116 research outputs found
Systematics of geometric scaling
Using all available data on the deep-inelastic cross-sections at HERA at
x<0.01, we look for geometric scaling of the form \sigma^{\gamma^*p}(\tau)
where the scaling variable \tau behaves alternatively like \log(Q^2)-\lambda Y,
as in the original definition, or \log(Q^2)-\lambda \sqrt{Y}, which is
suggested by the asymptotic properties of the Balitsky-Kovchegov (BK) equation
with running QCD coupling constant. A ``Quality Factor'' (QF) is defined,
quantifying the phenomenological validity of the scaling and the uncertainty on
the intercept \lambda. Both choices have a good QF, showing that the second
choice is as valid as the first one, predicted for fixed coupling constant. A
comparison between the QCD asymptotic predictions and data is made and the QF
analysis shows that the agreement can be reached, provided going beyond leading
logarithmic accuracy for the BK equation.Comment: 4 pages, 4 figure
Energy Conservation Constraints on Multiplicity Correlations in QCD Jets
We compute analytically the effects of energy conservation on the
self-similar structure of parton correlations in QCD jets. The calculations are
performed both in the constant and running coupling cases. It is shown that the
corrections are phenomenologically sizeable. On a theoretical ground, energy
conservation constraints preserve the scaling properties of correlations in QCD
jets beyond the leading log approximation.Comment: 11 pages, latex, 5 figures, .tar.gz version avaliable on
ftp://www.inln.unice.fr
Diffractive SUSY particle production at the LHC
We give detailed predictions for diffractive SUSY Higgs boson and top squark
associated productions at the LHC via the exclusive double pomeron exchange
mechanism. We study how the SUSY Higgs cross section and the signal over
background ratio are enhanced as a function of tangent beta in different
regimes. The prospects are particularly promising in the ``anti-decoupling''
regime, which we study in detail. We also give the prospects for a precise
measurement of the top squark mass using the threshold scan of central
diffractive associated top squark events at the LHC.Comment: 14 pages, 6 fig
Do Quarks Obey D-Brane Dynamics?
The potential between two D0-branes at rest is calculated to be a linear.
Also the potential between two fast decaying D0-branes is found in agreement
with phenomenological heavy-quark potentials.Comment: 7 pages, no figures, LaTe
The potential of structured narratives for computational journalism: journalistic skills in the elaboration of database generated texts
Sem informaçãoNeste artigo, explora-se as competências digitais desenvolvidas por jornalistas no contexto informacional do Big Data que levantam a viabilidade de intersecção entre Ciências da Computação e Jornalismo. Nesse sentido, autores propõem diferentes entendimentos sobre o Jornalismo Computacional, campo hipotético no qual a prática jornalística agrega um direcionamento técnico, o que expande o horizonte de entendimento da relação do jornalista com a construção narrativa no ambiente de abundância de dados. Observa-se nesse cenário a emergência de experimentações com narrativas estruturadas, entendidas como textos verbais automatizados a partir de moldes pré-determinados que processam dados de bancos de dados estruturados. Com isso, o artigo reflete sobre os softwares de Natural Language Generation (NLG) na composição de notícias e apresenta resultados do desenvolvimento da ferramenta Mbabel para geração de rascunhos estruturados para verbetes temáticos na Wikipédia a partir do banco de dados Wikidata.121138152Sem informaçãoSem informaçãoSem informaçã
Gaugino Condensation, Duality and Supersymmetry Breaking
The status of gaugino condensation in low-energy string theory is reviewed.
Emphasis is given to the determination of the efective action below
condensation scale in terms of the 2PI and Wilson actions. We illustrate how
the different perturbative duality symmetries survive this simple
nonperturbative phenomenon, providing evidence for the believe that these are
exact nonperturbative symmetries of string theory. Consistency with T duality
lifts the moduli degeneracy. The duality also survives in a
nontrivial way in which the degree of freedom corresponding to is
replaced by a massive field but duality is preserved. S
duality may also be implemented in this process. Some general problems of this
mechanism are mentioned and the possible nonperturbative scenarios for
supersymmetry breaking in string theory are discussed.Comment: Contribution to Trieste Conference on S-Duality and Mirror Symmetry,
20 pages. Late
Resummation in nonlinear equation for high energy factorizable gluon density and its extension to include coherence
Motivated by forthcoming p-Pb experiments at Large Hadron Collider which
require both knowledge of gluon densities accounting for saturation and for
processes at a wide range of we study basic momentum space evolution
equations of high energy QCD factorization. Solutions of those equations might
be used to form a set of gluon densities to calculate observables in
generalized high energy factorization. Moreover in order to provide a framework
for predictions for exclusive final states in p-Pb scattering with high
we rewrite the equation for the high energy factorizable gluon density in a
resummed form, similarly to what has been done in \cite{Kutak:2011fu} for the
BK equation. The resummed equation is then extended to account for colour
coherence. This introduces an external scale to the evolution of the gluon
density, and therefore makes it applicable in studies of final states.Comment: 14 pages, appendix added, accepted for publication in JHE
QCD at small x and nucleus-nucleus collisions
At large collision energy sqrt(s) and relatively low momentum transfer Q, one
expects a new regime of Quantum Chromo-Dynamics (QCD) known as "saturation".
This kinematical range is characterized by a very large occupation number for
gluons inside hadrons and nuclei; this is the region where higher twist
contributions are as large as the leading twist contributions incorporated in
collinear factorization. In this talk, I discuss the onset of and dynamics in
the saturation regime, some of its experimental signatures, and its
implications for the early stages of Heavy Ion Collisions.Comment: Plenary talk given at QM2006, Shanghai, November 2006. 8 pages, 8
figure
Holographic equations of state and astrophysical compact objects
We solve the Tolman-Oppenheimer-Volkoff equation using an equation of state
(EoS) calculated in holographic QCD. The aim is to use compact astrophysical
objects like neutron stars as an indicator to test holographic equations of
state. We first try an EoS from a dense D4/D8/\textoverline {D8} model. In this
case, however, we could not find a stable compact star, a star satisfying
pressure-zero condition with a radius , , within a reasonable value
of the radius. This means that the EoS from the D4/D8/\textoverline {D8} model
may not support any stable compact stars or may support one whose radius is
very large. This might be due to a deficit of attractive force from a scalar
field or two-pion exchange in the D4/D8/\textoverline {D8} model. Then, we
consider D4/D6 type models with different number of quark flavors, .
Though the mass and radius of a holographic star is larger than those of normal
neutron stars, the D4/D6 type EoS renders a stable compact star.Comment: 12 pages, 9 figure
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