8,339 research outputs found
Impact of the transport supercurrent on the Josephson effect
We study the weak link between current-carrying superconductors, both
conventional and d-wave. The state of the system is controlled by two
parameters: the order parameter phase difference and the superfluid
velocity , which parameterizes the parallel to the boundary transport
supercurrent which is injected externally. The low-temperature current-phase
relations are derived. We consider two models of weak links: a constriction
between two conventional superconductors and a plane boundary between two
differently orientated d-wave superconductors. We show that for some relation
between and quasiparticles create the current along the
boundary which flows in the direction opposite to the transport supercurrent.Comment: 5 pages, 3 figures; submitted for publication in Proceedings of
MS+S2004 symposium (without Sec.V and the last part of Sec.III
Resonant effects in the strongly driven phase-biased Cooper-pair box
We study the time-averaged upper level occupation probability in a strongly
driven two level system, particularly its dependence on the driving amplitude,
frequency and the energy level separation. In contrast to the case of weak
driving, when the positions of the resonances almost do not depend on the
driving amplitude, in the case of the strong diving their positions are
strongly amplitude-dependent. We study these resonances in the concrete system
-- the strongly driven phase-biased Cooper-pair box, which is considered to be
weakly coupled to the tank circuit
Capture of slow antiprotons by helium atoms
A consistent quantum mechanical calculation of partial cross-sections leading
to different final states of antiprotonic helium atom was performed. For the
four-body scattering wave function, corresponding to the initial state, as well
as for the antiprotonic helium wave function, appearing in the final tate,
adiabatic approximations was used. Calculations were carried out for a wide
range of antiprotonic helium states and incident energies of the antiproton.
Obtained energy dependances of some cross sections show a rich low energy
structure.Comment: 16 pages, 8 color pictures; the text, the bibliography, and the
pictures were slightly correcte
Exact calculations of a quasi-bound state in the system
Dynamically exact calculations of a quasi-bound state in the
three-body system are performed using Faddeev-type AGS
equations. As input two phenomenological and one chirally motivated
potentials are used, which describe the experimental information on the
system equally well and produce either a one- or two-pole structure
of the resonance. For the interaction
separable potentials are employed that are fitted to phase shifts obtained from
two theoretical models. The first one is a phenomenological
potential based on meson exchange, which is derived by SU(3) symmetry arguments
from the J\"ulich coupled-channels model. The other
interaction is a variant of the first one, which is adjusted to the s-wave
scattering length recently determined in lattice QCD simulations. The position
and width of the quasi-bound state is evaluated in two ways:
(i) by a direct pole search in the complex energy plane and (ii) using an
"inverse determinant" method, where one needs to calculate the determinant of
the AGS system of equations only for real energies. A quasi-bound state is
found with binding energy MeV and width
MeV, which could correspond to the
experimentally observed state.Comment: 18 pages, 2 figures, 2 table
NLO QCD method of the polarized SIDIS data analysis
Method of polarized semi-inclusive deep inelastic scattering (SIDIS) data
analysis in the next to leading order (NLO) QCD is developed. Within the method
one first directly extracts in NLO few first truncated (available to
measurement) Mellin moments of the quark helicity distributions. Second, using
these moments as an input to the proposed modification of the Jacobi polynomial
expansion method (MJEM), one eventually reconstructs the local quark helicity
distributions themselves. All numerical tests demonstrate that MJEM allows us
to reproduce with the high precision the input local distributions even inside
the narrow Bjorken region accessible for experiment. It is of importance
that only four first input moments are sufficient to achieve a good quality of
reconstruction. The application of the method to the simulated SIDIS data on
the pion production is considered. The obtained results encourage one that the
proposed NLO method can be successfully applied to the SIDIS data analysis. The
analysis of HERMES data on pion production is performed. To this end the pion
difference asymmetries are constructed from the measured by HERMES standard
semi-inclusive spin asymmetries. The LO results of the valence distribution
reconstruction are in a good accordance with the respective leading order SMC
and HERMES results, while the NLO results are in agreement with the existing
NLO parametrizations on these quantities
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