Color reconnection and flowlike patterns in pp collisions.

Increasingly, with the data collected at the LHC we are confronted with the possible existence of flow in pp collisions. In this work, we show that PYTHIA 8 produces flowlike effects in events with multiple hard subcollisions due to color string formations between final partons from independent hard scatterings, the so-called color reconnection. We present studies of different identified hadron observables in pp collisions at 7 TeV. Studies have been done both for minimum bias and multiplicity intervals in events with and without color reconnection to isolate the flowlike effect.

Three and two hadron correlations in sq.rt.(S(NN))=200 GeV proton-proton and nucleus-nucleus collisions.

We compare the azimuthal correlations arising from three and two hadron production in p+p and Au+Au collisions at sq.rt.(S(NN))=200 GeV. We show that in Au+Au, the two away side partons in two-to-three processes have in average a smaller and a greater path length than the average path length of the away-side parton in two-to-two processes. Since in average the particle with the shortest path length in two-to-three processes loses less energy, with respect to the away-side particle in two-to-two processes, this effect leads to a relative enhancement of the ratio of two-to-three to two-to-two processes in Au+Au compared to p+p collisions. We argue that this phenomenon may be responsible for the shape of the away side in azimuthal correlations at the Relativistic Heavy-Ion Collider.

Two-kaon correlations in central Pb+Pb collisions at 158 a GeV/c.

Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.