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J/ψ Elliptic Flow in Pb-Pb Collisions at sqrt[s_{NN}]=5.02 TeV
S Acharya1, D Adamová2, J Adolfsson3
1Variable Energy Cyclotron Centre, Kolkata, India.
Physical Review Letters
|December 30, 2017
Summary
We measured J/ψ elliptic flow in lead-lead collisions at the LHC. Results confirm J/ψ flow originates from charm quark thermalization in the deconfined medium, suggesting models may need refinement.
Area of Science:
- High-energy nuclear physics
- Quark-gluon plasma studies
- Particle physics
Background:
- Investigating the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions is crucial for understanding the early universe.
- J/ψ mesons, composed of charm and anticharm quarks, are sensitive probes of the QGP due to their binding energy and mass.
Purpose of the Study:
- To precisely measure the elliptic flow (v₂) of J/ψ mesons in lead-lead (Pb-Pb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV.
- To study the J/ψ elliptic flow as a function of transverse momentum (pT) and centrality at both midrapidity and forward rapidity.
- To compare experimental results with theoretical transport model calculations to understand the J/ψ production mechanisms in the QGP.
Main Methods:
- Utilized the ALICE detector at the Large Hadron Collider (LHC) for Pb-Pb collisions at √sNN = 5.02 TeV.
- Reconstructed J/ψ mesons via their dielectron decay channel at midrapidity (|y|<0.9) and dimuon channel at forward rapidity (2.5
- Analyzed J/ψ elliptic flow (v₂) as a function of transverse momentum (pT) and collision centrality.
Main Results:
- Observed a positive J/ψ elliptic flow (v₂) for transverse momentum (pT) between 2 and 8 GeV/c across studied centralities at forward rapidity.
- Confirmed previous findings at √sNN = 2.76 TeV with higher statistical precision.
- Measured J/ψ elliptic flow at midrapidity in agreement with forward rapidity measurements, supporting a common origin.
Conclusions:
- The results support the hypothesis that J/ψ elliptic flow at low transverse momentum (pT) arises from the thermalization of charm quarks within the deconfined medium.
- The comparison with transport models suggests that current models may not fully capture all relevant mechanisms for J/ψ production and flow in the QGP.
- Further theoretical development is needed to accurately describe the observed J/ψ elliptic flow behavior across different kinematic regions.
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