Single spin asymmetries of inclusive hadrons produced in electron scattering from a transversely polarized ${}^3$He target

We report the first measurement of target single spin asymmetries ($A$${}_N$) in the inclusive hadron production reaction, $e+{}^3{\text{He}}^{\uparrow }\to h+X$, using a transversely polarized ${}^3$He target. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Three types of hadrons (${\pi }^{\pm }$, $K^{\pm }$, and proton) were detected in the transverse hadron momentum range 0.54 $<p_T<$ 0.74 GeV/c. The range of $x_F$ for pions was $-$0.29 $<x_F<$ $-$0.23 and for kaons was $-$0.25 $<x_F<$ $-$0.18. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for ${\pi }^{+}$ and $K^{+}$. A negative asymmetry is observed for ${\pi }^{-}$. The magnitudes of the asymmetries follow $|A^{{\pi }^{-}}|<|A^{{\pi }^{+}}|<|A^{K^{+}}|$. The K${}^{-}$ and proton asymmetries are consistent with zero within the experimental uncertainties. The ${\pi }^{+}$ and ${\pi }^{-}$ asymmetries measured for the ${}^3$He target and extracted for neutrons are opposite in sign with a small increase observed as a function of $p_T$.

Figure 1

Kinematical configuration in the laboratory coordinate system for the $l{N}^{\uparrow }\to hX$ process. ${\vec{P}}_h$ represents the momentum direction of the produced hadron, and $\vec{S}$ is the spin vector of the nucleon. The polarized nucleon's momentum is along the $-z$ direction in the $e+N$ center-of-mass frame.

Figure 2

Inclusive SSA results on a ${}^3$He target for ${\pi }^{\pm }$, $K$${}^{\pm }$, and protons in the vertical target spin configuration (${\varphi }_S=\pm {90}^{\circ }$). The error bars on the points represents the statistical uncertainty. The gray band shows the magnitude of the overall systematic uncertainty for each hadron channel.

Figure 3

$A_N$ results on a ${}^3$He target for the ${\pi }^{\pm }$ channel as a function of $p_T$. The solid band on the bottom of each panel shows the magnitude of the systematic uncertainty for each momentum bin.

Figure 4

(a) $A$${}_N$ results on a neutron target extracted from the measured ${}^3$He asymmetries. The solid band on the bottom of each panel shows the magnitude of the systematic uncertainty for each momentum bin. The lower plot (b) is the $x_F$ and $p_T$ correlation in this measurement.