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observation of long-range elliptic azimuthal anisotropies in vs = 13 and 2.76 TEV pp collisions with the ATLAS detector

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posted on 2023-06-09, 05:41 authored by Benedict AllbrookeBenedict Allbrooke, Lily AsquithLily Asquith, Alessandro Cerri, C A Chavez Barajas, Antonella De SantoAntonella De Santo, Fabrizio SalvatoreFabrizio Salvatore, I Santoyo Castillo, K Suruliz, Mark SuttonMark Sutton, Iacopo Vivarelli, The ATLAS Collaboration
ATLAS has measured two-particle correlations as a function of the relative azimuthal angle, ??, and pseudorapidity, ??, in vs=13 and 2.76 TeV pp collisions at the LHC using charged particles measured in the pseudorapidity interval |?|<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at ??~0 that extends over a wide range of ??, which has been referred to as the “ridge.” Per-trigger-particle yields, Y(??), are measured over 2<|??|<5. For both collision energies, the Y(??) 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(2??). The fitted Fourier coefficient, v2,2, exhibits factorization, suggesting that the ridge results from per-event cos(2?) modulation of the single-particle distribution with Fourier coefficients v2. The v2 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 v2 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 vs dependence.

Funding

ATLAS; G0275; STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCIL; ST/I006048/1

History

Publication status

  • Published

File Version

  • Published version

Journal

Physical Review Letters

ISSN

0031-9007

Publisher

American Physical Society

Issue

17

Volume

116

Article number

a172301

Department affiliated with

  • Physics and Astronomy Publications

Research groups affiliated with

  • Experimental Particle Physics Research Group Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2017-04-10

First Open Access (FOA) Date

2017-04-10

First Compliant Deposit (FCD) Date

2017-04-10

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