1,032 research outputs found
Semi-inclusive structure functions in the spectator model
We establish the relationship between distribution and fragmentation
functions and the structure functions appearing in the cross section of
polarized 1-particle inclusive deep-inelastic scattering. We present spectator
model evaluations of these structure functions focusing on the case of an
outgoing spin-1/2 baryon. Distribution functions obtained in the spectator
model are known to fairly agree at low energy scales with global
parameterizations extracted, for instance, from totally inclusive DIS data.
Therefore, we expect it to give good hints on the functional dependence of the
structure functions on the scaling variables x(Bjorken), z and on the
transverse momentum of the observed outgoing hadron, P_{h\perp}. Presently,
this dependence is not very well known, but experiments are planned in the near
future.Comment: 19 pages, 16 figures, submitted to Eur. Phys. J.
Application of crossflow ultrafiltration for scaling up the purification of a recombinant ferritin
Ferritin proteins are taking center stage as smart nanocarriers for drug delivery due to their hollow cage-like structures and their unique 24-meric assembly. Among all ferritins, the chimeric Archaeoglobus ferritin (HumFt) is able assemble/disassemble varying the ionic strength of the medium while recognizing human TfR1 receptor overexpressed in cancer cells. In this paper we present a highly efficient, large scale purification protocol mainly based on crossflow ultrafiltration, starting from fermented bacterial paste. This procedure allows one to obtain about 2 g of purified protein starting from 100 g of fermented bacterial paste. The current procedure can easily remove contaminant proteins as well as DNA molecules in the absence of expensive and time consuming chromatographic steps
Azimuthal spin asymmetries in light-cone constituent quark models
We present results for all leading-twist azimuthal spin asymmetries in
semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even
transverse-momentum dependent parton distribution functions on the basis of a
light-cone constituent quark model. Attention is paid to discuss the range of
applicability of the model, especially with regard to the scale dependence of
the observables and the transverse-momentum dependence of the distributions. We
find good agreement with available experimental data and present predictions to
be further tested by future CLAS, COMPASS and HERMES data.Comment: 23 pages, 14 figures, 1 tabl
Transverse momentum dependent parton distributions and azimuthal asymmetries in light-cone quark models
We review the information on the spin and orbital angular momentum structure
of the nucleon encoded in the T-even transverse momentum dependent parton
distributions within light-cone quark models. Model results for azimuthal spin
asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering are
discussed, showing a good agreement with available experimental data and
providing predictions to be further tested by future CLAS, COMPASS and HERMES
data.Comment: 6 pages, 4 figures; proceedings of the "XIII Workshop On High Energy
Spin Physics Dubna Spin 2009", 1-5 September 2009, Dubna, Russi
TMDs and Azimuthal Spin Asymmetries in a Light-Cone Quark Model
The main properties of the leading-twist transverse momentum dependent parton
distributions in a light-cone constituent quark model of the nucleon are
reviewed, with focus on the role of the spin-spin and spin-orbit correlations
of quarks. Results for azimuthal single spin asymmetries in semi-inclusive deep
inelastic scattering are also discussed.Comment: Proceedings of SPIN2008, 6-11 October 2008, Charlottesville, VA, US
Nuclear transparency in quasielastic A(e,e'p): intranuclear cascade versus eikonal approximation
The problem of nuclear propagation through the nuclear medium in quasielastic
A(e,e'p) reactions is discussed in the kinematic range 1<Q^2<7 (GeV/c)^2. The
coefficient of nuclear transparency is calculated for each Q^2 in the framework
of the intranuclear cascade model (INC) and of the eikonal approximation (EA).
The predictions of both models are in good agreement with each other and with
experimental data recently obtained at SLAC, BATES and TJNAF. The EA gives an
explanation of the Q^2 behaviour of the transparency coefficient as a kinematic
effect related to the superposition of contributions from each target shell.Comment: RevTeX, 23 pages, 11 figures separately, submitted to Phys. Rev.
Calculation of fragmentation functions in two-hadron semi-inclusive processes
We investigate the properties of interference fragmentation functions arising
from the emission of two leading hadrons inside the same jet for inclusive
lepton-nucleon deep-inelastic scattering. Using an extended spectator model for
the mechanism of the hadronization, we give a complete calculation and
numerical estimates for the examples of a proton-pion pair produced with
invariant mass on the Roper resonance, and of two pions produced with invariant
mass close to the mass. We discuss azimuthal angular dependence of the
leading order cross section to point up favourable conditions for extracting
transversity from experimental data.Comment: 5 pages, 3 figures in .eps format, AIP and epsfig styles included, to
appear in proceedings of "Second Workshop on Physics with an Electron
Polarized Light Ion Collider", MIT, Sept. 14-16, 200
High-momentum proton removal from 16O and the (e,e'p) cross section
The cross section for the removal of high-momentum protons from 16O is
calculated for high missing energies. The admixture of high-momentum nucleons
in the 16O ground state is obtained by calculating the single-hole spectral
function directly in the finite nucleus with the inclusion of short-range and
tensor correlations induced by a realistic meson-exchange interaction. The
presence of high-momentum nucleons in the transition to final states in 15N at
60-100 MeV missing energy is converted to the coincidence cross section for the
(e,e'p) reaction by including the coupling to the electromagnetic probe and the
final state interactions of the outgoing proton in the same way as in the
standard analysis of the experimental data. Detectable cross sections for the
removal of a single proton at these high missing energies are obtained which
are considerably larger at higher missing momentum than the corresponding cross
sections for the p-wave quasihole transitions. Cross sections for these
quasihole transitions are compared with the most recent experimental data
available.Comment: 26 RevTex pages, 7 ps figure
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