Abstract
The fiducial cross section for Y(1S) pair production in proton-proton collisions at a center-of-mass energy
of 13 TeV in the region where both Y(1S) mesons have an absolute rapidity below 2.0 is measured to be
79 ± 11 (stat) ± 6 (syst) ± 3 (B) pb assuming the mesons are produced unpolarized. The last uncertainty
corresponds to the uncertainty in the Y(1S) meson dimuon branching fraction. The measurement is
performed in the final state with four muons using proton-proton collision data collected in 2016 by
the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb−1. This process
serves as a standard model reference in a search for narrow resonances decaying to Y(1S)μ+μ− in the
same final state. Such a resonance could indicate the existence of a tetraquark that is a bound state of
two b quarks and two b antiquarks. ¯ The tetraquark search is performed for masses in the vicinity of four
times the bottom quark mass, between 17.5 and 19.5 GeV, while a generic search for other resonances is
performed for masses between 16.5 and 27 GeV. No significant excess of events compatible with a narrow
resonance is observed in the data. Limits on the production cross section times branching fraction to four
muons via an intermediate Y(1S) resonance are set as a function of the resonance mass.