Observation of Long-Range Elliptic Azimuthal Anisotropies in √s = 13 and 2.76 TeV p p Collisions with the ATLAS Detector
Name
Observation of Long-Range Elliptic.pdf
Size
567.12 KB
Format
Adobe PDF
Checksum (MD5)
e5853bc29f74a4d41040f60962518992
Author(s)
Taylor, Frank E
Date Issued
April 2016
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Aad, G. et al. “Observation of Long-Range Elliptic Azimuthal Anisotropies in √S = 13 and 2.76 TeV P P Collisions with the ATLAS Detector.” Physical Review Letters 116.17 (2016): n. pag. © 2016 CERN for the ATLAS Collaboration
Version
Final published version
Abstract
ATLAS has measured two-particle correlations as a function of the relative azimuthal angle, Δϕ, and pseudorapidity, Δη, in √s=13 and 2.76 TeV pp collisions at the LHC using charged particles measured in the pseudorapidity interval |η|<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at Δϕ∼0 that extends over a wide range of Δη, which has been referred to as the “ridge.” Per-trigger-particle yields, Y(Δϕ), are measured over 2<|Δη|<5. For both collision energies, the Y(Δϕ) distribution in all multiplicity intervals is found to be consistent with a linear combination of the per-trigger-particle yields measured in collisions with less than 20 reconstructed tracks, and a constant combinatoric contribution modulated by
cos (2Δϕ). The fitted Fourier coefficient, v2, 2, exhibits factorization, suggesting that the ridge results from per-event cos(2ϕ) modulation of the single-particle distribution with Fourier coefficients v[subscript 2]. The v[subscript 2] values are presented as a function of multiplicity and transverse momentum. They are found to be approximately constant as a function of multiplicity and to have a pT dependence similar to that measured in p+Pb and Pb+Pb collisions. The v[subscript 2] values in the 13 and 2.76 TeV data are consistent within uncertainties. These results suggest that the ridge in pp collisions arises from the same or similar underlying physics as observed in p+ Pb collisions, and that the dynamics responsible for the ridge has no strong
√s dependence.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1103/PhysRevLett.116.172301
