Event-by-event long-range correlations of azimuthal anisotropy Fourier
coefficients (v(n)) in 8.16 TeV pPb data, collected by the CMS
experiment at the CERN Large Hadron Collider, are extracted using a
subevent four-particle cumulant technique applied to very low
multiplicity events. Each combination of four charged particles is
selected from either two, three, or four distinct subevent regions of a
pseudorapidity range from -2.4 to 2.4 of the CMS tracker, and with
transverse momentum between 0.3 and 3.0 GeV. Using the subevent cumulant
technique, correlations between v(n) of different orders are measured as
functions of particle multiplicity and compared to the standard cumulant
method without subevents over a wide event multiplicity range. At high
multiplicities, the v(2) and v(3) coefficients exhibit an
anticorrelation; this behavior is observed consistently using various
methods. The v(2) and v(4) correlation strength is found to depend on
the number of subevents used in the calculation. As the event
multiplicity decreases, the results from different subevent methods
diverge because of different contributions of noncollective or
few-particle correlations. Correlations extracted with the four-subevent
method exhibit a tendency to diminish monotonically toward the lowest
multiplicity region (about 20 charged tracks) investigated. These
findings extend previous studies to a significantly lower event
multiplicity range and establish the evidence for the onset of
long-range collective multiparticle correlations in small system
collisions