Abstract
We calculate the production cross-section and the transverse single-spin asymmetry for pion in $p^{\uparrow}+p\to \pi^0 + X$. Our computation is based on existence of the instanton induced effective quark-gluon and quark-gluon-pion interactions with a strong spin dependency. In this framework we calculate the cross section without using fragmentation functions. We compare predictions of the model with data from RHIC. Our numerical results, based on the instanton liquid model for QCD vacuum, are in agreement with unpolarized cross section data. The asymmetry grows with the transverse momentum of pion $k_t$ in accordance with experimental observations. It reach value $\sim 10\%$ but at higher $k_t$ than experiment shows.
Highlights
Transverse single-spin asymmetries (TSSAs) have been puzzling physicists more than three decades
In this paper we focus on transverse single-spin asymmetry for pion production in nucleon–nucleon scattering
In present paper we propose an alternative mechanism for TSSA in pp → πX, based on existence of novel effective interaction induced by instantons
Summary
Transverse single-spin asymmetries (TSSAs) have been puzzling physicists more than three decades. In this paper we focus on transverse single-spin asymmetry for pion production in nucleon–nucleon scattering It is often called as analyzing power and denoted as AN. Unambiguous effects were measured and they triggered renewed interest on TSSAs. A popular approach to describe observed spin effects is based on the extension of the collinear parton model with inclusion of parton’s transverse motion. A popular approach to describe observed spin effects is based on the extension of the collinear parton model with inclusion of parton’s transverse motion It utilizes the Transverse Momentum Dependent(TMD) factorization scheme. The Sivers effect can exist both for quarks and gluons This intrinsic asymmetry is represented by Sivers function of the unpolarized partons in a transversely polarized proton. The low-energy effective interaction generated by instantons provides us the other solution
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