Measurement of the inclusive J/ $\psi $ polarization at forward rapidity in pp collisions at $\mathbf {\sqrt{s} = 8}$  TeV

Acharya, S.; Torales - Acosta, Fernando; Adamova, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan Mohan; Aglieri Rinella, Gianluca; Agnello, Michelangelo; Agrawal, Neelima; Ahammed, Zubayer; Ahn, Sang Un

doi:10.1140/epjc/s10052-018-6027-2

Measurement of the inclusive J/ $\psi$ polarization at forward rapidity in pp collisions at $\mathbf {\sqrt{s} = 8}$ TeV

ALICE

Collaboration

May 11, 2018

20 pages

Published in:

Eur.Phys.J.C 78 (2018) 7, 562

Published: Jul 9, 2018

e-Print:

1805.04374 [hep-ex]

DOI:

10.1140/epjc/s10052-018-6027-2

Report number:

CERN-EP-2018-098

Experiments:

CERN-LHC-ALICE

View in:

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Abstract: (Springer)

We report on the measurement of the inclusive J/

\psi

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/

\psi

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< p_\mathrm{T} < 15

\mathrm {GeV}/c

. The three polarization parameters (

\lambda _\theta

,

\lambda _\varphi

,

\lambda _{\theta \varphi }

) are measured as a function of

p_\mathrm{T}

both in the helicity and Collins-Soper reference frames. The measured J/

\psi

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.

Note:

20 pages, 6 captioned figures, 4 tables, authors from page 15, submitted to EPJC, figures at http://aliceinfo.cern.ch/ArtSubmission/node/4282

p p: scattering
p p: colliding beams
J/psi(3100): hadroproduction
J/psi(3100): leptonic decay
muon: pair production
J/psi(3100): polarization
rapidity dependence
transverse momentum dependence
CERN LHC Coll
helicity

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