samples. No significant excess over the expected number of background events is observed, and exclusion limits on various SUSY models are derived.