520 research outputs found
Positivity bounds on generalized parton distributions in impact parameter representation
New positivity bounds are derived for generalized (off-forward) parton
distributions using the impact parameter representation. These inequalities are
stable under the evolution to higher normalization points. The full set of
inequalities is infinite. Several particular cases are considered explicitly.Comment: 8 page
Thermodynamics of a Trapped Bose-Fermi Mixture
By using the Hartree-Fock-Bogoliubov equations within the Popov
approximation, we investigate the thermodynamic properties of a dilute binary
Bose-Fermi mixture confined in an isotropic harmonic trap. For mixtures with an
attractive Bose-Fermi interaction we find a sizable enhancement of the
condensate fraction and of the critical temperature of Bose-Einstein
condensation with respect to the predictions for a pure interacting Bose gas.
Conversely, the influence of the repulsive Bose-Fermi interaction is less
pronounced. The possible relevance of our results in current experiments on
trapped {\rm K} mixtures is discussed.Comment: 5 pages + 4 figures; minor changes, final version to appear in Phys.
Rev. A; the extension work on the finite-temperature low-lying excitations
can be found in cond-mat/030763
Regulatory Taking: A Contract Approach
This Article begins by defining the parameters of the fifth amendment\u27s taking clause. The Article then reviews the various tests used in determining whether governmental action constitutes a taking, and discusses the recent Supreme Court decisions within the framework of case law as it has evolved since the Court\u27s 1922 landmark decision, Pennsylvania Coal Co. v. Mahon. Finally, the Article suggests a formula based on well-established contract principles for analyzing the impact of land use regulation on private property interests
A lattice calculation of the nucleon's spin-dependent structure function g_2 revisited
Our previous calculation of the spin-dependent structure function g_2 is
revisited. The interest in this structure function is to a great extent
motivated by the fact that it receives contributions from twist-two as well as
from twist-three operators already in leading order of 1/Q^2 thus offering the
unique possibility of directly assessing higher-twist effects. In our former
calculation the lattice operators were renormalized perturbatively and mixing
with lower-dimensional operators was ignored. However, the twist-three operator
which gives rise to the matrix element d_2 mixes non-perturbatively with an
operator of lower dimension. Taking this effect into account leads to a
considerably smaller value of d_2, which is consistent with the experimental
data.Comment: 25 pages, 11 figure
Deeply virtual electroproduction of photons and mesons on the nucleon : leading order amplitudes and power corrections
We estimate the leading order amplitudes for exclusive photon and meson
electroproduction reactions at large Q^2 in the valence region in terms of
skewed quark distributions. As experimental investigations can currently only
be envisaged at moderate values of Q^2, we estimate power corrections due to
the intrinsic transverse momentum of the partons in the meson wavefunction and
in the nucleon. To this aim the skewed parton distribution formalism is
generalized so as to include the parton intrinsic transverse momentum
dependence. Furthermore, for the meson electroproduction reactions, we
calculate the soft overlap type contributions and compare with the leading
order amplitudes. We give first estimates for these different power corrections
in kinematics which are relevant for experiments in the near future.Comment: 59 pages, 21 figure
Skewed and double distributions in pion and nucleon
We study the non-forward matrix elements of twist-2 QCD light-ray operators
and their representations in terms of skewed and double distributions,
considering the pion as well as the nucleon. We point out the importance of
explicitly including all twist-2 structures in the double distribution
representation, which naturally leads to a ``two-component'' structure of the
skewed distribution, with different contributions in the regions |X| > xi/2 and
|X| < \xi/2. We compute the skewed and double quark distributions in the pion
at a low normalization point in the effective chiral theory based on the
instanton vacuum. Also, we derive the crossing relations expressing the skewed
quark distribution in the pion through the distribution amplitude for two--pion
production. Measurement of the latter in two-pion production in gamma^* gamma
and gamma^* N reactions could provide direct information about the skewed as
well as the usual quark/antiquark-distribution in the pion.Comment: 37 pages, LaTeX. 5 figures included using eps
Accessing Transversity in Double-Spin Asymmetries at the BNL-RHIC
We give upper bounds for transverse double-spin asymmetries in polarized
proton-proton collisions by saturating the positivity constraint for the
transversity densities at a low hadronic resolution scale. We consider prompt
photon, jet, pion, and heavy flavor production at the BNL Relativistic Heavy
Ion Collider (RHIC). Estimates of the expected statistical accuracy for such
measurements are presented, taking into account the acceptance of the RHIC
detectors.Comment: 15 pages, LaTeX, 2 figures as eps file
Finite temperature effects on the collapse of trapped Bose-Fermi mixtures
By using the self-consistent Hartree-Fock-Bogoliubov-Popov theory, we present
a detailed study of the mean-field stability of spherically trapped Bose-Fermi
mixtures at finite temperature. We find that, by increasing the temperature,
the critical particle number of bosons (or fermions) and the critical
attractive Bose-Fermi scattering length increase, leading to a significant
stabilization of the mixture.Comment: 5 pages, 4 figures; minor changes, proof version, to appear in Phys.
Rev. A (Nov. 1, 2003
Determination of trace elements in natural water samples by air-segmented flow-injection/ICP-MS after preconcentration with a chitosan-based chelating resin
本法では,各種天然水中の極微量金属成分を同時定量する目的で空気分節試料導入/ICP-MSシステムを用いて,微少量試料(数十μl)を前処理せずにネブライザーに送り込み,多数の金属成分の定量が可能であった。共存主成分による質量干渉を受ける一部遷移金属や直接試料導入では感度の足りない元素については,イミノ二酢酸型キトサンキレート樹脂充填カラムによる分離·濃縮操作の併用によって更に信頼性の高いデータが得られることが分かった。前処理においては,体積1mlのミニカラムを用いて50mlの溶液試料から50倍濃縮を行い,試料·試薬·廃液すべてを少量化することができた。本ICP-MSシステムでは試料導入量は80μlで十分であり,1mlでも数回繰り返し測定が可能で,しかも多元素同時分析ができた。確立した分析法を用いて河川水や市販のミネラルウォーターに応用し,希土類を含め45種の微量元素の定量が可能となった。Ultratrace elements in natural water samples were determined simultaneously by air-segmented flow-injection/inductively coupled plasma-mass spectrometry(SFI/ICP-MS).A small volume of the sample solutions(80μl) was introduced into a nebulizer by an air-segmented flow-injection(SFI) system, and a maximum of fifteen elements were measured during each run.A chitosan-based chelating resin containing functional groups of iminodiacetate was used to separate and enrich analyte metal ions.A 50-fold preconcentration using 50ml of sample solutions was achieved by the proposed method, where 1ml of 0.1M nitric acid was added to residues after drying the chelating column effluent.At pH6, several heavy metals(Fe, Ni, Co, Cu, Zn, Ag, Cd, Pb and U) and rare earth elements(REEs) were quantitatively retained on the chelating resin column, whereas alkali and alkaline earth metals were eluted from the column by rinsing with 5ml of a 0.2M ammonium acetate solution.Metals adsorbed on the chelating resin column were recovered by elution with 10ml of 1M nitric acid.The proposed method was applied to the determination of trace elements in several natural water samples, such as river water and mineral drinking water
Next-to-leading order QCD corrections to A_TT for prompt photon production
We present a next-to-leading order QCD calculation of the cross section for
isolated large-p_T prompt photon production in collisions of transversely
polarized protons. We devise a simple method of dealing with the phase space
integrals in dimensional regularization in the presence of the cos(2 phi)
azimuthal-angular dependence occurring for transverse polarization. Our results
allow to calculate the double-spin asymmetry A_TT for this process at
next-to-leading order accuracy, which may be used at BNL-RHIC to measure the
transversity parton distributions of the proton.Comment: 19 pages, LaTeX, 2 figures as eps file
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