Beam Spin Asymmetries of Charged and Neutral Pion Productions in Semi-inclusive DIS

TL;DR

This paper investigates beam spin asymmetries in semi-inclusive deep inelastic scattering for charged and neutral pions, using a spectator model to calculate twist-3 distributions and compare with experimental data, highlighting model sensitivities.

Contribution

It introduces a detailed spectator model calculation of twist-3 distributions for pion production asymmetries, considering different diquark propagator forms and parameter choices.

Findings

Model can describe some asymmetries but not all for different pions.

Different diquark propagator choices significantly affect asymmetry predictions.

Predictions made for CLAS at 5.5 GeV beam energy.

Abstract

We present a study on the beam single spin asymmetries $A_{LU}^{\sin\phi_h}$ of $\pi^+$, $\pi^-$ and $\pi^0$ production in semi-inclusive deep inelastic scattering process, by considering Collins effect and the $g^\perp D_1$ term simultaneously. We calculate the twist-3 distributions $e(x, \bm k_T^2)$ and $g^\perp(x,\bm k_T^2)$ for the valence quarks inside the proton in a spectator model. We consider two different options for the form of diquark propagator, as well as two different choices for the model parameters in the calculation. Using the model results, we estimate the beam spin asymmetries $A_{LU}^{\sin\phi_h}$ for the charged and neutral pions and compare the results with the measurement from the HERMES Collaboration. We also make predictions on the asymmetries at CLAS with a $5.5 \,\textrm{GeV}$ beam using the same model results. It is found that different choices for the diquark propagator will not only lead to different expressions for the distribution functions, but also result in different sizes of the asymmetries. Our study also shows that, although the spectator model calculation can describe the asymmetries for certain pion production in some kinematic regions, it seems difficult to explain the asymmetries of pion production for all three pions in a consistent way from the current versions.