Transverse single-spin asymmetry of forward $\hat{I}\cdot$ mesons in $p^{\uparrow }+p$ collisions at $\sqrt{s}=200$ GeV

Abstract

Utilizing the 2012 transversely polarized proton data from the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, the forward $\hat{I}\cdot$-meson transverse single-spin asymmetry ($A_N$) was measured for $p^{\uparrow }+p$ collisions at $\sqrt{s}=200$ GeV as a function of Feynman-x ($x_F$) for $0.2<|x_F|<0.8$ and transverse momentum ($p_T$) for $1.0<p_T<5.0$ GeV/$c$. Large asymmetries at positive $x_F$ are observed ($⟨A_N⟩=0.086\pm 0.019$), agreeing well with previous measurements of $\ddot{I}{€}^0$ and $\hat{I}\cdot$ $A_N$, but with reach to higher $x_F$ and $p_T$. The contribution of initial-state spin-momentum correlations to the asymmetry, as calculated in the collinear twist-3 framework, appears insufficient to describe the data and suggests a significant impact on the asymmetry from fragmentation.

383 authors from 74 institutions, 11 pages, 5 figures, 2 tables. v1 is version submitted to Physical Review D. The numerical values for data shown in Figs. 3 and 4 are given in Table I and for data shown in Fig. 5 are given in Table II. All values in the plots associated with this article will be stored in HEPData at https://www.hepdata.net/record/TBD