6,475 research outputs found
Hadronization of Dense Partonic Matter
The parton recombination model has turned out to be a valuable tool to
describe hadronization in high energy heavy ion collisions. I review the model
and revisit recent progress in our understanding of hadron correlations. I also
discuss higher Fock states in the hadrons, possible violations of the elliptic
flow scaling and recombination effects in more dilute systems.Comment: 8 pages, 4 figures; plenary talk delivered at SQM 2006, to appear in
J. Phys.
Jet-Tagged Back-Scattering Photons For Quark Gluon Plasma Tomography
Several sources of direct photons are known to contribute to the total photon
yield in high energy nuclear collisions. All of these photons carry
characteristic and important information on the initial nuclei or the hot and
dense fireball created in the collision. We investigate the possibility to
separate photons from back-scattering of high momentum quarks off quark gluon
plasma from other sources. Their unique kinematics can be utilized through high
energy jet triggers on the away-side. We discuss the basic idea and estimate
the feasibility of such a measurement at RHIC and LHC.Comment: Contribution to Hard Probes 2012; 4 pages, 4 figure
Competition, restructuring and firm performance: evidence of an inverted-U relationship from a cross-country survey of firms in transition economies
This paper examines the importance of competition in the growth anddevelopment of firms. We draw on a survey of 3,300 firms in 25transition countries to shed light on the factors that influencerestructuring by firms and their subsequent performance. These datahave three main advantages over those used in previous work. First,they measure directly the degree of competition perceived by each firmin its principal market rather than attempting to infer this from marketdata as measured by statistical agencies. Second, the fact that transitioncountries have market structures inherited from the past avoids some ofthe endogeneity problems associated with measures of competition inmarket economies. Third, the breadth of cross-country variationprovides a method of dealing with the fact that firm-level measures ofthe external environment will not be independent of the firm?s ownperformance. We find evidence of a robust inverted-U effect ofcompetition on performance that is both statistically and economicallysignificant. This paper examines the importance of competition in the growth anddevelopment of firms. We draw on a survey of 3,300 firms in 25transition countries to shed light on the factors that influencerestructuring by firms and their subsequent performance. These datahave three main advantages over those used in previous work. First,they measure directly the degree of competition perceived by each firmin its principal market rather than attempting to infer this from marketdata as measured by statistical agencies. Second, the fact that transitioncountries have market structures inherited from the past avoids some ofthe endogeneity problems associated with measures of competition inmarket economies. Third, the breadth of cross-country variationprovides a method of dealing with the fact that firm-level measures ofthe external environment will not be independent of the firm?s ownperformance. We find evidence of a robust inverted-U effect ofcompetition on performance that is both statistically and economicallysignificant
Finite hadronization time and unitarity in quark recombination model
The effect of finite hadronization time is considered in the recombination
model, and it is shown that the hadron multiplicity turns out to be
proportional to the initial quark density and unitarity is conserved in the
model. The baryon to meson ratio increases rapidly with the initial quark
density due to competition among different channels.Comment: 4 pages in RevTeX, 3 eps figures, to appear in J. Phys.G as a lette
Correlated Emission of Hadrons from Recombination of Correlated Partons
We discuss different sources of hadron correlations in relativistic heavy ion
collisions. We show that correlations among partons in a quasi-thermal medium
can lead to the correlated emission of hadrons by quark recombination and argue
that this mechanism offers a plausible explanation for the dihadron
correlations in the few GeV/c momentum range observed in Au+Au collisions at
RHIC.Comment: 4 pages, 2 figures; v2: typo on p.4 correcte
Entropy of expanding QCD matter
Using the lattice QCD equation of state for an isentropically expanding
fireball we follow the evolution of the effective number of particles in an
ideal gas pV/T. This number reduces roughly to its third around the crossover
temperature, which helps to circumvent the entropy obstacle inherent in quark
coalescence models of the hadronization.Comment: 5 pages 4 eps figures LaTe
Jet Fragmentation via Recombination of Parton Showers
We study hadron production in jets by applying quark recombination to jet
shower partons. With the jet showers obtained from PYTHIA and augmented by
additional non-perturbative effects, we compute hadron spectra in e+ +
e-collisions at sqrt(s)=200 GeV. Including contributions from resonance decays,
we find that the resulting transverse momentum spectra for pions, kaons, and
protons reproduce reasonably those from the string fragmentation as implemented
in PYTHIA.Comment: 4 pages, 3 figures, contribution to Nucleus-Nucleus Collisions 201
Almost exponential transverse spectra from power law spectra
We point out that exponential shape of transverse spectra can be obtained as
the Fourier transform of the limiting distribution of randomly positioned
partons with power law spectra given by pQCD, which actually realize Tsallis
distributions. Such spectra were used to obtain hadron yields by recombination
in relativistic heavy-ion collisions at RHIC energies.Comment: 5 pages, 3 figures, Phys.rev. styl
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