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Proposals for Master or PhD thesis at LPTHE
Internship/PhD in theoretical high energy physics
Advisors: Silvia Manconi (Junior Professor joining December 2024) and Marco Cirelli
About 85% of the matter in the Universe is in the form of an unknown substance dubbed Dark Matter (DM). While some of its general properties are known, its actual nature is still undetermined. The most popular hypothesis is that it consists of a new, yet-to-be-discovered elementary particle. One of the possible strategies to investigate it is via the so-called Indirect Detection (ID): studying the possible excesses in charged cosmic rays and photons at different energies that could produced by the annihilations (or decays) of DM particles in the DM halo of our Galaxy or in extragalactic objects, and comparing them with the theoretical predictions from particle physics models.
Within this broad context, the proposed Master 2 internship (and the possible ensuing PhD project) will proceed in different directions: X-rays, TeV gamma rays, antimatter, velocity-dependent annihilations, primordial black holes constraints, synchrotron bounds, purely gravitational effects... (to be decided according to the interests and the opportunities).
Following the typical course, after the Master 2 internship lasting a few months during Spring 2025 and subject to mutual agreement, the student can then apply for a PhD fellowship (from EDPIF or from other sources) and, if successful, start the PhD in Fall 2025, for a duration of 3 years.
Application procedure: Candidates should send by email to applications.astroparticle.lpthe_AT_gmail.com:
i. their CV,
ii. a transcript of their academic records,
iii. a short description of their interests (optional, and in any case no
longer than 1 page).
iv. They should also arrange for 1 or 2 short letters of recommendation to be sent to the same address, by scientists familiar with their studies and academic record.
Applications are preferred within December 31st, 2024, but will be considered afterwards if the position is not filled. Short-listed candidates will be invited for a meeting, either in person or remotely.
Internship/PhD: Generic Phenomenology at the LHC and beyond
Advisor: Mark Goodsell
Following the discovery of the Higgs boson there was a fear in the high-energy physics community that no new indications as to the nature of physics beyond the Standard Model may be seen at current high-energy physics experiments, since new colourful particles were not immediately seen at the Large Hadron Collider (LHC). On the theory side, this has cooled optimism that supersymmetric particles would be seen, and there is therefore no clear indication as to what models are most promising from both a theoretical and experimental point of view. It is time to look for new solutions to the problems of the Standard Model and try to understand them based not only on the available data but also constraints from top-down consistency conditions of the underlying theory. As a consequence, it is not sensible to focus all effort on studying just the phenomenology of one model (which might have constituted a thesis' work in the past). Instead, theoreticians' efforts are focussed on two main (quasi) model-agnostic strategies.
The first is to construct effective field theories to describe deviations, either using only the degrees of freedom of the Standard Model itself and extending with effective operators (the SMEFT), or to construct effective theories of new particle interactions which parametrise their interactions in the most general way possible; it is in particular becoming increasingly useful to construct dark matter effective field theories and axion-like particle effective field theories.
There is also a direction of research, where I play a central role, of generic phenomenology, which aims to perform calculations for all models in a given class and create symbolic tools to automate the study of any particular model as much as possible. In this way, complete and realistic models (rather than effective field theories or simplified models) can be written down and explored in all detail automatically. This has advanced to the state that most models beyond the Standard Model can be studied with a comparable accuracy (in terms of the prediction for any given observable) to the best computations in the literature for any example except for the Standard Model (and equal accuracy to the Standard Model is available in some cases).
Recently, I (with collaborators at the LPTHE) identified four excesses in different LHC searches and showed that they could all be related to the same types of model. Part of my current research aims to pin down the best explanation for these excesses and make projections or proposals for future searches.
I propose an internship leading (hopefully) to a PhD thesis on a subject in one of these directions, with the precise project to be determined based on the student's interests: for the internship, this could be working on reinterpreting LHC analyses in the context of the above excesses, model building for the excesses, working on unitarity calculations, precision computations, theoretical developments for matching BSM theories onto effective theories, ...
For more information, see my personal website or contact me!
Master project : Application of Witten anomalies to Sp(2N) gauge
theories
Advisor: Giacomo Cacciapaglia
Anomalies are essential features of gauge theories with massless fermions, as their presence deems certain models inconsistent. Chiral anomalies apply to theories with complex fermion representations. Instead, theories with pseudo-real representations need to satisfy the absence of Witten anomalies [1,2]. The conditions have been explicitly computed for SU(2) gauge theories with a singe fermion representation. The aim of the project is to understand the Witten anomalies and extend the conditions for their absence to Sp(2N) gauge theories with general representations. As a second step, anomaly cancellation rules among di erent representations of SU(2) and Sp(2N) will be derived. Such conditions will lead to the de nition of a new class of consistent gauge theories with chiral fermions.
The master project may be followed by a PhD thesis based on the identification and study of grand unified theories in five dimensions [3], and in four dimensions with extended gauge sectors at low energies. As an example of the latter, we will consider models leading to a composite Higgs sector [4].
[1] E. Witten, "An SU(2) Anomaly", Phys.Lett.B 117 (1982), 324-328, DOI: 10.1016/0370-2693(82)90728-6
[2] J. Wang X-G. Wen, E. Witten, "A New SU(2) Anomaly", J.Math.Phys. 60 (2019) 5, 052301, DOI: 10.1063/1.5082852
[3] G. Cacciapaglia, "Systematic classification of aGUT models in five dimensions: the SU(N) kinship", JHEP 12 (2023), 162, DOI: 10.1007/JHEP12(2023)162 [4] G. Cacciapaglia, S. Vatani, C. Zhang, "Composite Higgs Meets Planck Scale: Partial Compositeness from Partial Unification ", Phys.Lett.B 815 (2021), 136177, DOI: 10.1016/j.physletb.2021.136177
