The nucleon as a QCD bound state in a Faddeev approach

Established results for the quark propagator of Landau gauge QCD, together with a detailed comparison to lattice data, are implemented in a Poincaré-covariant Faddeev approach to the nucleon. The nucleon mass and its electromagnetic form factors, together with charge radii and magnetic moments, are calculated as a function of the current-quark mass. The role of the pion cloud is discussed.     

Electron capture in the collision of a proton with a hydrogen atom

Electron capture in the collision of a proton with a hydrogen atom is investigated. The probability of electron capture is calculated from first principles by the direct solving of the three-dimensional nonstationary Schr?dinger equation. The dependence of the probability of electron capture by a proton on the proton??s velocity and impact parameter is obtained and analyzed thanks to highly efficient computations with the use of graphic processing units.     

The weak bound state with the non-zero charge density as the LHC 126.5 GeV state

The self-consistent model of classical field interactions formulated as the counterpart of the quantum electroweak model leads to homogeneous boson ground state solutions in presence of non-zero extended fermionic charge density fluctuations. Two different types of electroweak configurations of fields are analyzed. The first one has non-zero electric and weak charge fluctuations. The second one is electrically uncharged but weakly charged. Both types of configurations have two physically interesting solutions which possess masses equal to 126.67 GeV at the value of the scalar fluctuation potential parameter λ equal to ~0.0652. The spin zero electrically uncharged droplet formed as a result of the decay of the charged one is interpreted as the ~126.5 GeV state found in the Large Hadron Collider (LHC) experiment. (The other two configurations correspond to solutions with masses equal to 123.7 GeV and λ equal to ~0.0498 and thus the algebraic mean of the masses of two central solutions, i.e., 126.67 GeV and 123.7 GeV, is equal to 125.185 GeV.) The problem of a mass of this kind of droplets will be considered on the basis of the phenomenon of the screening of the fluctuation of charges. Their masses are found in the thin wall approximation.     

Potential of interaction of an Ar atom with a proton

The potential of interaction of an Ar atom with a proton is calculated. To verify the result obtained, the wave numbers of the vibrational-rotational spectral lines and the spectroscopic constants for the X¹Σ⁺ state of the ⁴⁰ArH⁺ molecular ion are calculated. The calculated wave numbers of the spectral lines and molecular constants are compared with experimental data.     

On the bound state spectrum of a many-electron-proton system

An equation is obtained for the pairing amplitude in a many-electron-proton system at finite temperature. It is noted that under certain approximations it can be solved to give temperature-dependent discrete energy spectra.     

Two-particle bound states in the field of a heavy nucleus

We calculate the wavefunction and the energy eigenvalues of two non-relativistic interacting particles in an external field with spherical symmetry. The techniques used and the formalism developed are suitable for all problems of this kind. We give explicit formulae for the matrixelements. As an example we discuss the case of a light charged fermion-antifermion pair in the Coulomb field of a heavy nucleus, assuming a confining potential between the fermions.     

Frequency shift in the system formed by a metastable helium atom and a lithium atom in the ground state

The cross sections of magnetic resonance frequency shifts are calculated for the first time in the system formed by a metastable helium atom and a lithium atom in the ground state. The results are compared with the results of calculations for He-K systems. It is shown that the shift cross section increases upon heating from 50 to 550 K, changing its sign near T = 80 K.     

Probing the quantum state of a guided atom laser pulse

We describe bichromatic superradiant pump-probe spectroscopy as a tomographic probe of the Wigner function of a dispersing particle beam. We employed this technique to characterize the quantum state of an ultracold atomic beam, derived from a 87Rb Bose-Einstein condensate, as it propagated in a 2.5 mm diameter circular waveguide. Our measurements place an upper bound on the longitudinal phase space area occupied by the 3 x 10(5) atom beam of 9(1)Planck's constant and a lower bound on the coherence length of L>or=13(1) microm. These results are consistent with full quantum degeneracy after multiple orbits around the waveguide.     

Vibrational states in a heavy quark bound system

There are numerous speculations on the existence of heavy quarks Q. In the context of the quark-confining string model, the (Q$\text{Q}$) bound system is predicted to exhibit, below the continuum threshold, vibrational levels in addition to the states expected from the charmonium picture. This is applied to the recent discovery of the upsilon (9.4).     

Experimental bound entanglement in a four-photon state

Bound entanglement is central to many exciting theoretical results in quantum information processing, but has thus far not been experimentally realized. In this work, we consider a one-parameter family of four-qubit Smolin states. We experimentally produce these states in the polarization of four optical photons produced from parametric down-conversion. Within a range of the parameter, we show that our states are entangled and undistillable, and thus bound entangled. Using these bound-entangled states we demonstrate entanglement unlocking.     

On the cross-section peaks for a heavy-quark bound state

We discuss the values of resonance peaks of the cross section of a heavy-quark bound state obtained by means of a Green function method applied to a Coulombic model and compare the result to the ϒ and J/ψ data.     

The spreading of the proton of a hydrogen atom in strong magnetic fields

In the problem of a hydrogen atom in a strong magnetic field, the center-of-mass motion and the relative motion of the particles cannot be separated. At very high fields, the transversal wave function both of the electron and of the proton is determined dominantly by the interaction with the magnetic field. The proton spread leads to a substantial reduction of the binding energy.     

Reconstruction of the two-mode vibronic quantum state of a trapped atom

We present a method for the direct measurement of the Wigner-function matrix for complex vibronic states of a trapped atom, that is suited to analyse the entanglement between two motional degrees of freedom and the internal electronic dynamics. It is a generalisation of the method for the determination of vibronic quantum states [S. Wallentowitz, R.L. de Matos Filho, W. Vogel, Phys. Rev. A 56, 1205 (1997)] in conjunction with the scheme for the direct observation of the Wigner function of a single motional degree of freedom [L.G. Lutterbach, L. Davidovich, Phys. Rev. Lett. 78, 2547 (1997)]. The major advantage of the present method is that it reduces the experimental efforts substantially. On the other hand, it is demonstrated that the nonlinear vibronic coupling necessary for this method turns out to be its main limitation. Received: 5 August 1998     

Effect of noise on a quantum bound state

The evolution of a quantum wave function on a lattice with time-dependent random disorder is studied. It is found that the bound state wave function of a quantum system exhibits intrinsic instability with respect to noisy disorder in the statistical sense. Under the general scheme of time coarse graining, we show nonperturbatively that the stationary attractive potential is completely washed out at large time scales by the existence of the noisy disorder to any order of density correlations.     

Ground state energy of a bound piezoelectric polaron

The ground state energy of a piezoelectric polaron bound in a Coulomb potential is calculated analytically in the weak coupling limit.     

Shift of the magnetic resonance frequency in a system consisting of a metastable helium atom and a potassium atom in the ground state

The shifts of the magnetic resonance frequency in a system comprising a metastable helium atom and a potassium atom in the ground state are calculated. It is shown that the shift cross section decreases as the temperature grows from 50 to 400 K, remaining negative throughout the temperature range.