Author: Albert M. SirunyanPublisher:
ISBN:
Category :
Languages : en
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Book Description
Search for Dark Matter Produced in Association with a Leptonically Decaying Z Boson in Proton-proton Collisions at √s
Author: Albert M. SirunyanSearch for Associated Production of a Z Boson with an Invisibly Decaying Higgs Boson Or Dark Matter Candidates at [square Root]s
![Search for Associated Production of a Z Boson with an Invisibly Decaying Higgs Boson Or Dark Matter Candidates at [square Root]s PDF](https://books.google.com/books/content/images/frontcover/Z73bzwEACAAJ?fife=w80-h100)
Author: [Study Group] ATLAS Collaboration CERNPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Abstract: A search for invisible decays of the Higgs boson as well as searches for dark matter candidates, produced together with a leptonically decaying Z boson, are presented. The analysis is performed using proton−proton collisions at a centre-of-mass energy of 13 TeV, delivered by the LHC, corresponding to an integrated luminosity of 139 and recorded by the ATLAS experiment. Assuming Standard Model cross-sections for ZH production, the observed (expected) upper limit on the branching ratio of the Higgs boson to invisible particles is found to be 19% (19%) at the 95% confidence level. Exclusion limits are also set for simplified dark matter models and two-Higgs-doublet models with an additional pseudoscalar mediator
Search for Dark Matter and Unparticles Produced in Association with a Z Boson in Proton-proton Collisions at Sqrt(s)
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A search for evidence of particle dark matter (DM) and unparticle production at the LHC has been performed using events containing two charged leptons, consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 inverse femtobarns of pp collisions at the LHC at a center-of-mass energy of 8 TeV. No significant excess of events is observed above the number expected from the standard model contributions. The results are interpreted in terms of 90% confidence level limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios. Limits are set on the effective cutoff scale Lambda, and on the annihilation rate for DM particles, assuming that their branching fraction to quarks is 100%. Additionally, the most stringent 95% confidence level limits to date on the unparticle model parameters are obtained.
Search for Dark Matter Produced in Association with a Higgs Boson Decaying to a Pair of Bottom Quarks in Proton-proton Collisions at $\sqrt˜s}
Author: Albert M. SirunyanSearch for Dark Matter in Association with a Leptonically Decaying Z Boson in the ATLAS Detector at the Large Hadron Collider
Author: Alison A. ElliotPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This dissertation describes a search for the invisible decays of dark matter particles produced in association with a Z boson, where the latter decays to a charged lepton pair. The dataset for this search includes 13.3 1/fb of collisions recorded in 2015 and 2016 at a centre-of-mass energy of 13 TeV in the ATLAS detector at the Large Hadron Collider in Geneva, Switzerland. The invisible particles manifest themselves as missing transverse momentum, or MET, in the detector, while the charged leptons of interest are electron (e+e-) or muon (mu+mu-) pairs. The models simulated for this study are vector mediated simplified models with Dirac fermionic dark matter particles with couplings g_q = 0.25, g_X = 1 and g_l = 0 . The main background to this analysis, ZZ->llvv, is irreducible, as it shares the same signature as the signal. It is estimated with Monte Carlo simulations including contributions from both qq->ZZ and gg->ZZ production modes. Where possible, other backgrounds are estimated using data-driven techniques and reduced through various selection criteria. The final search is performed by looking for a deviation from the Standard Model background expectation in the MET distribution using two signal regions, e+e- and mu+mu-. This is done using statistical tools to make a likelihood fit and set a 95% confidence level limit as no deviations are found. Limits are placed on the presented model of dark matter for mediator masses up to 400 GeV and for a range of dark matter masses from 1 to ~200 GeV.
Search for Dark Matter and Unparticles Produced in Association with a Z Boson in Proton-proton Collisions at √s
Author: CMS CollaborationSearch for Dark Matter and Unparticles in Events with a Z Boson and Missing Transverse Momentum in Proton-proton Collisions at Sqrt(s)
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A search for dark matter and unparticle production at the LHC has been performed using events containing two charged leptons (electrons or muons), consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector in 2015, corresponding to an integrated luminosity of 2.3 inverse femtobarns of proton-proton collisions at the LHC, at a center-of-mass energy of 13 TeV. No excess over the standard model expectation is observed. Compared to previous searches in this topology, which exclusively relied on effective field theories, the results are interpreted in terms of a simplified model of dark matter production for both vector and axial vector couplings between a mediator and dark matter particles. The first study of this class of models using CMS data at sqrt(s)=13 TeV is presented. Additionally, effective field theories of dark matter and unparticle production are used to interpret the data.
Search for Associated Production of Dark Matter with a Higgs Boson Decaying to $b\bar{b}$ Or $\gamma\gamma$ at $\sqrt{s}$
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
A search for dark matter is performed using events with large missing transverse momentum and a Higgs boson decaying either to a pair of bottom quarks or to a pair of photons. The data from proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC, correspond to an integrated luminosity of 2.3 inverse-femtobarns. Results are interpreted in the context of a Z'-two-Higgs-doublet model, where a high-mass resonance Z' decays into a pseudoscalar boson A and a CP-even scalar Higgs boson, and the A decays to a pair of dark matter particles. No significant excesses are observed over the background prediction. Combining results from the two decay channels yields exclusion limits in the signal cross section in the m[Z']-m[A] phase space. The observed data exclude, for Z' coupling strength g[Z'] = 0.8 and m[A] = 300 GeV for example, the Z' mass range of 600 to 1860 GeV. This is the first result on a search for dark matter produced in association with a Higgs boson that includes constraints on h to gamma-gamma obtained at sqrt(s) = 13 TeV.
A Search for New Physics in Events with a Leptonically Decaying Z Boson and a Large Transverse Momentum Imbalance with the CMS Detector at the LHC
Author: Nicholas Charles SmithPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
A search for new physics in events with a leptonically decaying Z boson and a large transverse momentum imbalance in proton-proton collisions collected at sqrt(s) = 13 TeV in 2016 with the Compact Muon Solenoid detector at the Large Hadron Collider is presented. The results of this search are interpreted in terms of a simplified model of dark matter production via spin-0 or spin-1 mediators, a scenario with a standard-model-like Higgs boson produced in association with the Z boson and decaying invisibly, a model of unparticle production, and a model with large extra spatial dimensions. No significant deviations from the background expectations are found, and limits are set on relevant model parameters, significantly extending the results previously achieved in this channel.
Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks in Pp Collisions at S
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This study reports on a search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3 fb–1 of pp collisions at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the LHC. The decay of the Higgs boson is reconstructed as a high-momentum bb¯ system with either a pair of small-radius jets, or a single large-radius jet with substructure. The observed data are found to be consistent with the expected Standard Model backgrounds. Model-independent upper limits are placed on the visible cross sections for events with a Higgs boson decaying into bb¯ and large missing transverse momentum with thresholds ranging from 150 to 400 GeV. Results are interpreted using a simplified model with a Z' gauge boson decaying into different Higgs bosons predicted in a two-Higgs-doublet model, of which the heavy pseudoscalar Higgs decays into a pair of dark matter particles. Exclusion limits are also presented for the mass scales of various effective field theory operators that describe the interaction between dark matter particles and the Higgs boson.