Eccentricity Fluctuations Make Flow Measurable in High Multiplicity p−p Collisions

Elliptic flow is a hallmark of collectivity in hadronic collisions. Its measurement relies on analysis techniques which require high event multiplicity and so far can only be applied to heavy ion collisions. Here, we delineate the conditions under which elliptic flow becomes measurable in the samples of high-multiplicity ( d N ch / d y ≥ 50 ) p − p collisions, which will soon be collected at the LHC. We observe that fluctuations in the p − p interaction region can result in a sizable spatial eccentricity even for the most central p − p collisions. Under relatively mild assumptions on the nature of such fluctuations and on the eccentricity scaling of elliptic flow, we find that the resulting elliptic flow signal in high-multiplicity p − p collisions at the LHC becomes measurable with standard techniques