A1 Journal article (refereed)
Event-shape and multiplicity dependence of freeze-out radii in pp collisions at √s = 7 TeV (2019)

ALICE collaboration. (2019). Event-shape and multiplicity dependence of freeze-out radii in pp collisions at √s = 7 TeV. Journal of High Energy Physics, 2019(9), Article 108. https://doi.org/10.1007/JHEP09(2019)108

JYU authors or editors

Publication details

All authors or editors: ALICE collaboration

Journal or series: Journal of High Energy Physics

ISSN: 1126-6708

eISSN: 1029-8479

Publication year: 2019

Volume: 2019

Issue number: 9

Article number: 108

Publisher: Springer

Publication country: Germany

Publication language: English

DOI: https://doi.org/10.1007/JHEP09(2019)108

Publication open access: Openly available

Publication channel open access: Open Access channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/65827

Web address of parallel published publication (pre-print): https://arxiv.org/abs/1901.05518

Abstract

Two-particle correlations in high-energy collision experiments enable the extraction of particle source radii by using the Bose-Einstein enhancement of pion production at low relative momentum q ∝ 1/R. It was previously observed that in pp collisions at s√ = 7TeV the average pair transverse momentum kT range of such analyses is limited due to large background correlations which were attributed to mini-jet phenomena. To investigate this further, an event-shape dependent analysis of Bose-Einstein correlations for pion pairs is performed in this work. By categorizing the events by their transverse sphericity ST into spherical (ST > 0:7) and jet-like (ST < 0:3) events a method was developed that allows for the determination of source radii for much larger values of kT for the first time. Spherical events demonstrate little or no background correlations while jet-like events are dominated by them. This observation agrees with the hypothesis of a mini-jet origin of the non-femtoscopic background correlations and gives new insight into the physics interpretation of the kT dependence of the radii. The emission source size in spherical events shows a substantially diminished kT dependence, while jet-like events show indications of a negative trend with respect to kT in the highest multiplicity events. Regarding the emission source shape, the correlation functions for both event sphericity classes show good agreement with an exponential shape, rather than a Gaussian one.

Keywords: ions; particle physics

Free keywords: heavy ion experiments; particle correlations and fluctuations

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2019

JUFO rating: 2