Automated mass spectrum generation for new physics

We describe an extension of the FeynRules package dedicated to the automatic generation of the mass spectrum associated with any Lagrangian-based quantum field theory. After introducing a simplified way to implement particle mixings, we present a new class of FeynRules functions allowing both for the analytical computation of all the model mass matrices and for the generation of a C++ package, dubbed ASperGe. This program can then be further employed for a numerical evaluation of the rotation matrices necessary to diagonalize the field basis. We illustrate these features in the context of the Two-Higgs-Doublet Model, the Minimal Left-Right Symmetric Standard Model and the Minimal Supersymmetric Standard Model.Comment: 11 pages, 1 table; version accepted by EPJ

An MCMC study of general squark flavour mixing in the MSSM

We present an extensive study of non-minimally flavour violating (NMFV) terms in the Lagrangian of the Minimal Supersymmetric Standard Model (MSSM). We impose a variety of theoretical and experimental constraints and perform a detailed scan of the parameter space by means of a Markov Chain Monte-Carlo (MCMC) setup. This represents the first study of several non-zero flavour-violating elements within the MSSM. We present the results of the MCMC scan with a special focus on the flavour-violating parameters. Based on these results, we define benchmark scenarios for future studies of NMFV effects at the LHC.Comment: 8 pages, 3 figures. To appear in the proceedings of the European Physical Society Conference on High Energy Physics 2015 (EPS-HEP 2015), Vienna, Austria, 22nd to 29th of July 201

Obtaining insight in atmospheric trace organic compound concentrations and trends in Dronning Maud Land, East Antarctica by means of long term passive and active air sampling

info:eu-repo/semantics/publishe

Collider signatures of goldstini in gauge mediation

We investigate the collider signatures of the multiple goldstini scenario in the framework of gauge mediation. This class of models is characterized by a visible sector (e.g. the MSSM or any extension) coupled by gauge interactions to more than one SUSY breaking sector. The spectrum consists of a light gravitino LSP, behaving as a goldstino, and a number of neutral fermions (the pseudo-goldstini) with a mass between that of the LSP and that of the lightest particle of the observable sector (LOSP). We consider the two situations where the LOSP is either a gaugino-like neutralino or a stau and we assume only one pseudo-goldstino of a mass of O(100) GeV. The coupling of the LOSP to the pseudo-goldstino can be enhanced with respect to those of the gravitino giving rise to characteristic signatures. We show that the decay modes of the LOSP into a SM particle and a pseudo-goldstino can be significant. For both LOSP scenarios we analyze (pseudo)-goldstini production at colliders. Compared to standard gauge mediation the final state spectrum is softer and more structured.Comment: v2: analysis of the stau LOSP scenario added, sections rearranged, and Introduction and Conclusions rewritten to include the added scenario. Version to appear in JHE

Identifying source regions for airborne particles in East Antarctica, Dronning Maud Land, using backward trajectory modelling

Atmospheric composition plays an important role in present and near-future climate change. Airborne particles can serve as cloud condensation and ice nuclei and have therefore a strong influence on cloud formation and thus also on precipitation. This is in particular of interest in Antarctica, since precipitation is the only source of mass gain to the Antarctic ice sheet, which is expected to become the dominant contributor to global sea level rise in the 21st century. A detailed insight into the transport pathways and distribution of airborne particles is therefore essential. At the Belgian Antarctic research station Princess Elisabeth in Dronning Maud Land, East Antarctica, aerosol particles and their characteristics are measured. Atmospheric particles have been collected on filters during the last three austral summers for organic and inorganic chemical analysis by high-volume sampling. In addition, the atmospheric particle number concentration, size distribution and optical particle properties have been measured since 2010. The geographical source regions of airborne particles in Dronning Maud Land remain however to a large extent unknown. In this work, we investigate the climatology of the particle properties with respect to their source regions. To that end, we use the FLEXTRA model to calculate 10-day 3D backward trajectories over the past 10 years. We apply a non-hierarchical cluster method to identify and classify the dominant source regions

Multilepton signals of gauge mediated supersymmetry breaking at the LHC

We investigate multilepton LHC signals arising from electroweak processes involving sleptons. We consider the framework of general gauge mediated supersymmetry breaking, focusing on models where the low mass region of the superpartner spectrum consists of the three generations of charged sleptons and the nearly massless gravitino. We demonstrate how such models can provide an explanation for the anomalous four lepton events recently observed by the CMS Collaboration, while satisfying other existing experimental constraints. The best fit to the CMS data is obtained for a selectron/smuon mass of around 145 GeV and a stau mass of around 90 GeV. These models also give rise to final states with more than four leptons, offering alternative channels in which they can be probed and we estimate the corresponding production rates at the LHC

Sequential sampling of Volatile Organic Compounds (VOCs) and atmospheric oxidation products in the Sor Rondane Mountains, East-Antarctica

Antarctica is considered the most pristine environment on Earth. However, a detailed understanding of present-day atmospheric transport pathways of particles and volatile organic compounds (VOC) from source to deposition in Antarctica and the atmospheric reactions they undergo is essential to document biogeochemical cycles. Atmospheric composition plays an important role in present and near-future climate change. Airborne particles can serve as cloud condensation and ice nuclei and have therefore a strong influence on cloud formation and thus also on precipitation. This is of interest in Antarctica, since precipitation is the only source of mass gain to the Antarctic ice sheet which is expected to become the dominant contributor to global sea level rise in the 21st century. VOCs and their atmospheric oxidation products, secondary organic aerosols (SOA’s) can play an important role in this cloud formation process. However, current knowledge on VOCs and on the interaction between clouds, precipitation and aerosols in the Antarctic is still limited, both from direct observations and from regional climate models. VOCs are traditionally sampled using axial thermal desorption sampling tubes containing a sorbent such as Tenax TA in a passive or active (pumped) fashion. While with passive sampling it is possible to sample over longer periods of time, up to a year in clean air conditions, the temporal information is lost. Because of uncertainties on the sample rate, which is driven by diffusion, obtaining precise air concentrations with passive sampling can be difficult. To sample VOC’s and oxidations products unsupervised and in a remote environment such as Antarctica a new active sequential sorbent tube autosampler was developed and deployed at the atmospheric observatory of the Princess Elisabeth Antarctic research station (71.95° S, 23.35° E, 1390 m asl). The autosampler collected samples from December 2019 to October 2020 and from January 2021 to June 2021. The obtained data is also used to complement and interpret atmospheric aerosol in-situ measurements conducted at the same location. Furthermore, to identify potential source regions, backward trajectory and dispersion modelling using FLEXTRA and FLEXPART will be applied

Exploring the squark flavour structure of the MSSM

We present an extensive study of the MSSM parameter space allowing for general generation mixing in the squark sector. Employing an MCMC algorithm, we establish the parameter ranges which are allowed with respect to various experimental and theoretical constraints. Based on this analysis, we propose benchmark scenarios for future studies. Moreover, we discuss aspects of signatures at the LHC