Solving the R_AA ⊗ υ₂ puzzle

For the past ten years R_AA(p_T ), the nuclear modification factor that encodes the suppression of high p_T particles due to energy loss within the medium was fairly well described by many theoretical models. However, the same models systematically underpredicted the high p_T elliptic flow, υ₂, which is experimentally measured as the correlation between soft and hard hadrons. All previous calculations neglected the effect of event-by-event fluctuations of an expanding viscous hydrodynamical background as well as the soft-hard flow harmonic correlations in the experimentally measured υ₂. In this talk I show how event-by-event viscous hydrodynamics (computed using the v-USPhydro code) coupled to an energy loss model (BBMG) is able to simultaneously describe soft physics observables as well as the high-p_T R_AA and υ₂. Suggestions for future more differential calculations at the LHC run2 are made to explore soft-hard flow correlations.