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

## TL;DR

This paper uses a hydrodynamical model to predict elliptic flow ($v_2$) in proton-proton collisions at 14 TeV, highlighting the influence of proton density profiles on flow behavior.

## Contribution

It introduces a hydrodynamical approach to estimate $v_2$ in pp collisions and explores how proton density profiles affect elliptic flow predictions.

## Key findings

- $v_2$ depends strongly on the proton's parton density profile.
- Positive $v_2$ for surface diffuseness $\xi$=0.105.
- $v_2$ approaches zero or negative at higher $p_t$ for larger $\xi$.

## Abstract

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 $\surd$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.