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Event-shape and multiplicity dependence of freeze-out radii in pp collisions at √s = 7 TeV

Acharya, S ; Adolfsson, Jonatan LU ; Christiansen, Peter LU ; Ljunggren, Martin LU ; Nassirpour, Adrian LU ; Oskarsson, Anders LU ; Richert, Tuva LU ; Silvermyr, David LU ; Stenlund, Evert LU and Vislavicius, Vytautas LU , et al. (2019) In Journal of High Energy Physics 2019(9).
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... (More)
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. [Figure not available: see fulltext.]. © 2019, The Author(s). (Less)
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keywords
Heavy Ion Experiments, Particle correlations and fluctuations
in
Journal of High Energy Physics
volume
2019
issue
9
article number
108
publisher
Springer
external identifiers
  • scopus:85074488241
ISSN
1029-8479
DOI
10.1007/JHEP09(2019)108
language
English
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yes
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Export Date: 21 November 2019
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c46bbab1-c1d1-4320-bd49-535d06faad70
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2019-11-21 12:11:20
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2020-07-01 05:24:58
@article{c46bbab1-c1d1-4320-bd49-535d06faad70,
  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 &gt; 0:7) and jet-like (ST &lt; 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. [Figure not available: see fulltext.]. © 2019, The Author(s).},
  author       = {Acharya, S and Adolfsson, Jonatan and Christiansen, Peter and Ljunggren, Martin and Nassirpour, Adrian and Oskarsson, Anders and Richert, Tuva and Silvermyr, David and Stenlund, Evert and Vislavicius, Vytautas and Zinovjev, G},
  issn         = {1029-8479},
  language     = {eng},
  number       = {9},
  publisher    = {Springer},
  series       = {Journal of High Energy Physics},
  title        = {Event-shape and multiplicity dependence of freeze-out radii in pp collisions at √s = 7 TeV},
  url          = {http://dx.doi.org/10.1007/JHEP09(2019)108},
  doi          = {10.1007/JHEP09(2019)108},
  volume       = {2019},
  year         = {2019},
}