Exploiting intrinsic triangular geometry in relativistic (3)He+Au collisions to disentangle medium properties

Area of Science:

• Nuclear Physics
• High-Energy Physics
• Quantum Chromodynamics

Background:

• Recent experiments at RHIC and LHC show collective expansion and flow in d+Au and p+Pb collisions.
• Understanding the properties of the quark-gluon plasma (QGP) requires studying the initial conditions of heavy-ion collisions.
• The formation of a nearly inviscid hydrodynamic QGP droplet is a key area of research.

Purpose of the Study:

• To propose a control experiment comparing particle emission patterns from p+Pb, d+Au, and He-3+Au or t+Au collisions.
• To investigate the influence of the initial spatial distribution of deposited energy on the created medium's properties.
• To disentangle the effects of initial geometry and viscous damping on the system's evolution.

Main Methods:

• Utilizing Monte Carlo Glauber simulations with realistic wave function descriptions for projectiles.
• Analyzing particle emission patterns from different collision systems (one, two, and three initial hot spots).
• Comparing systems at the same center-of-mass energy per nucleon (sqrt[s_{NN}]).

Main Results:

• A He-3 or triton projectile induces a significant intrinsic triangular shape in the initial medium.
• This triangularity survives as a notable third-order flow moment (v3) even with viscous damping.
• The proposed comparison of systems allows for disentangling initial spatial distribution effects from viscous damping.

Conclusions:

• Comparing different collision systems provides crucial insights into the initial state of heavy-ion collisions.
• The initial geometry, particularly triangularity induced by specific projectiles, plays a significant role in the system's evolution.
• This approach is vital for determining the minimum size of a droplet required to form a nearly inviscid hydrodynamic QGP.