14,934 research outputs found
Nonlinear screening and stopping power in two-dimensional electron gases
We have used density functional theory to study the nonlinear screening
properties of a two-dimensional (2D) electron gas. In particular, we consider
the screening of an external static point charge of magnitude Z as a function
of the distance of the charge from the plane of the gas. The self-consistent
screening potentials are then used to determine the 2D stopping power in the
low velocity limit based on the momentum transfer cross-section. Calculations
as a function of Z establish the limits of validity of linear and quadratic
response theory calculations, and show that nonlinear screening theory already
provides significant corrections in the case of protons. In contrast to the 3D
situation, we find that the nonlinearly screened potential supports a bound
state even in the high density limit. This behaviour is elucidated with the
derivation of a high density screening theorem which proves that the screening
charge can be calculated perturbatively in the high density limit for arbitrary
dimensions. However, the theorem has particularly interesting implications in
2D where, contrary to expectations, we find that perturbation theory remains
valid even when the perturbing potential supports bound states.Comment: 23 pages, 15 figures in RevTeX
Ordering variable for parton showers
The parton splittings in a parton shower are ordered according to an ordering
variable, for example the transverse momentum of the daughter partons relative
to the direction of the mother, the virtuality of the splitting, or the angle
between the daughter partons. We analyze the choice of the ordering variable
and conclude that one particular choice has the advantage of factoring softer
splittings from harder splittings graph by graph in a physical gauge.Comment: 28 pages, 5 figure
Semiclassical model for calculating fully differential ionization cross sections of the H molecule
Fully differential cross sections are calculated for the ionization of H
by fast charged projectiles using a semiclassical model developed previously
for the ionization of atoms. The method is tested in case of 4 keV electron and
6 MeV proton projectiles. The obtained results show good agreement with the
available experimental data. Interference effects due to the two-center
character of the target are also observed and analyzed.Comment: 11 pages, 4 figure
Multi-jet cross sections in deep inelastic scattering at next-to-leading order
We present the perturbative prediction for three-jet production cross section
in DIS at the NLO accuracy. We study the dependence on the renormalization and
factorization scales of exclusive three-jet cross section. The perturbative
prediction for the three-jet differential distribution as a function of the
momentum transfer is compared to the corresponding data obtained by the H1
collaboration at HERA.Comment: 5 pages, 3 figure
Effect of the channel and interference phenomena in the two-pion transitions of charmonia and bottomonia
The basic shape of di-pion mass spectra in the two-pion transitions of both
charmonia and bottomonia states is explained by an unified mechanism based on
contributions of the , and coupled channels
including their interference. The role of the individual resonances in
shaping the di-pion mass distributions in the charmonia and bottomonia decays
is considered.Comment: 8 pages, 4 figures, Talk at the XXIII International Baldin Seminar on
High Energy Physics Problems "Relativistic Nuclear Physics \& Quantum
Chromodynamics" (Dubna, Russia, 19--24 September 2016). arXiv admin note:
text overlap with arXiv:1610.0789
The interference effects of multi-channel pion-pion scattering contributions to the final states of - and -meson family decays
It is shown that the basic shape of dipion mass distributions in the two-pion
transitions of both charmonia and bottomonia states are explained by an unified
mechanism based on the contribution of the , and
coupled channels including their interference.Comment: 5 pages, 3 figures, talk at the14th International Workshop on Meson
Production, Properties and Interaction (Krakow, Poland, 2nd - 7th June 2016
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