Measurement of the centrality and pseudorapidity dependence of the integrated elliptic flow in lead–lead collisions at $$\sqrt{s_{\mathrm {NN}}}=2.76$$ s NN = 2.76 TeV with the ATLAS detector

The integrated elliptic flow of charged particles produced in Pb+Pb collisions at $$\sqrt{{s}_{\mathrm {NN}}}=2.76$$  TeV has been measured with the ATLAS detector using data collected at the Large Hadron Collider. The anisotropy parameter, $$v_2$$ , was measured in the pseudorapidity range $$|\eta |\le 2.5$$ with the event-plane method. In order to include tracks with very low transverse momentum $$p_{\mathrm {T}}$$ , thus reducing the uncertainty in $$v_2$$ integrated over $$p_{\mathrm {T}}$$ , a $$1~\mu \hbox {b}^{-1}$$ data sample recorded without a magnetic field in the tracking detectors is used. The centrality dependence of the integrated $$v_2$$ is compared to other measurements obtained with higher $$p_{\mathrm {T}}$$ thresholds. The integrated elliptic flow is weakly decreasing with $$|\eta |$$ . The integrated $$v_2$$ transformed to the rest frame of one of the colliding nuclei is compared to the lower-energy RHIC data.