Production of light nuclei and anti-nuclei inppand Pb-Pb collisions at energies available at the CERN Large Hadron Collider

Abstract

The production of (anti-)deuteron and (anti-) 3 He nuclei in Pb-Pb collisions at √ s NN = 2.76 TeV has been studied using the ALICE detector at the LHC. The spectra exhibit a significant hardening with increasing centrality. Combined blast-wave fits of several particles support the interpretation that this behavior is caused by an increase of radial flow. The integrated particle yields are discussed in the context of coalescence and thermal-statistical model expectations. The particle ratios, 3 He /d and 3 He /p, in Pb-Pb collisions are found to be in agreement with a common chemical freeze-out temperature of T chem ≈ 156 MeV. These ratios do not vary with centrality which is in agreement with the thermal-statistical model. In a coalescence approach, it excludes models in which nucleus production is proportional to the particle multiplicity and favors those in which it is proportional to the particle density instead. In addition, the observation of 31 anti-tritons in Pb-Pb collisions is reported. For comparison, the deuteron spectrum in pp collisions at √ s = 7 TeV is also presented. While the p/π ratio is similar in pp and Pb-Pb collisions, the d/p ratio in pp collisions is found to be lower by a factor of 2.2 than in Pb-Pb collisions.

A Review of Elliptic Flow of Light Nuclei in Heavy-Ion Collisions at RHIC and LHC Energies

“…where the track length and momentum p are determined with the tracking detectors placed inside magnetic field [44,66,67,71]. After getting 2 for each particle, a selection cut is implemented to reject tracks which have their 2 several away from the true 2 value of the light nuclei, as done in the STAR experiment [63].…”

“…In the ALICE experiment, light nuclei in the low region (<1.0 GeV/c for , ) are identified by comparing the variance ( ⟨ / ⟩ ) of the measured ⟨ / ⟩ in the TPC with the corresponding theoretical estimate ( / | theo ) [67,71]. Light nuclei are considered identified if the measured ⟨ / ⟩ lies within ±3 ⟨ / ⟩ of the / | theo .…”

“…On the other hand, the light nuclei yield is extracted from the mass squared ( 2 TOF ) distribution using the TOF detector. The mass of each particle is calculated using the time-of-flight ( ) from the TOF detector and the momentum (p) information from the TPC [66,67,71]. Both the ALICE and PHENIX experiments use the TOF detector to identify light nuclei at high (>1.0 GeV/c).…”

“…Light nuclei are also identified via the time-of-flight measurement techniques using the Time-of-Flight (TOF) detector [66,67,[71][72][73][74].…”

“…In heavy-ion collisions, light nuclei are primarily identified by comparing the mean ionization energy loss per unit length (⟨ / ⟩) in the Time Projection Chamber (TPC) with that from the theoretical predictions ( / | theo ) [41,42,63,[67][68][69][70][71]. Light nuclei are also identified via the time-of-flight measurement techniques using the Time-of-Flight (TOF) detector [66,67,[71][72][73][74].…”