Charged particle elliptic flow in p+p collisions at LHC energies in a transport model PACIAE

The parton and hadron cascade model PACIAE based on PYTHIA was used to investigate the charged particle elliptic flow in minimum bias pp collisions at the LHC energies. The strings were distributed randomly in the transverse ellipsoid of the pp collision system with major axis of $R$ (proton radius) and minor axis of $R(1-xi)$ before parton rescattering. The charged particle elliptic flow as a function of the random number $xi$ and transverse momentum $p_T$ were investigated. The calculated $v_2/epsilon$ as a function of reaction energy increases monotonously with increasing reaction energy up to $sqrt{s}sim$7 TeV and then turns to saturation. With the parton-parton cross section enlarges three times in parton rescattering, the rapidity integrated charged particle elliptic flow may reach 0.025 at $p_T sim$2 GeV/c in the minimum bias pp collisions at $sqrt{s}$=7 TeV.