7,601 research outputs found
Chiral Structure of Vector and Axial-Vector Tetraquark Currents
We investigate the chiral structure of local vector and axial-vector
tetraquark currents, and study their chiral transformation properties. We
consider the charge-conjugation parity and classify all the isovector vector
and axial-vector local tetraquark currents of quantum numbers
I(G)J(PC)=1(-)1(-+), I(G)J(PC)=1(+)1(--), I(G)J(PC)=1(-)1(++) and
I(G)J(PC)=1(+)1(+-). We find that there is a one to one correspondence among
them. Using these currents, we perform QCD sum rule analyses. Our results
suggest that there is a missing b1 state having I(G)J(PC)=1(+)1(+-) and a mass
around 1.47-1.66 GeV.Comment: 27 pages, 8 figures, 3 tables, accepted by EPJC. arXiv admin note:
text overlap with arXiv:1311.443
Single soft gluon emission at two loops
We study the single soft-gluon current at two loops with two energetic
partons in massless perturbative QCD, which describes, for example, the soft
limit of the two-loop amplitude for . The results are presented as
Laurent expansions in in spacetime dimension. We
calculate the expansion to order analytically, which is a
necessary ingredient for Higgs production at hadron colliders at
next-to-next-to-next-to-leading order in the soft-virtual approximation. We
also give two-loop results of the single soft-gluon current in
Super-Yang-Mills theory, and find that it has uniform transcendentality. By
iteration relation of splitting amplitudes, our calculations can determine the
three-loop single soft-gluon current to order in
Super-Yang-Mills theory in the limit of large .Comment: typos corrected; journal versio
On the four-zero texture of quark mass matrices and its stability
We carry out a new study of quark mass matrices (up-type) and
(down-type) which are Hermitian and have four zero entries, and
find a new part of the parameter space which was missed in the previous works.
We identify two more specific four-zero patterns of and
with fewer free parameters, and present two toy flavor-symmetry
models which can help realize such special and interesting quark flavor
structures. We also show that the texture zeros of and
are essentially stable against the evolution of energy scales in
an analytical way by using the one-loop renormalization-group equations.Comment: 33 pages, 4 figures, minor comments added, version to appear in Nucl.
Phys.
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