1,634 research outputs found
Revealing Tripartite Quantum Discord with Tripartite Information Diagram
A new measure based on the tripartite information diagram is proposed for
identifying quantum discord in tripartite systems. The proposed measure
generalizes the mutual information underlying discord from bipartite to
tripartite systems, and utilizes both one-particle and two-particle projective
measurements to reveal the characteristics of the tripartite quantum discord.
The feasibility of the proposed measure is demonstrated by evaluating the
tripartite quantum discord for systems with states close to
Greenberger-Horne-Zeilinger, W, and biseparable states. In addition, the
connections between tripartite quantum discord and two other quantum
correlations---namely genuine tripartite entanglement and genuine tripartite
Einstein-Podolsky-Rosen steering---are briefly discussed. The present study
considers the case of quantum discord in tripartite systems. However, the
proposed framework can be readily extended to general N-partite systems
A Novel Investigation Method for the S21 Detection Circuit
This research proposes a novel method to investigate the performance of the S21 detection circuit. Aiming at low frequencies or DC, the method serves as an efficient way of verification and enjoys the benefit of low testing costs. The novel investigation method is demonstrated at 50 MHz and verified by the scattering parameters at 11.05 GHz. Based on the investigation, a model of process variations is constructed. The length of the interface paths is estimated by the model to be 63Β΅m, which is consistent with the corresponding length of 74.6Β΅m in the layout. For the measured phase and magnitude, the model indicates that the process variations in the device under test cause errors of 18.91% and 1.27%, whereas those in the interface paths lead to errors of 1.83% and 1%. Based on the model, practical recommendations are also proposed to further improve the measurement precision in the future
Quarkonium formation time in quark-gluon plasma
The quarkonium formation time in a quark-gluon plasma (QGP) is determined
from the space-time correlator of heavy quark vector currents using the
quarkonium in-medium mass and wave function obtained from heavy quark
potentials extracted from the lattice QCD. It is found that the formation time
of a quarkonium increases with the temperature of the QGP and diverges near its
dissociation temperature. Also, the quarkonium formation time is longer if the
heavy quark potential is taken to be the free energy from lattice calculations
for a heavy quark pair, compared to that based on the more negative internal
energy.Comment: 5 pages, 4 figure
Quarkonium formation time in relativistic heavy-ion collisions
We calculate the quarkonium formation time in relativistic heavy-ion
collisions from the space-time correlator of heavy quark vector currents in a
hydrodynamics background with the initial nonequilibrium stage expanding only
in the longitudinal direction. Using in-medium quarkonia properties determined
with the heavy quark potential taken to be the free energy from lattice
calculations and the fact that quarkonia can only be formed below their
dissociation temperatures due to color screening, we find that (1S),
(2S), (3S), and are formed,
respectively, at 1.2, 6.6, 8.8, 5.8, and 11.0 fm/c after the quark pair are
produced in central Au+Au collisions at the top energy of Relativistic Heavy
Ion Collider (RHIC), and these times become shorter in semi-central collisions.
We further show, as an example, that including the effect of formation time
enhances appreciably the survivability of (1S) in the produced hot
dense matter.Comment: 6 pages, 4 figure
Implications of the Little Higgs Dark Matter and T-odd Fermions
We study the phenomenology of dark matter in the Littlest Higgs model with
T-parity after the discovery of Higgs boson. We analyze the relic abundance of
dark matter, focusing on the effects of coannihilaitons with T-odd fermions.
After determining the parameter space that predicts the correct relic abundance
measured by WMAP and Planck collaborations, we evaluate the elastic scattering
cross section between dark matter and nucleon. In comparison with experimental
results, we find that the lower mass of dark matter is constrained mildly by
LUX 2013 while the future XENON experiment has potential to explore most of the
parameter space for both T-odd lepton and T-odd quark coannihilation scenarios.
We also study the collider signatures of T-odd fermion pair production at the
LHC. Even though the production cross sections are large, it turns out very
challenging to search for these T-odd fermions directly at the collider because
the visible charged leptons or jets are very soft. Furthermore, we show that,
with an extra hard jet radiated out from the initial state, the T-odd quark
pair production can contribute significantly to mono-jet plus missing energy
search at the LHC
production and elliptic flow in relativistic heavy-ion collisions
Using a two-component model for charmonium production, which includes
contributions from both the initial hard nucleon-nucleon scattering and from
the regeneration in the quark-gluon plasma, we study the nuclear modification
factor and elliptic flow of in relativistic heavy ion
collisions. For the expansion dynamics of produced hot dense matter, we
introduce a schematic fireball model with its transverse acceleration
determined from the pressure gradient inside the fireball and azimuthally
anisotropic expansion parameterized to reproduce measured of light
hadrons. We assume that light hadrons freeze out at the temperature of 120 MeV
while charmonia at 160 MeV, similar to the kinetic and chemical freeze-out
temperatures in the statistical model, respectively. For the properties of
charmonia in the quark-gluon plasma, we use the screening mass between their
charm and anticharm quarks and their dissociation cross sections given by the
perturbative QCD (pQCD) in the leading order and up to the next-to-leading
order, respectively. For the relaxation time of charm and anticharm quarks in
the quark-gluon plasma, we also use the one calculated in the leading order of
pQCD. Modeling the effect of higher-order corrections in pQCD by introducing
multiplicative factors to the dissociation cross section of charmonia and the
elastic scattering cross sections of charm and anticharm quarks, we find that
this effect is small for the of as they suppress the number
of initially produced but enhance the number of regenerated ones. The
higher-order corrections increase, however, the of . Our results
suggest that the of can play an important role in discriminating
between production from the initial hard collisions and from the
regeneration in the quark-gluon plasma.Comment: 15 pages, 14 figure
Heavy baryon/meson ratios in relativistic heavy ion collisions
Heavy baryon/meson ratios and in
relativistic heavy ion collisions are studied in the quark coalescence model.
For heavy baryons, we include production from coalescence of heavy quarks with
free light quarks as well as with bounded light diquarks that might exist in
the strongly coupled quark-gluon plasma produced in these collisions. Including
the contribution from decays of heavy hadron resonances and also that due to
fragmentation of heavy quarks that are left in the system after coalescence,
the resulting and ratios in midrapidity
() from central Au+Au collisions at GeV are
about a factor of five and ten, respectively, larger than those given by the
thermal model, and about a factor of ten and twelve, respectively, larger than
corresponding ratios in the PYTHIA model for collisions. These ratios are
reduced by a factor of about 1.6 if there are no diquarks in the quark-gluon
plasma. The transverse momentum dependence of the heavy baryon/meson ratios is
found to be sensitive to the heavy quark mass, with the
ratio being much flatter than the ratio. The latter peaks at
the transverse momentum GeV but the peak shifts to GeV in the absence of diquarks.Comment: 11 pages, 2 figure
Contributions of hyperon-hyperon scattering to subthreshold cascade production in heavy ion collisions
Using a gauged flavor SU(3)-invariant hadronic Lagrangian, we calculate the
cross sections for the strangeness-exchange reactions YY to N\Xi (Y=\Lambda,
\Sigma) in the Born approximation. These cross sections are then used in the
Relativistic Vlasov-Uehling-Uhlenbeck (RVUU) transport model to study \Xi
production in Ar+KCl collisions at incident energy of 1.76A GeV and impact
parameter b=3.5 fm. We find that including the contributions of hyperon-hyperon
scattering channels strongly enhances the yield of \Xi, leading to the
abundance ratio \Xi^{-}/(\Lambda+\Sigma^{0})=3.38E-3, which is essentially
consistent with the recently measured value of by the HADES collaboration at GSI.Comment: 8 pages, 5 figure
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