PT Journal
AU LHCb Collaboration (Aaij, Rea
   Jaimes Elles, SJ
   Jashal, BK
   Martinez-Vidal, F
   Oyanguren, A
   Rebollo De Miguel, M
   Sanderswood, I
   Zhuo, J
TI Measurement of J/ψ-pair production in pp collisions at √s=13 TeV and study of gluon transverse-momentum dependent PDFs
SO Journal of High Energy Physics
JI J. High Energy Phys.
PY 2024
BP 088
EP 40pp
VL 03
IS 3
DI 10.1007/JHEP03(2024)088
LA English
DE Hadron-Hadron Scattering; Multi-Parton Interactions; QCD; Quarkonium
AB The production cross-section of J/psi pairs in proton-proton collisions at a centre-of-mass energy of root s = 13TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb(-1) collected by the LHCb experiment. The measurement is performed with both J/psi mesons in the transverse momentum range 0 < p(T) < 14 GeV/c and rapidity range 2.0 < y < 4.5. The cross-section of this process is measured to be 16.36 +/- 0.28 (stat) +/- 0.88 (syst) nb. The contributions from single-parton scattering and double-parton scattering are separated based on the dependence of the cross-section on the absolute rapidity difference Delta y between the two J/psi mesons. The effective cross-section of double-parton scattering is measured to be sigma(eff) = 13.1 +/- 1.8 (stat) +/- 2.3 (syst) mb. The distribution of the azimuthal angle phi(CS) of one of the J/psi mesons in the Collins-Soper frame and the p(T)-spectrum of the J/psi pairs are also measured for the study of the gluon transverse-momentum dependent distributions inside protons. The extracted values of < cos4 phi(CS)> and < cos2 phi(CS)> are consistent with zero, but the presence of azimuthal asymmetry at a few percent level is allowed.
ER