51,758 research outputs found
Nonperturbative signatures in pair production for general elliptic polarization fields
The momentum signatures in nonperturbative multiphoton pair production for
general elliptic polarization electric fields are investigated by employing the
real-time Dirac-Heisenberg-Wigner formalism. For a linearly polarized electric
field we find that the positions of the nodes in momenta spectra of created
pairs depend only on the electric field frequency. The polarization of external
fields could not only change the node structures or even make the nodes
disappear but also change the thresholds of pair production. The momentum
signatures associated to the node positions in which the even-number-photon
pair creation process is forbid could be used to distinguish the orbital
angular momentum of created pairs on the momenta spectra. These distinguishable
momentum signatures could be relevant for providing the output information of
created particles and also the input information of ultrashort laser pulses.Comment: 8 pages, 4 figures, submitted to Europhysics Letter
The Influences of Outflow on the Dynamics of Inflow
Both numerical simulations and observations indicate that in an
advection-dominated accretion flow most of the accretion material supplied at
the outer boundary will not reach the inner boundary. Rather, they are lost via
outflow. Previously, the influence of outflow on the dynamics of inflow is
taken into account only by adopting a radius-dependent mass accretion rate
with . In this paper, based on a 1.5
dimensional description to the accretion flow, we investigate this problem in
more detail by considering the interchange of mass, radial and azimuthal
momentum, and the energy between the outflow and inflow. The physical
quantities of the outflow is parameterized based on our current understandings
to the properties of outflow mainly from numerical simulations of accretion
flows. Our results indicate that under reasonable assumptions to the properties
of outflow, the main influence of outflow has been properly included by
adopting .Comment: 16 pages, 5 figures. accepted for publication in Ap
Production rates for hadrons, pentaquarks and , and di-baryon in relativistic heavy ion collisions by a quark combination model
The hadron production in relativistic heavy ion collisions is well described
by the quark combination model. The mixed ratios for various hadrons and the
transverse momentum spectra for long-life hadrons are predicted and agree with
recent RHIC data. The production rates for the pentaquarks , and the di-baryon are estimated, neglecting
the effect from the transition amplitude for constituent quarks to form an
exotic state.Comment: The difference between our model and other combination models is
clarified. The scaled transverse momentum spectra for pions, kaons and
protoms at both 130 AGeV and 200 AGeV are given, replacing the previous
results in transverse momentum spectr
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