Figure. The upper panel is a schematic representation (due to Scott Pratt) of the
that produced hadron pairs of opposite charge will be closer in rapidity
a narrower Balance Function) if their production is delayed.
data from STAR at two energies indicate that the Balance Function width
axis) becomes progressively narrower with increasing collision centrality
Search for Evidence of Delayed Hadronization in Central Gold-Gold Collisions at RHIC
As a result of local charge conservation, when particle-antiparticle
pairs are produced,
they are correlated initially in position space. If hadronization occurs
early in the
scenario of a partonic phase followed by a hadronic phase, as depicted by
pair in the illustration, the two particles would be expected to separate
due to expansion and rescattering in the strongly interacting medium.
delayed hadronization (the lower pair in the illustration) would lead to a
correlation between the measured pairs in the final state.
Measurement of this correlation involves subtracting uncorrelated
particle pairs event-by-event. Among the remaining charge-anticharge
the correlation as a function of the rapidity difference between the
members of the
pair is characterized by the Balance Function. The Balance Function is
be narrower in the scenario of delayed hadronization, and thus has a
bearing on the
possible production of Quark Gluon Plasma.
The STAR data for more peripheral collisions are consistent with models
based on a
superposition of nucleon-nucleon scattering, while widths in central
smaller, consistent with the trends predicted by models incorporating late
Related STAR papers
Narrowing of the Balance Function with Centrality in Au+Au Collisions at sqrt(snn) = 130 GeV
Phys. Rev. Lett. 90 (2003) 172301
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