XXVIII International Workshop on Deep Inelastic Scattering and Related Subjects

Non-zero transverse single spin asymmetry of very forward π0 in polarized p+p collisions at s = 510 GeV

25 Mar 2020, 15:30

20m

Brooklyn, NY

Contributed Talk Spin Physics Spin Physics

Speaker

Mr Minho Kim (Korea University/ RIKEN)

Description

Through the 21st and 22nd International Workshop on Deep Inelastic Scattering, a possibility of the non-perturbative contribution for the non-zero transverse single spin asymmetry of forward ${\pi }^0$ ($2<\eta <4$) was brought up. Bigger asymmetry was observed with more isolated final state which was connected with the non-perturbative event topology. Since the non-perturbative contribution has been studied by only the forward ${\pi }^0$ production where the perturbative process was expected to be the major interaction rather than non-perturbative one, the RHICf experiment measured the very forward ($\eta >6$) ${\pi }^0$ to study the non-perturbative contribution in more detail. A new electromagnetic calorimeter was installed for the operation at the zero-degree region of the STAR experiment at RHIC and measured the ${\pi }^0$ over the kinematic range of $x_F>0.25$ and $0<p_T<1$ GeV/$c$ in June, 2017. A clear non-zero asymmetry was observed even in low $p_T<1$ GeV/$c$ showing a similar $x_F$ dependence with the forward ${\pi }^0$ one as the $p_T$ approached to 1 GeV/$c$. We present the first measurement of the very forward ${\pi }^0$ asymmetry, its analysis procedure and preliminary result. A future aspect to more precisely study the non-perturbative contribution will be also introduced.