Beam Spin Asymmetry in Semi-Inclusive Electroproduction of Hadron Pairs

(CLAS Collaboration)

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A first measurement of the longitudinal beam spin asymmetry ALU in the semi-inclusive electroproduction of pairs of charged pions is reported. ALU is a higher-twist observable and offers the cleanest access to the nucleon twist-3 parton distribution function e(x). Data have been collected in the Hall-B at Jefferson Lab by impinging a 5.498-GeV electron beam on a liquid-hydrogen target, and reconstructing the scattered electron and the pion pair with the CLAS detector. One-dimensional projections of the ALUsinφR moments are extracted for the kinematic variables of interest in the valence quark region. The understanding of dihadron production is essential for the interpretation of observables in single-hadron production in semi-inclusive DIS, and pioneering measurements of single-spin asymmetries in dihadron production open a new avenue in studies of QCD dynamics.

Original languageEnglish
Article number062002
Number of pages6
JournalPhysical Review Letters
Issue number6
Publication statusPublished - 12 Feb 2021

Bibliographical note

Funding Information:
We thank the staff of the Accelerator and Physics Divisions for making the experiment possible. Special thanks to A. Bacchetta, B. Pasquini, M. Polyakov, M. Radici, P. Schweitzer, and M. Wakamatsu for useful discussions. This work was supported in part by the U.S. Department of Energy (No. DE-FG02-96ER40950) and National Science Foundation, the French Centre National de la Recherche Scientifique and Commissariat à l’Energie Atomique, the French-American Cultural Exchange (FACE), the Italian Istituto Nazionale di Fisica Nucleare, the Chilean Comisión Nacional de Investigación Científica y Tecnológica (CONICYT), the Mexican Consejo Nacional de Ciencias y Tecnología (CONACyT), the National Research Foundation of Korea, and the UK Science and Technology Facilities Council (STFC). A. C. is supported by DGAPA-PAPIIT IA101720 and CONACyT Ciencia de Frontera No. 51244 (FORDECYT-PRONACES). The Jefferson Science Associates (JSA) operates the Thomas Jefferson National Accelerator Facility for the United States Department of Energy under Contract No. DE-AC05-06OR23177.

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