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Centrality dependence of pion freeze-out radii in Pb-Pb collisions at sNN =2.76 TeV

  • Author(s): Adam, J
  • Adamová, D
  • Aggarwal, MM
  • Aglieri Rinella, G
  • Agnello, M
  • Agrawal, N
  • Ahammed, Z
  • Ahn, SU
  • Aimo, I
  • Aiola, S
  • Ajaz, M
  • Akindinov, A
  • Alam, SN
  • Aleksandrov, D
  • Alessandro, B
  • Alexandre, D
  • Alfaro Molina, R
  • Alici, A
  • Alkin, A
  • Almaraz, JRM
  • Alme, J
  • Alt, T
  • Altinpinar, S
  • Altsybeev, I
  • Alves Garcia Prado, C
  • Andrei, C
  • Andronic, A
  • Anguelov, V
  • Anielski, J
  • Antičić, T
  • Antinori, F
  • Antonioli, P
  • Aphecetche, L
  • Appelshäuser, H
  • Arcelli, S
  • Armesto, N
  • Arnaldi, R
  • Arsene, IC
  • Arslandok, M
  • Audurier, B
  • Augustinus, A
  • Averbeck, R
  • Azmi, MD
  • Bach, M
  • Badalà, A
  • Baek, YW
  • Bagnasco, S
  • Bailhache, R
  • Bala, R
  • Baldisseri, A
  • Baltasar Dos Santos Pedrosa, F
  • Baral, RC
  • Barbano, AM
  • Barbera, R
  • Barile, F
  • Barnaföldi, GG
  • Barnby, LS
  • Barret, V
  • Bartalini, P
  • Barth, K
  • Bartke, J
  • Bartsch, E
  • Basile, M
  • Bastid, N
  • Basu, S
  • Bathen, B
  • Batigne, G
  • Batista Camejo, A
  • Batyunya, B
  • Batzing, PC
  • Bearden, IG
  • Beck, H
  • Bedda, C
  • Behera, NK
  • Belikov, I
  • Bellini, F
  • Bello Martinez, H
  • Bellwied, R
  • Belmont, R
  • Belmont-Moreno, E
  • Belyaev, V
  • Bencedi, G
  • Beole, S
  • Berceanu, I
  • Bercuci, A
  • Berdnikov, Y
  • Berenyi, D
  • Bertens, RA
  • Berzano, D
  • Betev, L
  • Bhasin, A
  • Bhat, IR
  • Bhati, AK
  • Bhattacharjee, B
  • Bhom, J
  • Bianchi, L
  • et al.
Abstract

© 2016 CERN. We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at sNN=2.76 TeV as a function of collision centrality and the average transverse momentum of the pair kT. Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged one-dimensional radii are extracted. The radii decrease with kT, following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with (dNch/dη)1/3. This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller sNN, a decrease in the ratio Rout/Rside is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider.

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