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- Burgman, Alexander, 1991-
(författare)
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Bright Needles in a Haystack : A Search for Magnetic Monopoles Using the IceCube Neutrino Observatory
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The IceCube Neutrino Observatory at the geographic South Pole is designed to detect the light produced by the daughter-particles of in-ice neutrino-nucleon interactions, using one cubic kilometer of ice instrumented with more than 5000 optical sensors.Magnetic monopoles are hypothetical particles with non-zero magnetic charge, predicted to exist in many extensions of the Standard Model of particle physics. The monopole mass is allowed within a wide range, depending on the production mechanism. A cosmic flux of magnetic monopoles would be accelerated by extraterrestrial magnetic fields to a broad final velocity distribution that depends on the monopole mass.The analysis presented in this thesis constitutes a search for magnetic monopoles with a speed in the range [0.750;0.995] in units of the speed of light. A monopole within this speed range would produce Cherenkov light when traversing the IceCube detector, with a smooth and elongated light signature, and a high brightness.This analysis is divided into two main steps. Step I is based on a previous IceCube analysis, developed for a cosmogenic neutrino search, with similar signal event characteristics as in this analysis. The Step I event selection reduces the acceptance of atmospheric events to lower than 0.1 events per analysis livetime. Step II is developed to reject the neutrino events that Step I inherently accepts, and employs a boosted decision tree for event classification. The (astrophysical) neutrino rate is reduced to 0.265 events per analysis livetime, corresponding to a 97.4 % rejection efficiency for events with a primary energy above 1E+5 GeV.No events were observed at final analysis level over eight years of experimental data. The resulting upper limit on the magnetic monopole flux was determined to 2.54E–19 per square centimeter per second per steradian, averaged over the covered speed region. This constitutes an improvement of around one order of magnitude over previous results.
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| 2. |
- Preston, Markus, 1989-
(författare)
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Developments for the FPGA-Based Digitiser in the PANDA Electromagnetic Calorimeters
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The strong interaction between quarks and gluons is one of the fundamental interactions described by the standard model of particle physics. Systems of quarks bound together by the strong interaction are known as hadrons, of which the proton and the neutron are the most common examples. The theoretical framework of quantum chromodynamics (QCD) is used to describe the strong interaction, but becomes increasingly difficult to use as the distance between the interacting particles increases. On the length scales relevant for hadrons, for instance, non-perturbative approaches to QCD have to be used. Experimental data are needed to verify these approaches. PANDA is one of the four experimental pillars of the upcoming FAIR facility in Darmstadt, Germany. In PANDA, an antiproton beam with a momentum between 1.5 and 15 GeV/c will interact in a hydrogen or nuclear target, allowing studies of various aspects of non-perturbative QCD. Motivated by the high interaction rates and the diverse physics goals of the experiment, a triggerless readout approach will be employed. In this approach, each detector subsystem will be equipped with intelligent front-end electronics that independently identify signals of interest in real time. In the electromagnetic calorimeter, FPGA-based digitiser modules will be used for this task. The high-radiation environment in PANDA will pose a challenge to these modules, due to both potential radiation damage and high signal rates from the calorimeter. In this thesis, these issues are addressed. First, the results from experimental measurements and Monte Carlo modelling of radiation-induced single event upsets in the FPGA are described. These studies have allowed predictions of the rate of single event upsets during operation of PANDA. Secondly, a newly developed algorithm for real-time processing of calorimeter signals in an FPGA at high pile-up rates is described. This algorithm provides a significant improvement in the time resolution of the calorimeter and allows reconstruction of the pulse height and timing of piled-up detector signals.
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