Carnegie Mellon University

Department of Physics

Mellon College of Science

News Snippets from CMU Physics

Spring 2017

Freeman PhD thesis defense

May 2017 – Krista Freeman earns Ph.D. with thesis on “Viral DNA Retention and Ejection controlled by Capsid Stability

Viruses are submicroscopic pathogens that infect every branch, twig and sprig of the tree of life. They consist of little more than a genome stored inside a protein shell, called the capsid, and exploit the cellular machinery of the organisms they infect for their own replication. Many bacterial viruses, and also some human ones, store their genome under enormous pressure in the capsid—more than 10 times that of an inflated car tire. Because such genomes consist of DNA that is several hundred times longer than the size of the capsid, the highly charged DNA strand must be very tightly squeezed to fit in. Upon infection, the capsid opens up and the DNA gets ejected into the host cell much like a jack-in-the-box.

In her thesis, Krista investigated the time course of this dynamic process and the physical principles underlying the construction of capsids that can withstand such enormous pressures. Besides gaining fascinating insights into these genome-loaded nano-machines, such studies also touch upon basic medical concerns: understanding the physical mechanisms that viruses rely on may open new avenues to combat them. And since this invokes general physical principles, the virus may not easily be able to respond with adaptive mutations.

Satpathy Hugh Grant teaching award

May 2017 – Sidd Satpathy receives Hugh Young Teaching Award

As a teaching assistant (TA), Siddharth Satpathy, a Ph.D. candidate in the Department of Physics, is described as conscientious, compassionate, dedicated, nurturing, and helpful – in short, “one of the best TA’s ever” by students and faculty alike. During the last three years, Satpathy – better known as Sidd – has taught five different sections of the introductory course Physics for Science Students and Calculus in Three Dimensions, the latter for the Department of Mathematical Sciences. Sidd also served for two years as an instructor in Carnegie Mellon University’s Summer Academy for Math and Science for high school students.

In recognition of his enthusiasm for teaching and his unyielding dedication to going above and beyond for his mentee students, Siddharth Satpathy has been awarded the 2017 Hugh Young Graduate Student Teaching Award. Congratulations, Sidd!

Belle II detector roll-in

April 2017 – Belle II Project at KEK in Tsukuba/Japan

The Belle experiments study collisions of electrons and positrons at a total energy of ~10 GeV. This energy is chosen to produce B mesons: particles composed of a heavy "bottom" quark and a light anti-quark. These are of special interest since they violate "CP symmetry", that is, they differ in the behavior of matter and anti-matter. This asymmetry poses one of the deepest mysteries of particle physics, and solving it may shed light on the unexplained observation that the Universe is dominantly made of matter, rather than anti-matter. Belle II is an improved version of the very successful first Belle experiment and aims to collect a larger data samples with an improved detector.

CMU is involved in a variety of activities at Belle II: Prof. Roy Briere is co-chair of the charm physics analysis group, exploring the physics reach and planning analyses on these topics. Postdoc Jake Bennett is data production coordinator, overseeing production and processing of simulated Monte-Carlo samples and preparing for real data-taking in the near future. Together, Jake and Roy are also responsible for calibrating dE/dx measurements from the CDC wire chamber, one of several methods employed to distinguish the identities of the various particles measured in the Belle II detector.