301,002 research outputs found
Spin Alignment of Heavy Meson Revisited
Using heavy quark effective theory a factorized form for inclusive production
rate of a heavy meson can be obtained, in which the nonperturbative effect
related to the heavy meson can be characterized by matrix elements defined in
the heavy quark effective theory. Using this factorization, predictions for the
full spin density matrix of a spin-1 and spin-2 meson can be obtained and they
are characterized only by one coefficient representing the nonperturbative
effect. Predictions for spin-1 heavy meson are compared with experiment
performed at colliders in the energy range from GeV to
GeV, a complete agreement is found for - and -meson.
There are distinct differences from the existing approach and they are
discussed.Comment: 6 pages, Talk given at 3rd Circum-Pan-Pacific Symposium on "High
Energy Spin Physics", Beijing, China, 8-13, 200
A QCD-Analysis for Radiative Decays of into
We perform a QCD analysis for the radiative decay of a heavy
quarkonium into the tensor meson . We make an attempt to separate
the nonperturbative effect related to the quarkonium and that related to the
tensor meson, the former is represented by NRQCD matrix elements, while the
later is parameterized by distribution amplitudes of gluons in the tensor meson
at twist-2 level and at twist-3 level. We find that at twist-2 level the
helicity of the tensor meson can be 0 and 2 and the amplitude with
is suppressed. At twist-3 level the tensor meson can have . A comparison with experiment is made, an agreement of our results with
experiment can be found. We also briefly discuss the radiative decay into
and obtain a prediction for .Comment: Corrections of two type-errors and a numerical error in the published
version in Nucl.Phys. B605 (2001) 625, conclusions remain the sam
Gauge Invariance and QCD Twist-3 Factorization for Single Spin Asymmetries
The collinear factorization at twist-3 for Drell-Yan processes is studied
with the motivation to solve the discrepancy in literature about the single
spin asymmetry in the lepton angular distribution, and to show how QCD gauge
invariance is realized in the hadronic tensor. The obtained result here agrees
with our early result derived with a totally different approach. In addition to
the asymmetry we can construct another two observables to identify the spin
effect. We show that the gauge invariance of different contributions in the
hadronic tensor is made in different ways by summing the effects of gluon
exchanges. More interestingly is that we can show that the virtual correction
to one structure function of the hadronic tensor, hence to some weighted SSA
observables, is completely determined by the quark form factor. This will
simplify the calculation of higher order corrections. The corresponding result
in semi-inclusive DIS is also given for the comparison with Drell-Yan
processes.Comment: Small changes, accepted by JHE
Twist-3 Contributions in Semi-Inclusive DIS with Transversely Polarized Target
We study semi-inclusive DIS with a transversely polarized target in the
approach of collinear factorization. The effects related with the transverse
polarization are at twist-3. We derive the complete result of twist-3
contributions to the relevant hadronic tensor at leading order of ,
and construct correspondingly experimental observables. Measuring these
observables will help to extract the twist-2 transversity distribution, twist-3
distributions and twist-3 fragmentation functions of the produced unpolarized
hadron. A detailed comparison with the approach of
transverse-momentum-dependent factorization is made.Comment: discussions and references are added. Published version in PL
QCD Evolutions of Twist-3 Chirality-Odd Operators
We study the scale dependence of twist-3 distributions defined with
chirality-odd quark-gluon operators. To derive the scale dependence we
explicitly calculate these distributions of multi-parton states instead of a
hadron. Taking one-loop corrections into account we obtain the leading
evolution kernel in the most general case. In some special cases the evolutions
are simplified. We observe that the obtained kernel in general does not get
simplified in the large- limit in contrast to the case of those twist-3
distributions defined only with chirality-odd quark operators. In the later,
the simplification is significant.Comment: 9 pages, 2 figure
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