Friday, September 20, 2013

Nima Arkani-Hamed Lectures

Nima Arkani-Hamed on developments in Physics and future vision

The Salam Lecture Series 2012, with a week-long series of lectures by renowned theoretical physicist Nima Arkani-Hamed. Giving his audience a panoramic view of 400 years of physics in his first lecture, Arkani-Hamed provided insights into the various concepts that have dominated the world of fundamental physics at different points in history. "Everything that we have learned [over the past 400 years] can be subsumed with a basic slogan, and the slogan is that of unification," he said. "More and more disparate phenomena turn out to be different aspects of the same thing." "Physics," he stressed "forces you to remove artificial distinction between disciplines.

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Sunday, September 15, 2013

Exploring Matter At the Dawn of Time

Physicist Paul Sorensen describes discoveries made at the Relativistic Heavy Ion Collider (RHIC), a particle accelerator at Brookhaven National Laboratory. At RHIC, scientists from around the world study what the universe may have looked like in the first microseconds after its birth, helping us to understand more about why the physical world works the way it does - from the smallest particles to the largest stars. See: Exploring Matter at the Dawn of Time and RHIC

Thursday, September 12, 2013

Detailed Characterization of Jets in Heavy Ion Collisions Using Jet Shapes and Jet Fragmentation Functions

The CMS detector has excellent capabilities for studying high-pT jets formed in heavy ion collisions. Previous CMS analyses have characterized the energy loss of hard-scattered partons traversing the medium produced in such collisions at a center of mass energy of 2.76 TeV using the momentum imbalance of di-jet and photon-jet events. In this paper, the fragmentation properties of inclusive jets with pT,jet>100~GeV/c in PbPb collisions are characterized by measuring differential and integated jet shapes, as well as charged particle fragmentation functions. A data sample of PbPb collisions collected in 2011 at a center of mass energy of sNN=2.76~TeV corresponding to an integrated luminosity of Lint=140 μb1 is used. The results for PbPb collisions as a function of collision centrality are compared to reference distributions based on pp data collected at the same collision energy. For both PbPb and pp collisions, jets are reconstructed with the anti-kT clustering algorithm with a resolution parameter of 0.3 and using ``Particle Flow'' objects that combine tracking and caloritmetry information. The jet shapes and fragmentation functions are measured for reconstructed charged particles with \pt>1~GeV/c within the jet cone. For the most central collisions indications of a broadening of the differential jet shape in PbPb collisions are observed, as well as a significant rise of the PbPb/pp fragmentation function ratio for the softest fragmentation products with pT<3~GeV/c. See: Detailed Characterization of Jets in Heavy Ion Collisions Using Jet Shapes and Jet Fragmentation Functions

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Hubble Movie Theater: Revelation

Take a thrill ride through 15 years of Hubble images, starting with Hubble’s first picture and ending with its anniversary image of the Whirlpool Galaxy. In less than three minutes, 800 Hubble images flash over the screen, sometimes as fast as 60 pictures per second.See:HUBBLE Site