233,284 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
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
Statistical nature of cluster emission in nuclear liquid-vapour phase coexistence
The emission of nuclear clusters is investigated within the framework of
isospin dependent lattice gas model and classical molecular dynamics model. It
is found that the emission of individual cluster which is heavier than proton
is almost Poissonian except near the transition temperature at which the system
is leaving the liquid-vapor phase coexistence and the thermal scaling is
observed by the linear Arrhenius plots which is made from the average
multiplicity of each cluster versus the inverse of temperature in the liquid
vapor phase coexistence. The slopes of the Arrhenius plots, {\it i.e.} the
"emission barriers", are extracted as a function of the mass or charge number
and fitted by the formula embodied with the contributions of the surface energy
and Coulomb interaction. The good agreements are obtained in comparison with
the data for low energy conditional barriers. In addition, the possible
influences of the source size, Coulomb interaction and "freeze-out" density and
related physical implications are discussed
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