5,823 research outputs found
Modeling Two Dimensional Magnetic Domain Patterns
Two-dimensional magnetic garnets exhibit complex and fascinating magnetic
domain structures, like stripes, labyrinths, cells and mixed states of stripes
and cells. These patterns do change in a reversible way when the intensity of
an externally applied magnetic field is varied. The main objective of this
contribution is to present the results of a model that yields a rich pattern
structure that closely resembles what is observed experimentally. Our model is
a generalized two-dimensional Ising-like spin-one Hamiltonian with long-range
interactions, which also incorporates anisotropy and Zeeman terms. The model is
studied numerically, by means of Monte Carlo simulations. Changing the model
parameters stripes, labyrinth and/or cellular domain structures are generated.
For a variety of cases we display the patterns, determine the average size of
the domains, the ordering transition temperature, specific heat, magnetic
susceptibility and hysteresis cycle. Finally, we examine the reversibility of
the pattern evolution under variations of the applied magnetic field. The
results we obtain are in good qualitative agreement with experiment.Comment: 8 pages, 12 figures, submitted to Phys. Rev.
On the rapidity dependence of the average transverse momentum in hadronic collisions
The energy and rapidity dependence of the average transverse momentum
in and collisions at RHIC and LHC energies are
estimated using the Colour Glass Condensate (CGC) formalism. We update previous
predictions for the - spectra using the hybrid formalism of the CGC
approach and two phenomenological models for the dipole - target scattering
amplitude. We demonstrate that these models are able to describe the RHIC and
LHC data for the hadron production in , and collisions at GeV. Moreover, we present our predictions for and
demonstrate that the ratio decreases with the rapidity and has a behaviour similar to that
predicted by hydrodynamical calculations.Comment: 11 pages, 7 figures; revised version: new results for the average
transverse momentum at partonic level added in fig. 4; Results and Discussion
section has been improved and enlarge
Testing the running coupling -factorization formula for the inclusive gluon production
The inclusive gluon production at midrapidities is described in the Color
Glass Condensate formalism using the - factorization formula, which was
derived at fixed coupling constant considering the scattering of a dilute
system of partons with a dense one. Recent analysis demonstrated that this
approach provides a satisfactory description of the experimental data for the
inclusive hadron production in collisions. However, these studies
are based on the fixed coupling - factorization formula, which does not
take into account the running coupling corrections, which are important to set
the scales present in the cross section. In this paper we consider the running
coupling corrected - factorization formula conjectured some years ago and
investigate the impact of the running coupling corrections on the observables.
In particular, the pseudorapidity distributions and charged hadrons
multiplicity are calculated considering , and
collisions at RHIC and LHC energies. We compare the corrected running coupling
predictions with those obtained using the original - factorization
assuming a fixed coupling or a prescription for the inclusion of the running of
the coupling. Considering the Kharzeev - Levin - Nardi unintegrated gluon
distribution and a simplified model for the nuclear geometry, we demonstrate
that the distinct predictions are similar for the pseudorapidity distributions
in collisions and for the charged hadrons multiplicity in
collisions. On the other hand, the running coupling corrected -
factorization formula predicts a smoother energy dependence for in
collisions.Comment: 9 pages and 4 figure
Signals for New Spin-1 Resonances in Electroweak Gauge Boson Pair Production at the LHC
The mechanism of electroweak symmetry breaking (EWSB) will be directly
scrutinized soon at the CERN Large Hadron Collider (LHC). We analyze the LHC
potential to look for new vector bosons associated with the EWSB sector. We
present a possible model independent approach to search for these new spin--1
resonances. We show that the analyses of the processes pp --> l^+ l^- Emiss_T,
l^\pm j j Emiss_T, l^\pm l^+ l^- Emiss_T, and l^+ l^- j j (with l=e or \mu and
j=jet) have a large reach at the LHC and can lead to the discovery or exclusion
of many EWSB scenarios such as Higgsless models.Comment: 10 pages, 11 figure
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