Multiplicity dependence of ${\rm Y}$ production at forward rapidity in pp collisions at $\sqrt{s}$ = 13 TeV

Abstract

The measurement of ${\rm Y}$(1S), ${\rm Y}$(2S), and ${\rm Y}$(3S) yields as a function of the charged-particle multiplicity density, $\text{d}{N}_{\text{ch}}/\text{d}\eta$, using the ALICE experiment at the LHC, is reported in pp collisions at $\sqrt{s}=$ 13 TeV. The ${\rm Y}$ meson yields are measured at forward rapidity ($2.5<y<4$) in the dimuon decay channel, whereas the charged-particle multiplicity is defined at central rapidity ($|\eta |<1$). Both quantities are divided by their average value in minimum bias events to compute the self-normalized quantities. The increase of the self-normalized ${\rm Y}$(1S), ${\rm Y}$(2S), and ${\rm Y}$(3S) yields is found to be compatible with a linear scaling with the self-normalized $\text{d}{N}_{\text{ch}}/\text{d}\eta$, within the uncertainties. The self-normalized yield ratios of excited-to-ground ${\rm Y}$ states are compatible with unity within uncertainties. Similarly, the measured double ratio of the self-normalized ${\rm Y}$(1S) to the self-normalized J/$\psi$ yields, both measured at forward rapidity, is compatible with unity for self-normalized charged-particle multiplicities beyond one. The measurements are compared with theoretical predictions incorporating initial or final state effects.

27 pages, 5 captioned figures, 4 tables, published version, figures at http://alice-publications.web.cern.ch/node/8399

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Cited by in corpus (1)

• Multiplicity dependence of ${\rm Y}$(nS) mean transverse momentum in proton-proton collisions