Dmytriiev M. Description of heavy wide resonances signals by the means of effective Lagrangians.

Українська версія

Thesis for the degree of Doctor of Philosophy (PhD)

State registration number

0824U002666

Applicant for

Specialization

  • 104 - Фізика та астрономія

Specialized Academic Board

ДФ 08.051.105 ID 6548 Дмитрієв М.С.

Oles Honchar Dnipro National University

Essay

Within the framework of the generalized Yukawa model we have shown that there exist new physics scenarios, where direct searches for new states of matter are inapplicable. This is so if resonances of the latter are wide. It was found out that wide resonances emerge if new physics particles are heavy or if their couplings are big. Signals of some wide resonances could not be described with the narrow width approximation. Hence, correct estimation of a new resonance width is essential for experimental searches of new physics. Indirect search methods should be applied for signals of wide resonances. There also exist scenarios within the considered Yukawa model where interference between known and new resonances is significant with respect to a new resonance contribution in a scattering process cross-section. One could not apply direct searches for new particles in such scenarios. In particular, this takes place if total energy of a reaction initial state is much less than a new particle mass. In this case its low-energy signal could be described with a low-energy effective Lagrangian (EL). Many collaborations across the world apply ELs to describe signals of new heavy particles. We have investigated applicability of a low-energy EL within the framework of generalized Yukawa model. The latter consists of light and heavy scalar fields and two light fermions. It was found out that the low-energy EL is applicable for scattering processes description if radiative corrections to the heavy boson mass are small and one-loop mixing of light and heavy scalars is negligible at low energies. It is so if Yukawa couplings of the model are small. In the other scenarios the low-energy EL is inapplicable for scattering processes description. Thus, magnitude of loop corrections coming from light sector of an extended model should be estimated when EL of the model is considered in experimental data analysis. Taking into account these results, we have researched heavy states decoupling scenarios in a realistic new physics model, which is the two-Higgs-doublet model (2HDM). We derived the low-energy EL for the 2HDM with small CP violation. There are five scalar resonances in this model, and one of them corresponds to the field h of mass 125 GeV, discovered at the LHC. The other resonances in this scenario are much heavier than h, so they have not been observed experimentally, yet. The EL of the 2HDM derived in this thesis describes the limit in this scenario when heavy scalars decouple. It was found out that the potential of the scalar field h in this Lagrangian does not match corresponding potential in the SM with one Higgs doublet. Besides, unlike the SM, in the considered model h is not an eigenstate of CP transformation even when heavy 2HDM scalars decouple. CP-violation existence in the scalar sector could be tested if one measures width of h decay into CP-odd states. This width depends on the parameters which govern magnitude of CP-violation in the 2HDM. Besides, the derived EL contains vertexes which contribute to the cross-section of h pairs production. According to the SM, this process is quite rare at the LHC, so its cross-section value is sensitive to the couplings of contributing EL vertexes. Hence, one could derive constraints on the EL effective couplings and parameters of the 2HDM from the experimentally measured value of this cross-section. Applicability of the one-Higgs-doublet SM could be tested with the signals described in this paragraph. Magintudes of loop corrections to the heavy bosons masses and one-loop mixing of heavy scalars with the SM states should be estimated when heavy particles decouple. This estimate would limit the applicability range of the 2HDM EL. Constraints on the low-energy signals of the 2HDM heavy scalars described with the EL could be derived from these conditions. Thus, such analysis is essential to identify the experimental scenario which is optimal for the heavy 2HDM scalars searches on the modern accelerators. Discovery of new states beyond the Standard model could dramatically advance our understanding of the matter properties and the Universe evolution. Hence, conclusions of this research are actual and important in the context of modern physics.

Research papers

Dmytriiev M., & Skalozub V. (2023). One-loop correction contributions in the decoupling limit of generalized Yukawa model. Journal of Physics and Electronics, 31 (2), 3-20. doi:10.15421/332314

Skalozub V., & Dmytriiev M. (2021). On direct search for dark matter in scattering processes within Yukawa model. Ukrainian Journal of Physics, 66 (11), 936- 944. doi:10.15407/ujpe66.11.936

Dmytriiev M., & Skalozub V. (2021). Low-energy effective Lagrangian of the two-Higgs-doublet model. Journal of Physics and Electronics, 29 (2), 8-20. doi:10.15421/332118

Dmytriiev M., & Skalozub V. Dark matter wide resonances in the generalized yukawa model, V All-Ukrainian scientific and practical conference "ПЕРСПЕКТИВНІ НАПРЯМКИ СУЧАСНОЇ ЕЛЕКТРОНІКИ, ІНФОРМАЦІЙНИХ І КОМП’ЮТЕРНИХ СИСТЕМ" MEICS-2020, p. 206-207, November 25-27, 2020, Dnipro, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. Dark Matter Polarization Operator in the Generalized Yukawa Model, XI Conference of Young Scientists "Problems of Theoretical Physics", p. 41-42, December 21-23, 2020, Kyiv, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. Effective Lagrangian in the generalized Yukawa model, XXIII International youth scientific and practical conference "Human and space", p. 26, April 14-16, 2021, Dnipro, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. Low-energy effective Lagrangian of the two-Higgs-doublet model., VI All-Ukrainian scientific and practical conference "ПЕРСПЕКТИВНІ НАПРЯМКИ СУЧАСНОЇ ЕЛЕКТРОНІКИ, ІНФОРМАЦІЙНИХ І КОМП’ЮТЕРНИХ СИСТЕМ" MEICS-2021, p. 172, November 24-26, 2021, Dnipro, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. Low-energy effective Lagrangian of the two-Higgsdoublet model with the CP-violation. XXIV International youth scientific and practical conference "Human and space", p. 18, May 25-27, 2022, Dnipro, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. Observable effects of heavy decoupled scalar bosons within the generalized Yukawa's model. XXV International youth scientific and practical conference "Human and space”, p. 20, April 12-14, 2023, Dnipro, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. One-loop correction contributions in the decoupling limit of generalized Yukawa model. VIII All-Ukrainian scientific and practical conference "ПЕРСПЕКТИВНІ НАПРЯМКИ СУЧАСНОЇ ЕЛЕКТРОНІКИ, ІНФОРМАЦІЙНИХ І КОМП’ЮТЕРНИХ СИСТЕМ" MEICS-2023, p. 241-242, November 22-24, 2023, Dnipro, Ukraine. Форма участі: очна.

Dmytriiev M., & Skalozub V. Contribution of one-loop corrections in the decoupling limit of generalized Yukawa model. XIV Conference of young scientists "Problems of theoretical physics", p. 20-21, January 16-18, 2024, Kyiv, Ukraine. Форма участі: очна.

Similar theses

Buy Me A Coffee
Thank you for your visit! If the resource turned out to be useful for you - you can buy us a coffee ;)