Feb 5 – 11, 2017
Hyatt Regency Chicago
America/Chicago timezone

Mixed higher-order flow harmonics and nonlinear response coefficients in PbPb collisions at 2.76 and 5.02 TeV with CMS

Feb 8, 2017, 8:50 AM
Regency A

Regency A


Shengquan Tuo (Vanderbilt University (US))


Higher-order flow harmonics ($v_{n}$ with n $\gt$ 3) can be measured either with respect to the event plane of the same order, a lower order event plane, or a mixture of lower order planes (also called mixed higher-order harmonics). Studies of flow harmonics using the same order event plane have been used to extract the transport properties of the hot and dense medium produced in the collisions and to explore initial state effects. The mixed higher-order harmonics have been proposed to have strong sensitivity to the shear viscosity over entropy density ratio ($\eta$/s) of the medium. In this talk, for the first time, the $v_{5}$ and $v_{7}$ are measured with respect to the second and third order planes. With the nonlinear component of the flow harmonics extracted based on lower order event planes, the nonlinear response coefficients for n=4, 5, 6, 7 are also presented. The mixed harmonic coefficients are studied as a function of charged particle transverse momentum and collision centrality at $\sqrt{s_{NN}}$ = 2.76 and 5.02 TeV with the CMS detector. It is found that the nonlinear response coefficients for the odd flow harmonics are larger than for the even harmonics, reflecting a stronger contributions of the nonlinear part for odd harmonics. The results are compared to theoretical calculations with different $\eta$/s values and provide stringent constraints on the transport properties of the medium produced in heavy ion collisions.

Preferred Track Collective Dynamics
Collaboration CMS

Primary author

Shengquan Tuo (Vanderbilt University (US))

Presentation materials