Investigating the Cronin Cartoon - Abstract

Jason Kamin, Hampshire College; Thomas Hemmick, Ralf Averbeck, Axel Drees, Felix Matathias, Department of Physics and Astronomy, Stony Brook University. 


The Cronin Effect occurs when a deuteron collides with a large nucleus (such as Au at RHIC).  The transverse momentum (PT) spectra of the particles that are produced in the most central collisions are different than the spectra produced in the most peripheral ones.  There are more particles with higher PT and less at low PT.  In addition, the degree to which this difference is observed seems to be correlated with the mass of the particles that are produced. 

In deuteron-gold collisions, the most peripheral events (60 – 90 % centrality) are generally thought of as simple nucleon-nucleon interactions while the most central events (0 – 20 % centrality) are thought to consist of a cascade of deflecting collisions within the nucleus.  A typical “cartoon” of the collision process envisions the deuteron getting knocked around many times as it bounces it’s way through the nucleus, colliding at different angles with the Au nucleons along the way. 

The goal of this project was to determine if this widely accepted “cartoon” explanation of the Cronin Effect is able to account for the particle species dependence of this phenomenon.  We modeled the high centrality collisions identically to the peripheral ones except for one major difference: we treated the high centrality interactions as taking place at an angle rather than head-on.  Applying the necessary relativistic transformations we were able to treat these as identical interactions taking place in different frames.  

We found that when using identical primordial spectra for all species, our intuition is indeed confirmed; the purely naïve Cronin cartoon produces a species dependent effect similar to that found in the data.  However, we additionally found that the strength of the effect is highly sensitive to the primordial spectrum.  Several more realistic initial state distributions were tried, all of which exhibited reduced species dependence of the Cronin enhancement and did not adequately describe the data.  We thus conclude that this “cartoon” description of the Cronin Effect is not able to solely account for the particle species dependence.


This Work was supported by a grant from the National Science Foundation (Phy – 0243935).

Click here for PowerPoint presentation