969 research outputs found
Azimuthal flow in hadron collisions from quark-gluon string repulsion
Color flux tubes (quark-gluon strings), formed at early stages of
hadron-hadron collisions, may overlap in case of sufficiently high densities
and interact, producing long-range azimuthal correlations. In the hypothesis of
repulsive interaction, each string may acquire, before the hadronization, the
additional transverse boost, which is an efficient sum of all accounted
string-string interactions. This modifies transverse momenta to the particles
formed in string decay, leading to modification of event-wise observables, like
azimuthal asymmetry of two-particle correlations, over a wide range of
rapidity.
In this article we discuss results of Monte Carlo model with string
repulsion, where efficient string-string interaction radius is introduced. We
show that the effect of string repulsion can be the main dynamic origin of the
elliptic flow and of the higher harmonics, which are reflected in the
complicated structures observed in two-particle long-range correlation topology
in nucleus-nucleus collisions at RHIC and at LHC.Comment: 9 pages, http://dx.doi.org/10.1051/epjconf/20161250401
Classifiers for centrality determination in proton-nucleus and nucleus-nucleus collisions
Centrality, as a geometrical property of the collision, is crucial for the
physical interpretation of nucleus-nucleus and proton-nucleus experimental
data. However, it cannot be directly accessed in event-by-event data analysis.
Common methods for centrality estimation in A-A and p-A collisions usually rely
on a single detector (either on the signal in zero-degree calorimeters or on
the multiplicity in some semi-central rapidity range). In the present work, we
made an attempt to develop an approach for centrality determination that is
based on machine-learning techniques and utilizes information from several
detector subsystems simultaneously. Different event classifiers are suggested
and evaluated for their selectivity power in terms of the number of
nucleons-participants and the impact parameter of the collision. Finer
centrality resolution may allow to reduce impact from so-called volume
fluctuations on physical observables being studied in heavy-ion experiments
like ALICE at the LHC and fixed target experiment NA61/SHINE on SPS.Comment: To be published in proceedings of the "XIIth Quark Confinement and
the Hadron Spectrum" conference (Thessaloniki, 2016
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