Aleksandrs Aleksejevs

According to the Standard Model of particle physics, there are six types of quarks, six types of leptons, and corresponding anti-particles connected by four fundamental interactions. However, the recent evidence coming from neutrino oscillation, dark matter and dark energy, and quantum gravity showed that the 40-year old Standard Model may be incomplete, and that we may be at the threshold of a new theory and "New Physics". One way to look for possible signals of new physics is with high-precision experiments at lower energy, which can provide indirect access to physics at multi-TeV scales and play an important complementary role to the Large Hadron Collider research program. This research requires both experimental and theoretical effort, and the new-generation experiments will need a new degree of precision from theory. 

Our group is working on subatomic physics computations and provide the most precise theoretical input for the high-precision experiments by taking advantage of the new semi-automated symbolic computing methods. Our computational models can be used for a wide range of applications, including next-to-leading and next-to-next-to-leading electroweak radiative corrections for Møller scattering, electron-proton and positron-proton scattering, modeling pion electroproduction and many others. 

Properties of Hadrons in the Effective Field Theories 

The electromagnetic polarizabilities of a particle with a structure characterize the dipole moments induced by the presence of an external electromagnetic field. They therefore constitute fundamental quantities, which represent a measure of the rigidity, stiffness or resistance to deformation of the internal structure of the composite system upon imposition of an external electromagnetic field. One of the ways to study response of the baryons and mesons to an external electromagnetic field is through a Compton scattering. This allows us to extract fundamental response structure functions such as electric and magnetic polarizabilities, and thus obtain information about the baryons and mesons internal degrees of freedom. Values of these polarizabilities are key to understanding of the internal dynamics of baryons and mesons in the external electromagnetic field. For instance, just a sign of magnetic polarizability will define whether mesons have paramagnetic or diamagnetic structure. In this project we developed Computations Hadronic Model, which can be used to provide a detailed study of the polarizabilities of all-lowest in mass baryons and mesons. This model was developed based on Chiral Perturbation Theory.