CMS-PAS-HIN-15-008

CMS-PAS-HIN-15-008
Differential flow harmonic $v_n$ in pPb and PbPb collisions
CMS Collaboration
September 2015

Abstract: Previous CMS measurements have demonstrated the collective nature of multiparticle correlations in high-multiplicity pPb collisions at the LHC. This collectivity is consistent with a hydrodynamic flow origin. However, it can also be interpreted in terms of initial state effects arising from gluon saturation. The pseudorapidity dependence of the azimuthal Fourier coefficients ( $v_n$ ) is expected to be sensitive to the underlying mechanism with, in the hydrodynamic picture, the longer lifetime of the fireball on the Pb-going side expected to lead to a larger flow signal than found on the p-going side. To investigate the detailed properties of the observed collectivity, differential $v_n$ values in transverse momentum ( $p_T$ ) and pseudorapidity ( $\eta$ ) are presented over the full range of the CMS tracker detector ( $-2.4 < \eta < 2.4$ ) for pPb collisions at a nucleon-nucleon center-of mass energy of 5.02 TeV. Results based on multiparticle analyses involving four or more particles are shown. An event plane analysis is presented where the influence of recently demonstrated event-plane decorrelation is considered. Comparisons are made with peripheral PbPb collisions measured at similar mid-rapidity particle multiplicities. The results will be discussed in the context of current models of the longitudinal dependence of the multiparticle correlations.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRC 98 (2018) 044902. The superseded preliminary plots can be found here.

CMS Publications