Open Thesis Topics

Investigating the polarization of vector bosons (VB) in VB production processes provides tests for the Standard Model's gauge symmetry structure and the concrete mechanism of electroweak symmetry breaking, as well as sensitivity to new physics. As one of the VB production processes with a very clean signature due to four charged leptons in the final state, the ZZ electroweak production process is very interesting for this purpose. Some literature studies on this process already exist. Since recently, the Monte-Carlo-Eventgenerator Sherpa is able to simulate polarized cross section of vector boson production. The goal of this thesis is to test this new feature with this process. Furthermore, aspects of this process not yet studied, such as the contribution of particle showers, can be investigated.

Investigating the polarization of vector bosons (VB) in VB production processes provides tests for the Standard Model's gauge symmetry structure and the concrete mechanism of electroweak symmetry breaking, as well as sensitivity to new physics. The ATLAS VB polarisation analysis is currently trying to measure the contribution of longitudinally-polarised W-bosons in the scattering of two same-charged W-bosons. To enhance the measurement’s sensitivity, artificial neural networks (ANNs) are used to separate the different VB polarisation components. At the moment, the Monte-Carlo simulations used to train the ANNs are based on the matrix element generator MadGraph.

Since recently, the event generator Sherpa is also able to simulate polarized cross sections of VB production processes. In preparation for its application in the ATLAS VB polarisation analysis, a first proof of concept study has been performed to investigate different methods to train ANNs to separate the VB polarisations. However, these investigations are so far based on “truth-level” simulations, i.e. without the inclusion of detector effects. In addition to extending the existing study to more complex training procedures, the goal of this Bachelor thesis is to apply the collected knowledge to “reconstruction-level” samples that include the effects of the detector simulation and object reconstruction. This allows a direct comparison of the expected measurement sensitivity when using ANNs trained on MadGraph vs. Sherpa-samples.

Triboson production V(->ll)V(->ll)V(->qq) is a component of the signal definition in vector boson scattering, but is sometimes ignored or generated as a separate process. This thesis should study the impact of the triboson component. In particular the effect of dim-8 EFT operators in the quartic vertex should be studied to quantify the effect of ignoring the triboson production in an EFT study.

In the Standard Model Effective Field Theory expansion operators of dim-6 can affect triple gauge couplings. Typically in VBS analysis dim-6 operators are not considered for EFT interpretations as they are better constrained on inclusive diboson analysis. Nevertheless, on the electroweak production of WZjj, diagrams with triple coupling play a role. In this thesis, we would like to quantify the possible effect of the dimension-6 operators when they are evaluated at their best limit value in the WZjj phase space. We will study as well the sensitivity of the WZjj to set limits on dim-6 operators by performing a fit to the data in this region only.

For the WZ fully leptonic resonant search the invariant mass distribution is used to look for a bump. Nevertheless in order to build the invariant mass using detector level information some assumptions are needed. One particularly important assumption we made is the W bosón is on-shell to be able to resolve the issue of the missing neutrino information. In this thesis, we would like to have a study of the impact of this assumption on the resonant mass reconstruction by comparing the detector reconstructed mass and the truth simulated mass.

The simulation of different polarisation states allows us to study effects from physics beyond the Standard Model in more detail. In this project we want to study, how effective-field-theory extensions of the Standard Model will affect different polarisations of W and Z bosons in WZ pair production at the LHC.

The simulation of different polarisation states allows us to study effects from physics beyond the Standard Model in more detail. In this project we want to study, how effective-field-theory extensions of the Standard Model will affect different polarisations of W bosons in W±W± pair production at the LHC.

The complexity of matrix element calculations for final states with a high multiplicity is so high, that their computational cost often limits theory simulations for the LHC. In this project we want to extend a machine learning based approach to simplify these calculations by approximating the matrix elements. The goal is to study various parameters for the architecture and training of deep neural networks in this approach.

For Heavy Ion collisions the Sherpa simulation program has to be able to simulate not only collisions from proton beams but also from neutron beams. This can be done by using some of the (few) available neutron PDFs or by a simple implementation of the (approximate) strong isospin symmetry, using proton PDFs with a swap of u and d quark densities. In this Bachelor project such a swapping should be implemented and validated against existing neutron PDF sets.

We will study a special effect in the matrix element of W+gamma production, where the differential cross section vanishes due to one specific polarisation combination. To this end we will use the Sherpa simulation program and analyse the simulation in analogy to analyses done with the ATLAS detector.

tbd

In parallel to our analysis of WZ final states at high transverse momentum we want to search for deviations from the Standard Model from new heavy particles decaying into a WZ boson pair.

TODO

The simulation program Sherpa can currently only simulate decay cascades with up to 3 final state particles in each step. For decays of the Higgs boson into 4 fermions via WW or ZZ diagrams it becomes important to simulate the full 1->4 decay. This thesis is about implementing such decays and make phenomenological comparisons to existing calculations.

Tbd

Es soll ein angeleitetes Rollenspiel für Jugendliche entwickelt und erprobt werden, in welchem die Lernenden Aspekte des wissenschaftlichen Erkenntnisprozesses nachvollziehen und reflektieren können. Der wissenschaftliche Kontext sowie die inhaltliche Schwerpunksetzung kann frei gewählt werden. Es kommen u. a. folgende Schwerpunkte in Frage:

• Kreislauf des wissenschaftlichen Arbeitens – Von der Fragestellung bis zur Veröffentlichung
• Unsicherheiten in der Wissenschaft
• Wissenschaftliche Streitkultur
• Der Prozess des Peer Review

Diese Arbeit soll in Kooperation mit der Didaktik der Physik erstellt werden. Der
Kontext des Rollenspiels muss jedoch nicht ausschließlich die Forschung in der Kern- und Teilchenphysik sein.

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Doktorand, wissenschaftlicher Mitarbeiter

Name

Philipp Lindenau

PSE, Lehre MS

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Professur für Didaktik der Physik

Professur für Didaktik der Physik

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Recknagel-Bau, B305 Haeckelstraße 3

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Ziel ist es, die Forschung zum Klimawandel mit der Teilchenphysik durch die Auseinandersetzung mit dem CLOUD-Experiment am CERN (siehe 1 und 2) in einer Unterrichtseinheit zu verknüpfen. Dies hat das Potenzial, die Kreativität, das kritische Denken und das Verständnis für die Natur der Wissenschaft bei den Schüler:innen zu fördern und ihr Verständnis der Teilchenphysik durch deren Anwendung in einem realen Kontext zu vertiefen. Die Unterrichtseinheit soll mit einer kleinen Gruppe von Schüler:innen erprobt werden. Die Arbeit soll in Kooperation mit der Didaktik der Physik erstellt werden.

(1) https://www.home.cern/science/experiments/cloud
(2) https://cerncourier.com/a/cloud-experiment-sharpens-climate-predictions/

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wissenschaftliche Mitarbeiterin

Name

Dr. Farahnaz Sadidi

PSE

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Professur für Didaktik der Physik

Professur für Didaktik der Physik

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Recknagel-Bau, B305 Haeckelstraße 3

01069 Dresden

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Im Netzwerk Teilchenwelt wurde umfangreiches Unterrichtsmaterial zur Teilchenphysik erstellt. Die Erkenntnisse des Standardmodells werden darin mithilfe des Konzepts von Ladungen und Wechselwirkungen beschrieben. Dieser Ansatz, der sich in der populärwissenschaftlichen Literatur und in Schulbüchern bislang kaum widerspiegelt, soll durch geeignete Arbeitsblätter ergänzt werden.

Diese Arbeit soll in Kooperation mit der Didaktik der Physik erstellt werden.

Kontakt:

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Doktorand, wissenschaftlicher Mitarbeiter

Name

Philipp Lindenau

PSE, Lehre MS

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Organization Name

Professur für Didaktik der Physik

Professur für Didaktik der Physik

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Büro:

Recknagel-Bau, B305 Haeckelstraße 3

01069 Dresden

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work Tel.

Mitgestaltung und Weiterentwicklung des ATLAS Open Data Portal am CERN (http://opendata.cern.ch/) mit folgenden Aufgaben zur Auswahl:

• Mitarbeit und Aufbereitung der Dokumentation zum ATLAS Datensatz
• Implementierung neuer Inhalte im Open data Portal (nur für Programmier-Profis)
• Entwicklung neuer Ideen für die Darstellung von Lerninhalten auf dem Open Data Portal

Die Arbeit soll in Kooperation mit der Didaktik der Physik erstellt werden.

Kontakt:

© P.

Doktorand, wissenschaftlicher Mitarbeiter

Name

Philipp Lindenau

PSE, Lehre MS

Send Email

Send encrypted mail via the SecureMail portal (for TUD external users only).

Organization Name

Professur für Didaktik der Physik

Professur für Didaktik der Physik

Address work

Büro:

Recknagel-Bau, B305 Haeckelstraße 3

01069 Dresden

Show map of this location.

work Tel.