10,194 research outputs found
Flow effects on jet profiles and multiplicities
We study the effects of low- collective flow on radiative energy loss
from high- partons traversing the QCD medium created in high-energy
nucleus-nucleus collisions. We illustrate this idea through three examples. Due
to longitudinal flow, jet profiles at the LHC present marked asymmetries in the
-plane, and widths in and of particle
distributions associated with a high- trigger at RHIC become different.
Finally, transverse flow implies an increase of high- at RHIC.Comment: LaTeX, 4 pages, 4 eps figs included using graphics, uses enclosed
svepj.clo and svjour.cls; proceedings of Hard Probes 2004, Ericeira,
Portugal, November 4th-10th 200
Medium Modification of the Jet Properties
In the case that a dense medium is created in a heavy ions collision,
high-E_t jets are expected to be broadened by medium-modified gluon emission.
This broadening is directly related, through geometry, to the energy loss
measured in inclusive high-p_t particle suppression. We present here the
modifications of jet observables due to the presence of a medium for the case
of azimuthal jet energy distributions and k_t-differential multiplicities
inside the jets.Comment: 4 pages, 3 postscript figures. Proceedings for Quark Matter 200
Even-dimensional topological gravity from Chern-Simons gravity
It is shown that the topological action for gravity in 2n-dimensions can be
obtained from the 2n+1-dimensional Chern-Simons gravity genuinely invariant
under the Poincare group. The 2n-dimensional topological gravity is described
by the dynamics of the boundary of a 2n+1-dimensional Chern-Simons gravity
theory with suitable boundary conditions. The field , which is
necessary to construct this type of topological gravity in even dimensions, is
identified with the coset field associated with the non-linear realizations of
the Poincare group ISO(d-1,1)
How sensitive are high-pt electron spectra at RHIC to heavy quark energy loss?
In nucleus-nucleus collisions, high-pt electron spectra depend on the medium
modified fragmentation of their massive quark parents, thus giving novel access
to the predicted mass hierarchy of parton energy loss. Here we calculate these
spectra in a model, which supplements the perturbative QCD factorization
formalism with parton energy loss. In general, we find - within large errors -
rough agreement between theory and data on the single inclusive electron
spectrum in pp, its nuclear modification factor, and its azimuthal anisotropy.
However, the nuclear modification factor depends on the relative contribution
of charm and bottom production, which we find to be affected by large
perturbative uncertainties. In order for electron measurements to provide a
significantly more stringent test of the expected mass hierarchy, one must then
disentangle the b- and c-decay contributions, for instance by reconstructing
the displaced decay vertices.Comment: 9 pages RevTex, 4 eps-figures, asci-file containing numerical tables
of results include
Ks1, an epithelial cell-specific gene, responds to early signals of head formation in Hydra
As a molecular marker for head specification in
Hydra, we
have cloned an epithelial cell-specific gene which responds
to early signals of head formation. The gene, designated
ks1, encodes a 217-amino acid protein lacking significant
sequence similarity to any known protein. KS1 contains a
N-terminal signal sequence and is rich in charged residues
which are clustered in several domains. ks1 is expressed in
tentacle-specific epithelial cells (battery cells) as well as in
a small fraction of ectodermal epithelial cells in the gastric
region subjacent to the tentacles. Treatment with the
protein kinase C activator 12-O-tetradecanoylphorbol-13-
acetate (TPA) causes a rapid increase in the level of ks1
mRNA in head-specific epithelial cells and also induces
ectopic ks1 expression in cells of the gastric region.
Sequence elements in the 5
¢-flanking region of ks1 that are
related to TPA-responsive elements may mediate the TPA
inducibility of ks1 expression. The pattern of expression of
ks1 suggests that a ligand-activated diacylglycerol second
messenger system is involved in head-specific differentiation
Medium-induced multi-photon radiation
We study the spectrum of multi-photon radiation off a fast quark in medium in
the BDMPS/ASW approach. We reproduce the medium-induced one-photon radiation
spectrum in dipole approximation, and go on to calculate the two-photon
radiation in the Moli\`{e}re limit. We find that in this limit the LPM effect
holds for medium-induced two-photon ladder emission.Comment: 5 pages, 1 figure. Proceedings of Hot Quarks 2010, La Londe Les
Maures, Franc
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