Precision Tests of the Standard Model and Low Energy Hadronic Interactions

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Search for physics beyond the Standard Model (BSM) has three major directions: energy, cosmic and precision frontiers. I am interested in the precision frontier driven by the indirect searches, where new particles could impact observables such as scattering cross section or asymmetry causing small deviations from original Standard Model (SM) predictions, and there are several upcoming new-generation, ultra-precise measurements with intense particle beams which could detect such small effect. One of such experiments, MOLLER, studying parity-violating Møller scattering, would allow a determination of the weak mixing angle with an uncertainty of 0.1%, an improvement of a factor of five in fractional precision compared with the previous E-158 measurement. At such precision, any inconsistency with the SM could signal BSM physics. Such precision will require a matching theoretical uncertainty, which can be achieved only by including electroweak calculations up to the two-loop order. We plan to construct Two-Loop Electroweak Computational Model (2L-ECM) for the particles of the Standard Model and calculate the full set of two-loop contributions to the Parity Violating (PV) asymmetry for electron-electron scattering required by the MOLLER experiment. Later, 2L-ECM should be extended to the broad spectrum of processes involving particles of SM. The next stage would be including the various hypothetical BSM particles up to one-loop level, and studying their impact on the electroweak observables. ******The second direction of my research program is in the Chiral Perturbation Theory (ChPT), which has been tremendously successful in describing low-energy hadronic properties in the non-perturbative regime of QCD. Some of the major goals of the low-energy QCD are the study of hadronic form factors, which reflect the static structure, and the investigation of the dynamical hadronic response to the external electromagnetic field via electric and magnetic polarizabilities. To study the dependence of the electric and magnetic polarizabilities on the photon energy, we used the relativistic ChPT while applying the multipole expansion approach for the Compton structure functions. Previously, we have developed the Computational Hadronic Model (CHM) based on relativistic ChPT, which operates up to one-loop expansion. The advantage of this model is that it allows avoiding various approximations in the calculations and retaining all the possible degrees of freedom arising from the SU(3) chiral Lagrangian. The next logical step would be to upgrade the CHM to two-loops. Based on the work from 2L-ECM, we plan to develop the Two-Loop Computational Hadronic Models (2L-CHM), which would allow us to extend our understanding of both static (formfactors) and dynamic (polarizabilities) structure of hadrons.**