6,160 research outputs found
Spin transfer and polarization of antihyperons in lepton induced reactions
We study the polarization of antihyperon in lepton induced reactions such as
and with polarized beams using
different models for spin transfer in high energy fragmentation processes. We
compare the results with the available data and those for hyperons. We make
predictions for future experiments.Comment: 31 pages, 6 figures. submitted to Phys. Rev. D. content changed,
references adde
Production mechanisms and single-spin asymmetry for kaons in high energy hadron-hadron collisions
Direct consequences on kaon production of the picture proposed in a recent
Letter and subsequent publications are discussed. Further evidence supporting
the proposed picture is obtained. Comparison with the data for the inclusive
cross sections in unpolarized reactions is made. Quantitative results for the
left-right asymmetry in single-spin processes are presented.Comment: 10 pages, 2 Postscript figure
Hyperon Polarization in Unpolarized Scattering Processes
Transverse polarization in the Hyperon production in the unpolarized deep
inelastic scattering and pp collisions is studied in the twist-three approach,
considering the contribution from the quark-gluon-antiquark correlation
distribution in nucleon. We further compare our results for deep inelastic
scattering to a transverse momentum dependent factorization approach, and find
consistency between the two approaches in the intermediate transverse momentum
region. We also find that in pp collisions, there are only derivative terms
contributions, and the non-derivative terms vanish.Comment: 13 pages, 1 figur
Transverse momentum dependent quark distributions and polarized Drell-Yan processes
We study the spin-dependent quark distributions at large transverse momentum.
We derive their transverse momentum behaviors in the collinear factorization
approach in this region. We further calculate the angular distribution of the
Drell-Yan lepton pair production with polarized beams and present the results
in terms of the collinear twist-three quark-gluon correlation functions. In the
intermediate transverse momentum region, we find that the two pproaches: the
collinear factorization and the transverse momentum dependent factorization
approaches are consistent in the description of the lepton pair angular
distributions.Comment: 25 pages, 2 figure
The Transverse-momentum-dependent Parton Distribution Function and Jet Transport in Medium
We show that the gauge-invariant transverse-momentum-dependent (TMD) quark
distribution function can be expressed as a sum of all higher-twist collinear
parton matrix elements in terms of a transport operator. From such a general
expression, we derive the nuclear broadening of the transverse momentum
distribution. Under the maximal two-gluon correlation approximation, in which
all higher-twist nuclear multiple-parton correlations with the leading nuclear
enhancement are given by products of twist-two nucleon parton distributions, we
find the nuclear transverse momentum distribution as a convolution of a
Gaussian distribution and the nucleon TMD quark distribution. The width of the
Gaussian, or the mean total transverse momentum broadening squared, is given by
the path integral of the quark transport parameter which can also be
expressed in a gauge invariant form and is given by the gluon distribution
density in the nuclear medium. We further show that contributions from
higher-twist nucleon gluon distributions can be resummed under the extended
adjoint two-gluon correlation approximation and the nuclear transverse momentum
distribution can be expressed in terms of a transverse scale dependent quark
transport parameter or gluon distribution density. We extend the study to hot
medium and compare to dipole model approximation and
Supersymmetric Yang-Mills (SYM) theory in the strong coupling limit. We find
that multiple gluon correlations become important in the strongly coupled
system such as SYM plasma.Comment: 22 pages in RevTex with 2 figures final published versio
QCD Evolution of the Transverse Momentum Dependent Correlations
We study the QCD evolution for the twist-three quark-gluon correlation
functions associated with the transverse momentum odd quark distributions.
Different from that for the leading twist quark distributions, these evolution
equations involve more general twist-three functions beyond the correlation
functions themselves. They provide important information on nucleon structure,
and can be studied in the semi-inclusive hadron production in deep inelastic
scattering and Drell-Yan lepton pair production in scattering process.Comment: 13 pages, 1 figur
Temperature behavior of the magnon modes of the square lattice antiferromagnet
A spin-wave theory of short-range order in the square lattice Heisenberg
antiferromagnet is formulated. With growing temperature from T=0 a gapless mode
is shown to arise simultaneously with opening a gap in the conventional
spin-wave mode. The spectral intensity is redistributed from the latter mode to
the former. For low temperatures the theory reproduces results of the modified
spin-wave theory by M.Takahashi, J.E.Hirsch et al. and without fitting
parameters gives values of observables in good agreement with Monte Carlo
results in the temperature range 0 <= T < 0.8J where J is the exchange
constant.Comment: 12 pages, 2 figure
One-loop approximation for the Heisenberg antiferromagnet
We use the diagram technique for spin operators to calculate Green's
functions and observables of the spin-1/2 quantum Heisenberg antiferromagnet on
a square lattice. The first corrections to the self-energy and interaction are
taken into account in the chain diagrams. The approximation reproduces main
results of Takahashi's modified spin-wave theory [Phys. Rev. B 40, 2494 (1989)]
and is applicable in a wider temperature range. The energy per spin calculated
in this approximation is in good agreement with the Monte Carlo and
small-cluster exact-diagonalization calculations in the range 0 <= T < 1.2J
where J is the exchange constant. For the static uniform susceptibility the
agreement is good for T < 0.6J and becomes somewhat worse for higher
temperatures. Nevertheless the approximation is able to reproduce the maximum
in the temperature dependence of the susceptibility near T = 0.9J.Comment: 15 pages, 6 ps figure
Probing gluon helicity distribution and quark transversity through hyperon polarization in singly polarized pp collisions
We study the polarization of hyperon in different processes in singly
polarized collisions, in particular its relation to the polarized parton
distributions. We show that by measuring hyperon polarization in particularly
chosen processes, one can extract useful information on these parton
distributions. We show in particular that, by measuring the
polarization in high direct photon production process, one can extract
information on the gluon helicity distribution; and by measuring the transverse
polarization of hyeprons with high in singly polarized reactions, one can
obtain useful information on the transversity distribution. We present the
numerical results obtained for those hyperon polarizations using different
models for parton distribution function and those for the spin transfer in
fragmentation processes.Comment: 25 pages, 8 figures, to appear in Phys. Rev.
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