Seminars are broadcast online at Zoom


Ranjan Laha

Indian Institute of Science, Bangalore


Masayuki Wada

Astrocent, Warsaw


Kodai Sakurai

University of Warsaw

ALP DM and Higgs bosons in a new renormalizable model for light dark sector

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Axion like particle (ALP) is one of the promising candidates of dark matter (DM). It can emerge from the dark sector with global U(1) symmetry. It is often assumed that the dark sector has CP symmetry. On the other hand, however, CP is already violated in the SM by the QCD theta term and quark mixing. The dark sector with CP violation is also an interesting possibility. In this talk, we propose a new renormalizable model for ALP with CP violation in the dark sector. We discuss the properties of the predicted ALP and how the ALP can be probed at ILC. In addition, we discuss quantum effect that affects a system with multi-Higgs states. It is shown that the mixing between two Higgs bosons is highly suppressed by the quantum effect in the regime where the decay rate for the extra Higgs boson is larger than the mass difference between two Higgs bosons.


Chunshan Lin

IInstitute of Theoretical Physics, Jagiellonian University

Sound Speed Resonance: A Novel Mechanism of Matter-Graviton Conversation

The matter-to-graviton conversion and the graviton-to-matter conversion can be realized by the oscillatory sound speed of the graviton and the matter fields respectively. This mechanism is in fact quite general. It can occur in a large class of theories, including the Einstein gravity minimally coupled with the standard model in particle physics, the Horndeski theory, and the theories beyond Horndeski.


Shoaib Munir

ICTP-EAIF, University of Rwanda

Hunting down minimally extended Higgs sectors

Additional Higgs bosons, besides the one that has properties consistent with the 125 GeV scalar discovered at the LHC in 2012, are highly motivated by cosmological observations in particular. Models of new physics therefore typically contain one of more of these, but despite dedicated searches, any new (pseudo)scalars have evaded detection at the LHC thus far. In this talk I will discuss some specific scenarios that are possible in minimal extensions of the Standard Model Higgs sector, but that may not be accessible with the existing general probes. I will make a case for certain non-standard approaches that might help uncover these elusive scenarios at the current and future runs of the LHC.



Dimitrios Karamitros

University of Manchester

Towards a Non-Local S-Matrix Theory

In this talk we will discuss a non-local formulation of the S-matrix. To better understand the significance of the emerging quantum phenomena, we consider a solvable field-theoretic model. Present and future experiments may benefit from such non-local S-matrix construction, as the transition amplitude depends on the distance between the production and detection vertices. This solvable model enables accurate descriptions of detection regions that are either close to or far from the source. In close analogy with light diffraction in classical optics, we call these two regions near-field and far-field zones, or the Fresnel and Fraunhofer regions. We revisit the question whether mixed mediators produce an oscillating pattern if their detection occurs in the Fresnel region. We observe several novel features with respect to its angular dependence which have not been accounted before in the literature. In particular, we obtain a ``quantum obliquity factor'' that suppresses particle propagation in the backwards direction, thereby providing an explicit quantum field-theoretic description for its origin in diffractive optics.