14,812 research outputs found
Radial excitations of mesons and nucleons from QCD sum rules
Within the framework QCD sum rules, we use the least square fitting method to
investigate the first radial excitations of the nucleon and light mesons such
as , , , . The extracted masses of these radial
excitations are consistent with the experimental data. Especially we find that
the decay constant of , which is the the first radial excitation of
, is tiny and strongly suppressed as a consequence of chiral symmetry.Comment: 19 page
New predictions on the mass of the light hybrid meson from QCD sum rules
We calculate the coefficients of the dimension-8 quark and gluon condensates
in the current-current correlator of light hybrid current
. With inclusion of these
higher-power corrections and updating the input parameters, we re-analyze the
mass of the light hybrid meson from Monte-Carlo based QCD sum rules.
Considering the possible violation of factorization of higher dimensional
condensates and variation of , we obtain a conservative
mass range 1.72--2.60\,GeV, which favors as a better hybrid
candidate compared with and .Comment: 12pages, 2 figures, the version appearing in JHE
CO preferential oxidation in a novel Au@ZrO₂ flow-through catalytic membrane reactor with high stability and efficiency
CO preferential oxidation (CO-PROX) achieves much interest as a strategy to remove trace CO in reformed gases for hydrogen utilization. Herein, we reported a novel Au@ZrO₂ catalytic membrane reactor by embedding gold nano-particles in ZrO₂ hollow fiber membrane for CO-PROX. The flow-through catalytic membrane exhibited high catalytic activity and oxygen selectivity, which gave a turnover frequency of 4.73 s⁻¹ at 60 °C, 2–3 times higher than conventional catalyst pellets. CO conversion of >95% was achieved over the catalytic membrane, which maintained great operational stability during 500-h operation even CO₂ and H₂O were added in the feed stream. The excellent catalytic performance of the flow-through catalytic membrane makes gold catalyst possible for practical application in the removal of CO from hydrogen
Instanton Effects in QCD Sum Rules for the Hybrid
In this paper, we study instanton contributions to the correlator of the
hybrid current . These contributions
are then included in a QCD sum-rule analysis of the isoscalar hybrid
mass. We find a mass at 1.83 GeV for the hybrid.
However, for the hybrid, we find the sum rules are unstable. We also
study non-zero width effects, which affect the mass prediction. The mixing
effects between these two states are studied and we find QCD sum rules support
the existence of a flavor singlet hybrid with mass at around 1.9 GeV. Finally,
we study the mixing effects between hybrid and glueball currents. The mixing
between the () and the glueball causes
two states, one in the region 1.4-1.8 GeV(1.4-2.2 GeV), and the other in the
range 1.8-2.2 GeV(2.2-2.6 GeV).Comment: 12 pages, revised versio
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