Long-range pseudorapidity dihadron correlations in $d$+Au collisions at $\sqrt{s_{\rm NN}}=200$ GeV

Dihadron angular correlations in d + Au collisions at root S-NN = 200 GeV are reported as a function of the measured zero-degree calorimeter neutral energy and the forward charged hadron multiplicity in the Au-beam direction. A finite correlated yield is observed at large relative pseudorapidity (Delta eta) on the near side (i.e. relative azimuth Delta phi similar to 0). This correlated yield as a function of Delta eta appears to scale with the dominant, primarily jet-related, away-side (Delta phi similar to pi) yield. The Fourier coefficients of the Delta phi correlation, V-n = < cosn Delta phi >, have a strong Delta eta dependence. In addition, it is found that V-1 is approximately inversely proportional to the mid-rapidity event multiplicity, while V-2 is independent of it with similar magnitude in the forward (d-going) and backward (Au-going) directions. (C) 2015 The Authors. Published by Elsevier B.V.