2024-2025

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Starting in academic year 2013/2014, the research group hosts a regular series of seminars, dedicated to our wide audience that includes physicists, students and engineers. These seminars feature excellent overviews presented by distinguished speakers and provide high value educational material for students . They prove to be the optimal venue for fruitful discussions between external experts and the group members. These seminars organised with the support of the Flemish Government. and UGent Doctoral Schools.

The program for academic year 2024-2025 can be found below:

February 4th, 2025

(11:00, Campus Proeftuin (INW) – N3, seminar room, 1st floor)

Speaker: Nicholas Kamp (Harvard University, USA)

Heavy Neutrinos in Ice, Water, Plastic, and Dirt

From the continuous energy spectrum of beta decay electrons to the disappearance of neutrinos from the Sun and the atmosphere, experimental anomalies have catalyzed progress in neutrino physics since the 1930s. One of the longest-standing anomalies in the neutrino sector is the 4.8𝜎 excess of electron-like events observed by the MiniBooNE experiment at Fermilab. This talk discusses a promising solution for the excess: heavy neutral leptons (HNLs) with a transition magnetic moment coupling to Standard Model neutrinos. We derive phenomenological constraints on these dipole-portal HNLs using data from the plastic scintillator tracking detector of MINERvA and the gaseous argon time projection chambers of ND280. Next, we discuss a novel search for “double cascades” from dipole-portal HNLs at the South-Pole-based IceCube and Mediterranean-Ocean-based KM3NeT observatories. We further examine the sensitivity of these neutrino telescopes to the minimal heavy neutral leptons that appear in Type I Seesaw models of neutrino mass. Finally, we introduce two new experimental concepts that take advantage of natural environment surrounding the Large Hadron Collider (LHC) to collect large samples of collider-generated neutrinos: SINE, which observes neutrino interactions in bedrock, and UNDINE, which observes neutrino interactions in Lake Geneva. Due to the high energy scale of LHC-generated neutrinos, these experiments can perform novel searches for minimal HNLs and constrain the forward production of charmed hadrons in proton-proton collisions. The latter of these has important implications for investigations into the origin of cosmic neutrinos at IceCube, KM3NeT, and beyond.

December 6th, 2024

(11:00, Campus Proeftuin (INW) – N3, lecture room, 2nd floor)

Speaker: Alessandro Vicini (Università degli Studi di Milano, Milan, Italy)

Precision electroweak physics at the LHC

The large amount of high-quality data collected at the LHC will bring the experimental error of several observables at the per mille level, also in the TeV mass range. The combination of this information, together with the precision studies of W and Z bosons properties, will allow a very severe test of the Standard Model. I will illustrate recent results about the determination of the W boson mass, of the weak mixing angle and about the study of the large mass tails of the Drell-Yan distributions, with the associated theoretical challenges.

December 3th, 2024

(11:00, Campus Proeftuin (INW) – N3, Room 2.01)

Speaker: Uddeepta Deka (ICTS Bangalore, India)

Microlensing of gravitational waves: prospects and challenges

Gravitational lensing of gravitational waves (GWs) offers a compelling opportunity to investigate the spacetime geometry in the vicinity of the lens. In this talk, we look into the effects of lensing-induced diffraction modulations in the GW signal and the prospects of constraining the lens parameters. Parameter inference of the lensed waveforms requires the template generation for these modulated signals to be computationally expeditious. We introduce a method founded on a ‘greedy algorithm’ for rapidly generating microlensed GW signals, tailored to astrophysically relevant lens models.

November 13th, 2024

(11:00, Campus Proeftuin (INW) – N3, Room 2.01)

Speaker:  Santiago Casas (RWTH Aachen University, Germany).

Towards a robust exploration of the Dark Sector with Euclid and Stage-IV surveys

The next generation of galaxy surveys—Euclid, LSST, DESI, Nancy Roman, SKAO—will deliver unprecedented precision in mapping the large-scale structure (LSS) of the Universe. These datasets will probe the expansion rate, non-linear structure growth, and the cosmic matter-energy budget, providing new insights into Dark Matter, Dark Energy, and persistent tensions in parameters like H0 and S8. Modified Gravity models, including f(R) and scalar field theories, will be rigorously tested, and next-generation galaxy surveys, in combination with current and upcoming CMB experiments, will reveal details about the composition of cosmic components and primordial fluctuations. Cross-correlations, such as those between optical and radio cosmology via 21cm intensity mapping, will enhance these efforts, providing better constraints but also creating new challenges in the modeling of systematics. Achieving robust results in the study of the Dark Sector requires addressing degeneracies such as massive neutrinos and baryonic feedback. I will discuss how the Euclid collaboration is integrating these factors into its photometric and spectroscopic likelihoods, using both machine learning methods like emulators and semi-analytic models like effective field theory of LSS to perform detailed forecasts for upcoming data analyses. I will also discuss ongoing work in provable computations and differentiable programming, which can improve the robustness and efficiency of our analysis.

October 29th, 2024

(11:00, Campus Proeftuin (INW) – N3, Room 2.01)

Speaker:  Laurids Jeppe (DESY, Germany).

Searching for new scalars, pseudoscalars and tt̅ bound states at CMS

I will present a search for heavy pseudoscalar or scalar bosons decaying to a top quark pair (tt̅) in final states with one or two charged leptons, using 138/fb of proton-proton collisions at √s = 13 TeV recorded by the CMS experiment. The invariant mass of the reconstructed $t\bar{t}$ system and variables sensitive to its spin state are used to discriminate against the standard model tt̅ background and to infer spin quantum numbers. An excess of the data above the background prediction, as modeled using perturbative quantum chromodynamics (QCD) only, is observed with a significance of above five standard deviations. I will discuss three possible hypotheses to interpret the excess, which is located close to the tt̅ production threshold: by production of an additional scalar or pseudoscalar boson, or by the existence of a color singlet pseudoscalar tt̅ bound state, as predicted in a simplified model of nonrelativistic QCD. For the first two hypotheses, I will outline upper limits on the coupling of pseudoscalar or scalar bosons to top quarks in a mass range of 365–1000 GeV and relative widths of 0.5–25%. For the third scenario, I will present and discuss an extracted cross section of 7.1 pb with an uncertainty of 11%.