ATLAS finds evidence for a quark-gluon plasma

The ATLAS Experiment, in which the Brandeis High Energy Physics Group participates, has announced evidence for a quark-gluon plasma. This is a state of matter that existed for the first few microseconds after the birth of the Universe when quarks and gluons roamed freely before the Universe cooled enough for them to combine into the protons and neutrons that make up the matter we know today. A phenomenon known as jet quenching, which is considered evidence for the production of a quark-gluon plasma, has been observed and accepted for publication in Physical Review Letters.

ATLAS is one of the experiments at the Large Hadron Collider (LHC). We have just completed a successful first year of running. At the end of the run we studied Heavy Ion collisions (lead on lead). Head-on collisions by two lead nuclei are expected to produce a quark-gluon plasma. In this process, the products of hard collision (jets) are reabsorbed by the plasma. Observation of this process by ATLAS is considered evidence for the production of a quark-gluon plasma. Being able to produce and study this phenomenon will help us understand behavior of matter at the very beginning of the Universe.

More information about this phenomenon and details about the ATLAS experiment can be found at the web site. The Brandeis High Energy Physics Group includes professors Jim Bensinger, Craig Blocker, Larry Kirsch, Gabriella Sciolla, Hermann Wellenstein and research scientist Christoph Amelung.

Chirality leads to self-limited self-assembly

Simple building blocks that self-assemble into ordered structures with controlled sizes are essential for nanomaterials applications, but what are the general design principles for molecules that undergo self-terminating self-assembly? The question is addressed in a recent paper in Physical Review Letters by Yasheng Yang, graduate student in Physics, working together with Profs. Meyer and Hagan,  The paper considers molecules that self assemble to form filamentous bundles, and shows that chirality, or asymmetry with respect to a molecule’s mirror image, can result in stable self-limited structures. Using modern computational techniques, the authors demonstrate that chirality frustrates long range order and thereby terminates assembly upon formation of regular self-limited bundles.  With strong interactions, however, the frustration is relieved by defects, which give rise to branched networks or irregular bundles.

Figure: (a) Snapshots of regular chiral bundles. Free energy calculations and dynamics demonstrate that the optimal diameter decreases with increasing chirality. (b) Branched bundles form with strong interactions

NSF gives Zvonimir Dogic Teacher-Scholar award

Asst. Professor of Physics Zvonimir Dogic has won a $500,000 award from the National Science Foundation (NSF) Early Career Development Program. The five-year award supports junior faculty who “exemplify the role of teacher-scholars through oustanding research, excellent education, and the integration of education and research within the context of the mission of their organizations,” according to the NSF. Dogic’s research seeks to explain how biopolymers organize themselves into macroscopic materials.

Physics Department welcomes new faculty member Aparna Baskaran

The physics department welcomes its newest faculty member, Professor Aparna Baskaran. Professor Baskaran is a theorist who studies non-equilibrium statistical mechanics and its biophysical applications.

Simulating viral capsid assembly

Viral capsids assemble into complex structures with high fidelity, but also can adapt when given other nucleic acids cargoes to package. In a recent paper in Nano Letters, Brandeis physics grad student Oren Elrad and Professor Michael Hagan used computer simulations to investigate the mechanisms by which this occurs. These simulations were done on the Brandeis High Performance Computing cluster.

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