https://doi.org/10.1051/epjconf/201817205002
Experimental overview of correlations in small collision systems A brief history
Department of Physics, Columbia University
* Corresponding author: soumya@cern.ch
Published online: 26 January 2018
The azimuthal anisotropies of particle yields observed in relativistic heavy ion collisions have been traditionally considered as a strong evidence of the formation of a deconfined quark-gluon plasma in these collisions. However multiple recent measurements in pp and p/D/He+A collisions show similar features as those observed in heavy ion collisions, indicating the possibility of the production of such a deconfined medium in smaller collision systems. This paper presents a comprehensive summary of such measurements in small systems. It includes measurements of identified and inclusive two-particle correlations in ΔΦ and Δη, with different procedures used to subtract the dijet contributions, as well as measurements of multi-particle cumulants cn{2 - 8}. The traditional cumulant measurements confirm presence of collective phenomena in p+A collisions, but are biased by non-flow correlations and are not able to provide evidence for collectivity in pp collisions. To address this, a new subevent cumulant method that further suppresses the contribution non-flow effects was developed, whose measurements are also discussed.
© The Authors, published by EDP Sciences, 2018
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