Thursday, May 29, 2008

The PHOBOS Glauber Monte Carlo

As a follow up to this post, several colleagues and I just posted a paper to the arxiv today: "The PHOBOS Glauber Monte Carlo."  This is one of those technical-sounding things, but which has had a surprising relevance to understanding actual RHIC data.  Many people treat nuclear collisions by considering the nuclei to be overlapping smooth distribution of protons and neutrons.  However, it is also reasonable to treat nuclei as clumps of protons and neutrons as individual particles, especially since that's, um, what they are.  The interesting part is that the positions jiggle around collision to collision, and those fluctuations seem to have real manifestations in physical phenomena (see, e.g., this paper).  

Anyway, there is an amusing back story here: when we were writing one of the early PHOBOS papers back in 2000, we discovered that we needed our own implementation this kind of thing.  I was on a trip to South Africa at the time, so I cobbled something together on the plane -- and this is the core of what we've now put out for public release almost 8 years later.  That said, it's not rocket science (i.e. every experiment has their own version), but despite a ream of papers and Glauber reviews, there have been relatively few codes available until now.  Enjoy.

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