Master's Theses on Data Analysis
| Topic: | Search for Displaced Dark Higgs Decays from Dark Photon Higgs Strahlung at Belle II |
| Summary: | Belle II provides an opportunity to probe dark sector scenarios in which a dark photon couples to the Standard Model through kinetic mixing: Most searches concentrate on final states that are either fully visible or fully invisible. In this project you will study a different process in which a dark Higgs boson is emitted together with the dark photon. This mechanism is tied to the mass generation of the dark photon. If the dark Higgs boson is the lightest state in the dark sector, it is expected to have a long lifetime and to decay into Standard Model particles through mixing with the Higgs field. You will learn how to generate simulated samples with Monte Carlo tools and how to perform statistical analyses needed to evaluate the sensitivity of Belle II to this process. More details can be found in . |
| What you will learn: | Python programming, data analysis, statistics |
| Advisor: | Prof. Dr. Torben Ferber and Prof. Dr. Felix Kahlhoefer |
| Contact: | Dr. Giacomo De Pietro (Team Dark Physics) |
| Last change: | 28.11.2025 |
| Topic: | First search for B0 → p anti-n ℓ ν at Belle II |
| Summary: | The persistent disagreement between inclusive and exclusive determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |Vub| limits the possibility to overconstrain the CKM unitarity triangle in efforts to test the Standard Model (SM). A well-established strategy to determine |Vub| is to use measurements of semileptonic B-meson decays with b → uℓν transitions. These relatively abundant decays offer theoretically clean avenues to perform precise measurements of SM parameters, due to the factorization of the leptonic and hadronic final states. However, a major challenge for determinations of |Vub| is suppressing the CKM-favoured B → Xcℓν background, which exhibits a similar experimental signature and is O(100) times more abundant than B → Xuℓν decays. The signal extraction process is further complicated by the known resonant states comprising only a third of the total inclusive branching fraction, while non-resonant contributions of B → Xuℓν remaining poorly understood. For these reasons, the B → Xuℓν modelling uncertainty is hard to quantify and becomes dominant for both inclusive and exclusive studies. Decays involving baryons have remained largely unmeasured and could potentially constitute a sizeable component of the total inclusive B → Xuℓν branching. A first measurement of B0 → p anti-nℓν decays, a mode only accessible at Belle II, would provide much needed input to reduce modelling uncertainties in future B → Xuℓν studies, increase our current understanding of b → uℓν transitions, and shed light on the possible reasons for the infamous inclusive/exclusive puzzle. |
| What you will learn: | Python programming, machine learning, track reconstruction, algorithm optimization |
| Advisor: | Prof. Dr. Torben Ferber |
| Contact: | Dr. Raynette Van Tonder (Team Flavour Physics) |
| Last change: | 28.11.2025 |
| Topic: | Search for dark photons and axionlike particles in single-photon events at Belle II |
| Summary: | Belle II is a world-leading experiment in the search for dark sector candidates in the GeV range, such as dark photons or axion-like particles (ALPs). Invisibly decaying or long-lived dark photons and ALPs give rise to events with a single, monochromatic photon in the event, a unique and very challenging experimental signature. You will join our team our team to work on this search, which is currently focused on on-shell dark photons, with the aim of extending it to so-called off-shell (heavy) dark photons and ALPs. You will learn how to use tools for generating simulated datasets with Monte Carlo techniques and for statistical analysis. |
| What you will learn: | Python programming, data analysis, statistics |
| Advisor: | Prof. Dr. Torben Ferber |
| Contact: | Dr. Giacomo De Pietro (Team Dark Physics) |
| Last change: | 28.11.2025 |
| Topic: | Search for long-lived dark photons decaying into visible final states at Belle II |
| Summary: | Among all the dark sector searches, the Belle II experiment has a unique sensitivity to a weakly coupled dark photon whose decays have a displaced vertex. You will start a new search for long-lived dark photons decaying into a pair of muons, pions, kaons and, more challenging, electrons, with the aim of exploring previously unexplored parameters’ space. You will learn how to characterise the detector performance for the reconstruction of displaced vertices and use tools for statistical analysis. |
| What you will learn: | Python programming, data analysis, statistics |
| Advisor: | Prof. Dr. Torben Ferber |
| Contact: | Dr. Giacomo De Pietro (Team Dark Physics) |
| Last change: | 28.11.2025 |
| Topic: | Search for B+→l nu gamma at Belle II |
| Summary: | The radiative leptonic decay B+ -> l+nu gamma yields important information for the theoretical predictions of non-leptonic B meson decays into light-meson pairs. The emission of the photon probes the first inverse moment λ_B of the light-cone distribution amplitude (LCDA) of the B meson. This parameter is a vital input to QCD factorisation schemes for the non-perturbative calculation of non-leptonic B meson decays. This project aims to observe the B+→l+nu gamma decay for the first time and set an improved limit on λ_B using modern machine learning analysis techniques. |
| What you will learn: | python programming, data analysis |
| Advisor: | Prof. Dr. Torben Ferber |
| Contact: | Dr. Pablo Goldenzweig |
| Last change: | 28.11.2025 |
| Topic: | Search for Bs→φπ0 decays at Belle |
| Summary: | The Belle experiment, which concluded in 2011, collected a unique sample of Υ(5S) decays to Bs meson pairs in the clean e+e- collision environment. This dataset has yet to be fully exploited. The rare decay Bs→φπ0 is strongly suppressed in the Standard Model and has yet to be observed. However, in a theoretical analysis motivated by the Kπ CP-puzzle, models with modified or additional Z bosons allow for an increase of the branching fraction by an order of magnitude without inconsistencies with other measurements. The Kπ CP-puzzle consists of an unexpectedly large direct CP asymmetry in the decays B± → K±π0 and B0 → K±π∓. These decays are dominated by isospin-conserving processes, but have a small contribution from isospin-violating penguin processes as well. In the isospin-violating decay Bs→φπ0 the penguin processes dominate, which means that potential NP contributions can have a much larger relative effect. If these contributions exist, an observation of the Bs→φπ0 decay may be possible with the Belle Υ(5S) dataset. |
| What you will learn: | python programming, data analysis |
| Advisor: | Prof. Dr. Torben Ferber |
| Contact: | Dr. Pablo Goldenzweig (Team Flavour Physics) |
| Last change: | 28.11.2025 |
| Topic: | Bs→K+ l- nu with Y(5S) using machine learning-based Full Event Interpretation |
| Summary: | There are two conceptually different methods to determine the CKM matrix element Vub, a factor in the amplitude of transitions from a b-quark to a u-quark and a W boson. As quarks cannot be detected directly, one has to handle the hadronisation to infer Vub, even in the simplest case, where the W boson decays into a charged lepton and a neutrino. One method, which is easier to calculate but is experimentally more challenging, takes into account all possible final states that typically occur during the hadronisation process (inclusive measurement). The other involves calculating the hadronisation effects and searching for only a single final state, e.g., B0->pi-l+nu (exclusive measurement). Both approaches have been pursued and the result is a tantalizing 3sigma discrepancy between the measurements of the same quantity Vub. By measuring Bs->K-l+nu we can shed light on the possible reasons or sources for this, as we replace the spectator d quark in B0->pi-l+nu with an s quark. Since the calculation of the hadronisation in the exclusive measurement relies on Lattice QCD, the kaon in the final state simplifies the calculation significantly. A result close to the existing exclusive measurement would strengthen the trust in that measurement and could hint to new particles beyond the Standard Model. A result closer to the inclusive measurement would more likely be interpreted as a hint that the calculations for the exclusive measurement are unreliable and that the inclusive measurement gives the real value of Vub. This will constitute a first measurement of the rare Bs→K-l+nu decay by employing a modern machine learning-based algorithm to reconstruct the full Y(5S) event for the first time. |
| What you will learn: | machine learning, python programming, data analysis |
| Advisor: | Prof. Dr. Torben Ferber |
| Contact: | Dr. Pablo Goldenzweig (Team Flavour Physics) |
| Last change: | 28.11.2025 |
| Topic: | Search for Beyond the Standard Model (BSM) Higgs Bosons |
| Summary: |
We perform a search for additional Higgs bosons in the next-to-minimal supersymmetric standard model (NMSSM). In the signal process, a standard model (SM) Higgs boson (H) and a BSM Higgs boson Y are produced in the decay of a heavy particle X (X → YH).
We are performing this search in a final state, where one of the Higgs bosons decays into two τ-leptons and the other one into two bottom quarks.
With your thesis, you can contribute to the ongoing research based on the LHC Run-2 and Run-3 data, recorded with the CMS Detector in the years 2016--2025.
During your thesis, you can work on particular aspects of the analysis, a few example are:
|
| What you will learn: | BSM Higgs physics, data analysis, python programming, C++ programming, machine learning |
| Advisor: | Prof. Markus Klute, Priv. Doz. Dr. Roger Wolf |
| Contact: | Dr. Nikita Shadskiy, Moritz Molch |
| Last change: | 19.12.2025 |
| Topic: | Measurement of the Higgs self-coupling |
| Summary: | A measurement of the Higgs boson self-coupling and thus of the explicit form of the Higgs potential forms the next major scientific goal in the physics program of the CERN LHC. Experimental prerequisite to this is the observation of Higgs boson pair production in an event. A first evidence of this process may be already in reach based on the combined data of the LHC Run-2 and Run-3 running periods, spanning the years 2016--2025. This dataset forms the largest amount of high-quality data that has ever been collected and coherently analysed at a hadron collider. We are currently preparing a search for non-resonant Higgs boson pair production in bbττ final states, one of the most interesting final states for such a search, where one Higgs boson decays into τ-leptons and the other one into b-quarks. You have the chance to make essential contributions to this search. |
| What you will learn: | Higgs physics, data analysis, python programming, C++ programming, machine learning |
| Advisor: | Prof. Markus Klute, Priv. Doz. Dr. Roger Wolf |
| Contact: | Jan Voss |
| Last change: | 19.12.2025 |
| Topic: | Differential (STXS) cross section measurement of single Higgs boson production |
| Summary: | A differential measurement of single Higgs boson production in the ττ lepton final state based on the Simplified Template Cross Section (STXS) scheme provides a partitioning of the Higgs boson phase space that minimizes theoretical uncertainties. The resulting measurements allow for precise comparisons between experimental results and Standard Model (SM) predictions while being sensitive to potential deviations from the SM arising from new physics effects. Working on this topic, you can contribute to the analyses performed using LHC Run-2 data and extend them to the new Run-3 data-taking periods. You will gain hands-on experience with particle physics precision measurements, including state-of-the-art background estimation techniques, a sophisticated treatment of systematic uncertainties, and the practical use of machine learning techniques. |
| What you will learn: | Higgs physics, data analysis, python programming, C++ programming, machine learning |
| Advisor: | Prof. Markus Klute, Priv. Doz. Dr. Roger Wolf |
| Contact: | Artur Monsch, Sofia Giappichini |
| Last change: | 19.12.2025 |
| Topic: | Development of the τ-embedding in real CMS data |
| Summary: | The τ-embedding method is an approach to estimate the background, e.g., of Z → ττ events for H → ττ analyses at CMS, from data. The method has been invented by KIT students in 2011. Since then it has been continuously supported and developed. As a student working on this topic, you will get deep insights to the software framework used to record, reconstruct, and analyze the enormous amount of data collected by the CMS experiment. You will learn about the whole data processing chain of one of the largest experiments world-wide, from the taken data through the reconstruction up to visualizing the data. As the CMS software framework (CMSSW) itself is written in C++ and python, basic knowledge of writing code with these languages is required. |
| What you will learn: | data processing, data analysis, python programming, C++ programming, Monte Carlo simulation |
| Advisor: | Priv. Doz. Dr. Roger Wolf, Prof. Günter Quast |
| Contact: | Christian Winter |
| Last change: | 19.12.2025 |
| Topic: | Measurement of the WH charge asymmetry |
| Summary: | The production of a Higgs boson in association with a W boson is sensitive to the coupling of the Higgs boson to light quarks. Anomalous couplings may influence the abundance of positive over negative W bosons, in addition to the asymmetry implied by the structure functions of the proton. We are analyzing CMS data to target such measurements, focusing on the Higgs boson decay to W boson pairs. The analysis is set up and under review in CMS. We plan to conclude it, and then to combine it with the same analysis targeting the Higgs boson decay to a pair of tau leptons, also developed at KIT. |
| What you will learn: | Higgs physics, statistical analysis, data analysis, Python programming, C++ programming, ROOT |
| Advisor: | Prof. Markus Klute, Priv. Doz. Dr. Roger Wolf |
| Contact: | Dr. Nicolò Trevisani |
| Last change: | 19.12.2025 |