Speaker
Markus Kohler
(Weizmann Institute of Science (IL))
Description
Recent measurements in two- and multi-particle correlations in p+Pb collisions suggest collective behavior reminiscent of that observed in Pb+Pb. In addition, the data hint at interesting geometric behavior in ultra-central p+Pb events, where fluctuations in the size of the proton may become significant. Femtoscopic measurements may provide useful insight on both of these problems because they image the spatio-temporal size of the particle emitting region. In particular, the evolution of HBT radii with pair momentum should have a characteristic behavior in the presence of collective expansion. This talk will present identical-pion HBT measurements from ATLAS using one- and three-dimensional correlation functions. Pions are identified using $dE/dx$ measured in the pixel detector. Correlation functions and the resulting HBT radii will be presented as a function of pair momentum ($k_T$) and collision centrality. The contribution to the two-particle correlation function from hard processes is studied in depth, and a new method for completely constraining this background will be described. The measured source sizes are observed to decrease with $k_T$ and increase significantly in more central collisions.
| On behalf of collaboration: | ATLAS |
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Primary author
Markus Kohler
(Weizmann Institute of Science (IL))
