923 research outputs found
Kinematical Constraints on QCD Factorization in the Drell-Yan Process
We study factorization schemes for parton shower models in hadron-hadron
collisions. As an example, we calculate lepton pair production mediated by a
virtual photon in quark--anti-quark annihilation, and we compare factorized
cross sections obtained in the conventional scheme with those
obtained in a factorization scheme in which a kinematical constraint due to
parton radiation is taken into account. We discuss some properties of
factorized cross sections.Comment: 10 pages, PTPTeX.sty, 1 Postscript figur
Classical reconstruction of interference patterns of position-wavevector-entangled photon pairs by time-reversal method
The quantum interference of entangled photons forms a key phenomenon
underlying various quantum-optical technologies. It is known that the quantum
interference patterns of entangled photon pairs can be reconstructed
classically by the time-reversal method; however, the time-reversal method has
been applied only to time-frequency-entangled two-photon systems in previous
experiments. Here, for the first time, we apply the time-reversal method to the
position-wavevector-entangled two-photon systems: the two-photon Young
interferometer and the two-photon beam focusing system. We experimentally
demonstrate that the time-reversed systems classically reconstruct the same
interference patterns as the position-wavevector-entangled two-photon systems.Comment: 10 pages, 8 figure
Stereographical visualization of a polarization state using weak measurements with an optical-vortex beam
We propose a stereographical-visualization scheme for a polarization state by
two-dimensional imaging of a weak value with a single setup. The key idea is to
employ Laguerre-Gaussian modes or an optical vortex beam for a probe state in
weak measurement. Our scheme has the advantage that we can extract information
on the polarization state from the single image in which the zero-intensity
point of the optical vortex beam corresponds to a stereographic projection
point of the Poincare sphere. We experimentally perform single-setup weak
measurement to validate the stereographical relationship between the
polarization state on the Poincare sphere and the location of the
zero-intensity point.Comment: 6 pages, 4 figure
Drell-Yan Cross Section in the Jet Calculus Scheme
We calculate factorized cross sections for lepton pair production mediated by
a virtual photon in hadron-hadron collisions using the jet calculus scheme, in
which a kinematical constraint due to parton radiation is taken into account.
This method guarantees a proper phase space boundary for subtraction terms.
Some properties of the calculated cross sections are examined. We also discuss
matching between the hard scattering cross sections and parton showers at the
next-to-leading logarithmic (NLL) order of quantum chromodynamics (QCD).Comment: 18 pages, PTPTeX.sty, 3 Postscript figure
Isolation of phase edges using off-axis q-plate filters
Edge enhancement plays an important role in optical biological imaging that
highlights the contours of an object. Edge-enhanced microscopes are widely used
to enhance the edges of phase-amplitude objects due to their capability for
all-directional edge enhancement, while differential interference-contrast
microscopy enhances edges in only one-direction. However, edge-enhanced
microscopes cannot distinguish the edges of phase and amplitude objects, as
both edges are equally enhanced. This study introduces a novel method for
isolating the edge of a phase object from an amplitude object using an off-axis
q-plate filter in a system. Herein, we combined off-axis q-plates with
four different displacements to isolate the phase object edge from the
amplitude object. To verify the effectiveness of the proposed method, we
conducted experiments using two distinct samples. The first sample comprised a
phase test target surrounded by an aperture, and the second sample involved an
overlap between the phase test target and a white hair (with nonzero
transmittance). In the samples, the isolated phase object edge met the
requirements of theoretical expectations, and the amplitude object edge was
reduced by approximately 93\%. In summary, the proposed method is a novel and
effective approach for isolating the edge of a phase object from an amplitude
object and can be useful in various biological imaging applications.Comment: 12 pages, 9 figure
Time-reversed two-photon interferometry for phase super-resolution
We observed two-photon phase super-resolution in an unbalanced Michelson
interferometer with classical Gaussian laser pulses. Our work is a
time-reversed version of a two-photon interference experiment using an
unbalanced Michelson interferometer. A measured interferogram exhibits
two-photon phase super-resolution with a high visibility of 97.9% \pm 0.4%. Its
coherence length is about 22 times longer than that of the input laser pulses.
It is a classical analogue to the large difference between the one- and
two-photon coherence lengths of entangled photon pairs.Comment: 6 pages, 4 figure
Observation of nonlinear variations in three-vertex geometric phase in two-photon polarization qutrit
We experimentally observed nonlinear variations in the three-vertex geometric
phase in a two- photon polarization qutrit. The three-vertex geometric phase is
defined by three quantum states, which generally forms a three-state (qutrit)
system. By changing one of the three constituent states, we observed two rapid
increases in the three-vertex geometric phase. The observed variations are
inherent in a three-state system and cannot be observed in a two-state system.
We used a time-reversed two-photon interferometer to measure the geometric
phase with much more intense signals than those of a typical two-photon
interferometer.Comment: 6 pages, 5 figure
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