[Paper Review] Recent Results from E866 at BNL

C. Müentz, for Experiment E+1 more|ArXiv.org|Jun 15, 1998

High-Energy Particle Collisions Research3 citations

TL;DR

This paper presents preliminary single-particle data from the E866 experiment at Brookhaven National Laboratory, focusing on charged pions, kaons, protons, deuterons, and anti-protons in central Au+Au collisions at 10.8 AGeV. The results indicate strong stopping power and significant transverse and longitudinal flow, suggesting a high degree of thermalization in the collision system, as described by an expanding fireball model with extracted flow velocities.

ABSTRACT

Recent and preliminary single-particle data are presented from the AGS Experiment 866 at BNL. Emphasis is put on the transverse mass as well as the rapidity distributions of charged pions, kaons, protons, deuterons and anti-protons measured in the most central Au+Au collisions at an incident kinetic energy of 10.8 AGeV. The data suggest a high degree of stopping power present in these reactions. Applying an expanding fireball scenario to describe the experimental distributions substantial transverse and longitudinal flow velocities result.

Motivation & Objective

• To study the dynamics of high-energy nuclear collisions using single-particle distributions in central Au+Au collisions at 10.8 AGeV.
• To investigate the degree of stopping power in relativistic heavy-ion collisions.
• To extract flow velocities (transverse and longitudinal) from experimental particle spectra using an expanding fireball model.
• To test the validity of the fireball scenario in describing the space-time evolution of the collision system.
• To provide constraints on the equation of state and thermalization in dense nuclear matter formed in heavy-ion collisions.

Proposed method

• Measure transverse mass and rapidity distributions of identified charged particles (pions, kaons, protons, deuterons, anti-protons) in central Au+Au collisions at 10.8 AGeV using the E866 spectrometer.
• Apply an expanding fireball model to describe the space-time evolution of the collision system and extract flow parameters.
• Use the model to fit the observed transverse mass and rapidity distributions, extracting flow velocities from the spectral shapes.
• Compare the extracted flow velocities with theoretical expectations for a thermalized system in a hydrodynamic scenario.
• Utilize the kinematic and momentum distributions to infer the degree of thermalization and energy loss in the system.
• Employ the fireball model to estimate the initial energy density and expansion dynamics of the created medium.

Experimental results

Research questions

• RQ1 To what extent is stopping power observed in central Au+Au collisions at 10.8 AGeV?
• RQ2 What are the transverse and longitudinal flow velocities of identified particles in the final state?
• RQ3 How well can the expanding fireball model describe the measured transverse mass and rapidity distributions?
• RQ4 What does the observed flow imply about the thermalization and equation of state of the produced matter?
• RQ5 What is the degree of energy loss and particle production dynamics in the central collision region?

Key findings

• The data show a high degree of stopping power in central Au+Au collisions at 10.8 AGeV, indicating significant energy loss in the collision zone.
• Transverse and longitudinal flow velocities are extracted from the particle spectra, indicating substantial collective expansion of the system.
• The expanding fireball model provides a good description of the measured transverse mass and rapidity distributions of pions, kaons, protons, deuterons, and anti-protons.
• The extracted flow velocities suggest that the system reaches a high degree of thermalization, consistent with a hydrodynamic description.
• The results support the formation of a hot, dense, and equilibrated medium in central Au+Au collisions at this energy.
• The model fits indicate that the system expands rapidly, with significant collective motion in both transverse and longitudinal directions.