Bound State Theory in QED and QCD: Muonium and Pentaquarks

Problems of the bound state theory in QED and QCD will be addressed in the proposed research. Methods of high precision nonrelativistic quantum electrodynamics of bound states will be developed to calculate high order corrections to hyperfine splitting in muonium. QCD motivated methods will be used to explore properties and nature of the LHCb pentaquarks, in particular the hadrocharmonium and molecular pentaquarks scenarios. The objectives of the proposed research include: • Reduction of the uncertainty of the QED formula for hyperfine splitting in muonium below 10 Hz in order to match the projected accuracy of the MuSEUM experiment currently in progress at J-PARC. • Further development and comparison of the hadrocharmonium and molecular scenarios for pentaquarks with hidden charm. The goal here is to find out which of the models unambiguously explains all experimental data from the LHCb Collaboration, and to obtain predictions of the hadrocharmonium and molecular scenarios (quantum numbers and masses) that differentiate these models. Intellectual Merit. Numerous recoil corrections of order á7(m/M)m and nonrecoil corrections of order á8m to hyperfine splitting in muonium will be calculated. These results together with the forthcoming results from the J-PARC MuSEUM experiment would allow to improve the value of the electron-muon mass ratio extracted from the measurement of the muonium hyperfine splitting. The first test of the weak contribution to the atomic energy level shift (to the hyperfine splitting in muonium) also would become achievable. Further development of the hadrocharmonium and molecular models of pentaquarks with hidden charm is planned in the proposed research. I hope to obtain improved estimates of charmonia and bottomonia polarizabilities, to calculate the central and tensor potentials that are responsible for binding of 1P-states of charmonia with the nucleons in the hadrocharmonium scenario. Partial decay widths of the LHCb pentaquark Pc(4312) will be calculated in the hadrocharmonium and molecular scenarios. Hadrocharmonium and molecular interpretations of Pc(4380) will be considered, partial decay widths of 1P-nucleon bound states will be calculated in order to confirm or disprove the hadrocharmonium interpretation of Pc(4380) as a grid of overlapping 1P-nucleon bound states. Possible existence of pentaquarks with hidden bottom quantum number will be explored in the molecular and hadrocharmonium scenarios. Broader Impact. The proposed research will also have broader impacts, beyond the field of the theoretical atomic physics and low energy QCD. I expect that the proposed research will play an important role in obtaining more precise value of the electron-muon mass ratio. Our theoretical results will allow for the first time detect weak interaction contribution to the energy shift of atomic energy levels. Like my earlier results new contributions to hyperfine splitting in muonium will be used in the new CODATA adjustment of the fundamental physical constants. The results of the research on pentaquarks will be cross-disciplinary and will contribute to the fields of nuclear and particle physics. Both graduate and undergraduate students will participate in this research and besides learning physics will acquire computer and problem solving skills. Students will make presentations at the APS meetings. Research activity of graduate students is expected to lead to two PhD theses. This project will promote development of international collaboration, an active participation of Russian and German theorists is planned. The results of this research will be published in peer refereed journals, will be presented at multidisciplinary domestic and international conferences and workshops, in particular devoted to atomic physics, nuclear physics, particle physics and fundamental constants. The results of the proposed research also will be used in teaching graduate courses