Measurement of the inclusive J/ψ polarization at forward rapidity in pp collisions at √S=8 TeV
Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agrawal, Nikita; Ahammed, Zubayer; Ahn, Sang Un; Alme, Johan; Altenkaemper, Lucas; Djuvsland, Øystein; Ersdal, Magnus Rentsch; Fionda, Fiorella Maria Celeste; Nystrand, Joakim; Rehman, Attiq ur; Røhrich, Dieter; Tambave, Ganesh Jagannath; Ullaland, Kjetil; Wagner, Boris; Zhou, Zhuo; Arsene, Ionut Christian; Bätzing, Paul Christoph; Dordic, Olja; Lardeux, Antoine Xavier; Lindal, Svein; Mahmood, Sohail Musa; Malik, Qasim Waheed; Richter, Matthias Rudolph; Røed, Ketil; Skaali, Toralf Bernhard; Tveter, Trine Spedstad; Wikne, Jon Christopher; Zhao, Chengxin; Helstrup, Håvard; Hetland, Kristin Fanebust; Kileng, Bjarte; Nesbø, Simon Voigt; Storetvedt, Maksim Melnik; Langøy, Rune; Lien, Jørgen; Aiola, Salvatore; Akindinov, Alexander; Al-Turany, Mohammed; Alam, Sk Noor; De Albuquerque, Danilo Silva; Aleksandrov, Dimitry; Alessandro, Bruno; Alfaro Molina, José Rubén; ALICE, Collaboration
Journal article, Peer reviewed
Published version
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http://hdl.handle.net/11250/2560170Utgivelsesdato
2018Metadata
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Sammendrag
We report on the measurement of the inclusive J/ψ polarization parameters in pp collisions at a center of mass energy s√ = 8 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb − 1. J/ψ resonances are reconstructed in their di-muon decay channel in the rapidity interval 2.5 < y < 4.0 and over the transverse-momentum interval 2 < pT < 15 GeV/c. The three polarization parameters (λθ, λφ, λθφ) are measured as a function of pT both in the helicity and Collins-Soper reference frames. The measured J/ψ polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at s√ = 7 TeV.