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Mit dem Ausbau zum High Luminosity LHC (HL-LHC) wird der Spurdetekor des ATLAS-Experiments durch den Inner Tracker (ITk) ersetzt, der Pixel- und Streifensensoren aus Silizium nutzen wird. In Dortmund werden Module für die Endkappe des ITK Streifendetektors gebaut werden. In einem Teil der Arbeit wird der Ablauf derProduktion dieser Module entwickelt. Während des Betriebs werden Strahlenschäden den Leckstrom der Siliziumsensoren erhöhen. Mit Hilfe des Parameters Eeff kann dieser mit der Temper...
In this thesis, a search for flavour-changing neutral currents in processes involving a singly produced top quark and a photon is presented. In this search, proton-proton collision data are used which were collected by the ATLAS experiment at the LHC and correspond to an integrated luminosity of 81 fb⁻¹. The top quark is assumed to decay into a b quark and a W boson, which is supposed to decay leptonically. Events are selected whose final state contains exactly one photon, one charged lepton,...
Imaging atmospheric Cherenkov telescopes (IACT) observe the sky in the highest energy ranges. From the remnants of cataclysmic supernovae to jets powered by supermassive blackholes in the center of distant galaxies, IACTs can capture the light emerging from the most extreme sources in the universe. With the recent advent of multi-messenger astronomy it has become critical for IACTs to publicly share their data and software. For the first time since the inception of IACT technology, in a...
Der neutrinolose doppelte Beta-Zerfall ist ein hypothetischer Kernzerfall dessen Nachweis grundlegende Fragen über bislang unbekannte Eigenschaften von Neutrinos liefern und auf Physik jenseits des Standard Modells der Teilchenphysik hindeuten würde. Das COBRA Experiment sucht nach diesem Zerfall mit Hilfe von CdZnTe Halbleiter-Detektoren. In dieser Arbeit wird ein wesentlich verbesserter Aufbau des Experiments, genannt Extended Demonstrator (XDEM), präsentiert. Um diesen zur verwirklich...
Starting in 2021, the LHCb experiment will switch to a fully software-based trigger system. It is an ongoing challenge to ensure that this system will be able to process events at the required rate of 30 MHz. Two alternative approaches to improve and speed up the particle track reconstruction performed in the first stage of LHCb’s software trigger are presented. An alternative method to the Kalman filter track fit inside the VELO reconstruction is presented. This method uses neural networks t...
This thesis presents the first LHCb measurement of 𝐶𝑃 violation in 𝐵0 → 𝐷∗±𝐷∓ decays. Due to the 𝑏 → 𝑐𝑐𝑑 transition, 𝐵0 → 𝐷∗±𝐷∓ decays give access to higher-order Standard Model contributions. The decay-time-dependent measurement is performed on a dataset corresponding to an integrated luminosity of 9 fb−1 recorded by the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The 𝐶𝑃 observables are measured with an unbinned maximum likelihood fi...
A large fraction of the gamma-ray sources presented in the Third Fermi-LAT source catalog (3FGL) is affiliated with counterparts and source types, but 1010 sources remain unassociated and 573 sources are associated with active galaxies of uncertain type. The purpose of this study is to assign blazar classes to these unassociated and uncertain sources, and to link counterparts to the unassociated. A machine learning algorithm is used for the classification, based on properties extracted from t...
Astrophysical tau neutrinos are the last unidentified standard model messenger in astroparticle physics. Their identification can open new windows to neutrino physics, improve knowledge about cosmic neutrino sources and even test physics beyond the standard model. This work aims to constrain the tau neutrino component in the astrophysical neutrino flux observed by the IceCube Neutrino Observatory. Due to neutrino oscillations over cosmic baselines, a significant fraction of tau neutrinos...
S5 0716+714 is a well known BL Lac object, and one of the brightest and most active blazars. The discovery in the Very High Energy band (VHE, E > 100 GeV) by MAGIC happened in 2008. In January 2015, the source went through the brightest optical state ever observed, triggering MAGIC follow-up and a VHE detection with ∼ 13σ significance (ATel ♯6999 ). Rich multiwavelength coverage of the flare allowed us to construct the broad-band spectral energy distribution of S5 0716+714 during its brightes...
Blazars like Markarian 421 or Markarian 501 are active galactic nuclei (AGN), with their jets orientated towards the observer. They are among the brightest objects in the very high energy (VHE) gamma ray regime (>100 GeV). Their emitted gamma-ray fluxes are extremely variable, with changing activity levels on timescales between minutes, months, and even years. Several questions are part of the current research, such as the question of the emission regions or the engine of the AGN and the part...
Active Galactic Nuclei emit radiation over the whole electromagnetic spectrum up to TeV energies. Blazars are one subtype with their jets pointing towards the observer. One of their typical features is extreme variability on timescales, from minutes to years. The fractional variability is an often used parameter for investigating the degree of variability of a light curve. Different detection methods and sensitivities of the instruments result in differently binned data and light curves with ...
The presented thesis deals with the branching ratio measurement of the decay channel Bs0 → KS0 KS0 reconstructed as two charged pion pairs. The data correspond to an integrated luminosity of 5 fb^{-1} collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of sqrt{s} = 7 TeV (1 fb^{-1}), 8 TeV (2 fb^{-1}) and 13 TeV (2 fb^{-1}). As normalisation channel the decay B0 → φKS0 is used in which the φ meson is reconstructed as two charged kaons. The branching rat...
Blazars are known to show variability on time scales from minutes to years covering a wide range of flux states. Studying the flux distribution of a source allows for various insights. The shape of the flux distribution can provide information on the nature of the underlying variability processes. The level of a possible quiescent state can be derived from the main part of the distribution that can be described by a Gaussian distribution. Dividing the flux states into quiescent and active, th...
This thesis presents the measurement of decay-time-dependent 𝐶𝑃 violation in the decays of 𝐵0 → 𝜓(2𝑆)𝐾S0 and 𝐵0 → 𝐽/𝜓𝐾S0 using data collected with the LHCb experiment in 𝑝𝑝 collisions at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to a total integrated luminosity of 3 fb−1. In both considered decay modes, the 𝐾S0 meson is reconstructed from two charged pions, while the 𝜓(2𝑆) meson is reconstructed from two muons, whereas the 𝐽/𝜓 meson is reconstructed from...
In this thesis, the production of a single top quark in association with a Higgs boson (tH) is studied at √s = 13 TeV in the H → γγ decay channel at the ATLAS experiment. Similar to the production of a Higgs boson in association with a top-antitop quark pair (ttH), tH production allows for a direct measurement of the Yukawa coupling, Yt, of the top quark. Due to a destructive interference in tH production, it also provides sensitivity to negative values of the coupling strength modifier κt = ...
This thesis discusses two analyses of rareBmeson decays that are sensitive to effectsbeyond the Standard Model of particles physics. Both measurements are based on theLHCb Run 1 data sample of proton-proton collisions corresponding to an integratedluminosity of3 fb−1recorded at centre-of-mass energies of 7 and 8 TeV.The first measurement is a search for light scalar particles inB0(s)→μ+μ−μ+μ−decays. Additionally to the Standard Model contributions without intermediateresonances, a specific s...
The Dortmund Low Background Facility is a highly sensitive gamma ray spectrometry system, operated in a low-background environment, which enables the measurement of traces of radioactivity with high precision. A HPGe detector is set up within an artificial overburden, equivalent to 10 meters of water. This outer shielding reduces the contribution from cosmic muons during the measurement. Signals induced by cosmic muons that penetrate this shielding are suppressed by an active cosmic muon v...
Pencil beam scanning (PBS) proton therapy is due to its steep dose gradients a promising treatment option for many cancer patients, particularly if the tumour is surrounded by critical organs. Currently, organ motion often poses an obstacle for the irradiation of tumours in the thorax or abdomen since the interference of pencil beam and tumour motion can lead to distortions of the intended dose distribution and requires dedicated motion mitigation techniques. A technique which has been recomm...
The work presented in this thesis comprises two individual topics: While the first part presents a branching ratio measurement of the decay 𝐵0𝑠→ 𝐾0S𝐾0S, the second part discusses the author’s contribution to the simulation of the upgraded LHCb detector. To reduce systematic uncertainties, the branching ratio is measured normalised to the branching ratio ℬ(𝐵0 → 𝜙𝐾0S). The analysed data sample corresponds to an integrated luminosity of 3 fb−1 of 𝑝𝑝 collisions recorded at centre-of...
In this thesis, an approach is presented to probe the locations of track-like high energy starting events (HESE) for an additional clustering of neutrino events within six years of IceCube neutrino data at these positions. Two unbinned Likelihood stacking analyses using both a time-dependent, per-burst and a steady-state neutrino emission scenario are performed. This is done to be sensitive to a collection of weak fluxes, undetectable on their own and to test a rather broad regime of emi...