Measurement of the distribution of event-by-event harmonic flow in pb-pb collisions at $\sqrt{s_{NN}}=$2.76 TeV with the ATLAS detector

In recent years, the measurement of harmonic flow coefficients $v_n$ has provided important insight into the hot and dense matter created in heavy ion collisions at RHIC and LHC. These coefficients are now understood to reflect the hydrodynamic response to the collision geometry in the initial state. Due to finite number of nucleons in the system, the collision geometry can fluctuate event to event, and hence measuring the full distribution of the event-by-event $v_n$ coefficients can provide better insights on the nature of these fluctuations and possible non-linear effects in the hydrodynamic response. The key step in this measurement is to unfold the observed $v_n$ distribution for the smearing due to the effect of finite particle multiplicity in a event, as well as to suppress the possible influence of non-flow effects. We present the first measurement of the event-by-event $v_n$ for n=2-4 in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$~TeV.