3,209 research outputs found
Underlying Event Studies for LHC Energies
Underlying event was originally defined by the CDF collaboration decades ago.
Here we improve the original definition to extend our analysis for events with
multiple-jets. We introduce a definition for surrounding rings/belts and based
on this definition the jet- and surrounding-belt-excluded areas will provide a
good underlying event definition. We inverstigate our definition via the
multiplicity in the defined geometry. In parallel, mean transverse momenta of
these areas also studied in proton-proton collisions at TeV LHC
energy.Comment: 6 pages and 4 figure
Friedmann branes with variable tension
We introduce brane-worlds with non-constant tension, strenghtening the
analogy with fluid membranes, which exhibit a temperature-dependence according
to the empirical law established by E\"otv\"os. This new degree of freedom
allows for evolving gravitational and cosmological constants, the latter being
a natural candidate for dark energy. We establish the covariant dynamics on a
brane with variable tension in full generality, by considering asymmetrically
embedded branes and allowing for non-standard model fields in the 5-dimensional
space-time. Then we apply the formalism for a perfect fluid on a Friedmann
brane, which is embedded in a 5-dimensional charged Vaidya-Anti de Sitter
space-time.Comment: 12 pages, to appear in Phys. Rev.
Gravitational radiation reaction in compact binary systems: Contribution of the quadrupole-monopole interaction
The radiation reaction in compact spinning binaries on eccentric orbits due
to the quadrupole-monopole interaction is studied. This contribution is of
second post-Newtonian order. As result of the precession of spins the magnitude
of the orbital angular momentum is not conserved. Therefore a proper
characterization of the perturbed radial motion is provided by the energy
and angular average . As powerful computing tools, the generalized
true and eccentric anomaly parametrizations are introduced. Then the secular
losses in energy and magnitude of orbital angular momentum together with the
secular evolution of the relative orientations of the orbital angular momentum
and spins are found for eccentric orbits by use of the residue theorem. The
circular orbit limit of the energy loss agrees with Poisson's earlier result.Comment: accepted for publication in Phys. Rev.
Non-uniform Braneworld Stars: an Exact Solution
The first exact interior solution to Einstein's field equations for a static
and non-uniform braneworld star with local and non-local bulk terms is
presented. It is shown that the bulk Weyl scalar is always
negative inside the stellar distribution, in consequence it reduces both the
effective density and the effective pressure. It is found that the anisotropy
generated by bulk gravity effect has an acceptable physical behaviour inside
the distribution. Using a Reissner-N\"{o}rdstrom-like exterior solution, the
effects of bulk gravity on pressure and density are found through matching
conditions.Comment: 22 pages, 3 figures, version to be published in International Journal
of Modern Physics D (IJMPD
Differences in high p_t meson production between CERN SPS and RHIC heavy ion collisions
In this talk we present a perturbative QCD improved parton model calculation
for light meson production in high energy heavy ion collisions. In order to
describe the experimental data properly, one needs to augment the standard pQCD
model by the transverse momentum distribution of partons ("intrinsic k_T").
Proton-nucleus data indicate the presence of nuclear shadowing and
multiscattering effects. Further corrections are needed in nucleus-nucleus
collisions to explain the observed reduction of the cross section. We introduce
the idea of proton dissociation and compare our calculations with the SPS and
RHIC experimental data.Comment: Talk presented by G. Papp at Zakopane 2001 School, Zakopane, 2001
June; 10 pages with 3 EPS figure
Asymmetric Swiss-cheese brane-worlds
We study a brane-world cosmological scenario with local inhomogeneities
represented by black holes. The brane is asymmetrically embedded into the bulk.
The black strings/cigars penetrating the Friedmann brane generate a
Swiss-cheese type structure. This universe forever expands and decelerates, as
its general relativistic analogue. The evolution of the cosmological fluid
however can proceed along four branches, two allowed to have positive energy
density, one of them having the symmetric embedding limit. On this branch a
future pressure singularity can arise for either (a) a difference in the
cosmological constants of the cosmological and black hole brane regions (b) a
difference in the left and right bulk cosmological constants. While the
behaviour (a) can be avoided by a redefinition of the fluid variables, (b)
establishes a critical value of the asymmetry over which the pressure
singularity occurs. We introduce the pressure singularity censorship which
bounds the degree of asymmetry in the bulk cosmological constant. We also show
as a model independent generic feature that the asymmetry source term due to
the bulk cosmological constant increases in the early universe. In order to
obey the nucleosynthesis constraints, the brane tension should be constrained
therefore both from below and from above. With the maximal degree of asymmetry
obeying the pressure singularity censorship, the higher limit is 10 times the
lower limit. The degree of asymmetry allowed by present cosmological
observations is however much less, pushing the upper limit to infinity.Comment: v2: considerably expanded, 19 pages, 8 figures, many new references.
Pressure singularity censorship introduced, strict limits on the possible
degree of asymmetry derived. v3: model independent analysis shows that the
asymmetry bounds the brane tension from above. Limits on the maximal tension
set. Version published in JCA
Crystallization and preliminary crystallographic analysis of dUTPase from the helper phage Ί11 of Staphylococcus aureus
Staphylococcus aureus superantigen-carrying pathogenicity islands (SaPIs) have a
determinant role in spreading virulence genes among bacterial populations that constitute a
major health hazard. Repressor (Stl) proteins are responsible for transcriptional regulation of
pathogenicity island genes. Recently, a derepressing interaction between the repressor Stl
SaPIbov1 with dUTPase from the Ί11 helper phage was suggested [Tormo-Mas et al. (2010).
Nature 465, 779-782]. Towards elucidating the molecular mechanism of this interaction, this
study reports expression, purification, and X-ray analysis of Ί11 dUTPase that contains a
phage-specific polypeptide segment not present in other dUTPases. Crystals were obtained
using the hanging-drop vapor-diffusion method at room temperature. Data were collected
from one type of crystal to 2.98 Ă
resolution. The crystal of Ί11 dUTPase belonged to the
cubic space group I23, with unit-cell parameters a=98.16 Ă
, α=ÎČ=Îł= 90.00o
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