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Rene Bellwied | USLHC | USA

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The LHC Astro-Lab

Monday, May 5th, 2008

A few weeks ago the physics community got shaken by an announcement of the DAMA project (no not the bad guys on ‘Lost’, they’re the DHARMA initiative), an underground experiment in the Gran Sasso tunnel, which claimed to have found experimental evidence for Dark Matter. The claim is based on the fact that the motion of the earth around the sun should produce a modulation in the dark matter count rate, because the earth’s velocity needs to be added (or subtracted) to the dark matter (or halo) escape velocity. DAMA has found indeed an eight sigma signal of a modulation in their candidate count rate. The question remains whether any background source could cause this signal, and it will take scientists some time to exclude all reasons why this measurement might not be significant. Nevertheless the possibility of experimental evidence for dark matter is exciting. But what does this have to do with the LHC and in particular ALICE ?

Well, throughout the past few years relativistic heavy ion and high energy physics have stressed their significance towards understanding QCD and electro-weak symmetry breaking, but the original quest for the heavy ion program at RHIC and the LHC was to find a state of matter which would have taught us a lot about the evolution of the universe shortly after the Big Bang, at a time where matter as we know it (luminous and dark) should have formed. This original link has been disfavored for some time because scientists felt that the ‘Little Bang’ can not be easily applied to the ‘Big Bang’; the system is too small, the evolution is too fast. But several speculative explanations of experimental measurements at RHIC gave new life to the ‘astro-connection’ of relativistic heavy ion physics (see for example Peter Steinberg’s blog entries on Anti-de-Sitter space and Hawking-Unruh radiation). D.J.Schwarz from CERN in his very instructive article: ‘The first second of the universe’ showed the anticipated evolution of matter formation, and pointed out the relevance of the so-called QCD phase transition from quarks and gluons to hadrons for the evolution of the universe.

It is interesting to note that the LHC offers a two-prong approach to accelerator based astrophysics. Not only can the high energy proton proton collisions likely probe the Higgs field, extra dimensions, super symmetry and dark matter candidates, but the relativistic heavy ion collisions can probe physics in the strong force sector that has traditionally been assumed to occur at higher energies, such as CP violationwhich is necessary for baryogenesis in the universe, anti-baryonic dark matter candidates and the infamous 5-d quantum black holes.

So this is an exciting time, and the diversity of the LHC programme, bringing high energy and heavy ion physicists together by offering proton-proton and Pb-Pb collisions, will lead not only to breakthroughs in the understanding of QCD and potentially new physics beyond the standard model. It will also make the LHC the premier astro-lab in the world. I am glad that all three big experiments (ATLAS, CMS and ALICE) now feature a pp and a PbPb program. Although ALICE is the most versatile heavy ion detector, both ATLAS and CMS have strong programs with heavy ions, and only together and with the necessary verification of each other’s results will we be able to crack some of the cosmic mysteries that I am most interested in. I am looking forward to that and to your attempts of taking aim at some of my claims in this and future blogs

Cheers

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