9,888 research outputs found
Quark-antiquark contribution to the BFKL kernel
The quark-antiquark contribution to the BFKL kernel is calculated. Using the
effective vertex for the pair production in the Reggeon-Reggeon
collision we find this contribution by integrating the square of this vertex
over relative transverse momenta and fractions of longitudinal momenta of
produced particles.Comment: 12 pages, Late
How to measure the Pomeron phase in diffractive dipion photoproduction
The study of charge asymmetry of pions in the high-energy process gamma p ->
pi+ pi- p (e p -> e pi+ pi- p) at very small dipion momenta offers a method to
measure the phase of the forward hadronic (quasi)elastic amplitude gamma p ->
rho p. We estimate potential of such measurements at HERA.Comment: 12 pages, 2 figures; v4: more elaborate parametrizations of dipion
spectra implemented, discussion extende
q-Deformed quaternions and su(2) instantons
We have recently introduced the notion of a q-quaternion bialgebra and shown
its strict link with the SO_q(4)-covariant quantum Euclidean space R_q^4.
Adopting the available differential geometric tools on the latter and the
quaternion language we have formulated and found solutions of the
(anti)selfduality equation [instantons and multi-instantons] of a would-be
deformed su(2) Yang-Mills theory on this quantum space. The solutions depend on
some noncommuting parameters, indicating that the moduli space of a complete
theory should be a noncommutative manifold. We summarize these results and add
an explicit comparison between the two SO_q(4)-covariant differential calculi
on R_q^4 and the two 4-dimensional bicovariant differential calculi on the bi-
(resp. Hopf) algebras M_q(2),GL_q(2),SU_q(2), showing that they essentially
coincide.Comment: Latex file, 18 page
A Kinematically Complete Analysis of the CLAS data on the Proton Structure Function in a Regge-Dual model
The recently measured inclusive electron-proton cross section in the nucleon
resonance region, performed with the CLAS detector at the Thomas Jefferson
Laboratory, has provided new data for the nucleon structure function with
previously unavailable precision. In this paper we propose a description of
these experimental data based on a Regge-dual model for . The basic inputs
in the model are nonlinear complex Regge trajectories producing both isobar
resonances and a smooth background. The model is tested against the
experimental data, and the dependence of the moments is calculated. The
fitted model for the structure function (inclusive cross section) is a limiting
case of the more general scattering amplitude equally applicable to deeply
virtual Compton scattering (DVCS). The connection between the two is discussed.Comment: 21 pages, 12 figures, revtex style. Misprints in eqs. (15,17) are
corrected. To appear in Phys. Rev.
TMD PDF's: gauge invariance, RG properties and Wilson lines
The UV divergences associated with transverse-momentum dependent (TMD) parton
distribution functions (PDF) are calculated together with the ensuing one-loop
anomalous dimensions in the light-cone gauge. Time-reversal-odd effects in the
anomalous dimensions are observed and the role of Glauber gluons is discussed.
A generalized renormalization procedure of TMD PDFs is proposed, relying upon
the renormalization of contour-dependent operators with obstructions.Comment: 4 pages, 1 figure. Talk presented at the International Workshop on
Diffraction in High Energy and Nuclear Physics, La Londe-les-Maures, France,
9-14 Sept 2008. v2: 5 pages, preprint number and e-mail addresses adde
The spectrum of screening masses near T_c: predictions from universality
We discuss the spectrum of screening masses in a pure gauge theory near the
deconfinement temperature from the point of view of the dimensionally reduced
model describing the spontaneous breaking of the center symmetry. Universality
arguments can be used to predict the values of the mass ratios in the scaling
region of the deconfined phase when the transition is of second order. One such
prediction is that the scalar sector of the screening spectrum in SU(2) pure
gauge theory contains a bound state of the fundamental excitation,
corresponding through universality to the bound state found in the 3D Ising
model and phi^4 theory in the broken symmetry phase. A Monte Carlo evaluation
of the screening masses in the gauge theory confirms the validity of the
prediction. We briefly discuss the possibility of using similar arguments for
first order deconfinement transitions, and in particular for the physically
relevant case of SU(3).Comment: 12 pages, 3 figures. Some changes in the discussion, added
references, results unchanged. Version to appear in Phys. Rev.
Confocal laser scanning microscope, raman microscopy and western blotting to evaluate inflammatory response after myocardial infarction
Cardiac muscle necrosis is associated with inflammatory cascade that clears the infarct from dead
cells and matrix debris, and then replaces the damaged tissue with scar, through three overlapping phases: the
inflammatory phase, the proliferative phase and the maturation phase.
Western blotting, laser confocal microscopy, Raman microscopy are valuable tools for studying the inflammatory
response following myocardial infarction both humoral and cellular phase, allowing the identification and
semiquantitative analysis of proteins produced during the inflammatory cascade activation and the topographical distribution
and expression of proteins and cells involved in myocardial inflammation. Confocal laser scanning microscopy
(CLSM) is a relatively new technique for microscopic imaging, that allows greater resolution, optical sectioning of the
sample and three-dimensional reconstruction of the same sample. Western blotting used to detect the presence of a specific
protein with antibody-antigen interaction in the midst of a complex protein mixture extracted from cells, produced
semi-quantitative data quite easy to interpret. Confocal Raman microscopy combines the three-dimensional optical resolution
of confocal microscopy and the sensitivity to molecular vibrations, which characterizes Raman spectroscopy.
The combined use of western blotting and confocal microscope allows detecting the presence of proteins in the sample
and trying to observe the exact location within the tissue, or the topographical distribution of the same. Once demonstrated
the presence of proteins (cytokines, chemokines, etc.) is important to know the topographical distribution, obtaining in this
way additional information regarding the extension of the inflammatory process in function of the time stayed from the
time of myocardial infarction. These methods may be useful to study and define the expression of a wide range of inflammatory
mediators at several different timepoints providing a more detailed analysis of the time course of the infarct
Obtaining pressure versus concentration phase diagrams in spin systems from Monte Carlo simulations
We propose an efficient procedure for determining phase diagrams of systems
that are described by spin models. It consists of combining cluster algorithms
with the method proposed by Sauerwein and de Oliveira where the grand canonical
potential is obtained directly from the Monte Carlo simulation, without the
necessity of performing numerical integrations. The cluster algorithm presented
in this paper eliminates metastability in first order phase transitions
allowing us to locate precisely the first-order transitions lines. We also
produce a different technique for calculating the thermodynamic limit of
quantities such as the magnetization whose infinite volume limit is not
straightforward in first order phase transitions. As an application, we study
the Andelman model for Langmuir monolayers made of chiral molecules that is
equivalent to the Blume-Emery-Griffiths spin-1 model. We have obtained the
phase diagrams in the case where the intermolecular forces favor interactions
between enantiomers of the same type (homochiral interactions). In particular,
we have determined diagrams in the surface pressure versus concentration plane
which are more relevant from the experimental point of view and less usual in
numerical studies
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