Measurement of long-range pseudorapidity correlations and azimuthal harmonics in root s(NN)=5.02 TeV proton-lead collisions with the ATLAS detector
2014 (English)In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 90, no 4, 044906- p.Article in journal (Refereed) Published
Measurements of two-particle correlation functions and the first five azimuthal harmonics, v(1) to v(5), are presented, using 28 nb(-1) of p + Pb collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 5.02 TeV measured with the ATLAS detector at the LHC. Significant long-range "ridgelike" correlations are observed for pairs with small relative azimuthal angle (|Delta phi| < pi/3) and back-to-back pairs (|Delta phi| > 2 pi/3) over the transverse momentum range 0.4 < p(T) < 12 GeV and in different intervals of event activity. The event activity is defined by either the number of reconstructed tracks or the total transverse energy on the Pb-fragmentation side. The azimuthal structure of such long-range correlations is Fourier decomposed to obtain the harmonics v(n) as a function of p(T) and event activity. The extracted v(n) values for n = 2 to 5 decrease with n. The v(2) and v(3) values are found to be positive in the measured p(T) range. The v(1) is also measured as a function of p(T) and is observed to change sign around p(T) approximate to 1.5-2.0 GeV and then increase to about 0.1 for pT > 4 GeV. The v(2)(p(T)), v(3)(p(T)), and v(4)(p(T)) are compared to the v(n) coefficients in Pb + Pb collisions at root s(NN) = 2.76 TeV with similar event multiplicities. Reasonable agreement is observed after accounting for the difference in the average p(T) of particles produced in the two collision systems.
Place, publisher, year, edition, pages
2014. Vol. 90, no 4, 044906- p.
IdentifiersURN: urn:nbn:se:uu:diva-239693DOI: 10.1103/PhysRevC.90.044906ISI: 000343944700005OAI: oai:DiVA.org:uu-239693DiVA: diva2:775098
ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1103/PhysRevC.90.0449062014-12-302014-12-302014-12-30Bibliographically approved