Search for Dark Matter Particles Produced in Association with a Higgs Boson in Proton-proton Collisions at √s
Author: Albert M. Sirunyan
Publisher:
Published: 2019
Total Pages:
ISBN-13:
DOWNLOAD EBOOKRead and Download eBook Full
Author: Albert M. Sirunyan
Publisher:
Published: 2019
Total Pages:
ISBN-13:
DOWNLOAD EBOOKAuthor: Yangyang Cheng
Publisher: Springer
Published: 2016-09-29
Total Pages: 183
ISBN-13: 331944218X
DOWNLOAD EBOOKThis thesis reports on the search for dark matter in data taken with the ATLAS detector at CERN’s Large Hadron Collider (LHC). The identification of dark matter and the determination of its properties are among the highest priorities in elementary particle physics and cosmology. The most likely candidate, a weakly interacting massive particle, could be produced in the high energy proton-proton collisions at the LHC. The analysis presented here is unique in looking for dark matter produced together with a Higgs boson that decays into its dominant decay mode, a pair of b quarks. If dark matter were seen in this mode, we would learn directly about the production mechanism because of the presence of the Higgs boson. This thesis develops the search technique and presents the most stringent production limit to date.
Author:
Publisher:
Published: 2017
Total Pages:
ISBN-13:
DOWNLOAD EBOOKA 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.
Author: Albert M. Sirunyan
Publisher:
Published: 2018
Total Pages:
ISBN-13:
DOWNLOAD EBOOKAuthor:
Publisher:
Published: 2016
Total Pages:
ISBN-13:
DOWNLOAD EBOOKThis 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.
Author:
Publisher:
Published: 2016
Total Pages:
ISBN-13:
DOWNLOAD EBOOKA 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.
Author: Nikola Lazar Whallon
Publisher:
Published: 2018
Total Pages: 179
ISBN-13:
DOWNLOAD EBOOKIf Dark Matter particles interact with Standard Model particles, it could be possible to pair produce Dark Matter particles in association with a detectable Standard Model particle at a collider such as the LHC. If this associated particle is a Higgs boson, the process is called ``mono-Higgs,'' since the resulting signature is a single Higgs boson balanced by missing energy from the undetected Dark Matter particles. Various Dark Matter models predict that this process could result in very boosted Higgs bosons that, if they decay to a pair of b-quarks, are reconstructed as jets using boosted Higgs tagging techniques. This thesis presents the results of a mono-Higgs search using 79.8 fb−1 of proton-proton collision data collected at a center-of-mass energy of 13 TeV by the ATLAS detector. The observed data are found to be consistent with the expected Standard Model backgrounds. The results are interpreted and exclusion limits are set using a Z' two-Higgs-doublet model where the pseudo-scalar Higgs particle, A, couples to Dark Matter. In order to increase the sensitivity reach of the search, new boosted Higgs tagging techniques are explored and a variable radius track jet Higgs tagging technique is employed.
Author: [Study Group] ATLAS Collaboration CERN
Publisher:
Published: 2022
Total Pages: 0
ISBN-13:
DOWNLOAD EBOOKAbstract: 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
Author: Daniel Isaac Narrias Villar
Publisher:
Published: 2018
Total Pages:
ISBN-13:
DOWNLOAD EBOOKAuthor:
Publisher:
Published: 2015
Total Pages: 35
ISBN-13:
DOWNLOAD EBOOKA search is presented for particle dark matter produced in association with a pair of top quarks in pp collisions at a centre-of-mass energy of s√=8 TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 19.7 fb-1. This search requires the presence of one lepton, multiple jets, and large missing transverse energy. No excess of events is found above the SM expectation, and upper limits are derived on the production cross section. Interpreting the findings in the context of a scalar contact interaction between fermionic dark matter particles and top quarks, lower limits on the interaction scale are set. These limits are also interpreted in terms of the dark matter-nucleon scattering cross sections for the spin-independent scalar operator and they complement direct searches for dark matter particles in the low mass region.