Document Type

Article

Publication Date

2021

DOI

10.1103/PhysRevLett.126.152501

Publication Title

Physical Review Letters

Volume

126

Issue

15

Pages

152501 (1-6)

Abstract

The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G⊥1. A clear sign change is observed around the ρ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.

Comments

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license (CC BY 4.0). Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

Publisher's version available at: https://doi.org/10.1103/PhysRevLett.126.152501

Original Publication Citation

Hayward, T.B., Dilks, C., Vossen, A., ... Yale, B., Zachariou, N., Zhang, J., CLAS Collaboration (2021) Observation of beam spin asymmetries in the process ep → e'π⁺π⁻ X with CLAS 12. Physical Review Letters, 126(15),1-6, Article 152501. https://doi.org/10.1103/PhysRevLett.126.152501

ORCID

0000-0003-2243-6836 (Kuhn)

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