Narrow Results

We consider a spin-½ electron and a spin-½ nucleus interacting with the quantized electromagnetic field in the standard model of non-relativistic QED. For a fixed total momentum sufficiently small, we study the multiplicity of the ground state of the reduced Hamiltonian. We prove that the coupling between the spins of the charged particles and the electromagnetic field splits the degeneracy of the ground state.

The hyperfine splitting in heavy quarkonia is considered in its relation to the leptonic decay rates with the account of relativistic and radiative corrections. The calculated decay rates agree well with the available experimental data, while the predicted η_c(2S) mass is significantly smaller than the value measured recently by the Belle collaboration.

Regge trajectories and hyperfine splitting relations among spin-singlets and spin-triplets in charmonium spectrum were studied. Some interesting conclusions were obtained from the combination of these relations. Especially, the newly observed X(3872) and the old ψ(3836) were analyzed.

We consider hard three-loop nonlogarithmic corrections of order $m{\alpha }^7$ to hyperfine splitting in muonium and positronium. All these contributions are generated by the graphs with photon, electron and/or muon loop radiative insertions in the two-photon exchange diagrams. We calculate contributions of six gauge invariant sets of diagrams.

In this paper, we analyze scenario with strongly interacting massive particles which follows from the Standard Model extension with singlet quark. The lightest new neutral hadron is stable, it can be interpreted as a candidate for hadronic dark matter. Here, we consider principal features of this scenario: large mass of new hadrons, fine and hyperfine splitting in the spectrum of hadron states, low-energy interaction with the standard particles. Both splitting effects lead to processes which can be registered in cosmic rays and deciphered as the hadronic dark matter manifestations. In this work, we reconsider and specify some results from our previous papers.

In the pdμ system, fusion occurs from four incoherent hyperfine states, with varying combinations of pd nuclear spins (3/2 or 1/2). The two possible fusion products, 5.5 MeV gammas and 5.3 MeV conversion muons, is dependent on which nuclear hyperfine state the molecule is in (S=1/2 or 3/2). At low temperatures, the hyperfine splitting in the μd atom alters the final state of nuclear spins in the pdμ molecule. As deuterium concentration increases, so does the spin-flip rate, thus reducing the initial population of the quartet (S=3/2) nuclear spin of the pdμ molecule and enhancing the doublet (S=1/2) state. Since the fusion rates depend on the nuclear states, the quartet state only fuses with γ-emission, so having more of the doublet state changes the ratio of gamma to conversion muon yields. The doublet rate is dominant, thus total fusion yield increases with deuterium concentration until the lack of protium atoms significantly reduces the rate of pdμ molecule formation and ddμ fusion dominates completely. The kinematics of pdμ system are studied by Monte-Carlo method using "Lsode" computer code. The Wolfenstein–Gerstein effect and no-quartet theorem in the solid H/D mixture are considered by solving the muon dynamical equations for various deuterium concentrations. It is shown that the "no-quartet theorem" is not valid at low temperature and deuterium concentration, and is valid only if one neglects the mixed-symmetry components.

The Ramsauer–Townsend effect in hydrogen is used in a heterogeneous solid hydrogen-deuterium-tritium (H/D/T) multi-layer system to provide forced resonance muonic deuterium-tritium molecule formation. The effects of hyperfine splitting in the μd atom on the final state of nuclear spins are studied in the μpd molecule at low temperature. As deuterium concentration increases, so does the spin-flip rate, thus reducing the initial population of the quartet (s=3/2) nuclear spin of the μpd molecule and enhancing the doublet (s=1/2) state. The doublet rate is dominant, and total fusion yield increases with deuterium concentration until the lack of protium atoms significantly reduces the rate of μpd molecule formation and μdd fusion dominates completely. The Wolfenstein–Gerstein effect and the no-quartet theorem in the solid H/D layer are considered by solving the muon dynamical equations for various deuterium concentrations. It is shown that the no-quartet theorem is not valid at low temperature and deuterium concentration, but is valid only if one neglects the mixed-symmetry components. The written coupled linear point dynamical equations for the suggested system are solved using the "Lsode" computer code. The results obtained for the optimum layer thicknesses and deuterium concentration are compared with the results of a solid homogeneous deuterium-tritium system in the same physical condition (temperature, density and deuterium concentration). It is shown that for the same physical conditions, the muon cycling coefficient of two isotopes of deuterium-tritium (D/T) has only 2.7% of the muon cycling coefficient of the suggested forced solid heterogeneous H/D/T fusion system. It is shown that with very little deuterium concentration (c_d=0.005), the obtained muon cycling rate and coefficient are ~147 μs^-1 and 178, respectively.

High-precision laser spectroscopy of atomic energy levels enables the measurement of nuclear properties. Sensitivity to these properties is particularly enhanced in muonic atoms which are bound systems of a muon and a nucleus. Exemplary is the measurement of the proton charge radius from muonic hydrogen performed by the CREMA collaboration which resulted in an order of magnitude more precise charge radius as extracted from other methods but at a variance of 7 standard deviations. Here, we summarize the role of muonic atoms for the extraction of nuclear charge radii, we present the status of the so called “proton charge radius puzzle”, and we sketch how muonic atoms can be used to infer also the magnetic nuclear radii, demonstrating again an interesting interplay between atomic and particle/nuclear physics.