TY - JOUR
T1 - Azimuthally-differential pion femtoscopy relative to the third harmonic event plane in Pb-Pbcollisions at root(NN)-N-S=2.76TeV
AU - Acharya, S.
AU - Acosta, F.T.
AU - Adamova, D.
AU - Adolfsson, J
AU - Aggarwal, MM.
AU - Rinella, G.A.
AU - Agnello, Maria
AU - Agrawal, N.
AU - Ahammed, Z.
AU - Ahn, S.U.
AU - Aiola, S.
AU - Akindinov, A.
AU - Al-Turany, M.
AU - Alam, S.
AU - Albuquerque, DSD
AU - Aleksandrov, D.
AU - Alessandro, B
AU - Molina, Rafael A.
AU - Ali, Yusuf
AU - Alici, A.
AU - Alkin, A.
AU - Alme, J.
AU - Alt, T.
AU - Bearden, Ian
AU - Bilandzic, Ante
AU - bsm989, bsm989
AU - Gajdosova, Katarina
AU - Bourjau, Christian Alexander
AU - Gaardhøje, Jens Jørgen
AU - Nielsen, Børge Svane
AU - Thoresen, Freja
AU - Zhou, You
AU - Christensen, Christian Holm
AU - Chojnacki, Marek
AU - Ozelin De Lima Pimentel, Lais
PY - 2018/10/10
Y1 - 2018/10/10
N2 - 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.
AB - 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.
U2 - 10.1016/j.physletb.2018.06.042
DO - 10.1016/j.physletb.2018.06.042
M3 - Journal article
SN - 0370-2693
VL - 785
SP - 320
EP - 331
JO - Physics Letters B
JF - Physics Letters B
ER -