Abstract:
Measurements of anisotropic flow coefficients (π£π) and their cross-correlations using two- and multiparticle cumulant methods are reported in collisions of πβ’π at βπ =13ββTeV, πβPb at a center-of-mass energy per nucleon pair βπ NN=5.02ββTeV, Xe-Xe at βπ NN=5.44ββTeV, and Pb-Pb at βπ NN=5.02ββTeV recorded with the ALICE detector. The multiplicity dependence of π£π is studied in a very wide range from 20 to 3000 particles produced in the midrapidity region |π|<0.8 for the transverse momentum range 0.2<ππ<3.0ββGeV/π. An ordering of the coefficients π£2>π£3>π£4 is found in πβ’π and πβPb collisions, similar to that seen in large collision systems, while a weak π£2 multiplicity dependence is observed relative to nucleus-nucleus collisions in the same multiplicity range. Using a novel subevent method, π£2 measured with four-particle cumulants is found to be compatible with that from six-particle cumulants in πβ’π and πβPb collisions. The magnitude of the correlation between π£2π and π£2π, evaluated with the symmetric cumulants SCβ‘(π,π) is observed to be positive at all multiplicities for π£2 and π£4, while for π£2 and π£3 it is negative and changes sign for multiplicities below 100, which may indicate a different π£π fluctuation pattern in this multiplicity range. The observed long-range multiparticle azimuthal correlations in high multiplicity πβ’π and πβPb collisions can neither be described by pythia 8 nor by impact-parameter-Glasma, music, and ultrarelativistic quantum molecular dynamics model calculations, and hence, provide new insights into the understanding of collective effects in small collision systems.
[ALICE Collaboration] A. Dubla, S. Masciocchi, I. Selyuzhenkov et al., βInvestigations of Anisotropic
Flow Using Multiparticle Azimuthal Correlations in pp, p-Pb, Xe-Xe, and Pb-Pb Collisions at the LHCβ, Phys. Rev. Lett. 123, 142301 (2019).
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.142301
Related to Project C06, ABC