97 research outputs found
On correlations and discreteness in non-linear QCD evolution
We consider modifications of the standard non-linear QCD evolution in an
attempt to account for some of the missing ingredients discussed recently, such
as correlations, discreteness in gluon emission and Pomeron loops. The
evolution is numerically performed using the Balitsky-Kovchegov equation on
individual configurations defined by a given initial value of the saturation
scale, for reduced rapidities . We consider the
effects of averaging over configurations as a way to implement correlations,
using three types of Gaussian averaging around a mean saturation scale.
Further, we heuristically mimic discreteness in gluon emission by considering a
modified evolution in which the tails of the gluon distributions are cut-off.
The approach to scaling and the behavior of the saturation scale with rapidity
in these modified evolutions are studied and compared with the standard
mean-field results. For the large but finite values of rapidity explored, no
strong quantitative difference in scaling for transverse momenta around the
saturation scale is observed. At larger transverse momenta, the influence of
the modifications in the evolution seems most noticeable in the first steps of
the evolution. No influence on the rapidity behavior of the saturation scale
due to the averaging procedure is found. In the cut-off evolution the rapidity
evolution of the saturation scale is slowed down and strongly depends on the
value of the cut-off. Our results stress the need to go beyond simple
modifications of evolution by developing proper theoretical tools that
implement such recently discussed ingredients.Comment: 20 pages, LaTeX, 18 eps figures included using epsfig; changes in v3:
new kind of averaging added, 5 new plots, discussions and conclusions
extended, final versio
Nuclear size and rapidity dependence of the saturation scale from QCD evolution and experimental data
The solutions of the Balitsky-Kovchegov evolution equations are studied
numerically and compared with known analytical estimations. The rapidity and
nuclear size dependences of the saturation scale are obtained for the cases of
fixed and running coupling constant. These same dependences are studied in
experimental data, on lepton-nucleus, deuteron-nucleus and nucleus-nucleus
collisions, through geometric scaling and compared with the theoretical
calculations.Comment: 8 pages, 8 figures. Contribution based on talks given by J. G.
Milhano and C. A. Salgado to the proceedings of ``Hard Probes 2004'',
Ericeira (Portugal), November 4-10, 200
First correction to JIMWLK evolution from the classical equations of motion
We calculate some corrections to the JIMWLK kernel in
the framework of the light-cone wave function approach to the high energy limit
of QCD. The contributions that we consider originate from higher order
corrections in the strong coupling and in the density of the projectile to the
solution of the classical Yang-Mills equations of motion that determine the
Weizs\"acker-Williams fields of the projectile. We study the structure of these
corrections in the dipole limit, showing that they are subleading in the limit
of large number of colours , and that they cannot be fully recast in the
form of dipole degrees of freedom.Comment: 4 pages, LaTeX, 2 eps figures included using graphicx, uses enclosed
iopart.cls; contribution to the proceedings of Quark Matter 2006 (Shanghai,
November 14th-20th 2006
Jet quenching via jet collimation
The strong modifications of dijet properties in heavy ion collisions measured
by ATLAS and CMS provide important constraints on the dynamical mechanisms
underlying jet quenching. In this work, we show that the transport of soft
gluons away from the jet cone - jet collimation - can account for the observed
dijet asymmetry with values of that lie in the expected order of
magnitude. Further, we show that the energy loss attained through this
mechanism results in a very mild distortion of the azimuthal angle dijet
distribution.Comment: 4 pages, 2 figures; Proceedings of the "Quark Matter 2011" conferenc
Evidence of Bartonella spp., Rickettsia spp. and Anaplasma phagocytophilum in domestic, shelter and stray cat blood and fleas, Portugal.
Thirty-two fleas were collected from 18 Lisboncats, 29 of which (90.6%) were C. felis, one (3.1%)was C. canis and two (6.3%) were unidentifiable. Only C. felis fleas were infected, six (40.0%)withB. clarridgeiae and six (40.0% ) with R. felis; three(20.0%) were co-infected. No positive result wasfound for A. phagocytophilum. The infection prev-alence of B. clarridgeiae was higher in domestic(43.8%) than in shelter cat fleas (28.6%). However,the infection rate of R. felis was higher in shelter(42.9%) than in domestic cat fleas (25.0%). Straycat fleas were only infected with R. felis (11.1%).Twenty-five cats (67.7%) were bacteraemic(Table 1). Twenty-one of them (84.0%) wereless than 1 year old, 15 (60.0%) were femalea nd 10 (40.0%) had no Bartonella spp. antibodies, one of which (10.0%) was more than 1 year old. The prevalence of Bartonella bacteraemia is higher in shelter (76.9%) than in domestic cats(68.2%) and all stray cats tested (n = 2) were positive
Detection of Borrelia lusitaniae, Rickettsia sp. IRS3, Rickettsia monacensis and Anaplasma phagocytophilum in Ixodes ricinus collected in Madeira Island, Portugal
A total of 300 Ixodes ricinus ticks were tested by polymerase chain reaction (PCR) for the presence of Borrelia spp., Rickettsia spp., and Anaplasma phagocytophilum. Sequence analysis demonstrated 8 (2.7%) ticks infected with B. lusitaniae, 60 (20%) with Rickettsia spp., and 1 (0.3%) with A. phagocytophilum. Seven (2.3%) ticks were coinfected with B. lusitaniae and Rickettsia spp., 2 (0.6%) with R. monacensis, and 5 (1.7%) with Rickettsia sp. IRS3. The results of this study suggest simultaneous transmission of multiple tick-borne agents on Madeira Island, Portugal
Jet Quenching via Jet Collimation
The ATLAS Collaboration recently reported strong modifications of dijet
properties in heavy ion collisions. In this work, we discuss to what extent
these first data constrain already the microscopic mechanism underlying jet
quenching. Simple kinematic arguments lead us to identify a frequency
collimation mechanism via which the medium efficiently trims away the soft
components of the jet parton shower. Through this mechanism, the observed dijet
asymmetry can be accomodated with values of that lie in the
expected order of magnitude.Comment: 6 pages, 4 figure
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