6,749 research outputs found
Charmless Decays in Factorization-Assisted Topological-Amplitude Approach
Within the factorization-assisted topological-amplitude approach, we studied
the 33 charmless decays, where stands for a light vector
meson. According to the flavor flows, the amplitude of each process can be
decomposed into 8 different topologies. In contrast to the conventional flavor
diagrammatic approach, we further factorize each topological amplitude into
decay constant, form factors and unknown universal parameters. By
fitting 46 experimental observables, we extracted 10 theoretical parameters
with per degree of freedom around 2. Using the fitted parameters, we
calculated the branching fractions, polarization fractions, CP asymmetries and
relative phases between polarization amplitudes of each decay mode. The decay
channels dominated by tree diagram have large branching fractions and large
longitudinal polarization fraction. The branching fractions and longitudinal
polarization fractions of color-suppressed decays become smaller. Current
experimental data of large transverse polarization fractions in the penguin
dominant decay channels can be explained by only one transverse amplitude of
penguin annihilation diagram. Our predictions of those not yet measured
channels can be tested in the ongoing LHCb experiment and the Belle-II
experiment in future.Comment: 22 pages, 2 figure
Heterogeneity in structurally arrested hard spheres
When cooled or compressed sufficiently rapidly, a liquid vitrifies into a glassy amorphous state. Vitrification in a dense liquid is associated with jamming of the particles. For hard spheres, the density and degree of order in the final structure depend on the compression rate: simple intuition suggests, and previous computer simulation demonstrates, that slower compression results in states that are both denser and more ordered. In this work, we use the Lubachevsky-Stillinger algorithm to generate a sequence of structurally arrested hard-sphere states by varying the compression rate. We find that while the degree of order, as measured by both bond-orientation and translation order parameters, increases monotonically with decreasing compression rate, the density of the arrested state first increases, then decreases, then increases again, as the compression rate decreases, showing a minimum at an intermediate compression rate. Examination of the distribution of the local order parameters and the distribution of the root-mean-square fluctuation of the particle positions, as well as direct visual inspection of the arrested structures, reveal that they are structurally heterogeneous, consisting of disordered, amorphous regions and locally ordered crystal-like domains. In particular, the low-density arrested states correspond with many interconnected small crystal clusters that form a polycrystalline network interspersed in an amorphous background, suggesting that jamming by the domains may be an important mechanism for these states
Net charge fluctuation and string fragmentation
We present simulation results of net charge fluctuation in collisions
at =130 GeV from a dynamic model, JPCIAE. The calculations are
done for the quark-gluon phase before hadronization, the pion gas, the
resonance pion gas from and decays and so on. The simulations
of the charge fluctuation show that the discrepancy exists between the dynamic
model and the thermal model for a pion gas and a resonance pion gas from
and decays while the simulated charge fluctuation of the quark-gluon
phase is close to the thermal model prediction. JPCIAE results of net charge
fluctuation in the hardonic phase are nearly 4-5 times larger than one for the
quark-gluon phase, which implies that the charge fluctuation in the quark-gluon
phase may not survive the hadronization (string fragmentation) as implemented
in JPCIAE.Comment: 9 pages, 3 figure
An improved method to determine the mixing
We develop an improved method to explore the mixing which
arises from the flavor SU(3) and heavy quark symmetry breaking. In this method,
the flavor eigenstates under the SU(3) symmetry are at first constructed and
the corresponding masses can be nonperturbatively determined. Matrix elements
of the mass operators which break the flavor SU(3) symmetry sandwiched by the
flavor eigenstates are then calculated. Diagonalizing the corresponding matrix
of Hamiltonian gives the mass eigenstates of the full Hamiltonian and
determines the mixing. Following the previous lattice QCD calculation of
and , and estimating an off-diagonal matrix element, we extract
the mixing angle between the and . Preliminary numerical
results for the mixing angle confirm the previous observation that such mixing
is incapable to explain the large SU(3) symmetry breaking in semileptonic
decays of charmed baryons.Comment: 7 pages, 3 figure
Quantum phase transition of the two-dimensional Rydberg atom array in an optical cavity
We study the two-dimensional Rydberg atom array in an optical cavity with
help of the meanfield theory and the large-scale quantum Monte Carlo
simulations. The strong dipole-dipole interactions between Rydberg atoms can
make the system exhibit the crystal structure, and the coupling between
two-level atom and cavity photon mode can result in the formation of the
polariton. The interplay between them provides a rich quantum phase diagram
including the Mott, solid-1/2, superradiant and superradiant solid phases. As
the two-order co-existed phase, the superradiant solid phase breaks both
translational and U(1) symmetries. Based on both numerical and analytic
results, we found the region of superradiant solid is much larger than one
dimensional case, so that it can be more easily observed in the experiment.
Finally, we discuss how the energy gap of the Rydberg atom can affect the type
of the quantum phase transition and the number of triple points
Real-time Data Flow Control for CBM-TOF Super Module Quality Evaluation
Super module assembled with MRPC detectors is the component unit of TOF (Time
of Flight) system for the Compressed Baryonic Matter (CBM) experiment. Quality
of super modules needs to be evaluated before it is applied in CBM-TOF. Time
signals exported from super module are digitalized at TDC (Time to Digital
Converter) station. Data rate is up to 6 Gbps at each TDC station, which brings
a tremendous pressure for data transmission in real time. In this paper, a
real-time data flow control method is designed. In this control method, data
flow is divided into 3 types: scientific data flow, status data flow and
control data flow. In scientific data flow, data of each TDC station is divided
into 4 sub-flows, and then is read out by a parallel and hierarchical network,
which consists of multiple readout mother boards and daughter boards groups. In
status data flow, status data is aggregated into a specific readout mother
board. Then it is uploaded to DAQ via readout daughter board. In control data
flow, control data is downloaded to all circuit modules in the opposite
direction of status data flow. Preliminary test result indicated data of STS
was correctly transmitted to DAQ with no error and three type data flows were
control orderly in real time. This data flow control method can meet the
quality evaluation requirement of supper module in CBM-TOF
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