Observation of Beam Spin Asymmetries in the Process $ep\to e{\pi }^{+}{\pi }^{-}X$ with CLAS12

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 $G_1^{\perp }$. A clear sign change is observed around the $\rho$ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.

6 pages, 5 figures

References in corpus (6)

• Parton Fragmentation Functions
• Evidence for a Transverse Single-Spin Asymmetry in Leptoproduction of pi+pi- Pairs
• Production of two hadrons in semi-inclusive Deep Inelatic Scattering
• Dihadron fragmentation functions in the quark-jet model: Longitudinally polarized quarks
• Single-spin asymmetry in dihadron production in SIDIS off the longitudinally polarized nucleon target
• Spin Orbit Correlations and the Structure of the Nucleon

Cited by in corpus (7)

• 50 Years of Quantum Chromodynamics
• Precision Studies of QCD in the Low Energy Domain of the EIC
• The Present and Future of QCD
• Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab
• Extraction of the higher-twist parton distribution $e(x)$ from CLAS data
• A journey into the proton structure: Progresses and challenges
• Probing nucleon spin structure in deep-inelastic scattering, proton-proton collisions and Drell-Yan processes