113 research outputs found
Analysis of the spin structure function and twist-3 operators
We discuss the spin-dependent structure function in the
framework of the operator product expansion. It is noted that the anomalous
dimensions and coefficient functions for the twist-3 gluon-field-dependent
operators depend on the choice of the operator basis. The role played by the
operators proportional to the equation of motion is clarified.Comment: 10 pages, Latex, 1 figure (.ps files) appended after \end{document}
as an uuencoded compressed tar fil
Renormalization of gauge-invariant operators for the structure function g_2(x, Q^{2})
We investigate the nucleon's transverse spin-dependent structure function
g_2(x, Q^{2}) in the framework of the operator product expansion and the
renormalization group. We construct the complete set of the twist-3 operators
for the flavor singlet channel, and give the relations among them. We develop
an efficient, covariant approach to derive the anomalous dimension matrix of
the twist-3 singlet operators by computing the off-shell Green's functions. As
an application, we investigate the renormalization mixing for the lowest moment
case, including the operators proportional to the equations of motion as well
as the ``alien'' operators which are not gauge-invariant.Comment: 13 pages, 13 Postscript figures, psfig.sty and here.sty are require
Deep CO Observations and the CO-to-H_2 Conversion Factor in DDO 154, a Low Metallicity Dwarf Irregular Galaxy
We present a deep spectroscopic search for CO emission in the dwarf irregular
galaxy DDO154, which has an Oxygen abundance of only 1/20 the solar value. The
observations were conducted in order to constrain the CO-to-
conversion factor at low metallicity. No CO was detected, however, despite
being one of the sensitive observations done towards galaxies of this type. We
succeed in putting a strong lower limit on the conversion factor, at least 10
times the Galactic value. Our result supports previous studies which argue for
a high conversion factor at low metallicity.Comment: 11 pages, 4 figures. Accepted for publication in PAS
Fully stabilized 750-MHz Yb: fiber frequency comb
This study focuses on presenting a fully stabilized, self-referenced Yb:fiber frequency comb respectively phase locked to a microwave standard and an optical reference employing the highest, fundamental repetition rate of 750-MHz without additional external amplifiers and compressors. In addition, the challenge of phase locking the carrier envelop offset frequency for this high-repetition-rate fiber frequency comb is separately investigated in two schemes, namely, f-2f self-referencing and an approach of phase locking a beat note between the Yb: fiber frequency comb and a continuous wave laser
Spin Structure Function and Twist-3 Operators in QCD
We investigate the spin structure function in the framework
of the operator product expansion and the renormalization group. The twist-3
operators appearing in QCD are examined and their relations are studied. It is
noted that operators proportional to equation of motion appear in the operator
mixing through renormalization, which can be studied from the relevant Green's
functions. We also note that the coefficient functions can be properly fixed
after the choice of independent operators.Comment: LaTeX, 11 pages, KUCP-71; HUPD-941
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