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

Dihadron angular correlations in $d$+Au collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=200$ 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 ($\mathrm{\Delta }\eta$) on the near side (i.e. relative azimuth $\mathrm{\Delta }\varphi \sim 0$). This correlated yield as a function of $\mathrm{\Delta }\eta$ appears to scale with the dominant, primarily jet-related, away-side ($\mathrm{\Delta }\varphi \sim \pi$) yield. The Fourier coefficients of the $\mathrm{\Delta }\varphi$ correlation, $V_{n}=\langle\cos n\Delta\phi\rangle$,haveastrong$\Delta\eta$ 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.