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Predictions for azimuthal asymmetries in pion and kaon production in SIDIS off a longitudinally polarized deuterium target at HERMES

A. V. Efremov, K. Goeke, P. Schweitzer

TL;DR

The paper extends a parameter-free SIDIS framework by combining the Collins fragmentation function $H_1^p$ (from DELPHI) with transversity $h_1^a(x)$ from the chiral quark-soliton model to predict azimuthal asymmetries in pion and kaon production off a longitudinally polarized deuterium target at HERMES. It applies the same methodology that successfully described proton-target data, now to deuteron kinematics, producing expectations for $A_{UL,D}^{{}}$ and $A_{UL,D}^{{2}}$ that depend on the kaon analyzing power and the assumed suppression of strange transversity. The work highlights the interplay of twist-2 and twist-3 contributions, uses Gaussian transverse momenta, and relies on SU(2)/SU(3) fragmentation relations to relate hadron species. If forthcoming HERMES data confirm the assumed kaon analyzing power and the predicted deuteron asymmetries, this would reinforce the Collins mechanism and the χQSM transversity predictions and provide quantitative tests of flavor structure in transversity.

Abstract

Predictions are made for azimuthal asymmetries in pion and kaon production from SIDIS off a longitudinally polarized deuterium target for HERMES kinematics, based on information on the 'Collins fragmentation function' from DELPHI data and on predictions for the transversity distribution function from non-perturbative calculations in the chiral quark-soliton model. There are no free parameters in the approach, which has been already successfully applied to explain the azimuthal asymmetries from SIDIS off polarized proton targets observed by HERMES and SMC.

Predictions for azimuthal asymmetries in pion and kaon production in SIDIS off a longitudinally polarized deuterium target at HERMES

TL;DR

The paper extends a parameter-free SIDIS framework by combining the Collins fragmentation function (from DELPHI) with transversity from the chiral quark-soliton model to predict azimuthal asymmetries in pion and kaon production off a longitudinally polarized deuterium target at HERMES. It applies the same methodology that successfully described proton-target data, now to deuteron kinematics, producing expectations for and that depend on the kaon analyzing power and the assumed suppression of strange transversity. The work highlights the interplay of twist-2 and twist-3 contributions, uses Gaussian transverse momenta, and relies on SU(2)/SU(3) fragmentation relations to relate hadron species. If forthcoming HERMES data confirm the assumed kaon analyzing power and the predicted deuteron asymmetries, this would reinforce the Collins mechanism and the χQSM transversity predictions and provide quantitative tests of flavor structure in transversity.

Abstract

Predictions are made for azimuthal asymmetries in pion and kaon production from SIDIS off a longitudinally polarized deuterium target for HERMES kinematics, based on information on the 'Collins fragmentation function' from DELPHI data and on predictions for the transversity distribution function from non-perturbative calculations in the chiral quark-soliton model. There are no free parameters in the approach, which has been already successfully applied to explain the azimuthal asymmetries from SIDIS off polarized proton targets observed by HERMES and SMC.

Paper Structure

This paper contains 11 sections, 18 equations, 3 figures, 1 table.

Table of Contents

  1. Introduction
  2. Ingredients for prediction: $H_1^\perp$ and $h_1^a(x)$
  3. The T-odd fragmentation function $H_1^\perp$.
  4. $h_1^a(x)$ in nucleon.
  5. $h_1^s(x)$ and $h_1^{\bar{s}}(x)$ in nucleon.
  6. $h_L^a(x)$ in nucleon.
  7. Azimuthal asymmetries from deuteron
  8. Pion production
  9. Kaon production
  10. Comparison to $A_{UL}$ from proton target
  11. Conclusions

Figures (3)

  • Figure 1: The chiral quark-soliton model prediction for the proton $x h_1^a(x)$ vs. $x$ at the scale $Q^2=4\,{\rm GeV}^2$.
  • Figure 2: Kinematics of the process $lD\rightarrow l'h X$ in the lab frame.
  • Figure 3: Predictions for azimuthal asymmetries $A_{UL,D}^{W(\phi)}(x,h)$ vs. $x$ from a longitudinally polarized deuteron target for HERMES kinematics. a. Pions. The "data points" do not anticipate the experiment but correspond merely to a simple estimate of the expected error bars (see text). b. Kaons, based on assumption eq.(\ref{['apower-kaon']}). The results refer to the central value of the analyzing power $\langle H_1^\perp\rangle/\langle D_1\rangle=(12.5\pm 1.4)\%$, eq.(\ref{['apower']}).