Abstract
This Letter presents the measurement of near-side associated per-trigger yields, denoted ridge yields, from the analysis of angular correlations of charged hadrons in proton-proton collisions at βπ =13ββTeV. Long-range ridge yields are extracted for pairs of charged particles with a pseudorapidity difference of 1.4<|Ξβ’π|<1.8 and a transverse momentum of 1<πT<2ββGeV/π, as a function of the charged-particle multiplicity measured at midrapidity. This Letter extends the measurements of the ridge yield to the low multiplicity region, where in hadronic collisions it is typically conjectured that a strongly interacting medium is unlikely to be formed. The precision of the new low multiplicity results allows for the first direct quantitative comparison with the results obtained in e+β’eβ collisions at βπ =91ββGeV and βπ =183β209ββGeV, where initial-state effects such as preequilibrium dynamics and collision geometry are not expected to play a role. In the multiplicity range 8β²β¨πchβ©β²24 where the e+β’eβ results have good precision, the measured ridge yields in πβ’π collisions are substantially larger than the limits set in e+β’eβ annihilations. Consequently, the findings presented in this Letter suggest that the processes involved in e+β’eβ annihilations do not contribute significantly to the emergence of long-range correlations in πβ’π collisions.