972 research outputs found
Transverse-momentum-dependent wave functions and Soft functions at one-loop in Large Momentum Effective Theory
In large-momentum effective theory (LaMET), the transverse-momentum-dependent
(TMD) light-front wave functions and soft functions can be extracted from the
simulation of a four-quark form factor and equal-time correlation functions. In
this work, using expansion by regions we provide a one-loop proof of TMD
factorization of the form factor. For the one-loop validation, we also present
a detailed calculation of perturbative corrections to
these quantities, in which we adopt a modern technique for the calculation of
TMD form factor based the integration by part and differential equation. The
one-loop hard functions are then extracted. Using lattice data from Lattice
Parton Collaboration on quasi-TMDWFs, we estimate the effects from the one-loop
matching kernel and find that the perturbative corrections depend on the
operator to define the form factor, but are less sensitive to the transverse
separation. These results will be helpful to precisely extract the soft
functions and TMD wave functions from the first-principle in future
Revisiting mixing in QCD sum rules
We investigate the mixing caused by the flavor
symmetry breaking. The mixing angle is expressed by a matrix
element induced by the operators that breaks flavor symmetry. The QCD
contribution to this matrix element is assumed to be dominated and calculated
by QCD sum rules. A three-point correlation function is defined and handled
both at the hadron and quark-gluon levels. The quark-gluon level calculation is
based on operator product expansion up to dimension-5 condensates. A detailed
numerical analysis is performed to determine the Borel parameters, and the
obtained mixing angle is or
.Comment: 14 pages, 7 figures and 1 tabl
Shape coexistence and evolution in neutron-deficient krypton isotopes
Total Routhian Surface (TRS) calculations have been performed to investigate shape coexistence and evolution in neutron-deficient krypton isotopes 72,74,76Kr. The ground-state shape is found to change from oblate in 72Kr to prolate in 74,76Kr, in agreement with experimental data. Quadrupole deformations of the ground states and coexisting 0+2 states as well as excitation energies of the latter are also well reproduced. While the general agreement between calculated moments of inertia and those deduced from observed spectra confirms the prolate nature of the low-lying yrast states of all three isotopes (except the ground state of 72Kr), the deviation at low spins suggests significant shape mixing. The role of triaxiality in describing shape coexistence and evolution in these nuclei is finally discussed
Realization of Zero-Refractive-Index Lens with Ultralow Spherical Aberration
Optical complex materials offer unprecedented opportunity to engineer
fundamental band dispersion which enables novel optoelectronic functionality
and devices. Exploration of photonic Dirac cone at the center of momentum space
has inspired an exceptional characteristic of zero-index, which is similar to
zero effective mass in fermionic Dirac systems. Such all-dielectric zero-index
photonic crystals provide an in-plane mechanism such that the energy of the
propagating waves can be well confined along the chip direction. A
straightforward example is to achieve the anomalous focusing effect without
longitudinal spherical aberration, when the size of zero-index lens is large
enough. Here, we designed and fabricated a prototype of zero-refractive-index
lens by comprising large-area silicon nanopillar array with plane-concave
profile. Near-zero refractive index was quantitatively measured near 1.55 um
through anomalous focusing effect, predictable by effective medium theory. The
zero-index lens was also demonstrated to perform ultralow longitudinal
spherical aberration. Such IC compatible device provides a new route to
integrate all-silicon zero-index materials into optical communication, sensing,
and modulation, and to study fundamental physics on the emergent fields of
topological photonics and valley photonics.Comment: 14 pages, 4 figure
A new impedance matching method for an ultra-wide band and dual circularly polarised feed
In traditional antenna design, metal components are not placed in the central part of the antenna as they change the characteristics of near field radiation. However, we show that placing a metal ring in the centre of the strip lines, which connect the ends of folded high-frequency dipoles, does not damage the performance of the feed. Instead it significantly improves the voltage standing wave ratio of the feed whilst other performance indicators are not compromised. Thus, our findings show an excellent way of improving the wide band feed. Based on this foundation, a new circularly polarised feed for operation between 0.4 to 2 GHz is introduced for the Chinese Spectral Radioheliograph in this paper. The issue of a feed impedance matching network is investigated. By optimising the impedance matching, the performance of the feed is enhanced with respect to the previous realisations of the Eleven feed. The simulation and experimental results show that the gain of the feed is about 10 dBi, and the VSWR is less than 2:1. In addition, the feed has a low axial ratio, fixed phase centre location, and constant beam width in the range of 0.4 to 2 GHz
QED contributions to the mixing
We explore the QED corrections to the mixing within
the framework of light-front quark model (LFQM) in the three-quark picture.
After explicitly investigating the relation between the
mixing and the flavor and heavy quark symmetry breaking, we
derive the QED contributions to the mixing angle. Numerical results indicate
the QED contribution is smaller than the one from the mass difference between
the strange and up/down quark provided by a recent Lattice QCD analysis. Adding
these contributions together we find that at this stage the
mixing is small and still incapable to account for the
large symmetry breaking in the semi-leptonic decays.Comment: 7 pages, 4figure
A simulated study on the performance of diesel engine with ethanol-diesel blend fuel
This paper describes the simulated study on atomization, wall-film formation, combustion and emission forming process of ethanol-diesel blend fuels in a high speed light duty diesel engine. The result shows that increased ethanol volume percentage of the blend fuels could improve atomization and reduce wall-film formation. However, in the meanwhile, with the increased ethanol volume percentage, low heat values of blend fuels decrease, while both total heat releases and cylinder pressures drop. By adding codes into the FIRE software, the NOx and soot formation region mass fractions are outputted. The simulated results display a good correlation with the NOx and soot formation. Besides, the NOx, soot and CO emissions decrease with the increased ethanol volume percentage. The power output of engine penalize, while energy utilization of blend fuels improve and combustion noise reduce, owing to the increased ethanol volume percentage
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