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Azimuthally-differential pion femtoscopy relative to the third harmonic event plane in Pb–Pb collisions at sNN=2.76TeV

, ; Acharya, S; Adolfsson, Jonatan LU ; Christiansen, Peter LU ; Ljunggren, Martin LU ; Oskarsson, Anders LU ; Richert, Tuva LU ; Silvermyr, David LU ; Stenlund, Evert LU and Vislavicius, Vytautas LU , et al. (2018) In Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 785. p.320-331
Abstract
Azimuthally-differential femtoscopic measurements, being sensitive to spatio-temporal characteristics of the source as well as to the collective velocity fields at freeze out, provide very important information on the nature and dynamics of the system evolution. While the HBT radii oscillations relative to the second harmonic event plane measured recently reflect mostly the spatial geometry of the source, model studies have shown that the HBT radii oscillations relative to the third harmonic event plane are predominantly defined by the velocity fields. In this Letter, we present the first results on azimuthally-differential pion femtoscopy relative to the third harmonic event plane as a function of the pion pair transverse momentum kT for... (More)
Azimuthally-differential femtoscopic measurements, being sensitive to spatio-temporal characteristics of the source as well as to the collective velocity fields at freeze out, provide very important information on the nature and dynamics of the system evolution. While the HBT radii oscillations relative to the second harmonic event plane measured recently reflect mostly the spatial geometry of the source, model studies have shown that the HBT radii oscillations relative to the third harmonic event plane are predominantly defined by the velocity fields. In this Letter, we present the first results on azimuthally-differential pion femtoscopy relative to the third harmonic event plane as a function of the pion pair transverse momentum kT for different collision centralities in Pb–Pb collisions at sNN=2.76 TeV. We find that the Rside and Rout radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate in phase relative to the third harmonic event plane, similar to the results from 3+1D hydrodynamical calculations. The observed radii oscillations unambiguously signal a collective expansion and anisotropy in the velocity fields. A comparison of the measured radii oscillations with the Blast-Wave model calculations indicate that the initial state triangularity is washed-out at freeze out. © 2018 European Organization for Nuclear Research (Less)
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Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
volume
785
pages
12 pages
publisher
Elsevier
external identifiers
  • scopus:85053804355
ISSN
0370-2693
DOI
10.1016/j.physletb.2018.06.042
language
English
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yes
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871b6b0c-f255-444f-afdb-b83f75bc1dfe
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2018-10-09 11:12:08
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2019-02-20 11:30:23
@article{871b6b0c-f255-444f-afdb-b83f75bc1dfe,
  abstract     = {Azimuthally-differential femtoscopic measurements, being sensitive to spatio-temporal characteristics of the source as well as to the collective velocity fields at freeze out, provide very important information on the nature and dynamics of the system evolution. While the HBT radii oscillations relative to the second harmonic event plane measured recently reflect mostly the spatial geometry of the source, model studies have shown that the HBT radii oscillations relative to the third harmonic event plane are predominantly defined by the velocity fields. In this Letter, we present the first results on azimuthally-differential pion femtoscopy relative to the third harmonic event plane as a function of the pion pair transverse momentum kT for different collision centralities in Pb–Pb collisions at sNN=2.76 TeV. We find that the Rside and Rout radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate in phase relative to the third harmonic event plane, similar to the results from 3+1D hydrodynamical calculations. The observed radii oscillations unambiguously signal a collective expansion and anisotropy in the velocity fields. A comparison of the measured radii oscillations with the Blast-Wave model calculations indicate that the initial state triangularity is washed-out at freeze out. © 2018 European Organization for Nuclear Research},
  author       = {,  and Acharya, S and Adolfsson, Jonatan and Christiansen, Peter and Ljunggren, Martin and Oskarsson, Anders and Richert, Tuva and Silvermyr, David and Stenlund, Evert and Vislavicius, Vytautas and Zou, S.},
  issn         = {0370-2693},
  language     = {eng},
  pages        = {320--331},
  publisher    = {Elsevier},
  series       = {Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics},
  title        = {Azimuthally-differential pion femtoscopy relative to the third harmonic event plane in Pb–Pb collisions at sNN=2.76TeV},
  url          = {http://dx.doi.org/10.1016/j.physletb.2018.06.042},
  volume       = {785},
  year         = {2018},
}