Measurement of the long-range pseudorapidity correlations and associated Fourier harmonics in 5.02 TeV proton-lead collisions with the ATLAS detector

20 May 2014, 15:00
europium (darmstadtium)



Schlossgraben 1 64283 Darmstadt Germany
Contributed Talk Correlations and Fluctuations Correlations and fluctuations


Sooraj Krishnan Radhakrishnan (State University of New York (US))


Detailed measurement of the Fourier harmonics ($v_n$) associated with the azimuthal modulation of two-particle correlation structures over $-5 < \delta\eta < 5$ in 31 nb$^{-1}$ p + Pb collisions are presented. The $v_n$ results are presented as a function of $p_T$, \eta, and event activity characterized by the number of reconstructed tracks in $-2.5 < \eta < 2.5$, and the total transverse energy on the Pb-going side ($3.2 < \eta < 4.9$). The elliptic, triangular, and quadrangular coefficients, $v_2$, $v_3$ and $v_4$, are extracted for $0.5 < p_T < 15$ GeV, significantly extending the previous measurements. The v_n values are found to reach a maximum around 3-5 GeV and then decrease to a finite positive values at $p_T > 10$ GeV, similar to the behavior seen in Pb+Pb collisions. Evidence for rapidity-even dipolar flow $v_1$ is also observed, further supporting a collective origin of the long-range two-particle correlations. The first measurement of the eta dependence of these correlations suggests that the $v_2$ values are smaller in the proton-going side than those in the Pb-going side. Finally $v_n$ results are also extracted with four-particle cumulant method and compared with those obtained with two-particle correlation method. These results provide new important insights on the physics underlying the long-range pseudorapidity correlations.
On behalf of collaboration: ATLAS

Primary author

Sooraj Krishnan Radhakrishnan (State University of New York (US))

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