SNO+, the successor of the Sudbury Neutrino Observatory, is an upcoming low energy neutrino experiment, located in the 2 km deep laboratory SNOLAB, Canada. The spheric acrylic vessel in the detector center will contain 780 t of LAB. The main goal of SNO+ is the search for the neutrinoless double beta decay of 130Te, using a novel scintillator in which natural Te is bound with an initial loading of 0.3% via water and a surfactant. Within this thesis, the first measurement of the Alpha-particle and proton quenching parameters of loaded and unloaded LAB is described. These parameters are crucial for an efficient background suppression, necessary to reach a sensitivity above the current limit in 76Ge of T1/2(0v) > 2.1 x 10^(25) y (90% C.L.). For 0.3% Te-loading, the quenching parameter obtained is kB = (0.0070 +/- 0.0004) cm/MeV for Alpha-particles and kB = (0.0090 +/- 0.0003) cm/MeV for protons. Additionally, the spectral sensitivity of SNO+ to supernova electron anti-neutrinos and muon and tau (anti-)neutrinos is determined for the first time, using inverse beta decay and v-p elastic scattering with the measured quenching parameters. The obtained sensitivity to the mean energy of electron anti-neutrinos is E = 15.47^(+1.54)_(-2.43) MeV and of muon and tau (anti-)neutrinos is E = 17.81^(+3.49)_(-3.09) MeV. / SNO+, der Nachfolger des Sudbury Neutrino Observatorys, ist ein bevorstehendes Niederenergie-Neutrino-Experiment im 2 km tiefen Untergrundlabor SNOLAB in Kanada. Die Acryl-Kugel im Zentrum des Detektors wird mit 780 t LAB gefüllt werden. Das Hauptziel von SNO+ ist die Suche nach dem neutrinolosen Doppelbetazerfall von 130Te mit einem neuartigen Szintillator, in dem natürliches Te mit einer Anfangskonzentration von 0.3% über Wasser und ein Tensid gebunden wird. In dieser Arbeit wird erstmals die Messung der Alpha-Teilchen und Proton Quenching Parameter in diesem und in normalem LAB beschrieben. Die Parameter sind unverzichtbar für eine effiziente Untergrund Unterdrückung, die notwendig ist um auf das bestehende Limit in 76Ge von T1/2(0v) > 2.1 x 10^(25) y (90% C.L.) sensitiv zu sein. Der ermittelte Quenching Parameter bei 0.3% Te beträgt kB = (0.0070 +/- 0.0004) cm/MeV für Alpha-Teilchen und kB = (0.0090 +/- 0.0003) cm/MeV für Protonen. Zusätzlich wird erstmals die spektrale Sensitivität von SNO+ auf Supernova Elektron Anti-Neutrinos und Muon and Tau (Anti-)Neutrinos bestimmt über den inversen Betazerfall und die elastische v-p Streuung zusammen mit den gemessenen Quenching Parametern. Die ermittelte Sensitivität auf die mittlere Energie der Elektron Anti-Neutrinos ist E = 15.47^(+1.54)_(-2.43) MeV und der Muon und Tau (Anti-)Neutrinos ist E = 17.81^(+3.49)_(-3.09) MeV.

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The inference of massive neutrino states through the observation of flavor oscillations boosted the importance of direct and indirect mass searches, including the search for the hypothesized neutrinoless double beta decay (0νββ-decay). Nowadays, the search for this ultra-rare nuclear transition is one of the most active research fields at the intersection of nuclear, particle and astroparticle physics. Its main and evident feature is the explicit violation of the total lepton number, which is an accidentally conserved quantity in the Standard Model of particle physics, and would prove the Majorana nature of neutrinos. This, in turn, would support the theoretical explanation of the origin of the observed baryon asymmetry in the universe through the process of leptogenisis and could shed light on the role of neutrinos in the early universe’s structure formation. For the theoretical description of the 0νββ-decay, nuclear structure effects play an important role as they may affect considerably the decay rate. These nuclear effects are summarized as the nuclear matrix elements (NMEs), containing information about the initial and final states of the involved atomic nuclei and the decay mechanism. Under the assumption of light Majorana neutrino exchange, the inverse half-life is proportional to the effective Majorana neutrino mass, a kinematic phase-space factor, the involved NMEs and the fourth power of the weak axial-vector coupling gA. The search for the 0νββ-decay is driven by experiments and an accurate description of the nuclear structure effects is essential to estimate the required sensitivity to cover a certain mass range. In order to match theoretical calculations and the results of β-decay and ββ-decay studies, there is a scientific discussion regarding quenching effects of gA in nuclear media. Different methods are being investigated to determine an effective gA at the energy scale of nuclear transitions. One of those recently proposed methods exploits the dependency of the spectrum-shape of highly forbidden β-decays on gA. An ideal candidate for such an investigation is the fourfold forbidden non-unique β-decay of Cd-113, which is the most prominent signal in the current stage of the COBRA experiment searching for 0νββ-decays with cadmium zinc telluride (CZT) solid state detectors. The detector material CZT acts as a semiconductor at room temperature and contains intrinsically several candidates for rare nuclear transitions. The experiment is located at the LNGS underground facility in Italy, which is shielded against cosmic rays by a mean rock coverage of about 1400 m. In the present demonstrator phase, it consists of 64 coplanar grid (CPG) detectors that are arranged in four layers of 4 x 4 crystals. In the scope of this thesis, conventional and novel prototype CPG-CZT detectors, which are the basis for an anticipated large-scale experiment, are characterized by evaluating homogeneous and localized γ-ray irradiation measurements. Moreover, a novel pulse-shape discrimination (PSD) technique is established, optimized and applied in the analysis of the physics data obtained with the demonstrator array. The PSD optimization is complemented by dedicated laboratory measurements with the aim to create a pulseshape library of signal-like single-site events and high-energy cosmic muon interactions for which an analytic reconstruction model has been developed. For the first time, the COBRA demonstrator’s full exposure from Sept.’11 to Nov.’19 is analyzed, including a detailed background characterization as well as an automatized data partitioning to identify periods with increased backgrounds. The main subject is the study of the Cd-113 β-decay’s spectrum-shape to address the quenching of gA in lowmomentum exchange nuclear processes. The analysis of the experimental data is carried out in the context of three nuclear frameworks and confirms the idea of a significantly quenched gA. Furthermore, the data are analyzed with respect to the 2νββ-decay of Cd-116 and the long-lived α-decay of Pt-190 as a localized contaminant in the CZT detectors’ electrode metalization. Finally, the prospects of a search for excited state transitions of the ββ-nuclides Cd-116 and Te-130 are studied with elaborate Monte-Carlo simulations. The analysis section is concluded with an estimate of the achievable 0νββ-decay half-life sensitivity for multiple ββ-nuclides given the full exposure of the COBRA demonstrator and the recently achieved upgrade to the COBRA eXtended DEMonstrator (XDEM).

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We use Integral Field Unit (IFU) data for a subset of galaxies in the MaNGA (Mapping Nearby Galaxies at Apache Point Observatory) sample to investigate the environmental dependence of H-alpha properties for nearby star-forming galaxies. We characterize the non-AGN H-alpha emission for galaxies living in different host environments with radial gradient measurements, half-light radii, as well as measures of concentration and asymmetry. We find that global specific star formation rates (sSFR) are lower in nearby star-forming galaxies in groups and clusters compared to those in the field, and the lowest in high density environments such as group or cluster centres. From the resolved data we find that the overall reduction in H-alpha emission in star-forming galaxies in denser environments occurs across the face of these galaxies, suggesting starvation as a primary quenching mechanism. We further find that H-alpha disks are truncated in group galaxies that live nearer the center of the halo compared to those in the outer halo or field, which may be due to ram pressure stripping in these dense environments. / Thesis / Master of Science (MSc) / In order to understand the evolution of galaxies over time, it is necessary to determine the relative importance of external and internal factors that affect galaxy star formation. We know that galaxies in dense environments have less star formation (are quenched) compared to galaxies in the field. However, the mechanisms that dominate this quenching are less well constrained. We use a sample of galaxies in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey to investigate the dependence of star formation on other galaxy properties as well as properties of the host environment. We find that galaxies have reduced H-alpha emission, a signature of star formation, across the entire face of the galaxy in groups and clusters compared to galaxies in the field. We further find that galaxies nearer the centre of the group or cluster halo have truncated H-alpha disks compared to galaxies in the outer part of the halo or in the field.

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Quorum sensing (QS) is a type of microbial communication used by bacteria to coordinate their behavior based on population density, regulating complex processes like biofilm formation and virulence, among other behaviors. Quorum quenching (QQ), on the other hand, disrupts this communication, usually by degradation of the QS signaling molecule. QQ offers a potential strategy for controlling bacterial behaviors linked to pathogenicity and biofouling. Despite significant advances in understanding and modeling the spatial-temporal behavior of QS, predictive modeling of QQ remains nascent, with a notable gap in the quantitative assessment of QQ's impact on QS. Here we show quantitative evaluation and characterization of the effect of QQ on QS in agar-based experiments, combined with an experimentally validated computational model. This research utilizes green fluorescence in E. coli MG 1655 as an indicator of QS activation, focusing on the degradation of Acyl-Homoserine Lactone (AHL), a key QS molecule in Gram-negative bacteria linked to pathogenicity, by the AiiA enzyme in engineered AiiA-producing Salmonella Typhimurium 14028. Our findings suggest that QQ more effectively influences QS in spatial configurations of the populations with larger interaction surfaces and shorter diffusion distances. Contrary to our initially held hypothesis, the primary effect of QQ is not a delay in QS onset but rather an attenuation of QS activity, with the area-under-the-curve of fluorescence serving as a quantitative metric. This study also introduces, to the best of our knowledge, one of the first instances of experimentally validated predictive modeling for QQ, applied to agar-based experimental setups. We posit that the quantitative experimental characterization and modeling framework presented in this research will enhance the understanding of bacterial community interactions. Enhanced comprehension of QQ and QS behaviors holds significant promise for advancing practical applications, particularly in mitigating or diminishing undesirable QS-associated activities. This is especially relevant in areas like biofouling, waste treatment, and the reduction of infections and progression of diseases in plants and animals, areas increasingly important as concerns about drug resistance in microbes and food security escalates. / Master of Science / One of the ways bacteria communicate with each other is called quorum sensing (QS), where they use chemical signals to organize and time group behavior, including forming communities encapsulated in protective layers, called biofilms, and engaging in virulent attacks against hosts. Quorum quenching (QQ) in bacteria, however, disrupts this communication system, usually by breaking down the chemical signals that bacteria use to send messages to each other. Even though QS has been studied extensively, determining how to predict and control QQ is still a nascent area of research. Here, we studied and characterized how QQ affects QS by doing experiments with bacteria populations in agar (a jelly-like substance) and applied a computational model to explain and ultimately predict the experimental observations. Engineered QS population (E. coli MG 1655) produced Acyl-Homoserine Lactone (AHL) signaling molecules, and engineered QQ bacteria (S. Tm 14028) used the Autoinducer Inactivation A (AiiA) enzyme to break down the AHL. According to our results, QQ doesn't delay the QS bacteria's group behaviors (in our case, green fluorescent signal production); it weakens the signal instead. Understanding QQ and QS better, especially through measurements and modeling, could lead to expanded methods of deterring harmful bacterial behavior, managing waste better, and stopping diseases in plants, animals, and humans, especially with the concerning rise of drug-resistant microbes and food security. One exciting possibility is using QQ to protect plants from bacterial infections. This could be a way to shield our crops without always relying on antibiotics.

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