Download or read book Calibration of B tagging and Search for Dark Matter written by Anna Shcherbakova and published by . This book was released on 2017 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Dark Matter Produced in Association with a Higgs Boson Decaying to Two Bottom Quarks at ATLAS written by Yangyang Cheng and published by Springer. This book was released on 2016-09-29 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 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.
Download or read book Search for Dark Matter with ATLAS written by Ruth Pöttgen and published by Springer. This book was released on 2016-06-29 with total page 325 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 with the ATLAS Detector written by Johanna Gramling and published by Springer. This book was released on 2018-08-01 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses searches for Dark Matter at the CERN’s LHC, the world’s most powerful accelerator. It introduces the relevant theoretical framework and includes an in-depth discussion of the Effective Field Theory approach to Dark Matter production and its validity, as well as an overview of the formalism of Simplified Dark Matter models. Despite overwhelming astrophysical evidence for Dark Matter and numerous experimental efforts to detect it, the nature of Dark Matter still remains a mystery and has become one of the hottest research topics in fundamental physics. Two searches for Dark Matter are presented, performed on data collected with the ATLAS experiment. They analyze missing-energy final states with a jet or with top quarks. The analyses are explained in detail, and the outcomes and their interpretations are discussed, also in view of the precedent analysis of theoretical approaches. Given its depth of coverage, the book represents an excellent reference guide for all physicists interested in understanding the theoretical and experimental considerations relevant to Dark Matter searches at the LHC.
Download or read book Searching for Dark Matter with the ATLAS Detector written by Steven Schramm and published by Springer. This book was released on 2016-11-23 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the search for Dark Matter at the LHC in the mono-jet plus missing transverse momentum final state, using the full dataset recorded in 2012 by the ATLAS Experiment. It is the first time that the number of jets is not explicitly restricted to one or two, thus increasing the sensitivity to new signals. Instead, a balance between the most energetic jet and the missing transverse momentum is required, thus selecting mono-jet-like final states. Collider searches for Dark Matter have typically used signal models employing effective field theories (EFTs), even when comparing to results from direct and indirect detection experiments, where the difference in energy scale renders many such comparisons invalid. The thesis features the first robust and comprehensive treatment of the validity of EFTs in collider searches, and provides a means by which the different classifications of Dark Matter experiments can be compared on a sound and fair basis.
Download or read book Searches for the Supersymmetric Partner of the Top Quark Dark Matter and Dark Energy at the ATLAS Experiment written by Nicolas Maximilian Köhler and published by Springer Nature. This book was released on 2019-09-13 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astrophysical observations implying the existence of Dark Matter and Dark Energy, which are not described by the Standard Model (SM) of particle physics, have led to extensions of the SM predicting new particles that could be directly produced at the Large Hadron Collider (LHC) at CERN. Based on 2015 and 2016 ATLAS proton-proton collision data, this thesis presents searches for the supersymmetric partner of the top quark, for Dark Matter, and for DarkEnergy, in signatures with jets and missing transverse energy. Muon detection is key to some of the most important LHC physics results, including the discovery of the Higgs boson and the measurement of its properties. The efficiency with which muons can be detected with the ATLAS detector is measured using Z boson decays. The performance of high-precision Monitored Drift Tube muon chambers under background rates similar to the ones expected for the High Luminosity-LHC is studied.
Download or read book Calibrations for the Improved Search for Dark Matter with the LZ LUX ZEPLIN Experiment written by Madan K. Sharma Timalsina and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A hypothetical non-luminous existence of matter is known as dark matter, inferred by the convincing collection of astrophysical and cosmological indirect evidence. In spite of compelling indirect observations, the physical nature of dark matter remains one of the most profound questions in the field of modern physics. A Weakly Interacting Massive Particle (WIMP) is historically the most favored candidate particle for dark matter, which could nicely explain the observed indirect measurements with the direct detection of WIMPs for the first time. The new second-generation direct detection dark matter experiment LZ (LUXZEPLIN), designed for direct detection of WIMP dark matter, has performed the most sensitive search for spin-independent WIMP-nucleon interactions. LZ is located 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. LZ is employing a two-phase xenon detector with an active mass of 7 tonnes. With LZ we have recently managed in the summer of 2022 to provide the most rigorous exclusion limit for spin-independent WIMP-nucleon scattering with an upper limit on the cross-section of 6.5×10−48 cm2 (90 % confidence level) for a WIMP mass of 30 GeV/c2 . The first WIMP search result of LZ utilizes a fiducial mass of 5.5 tonnes of liquid xenon and an exposure time of 60 live days. WIMPs could interact in the cryogenic liquid xenon of the detector’s core by scattering off xenon nuclei, which would then recoil and produce both scintillation light and electric charge. The ratio of the immediately detected scintillation light (S1) and the delayed charge detection (S2) is characteristic for such a nuclear recoil (NR) from hypothesized dark matter, e.g. a WIMP, and differs significantly from an electron recoil (ER) produced by undesired background reactions. However, the precise knowledge of the energy-dependent ratio S1/S2, for which the ER-dominated regime transitions into the NR-dominated regime, is key hereby to separate WIMP dark matter signals from unwanted background signals. We performed calibrations with neutron sources to map out the NR signal region for the WIMP search. Instead, gamma- and beta-ray calibration sources were utilized to map out the ER region, characteristic for background signals to be discriminated against. In this thesis, the calibration data to map out the NR signal region has been extensively studied and compared to the results of a full LZ detector simulation. In addition, another crucial detector calibration, for which all LZ data has to be corrected, is the purity monitoring of the liquid xenon. The chemical purity determines the lifetime of signal electrons against the absorption on impurities during their drift within the liquid xenon time projection chamber of the LZ detector. This electron lifetime analysis has been performed on a daily basis within the framework of this thesis and results have been applied by every data evaluator within the large LZ collaboration and for obtaining the current world’s best exclusion limit on WIMP dark matter.
Download or read book B Tagging Calibration at the ATLAS Experiment written by Florian Hirsch and published by . This book was released on 2011 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Searching for Squarks written by Samuel Jones and published by Springer Nature. This book was released on 2020-08-27 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis focuses on searches for squarks with the ATLAS detector in "compressed" scenarios where the scalar top is very close in mass to the lightest supersymmetric particle. These models are theoretically appealing because the presence of a quasi-degenerate scalar top enhances the self-annihilation cross-section of the lightest supersymmetric particle, acting therefore as a regulator of the dark matter relic density. Two main analyses are presented: the first is a search for scalar tops decaying to charm quarks. The identification of jets originating from the charm quark is very challenging due to its short lifetime. The calibration of tools for charm-tagging has paved the way to measuring the decay of the Higgs boson to pairs of charm quarks. The second analysis presented is the development of a novel technique for reconstructing low momentum b-hadrons. This tool has enabled the ATLAS collaboration to explore topologies that were previously inaccessible.
Download or read book Direct Detection of Dark Matter with the PICO Experiment and the PICO 0 1 Calibration Chamber written by Frédéric Tardif and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dark matter detection remains one of the main unresolved problems in physics. Accounting for almost 85% of all the matter density in the Universe, it was inferred through many astronomical observations, but no dark matter particle has been detected yet. The PICO experiment has this objective as its purpose, using the bubble chamber in order to do so. PICO can detect extremely low-energy interactions in its superheated liquid detectors, located in the SNOLAB underground laboratory in Sudbury, Ontario. PICO has and has had multiple dark matter search detectors, as well as small detectors used to perform calibrations and tests. PICO-0.1 is a calibration chamber located at the University of Montreal and was used for the studies presented in this thesis. In this thesis, data and analysis of measurements made with PICO-0.1 are presented. A study of the Seitz threshold - theoretical energy threshold for an event to occur in a bubble chamber - is made, with the monoenergetic reaction 35Cl(nth,p)35S in C2ClF5; the study of the monoenergetic 35S recoil, directly inside the detector, is presented. Furthermore, the detection of proton recoils in PICO-0.1 is detailed; first through the analysis of the acoustic signal of the proton produced by 35Cl(nth,p)35S, and second through elastic scattering of neutrons and high energy gamma rays on hydrogen in C2H2F4.
Download or read book Continuous Calibration of B tagging Algorithms Mit PTrel and SPlot written by Timea Krones and published by . This book was released on 2022-05-12 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This diploma thesis examines b-tagging algorithms with the sPlot technique and the pTrel method based on Cern data from the Atlas experiment and data from simulation. Deviations between experimental data and the simulation data are investigated thoroughly based on statistical analysis using the sPlot technique and the pTrel method for evaluating the performance of b-tagging algorithms used at Cern. In principle, the calibration and continuous calibration of b-tagging algorithms with the sPlot technique and the pTrel method is investigated in this thesis.
Download or read book Calibration of the PICO 0 1 Bubble Chamber and Development of Coated Inner Vessels for Dark Matter Search written by Frédéric Girard and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The detection of dark matter is one of the biggest challenges in modern physics. The PICO experiment aims for the direct detection of Weakly Interacting Massive Particles (WIMPs) with bubble chambers. In this thesis, results from calibrations of the PICO-0.1 test chamber is presented. Calibrations were performed at the Tandem Van de Graaff facility of the Université de Montréal. Monoenergetic neutrons were produced from the 51V(p,n)51Cr reaction with a 1.6 MeV proton beam. Two 3He neutron counters used during calibrations for neutron flux normalization were also calibrated. This result is contributing in improving Monte Carlo simulations of PICO-0.1. Finally, preliminary work was done toward the use of new inner vessel materials with coated surfaces for bubble chambers. A Condensation Bubble Chambers (CBCs) was used as a test-bench. Progress has been made toward the usability of Poly-methyl-methacrylate vessels, but more work is needed to solve spontaneous wall nucleation problems.
Download or read book Point by Point Gain Calibration of the Dark Matter Time Projection Chamber written by Albert Hyunjick Lee and published by . This book was released on 2010 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since 1975 a growing body of astronomical evidence has given increasing credibility to the existence of dark matter. Once a simple proposition by Fritz Zwicky to explain discrepancies in the virial motion of galaxy clusters, dark matter can now explain galactic rotation curves, the hierarchical structure of the universe, and the gravitational lensing of the bullet cluster. Nonetheless, the exact particulate nature of dark matter remains a mystery. The Dark Matter Time Projection Chamber (DMTPC) is a directional detection experiment that will be able to measure the energy, length, and direction of nuclear recoil tracks induced by incoming weakly interacting massive particles (WIMPs). In this thesis I analyze nonuniformities in the CCD images used to record the nuclear recoils. I then identify the source of the nonuniformities and describe a method for calibrating the CCD images. The method improves the energy resolution by decreasing the uncertainty by a factor of 4 for the bottom time projection chamber (TPC) and a factor of 3 for the top TPC.
Download or read book LUX ZEPLIN Dark Matter Searches written by Billy Boxer and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Results from the Two tower Run of the Cryogenic Dark Matter Search written by Angela Jean Reisetter and published by . This book was released on 2005 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book B Flavor Tagging Calibration and Search for B s Oscillations in Semileptonic Decays with the CDF Detector at Fermilab written by Gavril A. Giurgiu and published by . This book was released on 2005 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we present a search for oscillations of B{sub s}{sup 0} mesons using semileptonic B{sub s}{sup 0} {yields} D{sub s}{sup -}{ell}{sup +}{nu} decays. Data were collected with the upgraded Collider Detector at Fermilab (CDFII) from events produced in collisions of 980 GeV protons and antiprotons accelerated in the Tevatron ring. The total proton-antiproton center-of-mass energy is 1.96 TeV. The Tevatron is the unique source in the world for B{sub s}{sup 0} mesons, to be joined by the Large Hadron Collider at CERN after 2007. We establish a lower limit on the B{sub s}{sup 0} oscillation frequency {Delta}m{sub s}> 7.7 ps{sup -1} at 95% Confidence Level. We also present a multivariate tagging algorithm that identifies semileptonic B {yields} {mu}X decays of the other B mesons in the event. Using this muon tagging algorithm as well as opposite side electron and jet charge tagging algorithms, we infer the B{sub s}{sup 0} flavor at production. The tagging algorithms are calibrated using high statistics samples of B{sup 0} and B{sup +} semileptonic B{sup 0/+} {yields} D{ell}{nu} decays. The oscillation frequency {Delta}m{sub d} in semileptonic B{sup 0} {yields} D{ell}{nu} decays is measured to be {Delta}m{sub d} = (0.501 {+-} 0.029(stat.) {+-} 0.017(syst.)) ps{sup -1}.
Download or read book Calibration of Hot and Cold Dark Matter Experiments written by Karen Bokeloh and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
