Theory Day March

Friday 22 Mar 2024, 10:00 → 17:00 Europe/Amsterdam

HG 00.071 (Radboud University Nijmegen)

10:30 → 11:15 The impact of CP-violating phases on DM observables in the complex pMSSM

Electric dipole moment measurements are powerful probes to search for new sources of CP violation beyond the SM, with current limits placing stringent bounds on the size of non-excluded phases. Simultaneously, the lack of any signal from dark matter searches has reduced the allowed size of the parameter space of the MSSM significantly. In this talk I will discuss the interplay between DM observables and the electron electric dipole moment in the complex pMSSM.

Speaker: Jochem Kip (RU)

11:15 → 12:00 Axion Clumps Meeting Neutron Stars

Axions are intriguing candidates for dark matter. Depending on the formation mechanism of axion dark matter, the axion field may exhibit large density fluctuations on small scales. These density fluctuations lead to the formation of self-gravitating clumps of axions, known as miniclusters and axion stars. In this talk, I will discuss these clumps, what is, and what is not, known about them, and how to, perhaps, find them. In one of the classical axion dark matter scenarios (where the Peccei-Quinn symmetry is broken after the end of inflation), most of the axion dark matter may be bound in such axion clumps. On the one hand, this makes "direct detection" type searches for axions such as ADMX more difficult, since the ambient axion density might be much lower than the usual ~0.3 GeV/cm^3 expectation. On the other hand, such axion clumps might offer new exciting possibilities for "indirect detection" of axions: if such an axion clump encounters a neutron star, the axions could resonantly convert into radiophotons in the neutron star's magnetosphere. The signal would be a narrow spectral line, strongly anisotropic, and lasting a typical time scale of ~1 year for an axion minicluster to ~1 minute for an axion star.

Speaker: Sebastian Baum (RWTH Aachen)

12:00 → 13:00 Lunch

13:00 → 14:00 The Bridge between Quantum Gravity and Black Hole Observations *only for students and postdocs*

The field of Quantum Gravity is in desperate need of
experimental guidance. In this talk I will discuss what observations of
black holes, in particular the ones made by the Event Horizon Telescope,
could potentially tell us about Quantum Gravity. To get to this I will
present descriptions of black hole like objects in higher derivative
theory (and motivate their importance) and show that despite Quantum
Gravity effects being tiny there still might be something we can learn
for this.

Speaker: Jesse Daas (RU)

14:00 → 14:10 Break

14:10 → 14:55 Spin Entanglement Witness for Quantum Gravity in a Laboratory

All observations to date are accurately modelled by quantum field theories and classical general relativity. Although theoretically, quantum gravity is much studied, it has no empirical evidence yet. This makes is gravity quantum?" one of the most important open questions of our time. I have pioneered an ambitious ideaspin entanglement witness for quantum gravity," to test the quantum nature of gravity in a lab with my collaborators. It exploits quantum information ideas and aptly combines a quantum spin with cooling/trapping quantum technologies. It is based on being able to entangle two neutral quantum masses solely by their gravitational interaction while all other interactions are mitigated, e.g. electromagnetic (EM) interactions between the masses. It proves the quantum nature of gravity, as classical gravity cannot mediate quantum correlations (entanglement). The protocol, potentially realizable, requires meeting a rich set of challenges: mitigating the EM interactions and background, creating spatial quantum superpositions for massive objects, and eventually measuring spin correlations to witness the entanglement. We must also protect the quantum superpositions from heating, blackbody radiation, acceleration, seismic and gravity gradient noises.

Speaker: Anupam Mazumdar (RUG)

14:55 → 15:40 Heavy quarks in polarised DIS at the EIC and towards a global extraction of polarized PDFs at NNLO

In this talk, we extend the FONLL general-mass variable-flavour-number scheme to the case of longitudinally polarised DIS structure functions and quantify its impact on projected measurements of inclusive and charm-tagged asymmetries at the Electron-Ion Collider (EIC). We show that the inclusion of these corrections is essential to compute predictions with an accuracy that matches the projected precision of future EIC measurements. Based on such a theoretical framework, I then review recent efforts in performing a global extraction of polarised parton distribution functions (pPDFs) at NNLO accuracy. I will present some preliminary results for the NNPDFpol2.0 release based on the latest machine learning framework and the new theory prediction pipeline.

Speaker: Tanjona Rabemananjara (Nikhef)

15:40 → 16:40 Borrel