Reviving the thermal dark matter paradigm with long-lived particles

The nature of dark matter is one of the most crucial open questions of modern fundamental physics. In this thesis, we aim to address this problem, focusing on minimal dark sector models that can be falsified with current experimental techniques. First, we study an effective theory of Higgs portal dark matter at the electroweak mass scale. We notice an almost unstudied mechanism of thermal dark matter production, the co-scattering mechanism, that is a general characteristic of models with extended dark sectors. Second, we connect the viable thermal dark sector theories with the corresponding collider signatures. We find that such sectors feature compressed mass spectra, resulting in long-lived mediators at colliders. We perform a comprehensive study of possible displaced signatures in the singlet-triplet Higgs portal model and find a remarkable potential of displaced searches in testing dark matter theories where traditional techniques fail. Finally, we extend our focus by exploring the prospects of long-lived particle searches at e+e− colliders. We predict the sensitivity of Belle II to displaced objects in rare meson decays, showing its ability to compete even with some of the long-baseline experiments

The Effects of Addition of Mononucleotides on Sma nuc Endonuclease Activity

Examination of the effects of mononucleotides on Sma nuc endonuclease originated from Gram negative bacterium Serratia marcescens displayed that any mononucleotide produced by Sma nuc during hydrolysis of DNA or RNA may regulate the enzyme activity affecting the RNase activity without pronounced influence on the activity towards DNA. The type of carbohydrate residue in mononucleotides does not affect the regulation. In contrast, the effects depend on the type of bases in nucleotides. AMP or dAMP was classified as a competitive inhibitor of partial type. GMP, UMP, and CMP were found to be uncompetitive inhibitors that suggest a specific site(s) for the nucleotide(s) binding in Sma nuc endonuclease

Employment in Small Business Sector and its Impact on Quality of Life in Russian Regions

Employment in small business sector is an essential factor in improving quality of life (QOL) for a region. Successful small businesses require human, financial, technological investments and result in improved QOL. “Small business and entrepreneurship is now commonly seen as the primary engine of economic development 1. Small business creates new workplaces, reduce unemployment payments and reduce crime in regions 2. An aging population pared with depopulation result in increased cost of benefits like pension payments which adversely impact the Russian national budget. Stimulation of secondary employment (employment for retired) in small business sector can result in improved QOL for the elderly. Problems of unemployment can be solved mostly through small business development 3. The objective of this research is to evaluate a relationship between employment in small business sector and QOL in 78 Russian regions. The regression model was used for an empirical analysis. The results show that there is an effect of employment in small business sector on QOL at a reasonable level. The findings and analysis revealed that employment in small business sector has a positive effect on QOL in all Russian regions analyzed

Long live the Higgs portal!

In Higgs portal models of fermion dark matter, scalar couplings are unavoidably suppressed by strong bounds from direct detection experiments. As a consequence, thermal dark matter relics must coexist with mediators in a compressed spectrum of dark particles. Small couplings and small mass splittings lead to slow mediator decays, leaving signatures with displaced vertices or disappearing tracks at colliders. We perform a comprehensive analysis of long-lived mediators at the LHC in the context of a minimal dark matter model with a naturally small Higgs portal, also known as the wino-bino scenario in supersymmetry. Existing searches for disappearing charged tracks and displaced hard leptons already exclude tiny portal couplings that cannot be probed by current direct and indirect detection experiments. For larger portal couplings, we predict new signatures with displaced soft leptons, which are accessible with run-II data. Searches for displaced particles are sensitive to weakly coupling mediators with masses up to the TeV scale, well beyond the reach of prompt signals.Comment: 18 pages, 7 figures, matches version published in JHE

Biochemical and toxicological effects of organic (herbicide Primextra® Gold TZ) and inorganic (copper) compounds on zooplankton and phytoplankton species

In Europe, mainly in the Mediterranean region, an intensive usage of pesticides was recorded during the past 30 years. According to information from agricultural cooperatives of the Mondego valley (Figueira da Foz, Portugal), Primextra® Gold TZ is the most used herbicide in corn crop fields and one of the 20 best-selling herbicides in Portugal. Copper is mainly used in pesticide formulations. This study aims to determine the ecotoxicological and biochemical (namely fatty acid profiles) effects of the herbicide Primextra® Gold TZ and the metal copper on marine plankton. The organisms used in this study are three planktonic species: the marine diatom Thalassiosira weissflogii, the estuarine copepod Acartia tonsa and nauplii of the marine brine shrimp Artemia franciscana. Fatty acids (FAs) are one of the most important molecules transferred across the plant-animal interface in aquatic food webs and can be used as good indicators of stress. The conducted lab incubations show that T. weissflogii is the most sensitive species to the herbicide followed by A. tonsa (EC50 =0;0.0078 mg/L and EC50 =0;0.925 mg/L, respectively), whereas the copepod was the most sensitive species to the metal followed by T. weissflogii (EC50 =0.234 mg/L and EC50 =0.383 mg/L, respectively). A. franciscana was the most tolerant organism both to the herbicide and to the metal (EC50 =20.35 mg/L and EC50 = 18.93 mg/L, respectively). Changes in the FA profiles of primary producer and primary consumers were observed, with the increase of saturated FA and decrease of unsaturated FA contents, especially of highly unsaturated FAs that can be obtained mainly from food and therefore are referred to as ‘essential FA’. The study suggests that discharges of Primextra® Gold TZ or other pesticides mainly composed by copper may be a threat to plankton populations causing changes in the FA contents and thus in their nutritive value, with severe repercussions for higher trophic levels and thus the entire food web