3,609 research outputs found
Meson Mass Decomposition
Hadron masses can be decomposed as a sum of components which are defined
through hadronic matrix elements of QCD operators. The components consist of
the quark mass term, the quark energy term, the glue energy term and the trace
anomaly term. We calculate these components of mesons with lattice QCD for the
first time. The calculation is carried out with overlap fermion on flavor
domain-wall fermion gauge configurations. We confirm that of the
light pion mass comes from the quark mass and comes from the quark
energy, whereas, the contributions are found to be the other way around for the
mass. The combined glue components contribute for both
mesons. It is interesting to observe that the quark mass contribution to the
mass of the vector meson is almost linear in quark mass over a large quark mass
region below the charm quark mass. For heavy mesons, the quark mass term
dominates the masses, while the contribution from the glue components is about
MeV for the heavy pseudoscalar and vector mesons. The charmonium
hyperfine splitting is found to be dominated by the quark energy term which is
consistent with the quark potential model.Comment: 7 Pages, 4 figures, contribution to the 32nd International Symposium
on Lattice Field Theory (Lattice 2014), 23-28 June 2014, Columbia University,
New York, NY, US
Active inductor shunt peaking in high-speed VCSEL driver design
An all transistor active inductor shunt peaking structure has been used in a
prototype of 8-Gbps high-speed VCSEL driver which is designed for the optical
link in ATLAS liquid Argon calorimeter upgrade. The VCSEL driver is fabricated
in a commercial 0.25-um Silicon-on-Sapphire (SoS) CMOS process for radiation
tolerant purpose. The all transistor active inductor shunt peaking is used to
overcome the bandwidth limitation from the CMOS process. The peaking structure
has the same peaking effect as the passive one, but takes a small area, does
not need linear resistors and can overcome the process variation by adjust the
peaking strength via an external control. The design has been tapped out, and
the prototype has been proofed by the preliminary electrical test results and
bit error ratio test results. The driver achieves 8-Gbps data rate as simulated
with the peaking. We present the all transistor active inductor shunt peaking
structure, simulation and test results in this paper.Comment: 4 pages, 6 figures and 1 table, Submitted to 'Chinese Physics C
Low-energy Scattering of System and the Resonance-like Structure
In this paper, low-energy scattering of the meson
system is studied within L\"uscher's finite-size formalism using
twisted mass gauge field configurations. With three different pion mass values,
the -wave threshold scattering parameters, namely the scattering length
and the effective range , are extracted in channel. Our
results indicate that, in this particular channel, the interaction between the
two vector charmed mesons is weakly repulsive in nature hence do not support
the possibility of a shallow bound state for the two mesons, at least for the
pion mass values being studied. This study provides some useful information on
the nature of the newly discovered resonance-like structure
observed in various experiments.Comment: 11 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1403.131
A Lattice Study of Near-threshold Scattering
In this exploratory lattice study, low-energy near threshold scattering of
the meson system is analyzed using lattice QCD with
twisted mass fermion configurations. Both s-wave () and p-wave
() channels are investigated. It is found that the interaction between
the two charmed mesons is attractive near the threshold in both channels. This
calculation provides some hints in the searching of resonances or bound states
around the threshold of system.Comment: 20 pages, 15 figures, matches the version on PR
Two Photon Decays of from Lattice QCD
We present an exploratory lattice study for the two-photon decay of
using twisted mass lattice QCD gauge configurations generated by the
European Twisted Mass Collaboration. Two different lattice spacings of
fm and fm are used in the study, both of which are of
physical size of 2. The decay widths are found to be KeV for the
coarser lattice and KeV for the finer lattice respectively where the
errors are purely statistical. A naive extrapolation towards the continuum
limit yields KeV which is smaller than the previous
quenched result and most of the current experimental results. Possible reasons
are discussed.Comment: 13 pages, 7 figures; matches the published versio
N-Phenyl-N-{4-[5-(4-pyridyl)-1,3,4-oxadiazol-2-yl]phenyl}aniline
The title compound, C25H18N4O, is a non-planar bipolar ligand containing triphenylamine and 1,3,4-oxadiazole units. In the molecule, the benzene ring, the 1,3,4-oxadiazole ring, and the pyridine ring are twisted slightly with respect to each other [dihedral angle between the benzene and 1,3,4-oxadiazole rings = 9.4 (4) and between the 1,3,4-oxadiazole and pyridine rings = 3.0 (4)°]. Moreover, the dihedral angles between the two phenyl rings and the benzene ring are 88.2 (4) and 113.3 (4)°, and that between the two phenyl rings is 67.9 (4)°. The closest distances between the pyridine ring and the 1,3,4-oxadiazole and benzene rings in adjacent molecules are 3.316 and 3.363 Å, respectively, indicating the existence of π–π interactions
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