5–12 Jul 2017
Venice, Italy
Europe/Zurich timezone
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New mechanisms in the production of two $J/\psi$ quarkonia in proton-proton scattering at the LHC.

8 Jul 2017, 10:30
15m
Room Mosaici-1 (Palazzo del Casinò)

Room Mosaici-1

Palazzo del Casinò

Parallel Talk QCD and Hadronic Physics QCD and hadronic physics

Speakers

Antoni Szczurek (Institute of Nuclear Physics) Wolfgang Schaefer (Institute of Nuclear Physics PAN)

Description

The presentation will be based on our paper in preparation [1].
We discuss production of pairs of $J/\psi$ in pp collisions in the context
of recent results obatained at the LHC at large transverse momenta.
The leading-order $O(\alpha_s^4)$ contribution
is calculated in both collinear and the $k_t$-factorization approach
with the KMR UGDF.
We include also two-gluon exchange contribution
($O(\alpha_s^6)$) (not included routinely).
This contribution is calculated only in the collinear approximation.
In addition we calculate cross sections for
$p p \to \chi_c(J_1) \chi_c(J_2)$.
A feed-down from double $\chi_c$ production to double $J/\psi$
production is estimated for a first time.
The double parton scattering cross section and differential
distributions are calculated using a parametrization
of experimental $J/\psi$ differential distributions in rapidity
and transverse momentum.
Results of our calculations are compared with very recent ATLAS data [2].
We find that the two-gluon exchange mechanism and feed down from
double $\chi_c$ production lead to very similar
distributions in rapidity distance between the $J/\psi$
mesons as for DPS.
Much larger cross sections are obtained in the $k_t$-factorization approach.
Including the mechanisms leaves much less room for the DPS contribution which cannot be calculated from first principle.
The $\sigma_{eff}$ parameter for DPS needed to describe the ATLAS data
is much larger than from previous analyses of double
quarkonium production, where a smaller number of mechanisms was included.
We present distributions in rapidity distance, two $J/\psi$ invariant
mass, azimuthal angle correlations between the two $J/\psi$ mesons
and transverse momentum of the pairs of quarkonia.
Ihe sum of the four considered contributions reminds
experimental ATLAS distributions.

1) A. Cisek, W. Sch\"afer and A. Szczurek, a paper in preparation.

2) ATLAS collaboration,
CERN-EP-2016-211, arXiv:161202950.

Primary authors

Antoni Szczurek (Institute of Nuclear Physics) Wolfgang Schaefer (Institute of Nuclear Physics PAN)

Presentation materials