Measurement of the inclusive J/$$\psi $$ polarization at forward rapidity in pp collisions at $$\mathbf {\sqrt{s} = 8}$$ TeV
Here, we report on the measurement of the inclusive J/ψ polarization parameters in pp collisions at a center of mass energy $$ \sqrt{s}=8 $$ 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 $$ \sqrt{s}=7 $$ TeV.
- Research Organization:
- Univ. of California, Berkeley, CA (United States). Nuclear Science and Security Consortium; Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation; USDOE Office of Science (SC), Nuclear Physics (NP)
- Contributing Organization:
- ALICE Collaboration
- Grant/Contract Number:
- NA0003180; AC05-00OR22725; AC02-05CH11231
- OSTI ID:
- 1462367
- Alternate ID(s):
- OSTI ID: 1481678; OSTI ID: 1506327
- Journal Information:
- European Physical Journal. C, Particles and Fields, Vol. 78, Issue 7; ISSN 1434-6044
- Publisher:
- SpringerCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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