Elliptic flow ($v_2$) in pp collisions at energies available at the CERN Large Hadron Collider: A hydrodynamical approach

At Large Hadron Collider energy, the expected large multiplicities suggests the presence of collective behavior even in pp collisions. A hydrodynamical approach has been applied to estimate the expected elliptic flow measured by the azimuthal asymmetry parameter $v_2$, in pp collisions at $\mathrm{\surd }$s = 14 TeV. $v_2$ of ${\pi }^{-}$ is found to be strongly dependent on the parton density profile inside a proton [e.g., surface diffuseness parameter ($\xi$)]. For $\xi$ = 0.105, $v_2$ is found to be positive while at $\xi$ = 0.25, $v_2$ is close to zero and approaches negative values at large $p_t$. The impact parameter dependence of $v_2$ has also been studied.