Azimuthal Asymmetries in Unpolarised Semi-Inclusive DIS at COMPASS
Abstract
In semi-inclusive deep inelastic scattering (SIDIS) the non-zero transverse momentum of partons induces azimuthal dependence of the cross-section. For an unpolarised nucleon, three azimuthal modulations that can be related to different combinations of twist-two or higher-twist transverse momentum dependent PDFs and fragmentation functions arise: the so-called Cahn effect reflected in a cos φ h modulation, the cos 2φ h term related to the Boer-Mulders PDF and sin φ h effect known as beam-spin asymmetry. In 2016 and 2017, the COMPASS experiment at CERN collected a large sample of SIDIS events using a longitudinally polarised 160 GeV/c muon beam scattering on a liquid hydrogen target. Amplitudes of the aforementioned azimuthal modulations have been extracted from part of the data. A new procedure has been developed to subtract a background coming from the decay of diffractively produced vector mesons. The results presented in this talk qualitatively agree with earlier COMPASS results obtained with an isoscalar target.
- Publication:
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Proceedings of the 24th International Spin Symposium (SPIN2021
- Pub Date:
- 2022
- DOI:
- 10.7566/JPSCP.37.020104
- arXiv:
- arXiv:2201.05205
- Bibcode:
- 2022spin.confb0104M
- Keywords:
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- High Energy Physics - Experiment
- E-Print:
- Proceedings of the 24th International Spin Symposium (SPIN 2021), Matsue, Shimane prefecture, Japan in October 18-22, 2021 5 pages, 7 figures