40 research outputs found
The Bose-Einstein effect and the joint WW decay
The influence of the Bose - Einstein interference effect on the joint WW
hadronic decay is discussed. It is shown that the weight method incorporating
this effect into Monte Carlo generators produces in a natural way an excess of
average multiplicity as compared to the independent decay of two W bosons. The
quantitative results for the average multiplicity and momentum distribution of
charged pions, obtained with a simple parametrization of weights compatible
with the observed shape of the "Bose - Einstein ratio", agree well with the
existing data.Comment: Latex, 7 pages including 2 .eps figure
A Remark on the Low Mass Dilepton Yield
The recent data on the enhancement of the low mass dilepton yield in heavy ion collisions are interpreted as an effect of the "prolonged life" of resonances in the hadron gas phase. The value of the enhancement factor gives an upper limit for the duration time of this phase
Remarks on the particle multiplicities at LHC energies
Recent ALICE data for the multiplicity distributions in the central rapidity
bins at LHC energies are compared with the results from two default versions of
the PYTHIA 8 generator. We find that, contrary to the earlier versions of
PYTHIA, the model overestimates the increase of average multiplicity with
energy. Tuning two of the model parameters one obtains reasonable agreement
with data. The dependence of the normalized moments of the distribution on the
rapidity bin width and on energy is also qualitatively correct.Comment: 6 pages, 1 figur
On the high order multiplicity moments
The description of multiplicity distributions in terms of the ratios of
cumulants to factorial moments is analyzed both for data and for the Monte
Carlo generated events. For the PYTHIA generated events the moments are
investigated for the restricted range of phase-space and for the jets
reconstructed from single particle momenta. The results cast doubts on the
validity of extended local parton-hadron duality and suggest the possibility of
more effective experimental investigations concerning the origin of the
observed structure in the dependence of moments on their order.Comment: 10 pages, 5 figures; corrected version to be published in JP
On the electroproduction on nuclei
Recent data on the electroproduction of hadrons on nuclei are discussed. The
effects of the nuclear absorption are investigated using the Lund model for
electroproduction on nucleons. A simple geometrical model with a minimal number
of assumptions and free parameters is shown to describe the data reasonably
well.Comment: 10 pages, 7 figures; minor corrections, version accepted for
publication in European Physical Journal
Superposition models and the multiplicity fluctuations in heavy ion collisions
A class of simple superposition models based on the Glauber picture of
multiple collisions is compared with the data on the centrality dependence of
the multiplicity distributions in a central rapidity bin. We show how the
results depend on the specific assumptions concerning the distributions in the
number of participants and their relations to the distributions of the number
of produced hadrons in various phase space bins. None of the versions of the
model describes satisfactorily the centrality dependence of the scaled
dispersion.Comment: 9 pages, 5 figures, a misprint in formula corrected, accepted for
publication in EPJ
Charge diffusion constant in hot and dense hadronic matter - A Hadro-molecular-dynamic calculation
We evaluate charge diffusion constant of dense and hot hadronic matter based
on the molecular dynamical method by using a hadronic collision generator which
describes nuclear collisions at energies 10 < E < 100 GeV/A and satisfies
detailed balance at low temperatures (T < 200 MeV). For the hot and dense
hadronic matter of the temperature range, 100 < T < 200 MeV and baryon number
density, 0.16 < nB < 0.32 fm^-3, charge diffusion constant D gradually
increases from 0.5 fm c to 2 fm c with temperature and is almost independent of
baryon number density. Based on the obtained diffusion constant we make simple
discussions on the diffusion of charge fluctuation in ultrarelativistic nuclear
collisions.Comment: 13 pages, 4 figure
The Bose-Einstein effect in Monte-Carlo generators: weight methods
We present a method which incorporates the Bose-Einstein effect into Monte
Carlo generators for multiple production by weighting the events. Various
aspects of weight calculations are discussed in detail. We show that our method
allows to describe reasonably well a sample of data and we outline the future
tests and applications.Comment: Latex, 10 pages including 4 .eps figure
Measuring charge fluctuations in high-energy nuclear collisions
Various measures of charge fluctuations in heavy-ion collisions are
discussed. Advantages of the Phi-measure are demonstrated and its relation to
other fluctuation measures is established. To get the relation, Phi is
expressed through the moments of multiplicity distribution. We study how the
measures act in the case of a `background' model which represents the classical
hadron gas in equilibrium. The model assumes statistical particle production
constrained by charge conservation. It also takes into account both the effect
of incomplete experimental apparatus acceptance and that of tracking
inefficiency. The model is shown to approximately agree with the PHENIX and
preliminary STAR data on the electric charge fluctuations. Finally,
`background-free' measures are discussed.Comment: 12 pages, 6 figures, numerous but minor changes, Phys. Rev. C in
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