  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, $\langle p_{T}\rangle$, 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 $\langle
p_{T}\rangle$ 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.
