J/ψ polarization in pp collisions at √s=7 TeV

Area of Science:

• High Energy Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• The J/ψ meson is a crucial probe for studying the quark-gluon plasma and heavy quarkonium production mechanisms.
• Understanding J/ψ polarization provides insights into the production processes and spin dynamics of heavy quarks.

Purpose of the Study:

• To measure the polarization of J/ψ mesons produced in proton-proton collisions at a center-of-mass energy of 7 TeV.
• To determine the J/ψ polarization parameters, λ(θ) and λ(φ), in specific kinematic regions.
• To compare polarization measurements in different reference frames.

Main Methods:

• Utilized data from proton-proton collisions at √s=7 TeV recorded by the ALICE experiment at the Large Hadron Collider.
• Studied J/ψ production via its decay into muon pairs.
• Analyzed the polar and azimuthal angle distributions of decay muons.
• Performed measurements in the helicity and Collins-Soper reference frames within the kinematic region 2.5

Main Results:

• The J/ψ polarization parameters, λ(θ) and λ(φ), were extracted from the angular distributions of decay muons.
• In both the helicity and Collins-Soper reference frames, the measured polarization parameters were found to be compatible with zero.
• These results were obtained within the specified kinematic region (2.5

Conclusions:

• The J/ψ polarization in proton-proton collisions at 7 TeV is consistent with being unpolarized within the studied kinematic range.
• The findings suggest that the production mechanism does not strongly favor any particular spin alignment for J/ψ mesons in this regime.
• Further studies may be needed to explore polarization in different collision systems or kinematic regions.