Geert-Jan Besjes

In this paper, we present a search for an exotic (= jargon for very, very unusual) decay of the Z boson, one of the particles in the Standard Model of particle physics. These are interesting to look for as they are predicted by lots of extensions of the Standard Model, which try to remedy some of its shortcomings by introducing new particle(s) or new ways existing particles could decay. Therefore, an observation of such a decay (or upper limit on how often such decays can occur) can help point… Mehr anzeigen

In this paper, we present a search for an exotic (= jargon for very, very unusual) decay of the Z boson, one of the particles in the Standard Model of particle physics. These are interesting to look for as they are predicted by lots of extensions of the Standard Model, which try to remedy some of its shortcomings by introducing new particle(s) or new ways existing particles could decay. Therefore, an observation of such a decay (or upper limit on how often such decays can occur) can help point the way as to which theories/models could be true, and which not.

We didn't observe any statistically significant deviations from the Standard Model prediction, that is, no exotic decays were seen. As a result, two limits on the possible decay fraction (or branching ratio) of the Z boson into the decays are presented, which are an improvement on the existing ones. Weniger anzeigen

This note describes the algorithms and selections used to trigger on (filter) events with hadronically decaying tau leptons in the ATLAS experiment at CERN's Large Hadron Collider.

First result on searches for particles predicted by supersymmetry from the ATLAS experiment after a two-year machine development hiatus. The almost twice as high collision energy used for the data used in this paper result in a substantial improvement of the results obtained between 2010 and 2012.

This paper summarises all the inclusive searches for squarks and gluinos, particles predicted by supersymmetry, from 2010-2012 with the ATLAS experiment at CERN's Large Hadron Collider. A novel statistical combination of several results is used to improve the results beyond the sum of its parts. My contribution is the development of this combination, as well as the main summary of results in a set of figures.

HistFitter is a software framework for statistical data analysis, used extensively to analyze big datasets originating from proton–proton collisions at the Large Hadron Collider at CERN. Since 2012 HistFitter is the standard statistical tool in searches for new particles predicted by a theory called supersymmetry performed by the ATLAS collaboration.

In my PhD thesis, I present a search for new elementary particles predicted by a theory called supersymmetry (SUSY), which attempts to address shortcomings in our current description of particle physics, the Standard Model. No events incompatible with the Standard Model are observed, however: limits on various models of supersymmetry are obtained. I use the results obtained in this search in fits to a larger supersymmetric model to provide the currently most probably masses of the new… Mehr anzeigen

In my PhD thesis, I present a search for new elementary particles predicted by a theory called supersymmetry (SUSY), which attempts to address shortcomings in our current description of particle physics, the Standard Model. No events incompatible with the Standard Model are observed, however: limits on various models of supersymmetry are obtained. I use the results obtained in this search in fits to a larger supersymmetric model to provide the currently most probably masses of the new particles, and I also combine the results with different analyses to obtain improved limits. In addition, I discuss the prospects for a similar search at the proposed high-luminosity LHC, which will record a dataset 150 times larger than the current one. Finally, I present HistFitter, a software framework written to facilitate statistical analyses and perform searches for new particles. Weniger anzeigen

In this paper, we presented a global fit to all available experimental results to find the most viable parameters of a theory called supersymmetry, which predicts the existence of many new particles but does not predict their properties. These properties are the parameters we sample. The paper is the first to include results from searches at CERN's Large Hadron Collider, and shows that the most likely manifestation of supersymmetry can be discovered or ruled out within the next few years.

In this paper, we present the results of a search for particles predicted by supersymmetry where many jets but no leptons (electrons or muons) are produced. No evidence of supersymmetry was found. The results include some of the world's best limits on several models of supersymmetry. The paper is one of the most-cited results from CERN's Large Hadron Collider (cited 100+ times) from 2010-2014, and often used by theorists to determine the feasibility of other models than the one described in the… Mehr anzeigen

In this paper, we present the results of a search for particles predicted by supersymmetry where many jets but no leptons (electrons or muons) are produced. No evidence of supersymmetry was found. The results include some of the world's best limits on several models of supersymmetry. The paper is one of the most-cited results from CERN's Large Hadron Collider (cited 100+ times) from 2010-2014, and often used by theorists to determine the feasibility of other models than the one described in the paper itself. My focus in this paper was the development of the complex statistical model used to interpret the results. Weniger anzeigen

In this note, we present a feasibility study for searches for heavy particles predicted by supersymmetry at the proposed high-luminosity Large Hadron Collider at CERN. The HL-LHC is a proposed upgrade foreseen for 2025 to increase the potential for discoveries at CERN. It requires additional upgrades of the ATLAS experiment at a cost of approx. $300M. The results of this study feed directly into the design considerations of these upgrades.

A semi-popular scientific article on searches for new particles at CERN's Large Hadron Collider, published in the monthly journal of the Dutch Physical Society. The audience consists of professional physicists in both industry and academia, as well as interested members of the general public.