A set of measurements of azimuthal asymmetries in the production of pairs of identified hadrons in deep-inelastic scattering of muons on transversely polarised 6LiD (deuteron) and NH3 (proton) targets is presented. All available data collected in the years 2003–2004 and 2007/2010 with the COMPASS spectrometer using a muon beam of 160GeV/c at the CERN SPS were analysed. The asymmetries provide access to the transversity distribution functions via a fragmentation function that in principle may be independently obtained from e+e annihilation data. Results are presented, discussed and compared to existing measurements as well as to model predictions. Asymmetries of π+π pairs measured with the proton target as a function of the Bjorken scaling variable are sizeable in the range x>0.032, indicating non-vanishing transversity distribution and di-hadron interference fragmentation functions. As already pointed out by several authors, the small asymmetries of π+π measured on the 6LiD target can be interpreted as indication for a cancellation of u and d-quark transversity distributions.

Original languageEnglish
Article number138155
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - 10 Oct 2023


FundersFunder number
Daiko and Yamada Foundations
National Science FoundationPHY-1506416
National Science Foundation
Univerzita Karlova v PrazePRIMUS/22/SCI/017
Univerzita Karlova v Praze
Deutsche Forschungsgemeinschaft
Japan Society for the Promotion of Science18002006, 20540299, 26247032, 18540281
Japan Society for the Promotion of Science
Ministry of Education, Culture, Sports, Science and Technology
Ministerstvo Školství, Mládeže a TělovýchovyLM2015058, LM2018104, LTT17018
Ministerstvo Školství, Mládeže a Tělovýchovy
Fundação para a Ciência e a TecnologiaCERN/FIS-PAR/0016/2021, CERN/FIS-PAR/0022/2019
Fundação para a Ciência e a Tecnologia
Bundesministerium für Bildung und Forschung
Israel Academy of Sciences and Humanities
LabexANR-10-LABX-0038, ANR-11-IDEX-0003-01
Narodowe Centrum Nauki2020/37/B/ST2/01547
Narodowe Centrum Nauki
Ministry of Science and Technology, Taiwan
Università degli Studi del Piemonte Orientale
Horizon 2020824093
Horizon 2020


    • Collins effect
    • Di-hadron
    • Fragmentation
    • SIDIS
    • Spin
    • Transversity


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