Underlying event measurements in $p$+$p$ collisions at $\sqrt{s}=200$ GeV at RHIC

Abstract

Particle production sensitive to non-factorizable and non-perturbative processes that contribute to the underlying event associated with a high transverse momentum ($p_T$) jet in proton+proton collisions at $\sqrt{s}$=200 GeV is studied with the STAR detector. Each event is divided into three regions based on the azimuthal angle with respect to the highest-$p_T$ jet direction: in the leading jet direction ("Toward"), opposite to the leading jet ("Away"), and perpendicular to the leading jet ("Transverse"). In the Transverse region, the average charged particle density is found to be between 0.4 and 0.6 and the mean transverse momentum, $⟨p_T⟩$, between 0.5-0.7 GeV/$c$ for particles with $p_T$$>$0.2 GeV/$c$ at mid-pseudorapidity ($|\eta |$$<$1) and jet $p_T$$>$15 GeV/$c$. Both average particle density and $⟨p_T⟩$ depend weakly on the leading jet $p_T$. Closer inspection of the Transverse region hints that contributions to the underlying event from initial- and final-state radiation are significantly smaller in these collisions than at the higher energies, up to 13 TeV, recorded at the LHC. Underlying event measurements associated with a high-$p_T$ jet will contribute to our understanding of QCD processes at hard and soft scales at RHIC energies, as well as provide constraints to modeling of underlying event dynamics.

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Cited by in corpus (14)

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• Experimental Aspects of Jet Physics at a Future EIC
• Azimuthal transverse single-spin asymmetries of inclusive jets and identified hadrons within jets from polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV
• Disentangling the hard gluon Bremsstrahlung effects from the relative transverse activity classifier in pp collisions
• Effects of the formation time of parton shower on jet quenching in heavy-ion collisions
• Apparent modification of the jet-like yield in proton-proton collisions with large underlying event
• Study of charged particle production at high $p_{\mathrm{T}}$ using event topology in pp, p$-$Pb and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Energy dependence of underlying-event observables from RHIC to LHC energies
• Correlations of event activity with hard and soft processes in $p$ + Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV at STAR
• Precision measurement of the longitudinal double-spin asymmetry for dijet production at intermediate pseudorapidity in polarized $pp$ collisions at $\sqrt{s}$ = 200 GeV
• A New Herwig7 Underlying Event Tune: from RHIC to LHC Energies
• Understanding the medium-like effects in the jet-like yield in pp and p-Pb collisions using event generators