A phenomenological study of single transverse-spin asymmetry for inclusive light-hadron productions at RHIC

Abstract

We study the single transverse-spin asymmetry for inclusive light-hadron productions in the protonproton collision, p " p ! hX (h ¼ , K, ), for the RHIC kinematics based on the twist-3 mechanism in the collinear factorization. The analysis includes all the contributions from the soft-gluon pole and the soft-fermion pole for the twist-3 quark-gluon correlation functions in the transversely polarized proton. After discussing the flavor decomposition and the P T -dependence of the asymmetry obtained in the previous analysis at the center-of-mass energy ffiffiffi S p ¼ 62:4 and 200 GeV, we will give a prediction for the asymmetry at ffiffiffi S p ¼ 500 GeV and also for the -meson production. We found slightly smaller asymmetry at ffiffiffi S p ¼ 500 GeV for AE;0 and K þ compared with those at the lower energies. The asymmetry for the -meson turned out to be significantly larger than that for 0 .

Transverse single-spin asymmetry and cross section forπ0andηmesons at large FeynmanxinAdamczyk1, Agakishiev2, Aggarwal3 et al. 2012Phys. Rev. D821330View full textAdd to dashboardCite

“…This suggests that the measured η asymmetry can be understood within the framework of pQCD. While several calculations exist for pion and kaon asymmetries [10,[38][39][40][41], the first pQCD calculation of A N for the η meson was performed only recently [42]. This model generates an η asymmetry that is substantially larger than that for the π 0 via a sizable initialstate twist-3 effect for strange quarks.…”

Transverse single spin and azimuthal asymmetries in hadronic collisions at PHENIX

“…The bottom panel shows A N as a function of p T for forward and backwards x F . The p T dependence of A N at forward x F is compared with a twist-3 calculation [13], which describes the magnitude of the asymmetry well at the lowest and highest points in p T , but it is unclear whether the observed shape for the middle p T values is well described. However, the theoretical uncertainty is not available for the twist-3 calculation, and this new η meson A N result will help disentangle various twist-3 interpretations.…”

“…While these correlation functions do not contain direct information on the transverse momentum distributions of partons, this approach has been related to k T -moments of TMD PDFs and FFs such as the Sivers and Collins functions for multiparton correlations in the initial and final state, respectively [11]. Prior RHIC transverse SSA measurements for inclusive hadron production have been described relatively well by a combination of twist-3 effects in the initial and final states [12][13][14][15].…”

Neutral pion cross section and spin asymmetries at intermediate pseudorapidity in polarized proton collisions ats=200 GeV

“…For example, while a recent model prediction based on the Collins effect in the color-glass condensate formalism [30] expects a 1=p T scaling modified by the transverse-momentum dependence of the fragmentation function in the unpolarized cross section, a recent twist-3 model [34] predicts A N of a few percent at forward pseudorapidity that should persist out to p T ∼ 15 GeV=c. The A N measurements described in this paper cover the previously unmeasured region 0.06 < x F < 0.27 and 5 < p T < 12 GeV=c.…”

“…However, sizable asymmetries are observed for inclusive π 0 production at forward pseudorapidity (η ≈ 3) by several experiments over a wide range of ffiffi ffi s p with no sign of ffiffi ffi s p dependence [9,11,13,[23][24][25]. It is expected that the Sivers and Collins effects at twist-2 [26][27][28][29][30] as well as higher twist effects [31][32][33][34] contribute to these asymmetries (in particular at higher ffiffi ffi s p ), and measurements which map the dependence in x F and p T may help elucidate the underlying mechanisms. While at large p T , A N is expected to scale as 1=p T [29,30,35,36], previous results at forward pseudorapidity do not exhibit this behavior [23][24][25].…”