Download or read book Search for Dark Matter and Unparticles in Events with a Z Boson and Missing Transverse Momentum in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Search for Dark Matter and Unparticles Produced in Association with a Z Boson in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons in Pp Collisions at S u221A written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results of a search for new phenomena in events with large missing transverse momentum and a Higgs boson decaying to two photons are reported. Data from proton-proton collisions at a center-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb-1 have been collected with the ATLAS detector at the LHC. The observed data are well described by the expected standard model backgrounds. Upper limits on the cross section of events with large missing transverse momentum and a Higgs boson candidate are also placed. Exclusion limits are presented for models of physics beyond the standard model featuring dark-matter candidates.

Download or read book Search for Dark Matter Extra Dimensions and Unparticles in Monojet Events in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented from a search for particle dark matter (DM), extra dimensions, and unparticles using events containing a jet and an imbalance in transverse momentum. The data were collected by the CMS detector in proton-proton collisions at the LHC and correspond to an integrated luminosity of 19.7 fb$^{-1}$ at a centre-of-mass energy of 8 TeV. The number of observed events is found to be consistent with the standard model prediction. Limits are placed on the DM-nucleon scattering cross section as a function of the DM particle mass for spin-dependent and spin-independent interactions. Limits are also placed on the scale parameter $M_\mathrm{D}$ in the ADD model of large extra dimensions, and on the unparticle model parameter $\Lambda_\mathrm{U}$. The constraints on ADD models and unparticles are the most stringent limits in this channel and those on the DM-nucleon scattering cross section are an improvement over previous collider results.

Download or read book Precision Measurement of and Search for Dark Matter in the Transverse Momentum Spectra of Z Bosons written by Dylan George Hsu and published by . This book was released on 2019 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: A measurement of the differential Z boson production cross section in proton-proton collisions is presented. It furnishes a precision test of the Standard Model, and constrains the parton distribution functions of the proton. Moreover, it is a building block for future measurements of the mass of the W± boson. A study of the efficiency of lepton identification algorithms is performed which drives the precision of the measurement at lower values of transverse momentum. In tandem, a search for new physics in events with a Z boson produced in association with large missing transverse momentum is presented. The results of this search are interpreted in the context of several dark matter models: generic spin-0 or spin-1 mediators, invisible decays of a Higgs-like boson, unparticles, and large extra spatial dimensions. A multivariate analysis was developed to enhance the sensitivity of the invisible Higgs interpretation. The theoretical uncertainty on the irreducible background from electroweak diboson processes is constrained by emulating the missing energy using pure control samples in the fully leptonic final states. The data were collected with the Compact Muon Solenoid detector at the Large Hadron Collider and correspond to an integrated luminosity of 35.9 fb-1. No significant deviations from the Standard Model are found.

Download or read book Search for Dark Matter in Proton proton Collisions at 8 TeV with Missing Transverse Momentum and Vector Boson Tagged Jets written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS experiment at the LHC. The results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. Additional sensitivity is achieved by tagging events consistent with the jets originating from a hadronically decaying vector boson. This search uses jet substructure techniques to identify hadronically decaying vector bosons in both Lorentz-boosted and resolved scenarios. This analysis yields improvements of 80% in terms of excluded signal cross sections with respect to the previous CMS analysis using the same data set. No significant excess with respect to the standard model expectation is observed and limits are placed on the parameter space of the simplified models. Mediator masses between 80 and 400 GeV in the scalar and pseudoscalar models, and up to 1.5 TeV in the vector and axial vector models, are excluded.

Download or read book Search for Dark Matter in Events with a Highly Energetic Jet and Missing Transverse Momentum in Proton proton Collisions at Root Out S written by Ruth Pöttgen and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Search for Dark Matter with ATLAS written by Ruth Pöttgen and published by Springer. This book was released on 2018-05-31 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes in detail a search for weakly interacting massive particles as possible dark matter candidates, making use of so-called mono-jet events. It includes a detailed description of the run-1 system, important operational challenges, and the upgrade for run-2. The nature of dark matter, which accounts for roughly 25% of the energy-matter content of the universe, is one of the biggest open questions in fundamental science. The analysis is based on the full set of proton-proton collisions collected by the ATLAS experiment at the Large Hadron Collider at √s = 8 TeV. Special attention is given to the experimental challenges and analysis techniques, as well as the overall scientific context beyond particle physics. The results complement those of non-collider experiments and yield some of the strongest exclusion bounds on parameters of dark matter models by the end of the Large Hadron Collider run-1. Details of the upgrade of the ATLAS Central Trigger for run-2 are also included.

Download or read book Search for Dark Matter in Events with a Photon and Missing Transverse Momentum in Pp Collisions at S written by Fuquan Wang and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the search for dark matter in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC. The data of proton-proton collisions is collected in 2012 and 2015, corresponds to 20.3 fb−1 data with center-of-mass energy of 8 TeV and 3.2 fb−1data with center-of-mass energy of 13 TeV, respectively. The observed data is well described by the expected Standard Model backgrounds. The expected (observed) upper limit on the fiducial cross section for the production of events with a photon and large missing transverse momentum at 95% confidence level is 6.1 (5.3) fb with the 8 TeV data set and 25.5 (17.8) fb with the 13 TeV data set. Exclusion limits are presented on models of direct pair production of dark-matter candidates.

Download or read book Search for New Phenomena in Events with a Photon and Missing Transverse Momentum in Pp Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the Large Hadron Collider are reported. The data were collected in proton-proton collisions at a centre-of-mass energy of 13 TeV and correspond to an integrated luminosity of 3.2 fb-1. The observed data are in agreement with the Standard Model expectations. Exclusion limits are presented in models of new phenomena including pair production of dark matter candidates or large extra spatial dimensions. In a simplified model of dark matter and an axial-vector mediator, the search excludes mediator masses below 710 GeV for dark matter candidate masses below 150 GeV. In an effective theory of dark matter production, values of the suppression scale M * up to 570 GeV are excluded and the effect of truncation for various coupling values is reported. Finally, for the ADD large extra spatial dimension model the search places more stringent limits than earlier searches in the same event topology, excluding M D up to about 2.3 (2.8) TeV for two (six) additional spatial dimensions; the limits are reduced by 20-40% depending on the number of additional spatial dimensions when applying a truncation procedure.

Download or read book A Search for Dark Matter in Events with One Jet and Missing Transverse Energy in Pp bar Collisions at Sqrt s written by and published by . This book was released on 2013 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Search for Dark Matter and Unparticles Produced in Association with a Z Boson in Proton proton Collisions at s written by CMS Collaboration and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Search for Dark Matter in Events with Heavy Quarks and Missing Transverse Momentum in Pp Collisions with the ATLAS Detector written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This article reports on a search for dark matter pair production in association with bottom or top quarks in 20.3 fb-1 of pp collisions collected at √s=8 TeV by the ATLAS detector at the LHC. Events with large missing transverse momentum are selected when produced in association with high-momentum jets of which one or more are identified as jets containing b-quarks. Final states with top quarks are selected by requiring a high jet multiplicity and in some cases a single lepton. The data are found to be consistent with the Standard Model expectations and limits are set on the mass scale of effective field theories that describe scalar and tensor interactions between dark matter and Standard Model particles. Limits on the dark-matter-nucleon cross-section for spin-independent and spin-dependent interactions are also provided. These limits are particularly strong for low-mass dark matter. Using a simplified model, constraints are set on the mass of dark matter and of a colored mediator suitable to explain a possible signal of annihilating dark matter.

Download or read book Search for Dark Matter Particles in Proton proton Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for dark matter particles directly produced in proton-proton collisions recorded by the CMS experiment at the LHC is presented. The data correspond to an integrated luminosity of 18.8 inverse femtobarns, at a center-of-mass energy of 8 TeV. The event selection requires at least two jets and no isolated leptons. The razor variables are used to quantify the transverse momentum balance in the jet momenta. The study is performed separately for events with and without jets originating from b quarks. The observed yields are consistent with the expected backgrounds and, depending on the nature of the production mechanism, dark matter production at the LHC is excluded at 90% confidence level for a mediator mass scale Lambda below 1 TeV. The use of razor variables yields results that complement those previously published.

Download or read book Search for Dark Matter and Supersymmetry with a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A first search for pair production of dark matter candidates through vector boson fusion in proton-proton collisions at sqrt(s) = 8 TeV is performed with the CMS detector. The vector boson fusion topology enhances missing transverse momentum, providing a way to probe supersymmetry also in the case of a compressed mass spectrum. The data sample corresponds to an integrated luminosity of 18.5 inverse femtobarns recorded by the CMS experiment. The observed dijet mass spectrum is consistent with the standard model expectation. In an effective field theory, dark matter masses are explored as a function of contact interaction strength. The most stringent limit on bottom squark production with mass below 315 GeV is also reported, assuming a 5 GeV mass difference with respect to the lightest neutralino.

Download or read book Search for Dark Matter in Final States Containing Semi visible Jets from Proton proton Collisions at square Root s written by Colin Terrence Fallon and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This dissertation presents a novel search for new physics using the full Run 2 dataset of 137.6 fb-1 collected by the Compact Muon Solenoid during proton-proton runs of the Large Hadron Collider. The new physics in question is dark matter production in a unique signature called semi-visible jets. Semi-visible jets are produced when a new massive mediator particle emerges from the proton-proton interaction. This mediator then decays to unstable dark matter particles which hadronize and produce a mixture of standard model particles and stable dark matter particles. The stable dark particles are only detectable as missing transverse momentum, and the standard particles are detectable as jets. This produces a signature where two jets are produced, one of which is aligned with the total missing transverse momentum. The search is presented in two phases: a classical cut-based search which uses a series of cuts based on event kinematics to select events which look like the signal signature, and a machine learning based search which uses a technique called boosted decision trees to identify semi-visible jets in a more powerful but model-dependent way. No evidence for Physics Beyond the Standard Model is observed in either search. The classical search excludes the possibility that the mediator could have a mass between 1.5 TeV and 3.98 TeV, while the model-dependent search excludes mediators with masses between 1.5 TeV and 5.08 TeV. Additionally, ranges of other signal parameters are excluded"--Page viii.

Download or read book Search for W u2192 Tb in Proton proton Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for dark matter particles directly produced in proton-proton collisions recorded by the CMS experiment at the LHC is presented. The data correspond to an integrated luminosity of 18.8 inverse femtobarns, at a center-of-mass energy of 8 TeV. The event selection requires at least two jets and no isolated leptons. The razor variables are used to quantify the transverse momentum balance in the jet momenta. The study is performed separately for events with and without jets originating from b quarks. The observed yields are consistent with the expected backgrounds and, depending on the nature of the production mechanism, dark matter production at the LHC is excluded at 90% confidence level for a mediator mass scale Lambda below 1 TeV. The use of razor variables yields results that complement those previously published.