May 17, 2013 Mary Gates Hall

ASTRONOMYAND PHYSICS 2S Session Moderator: Suzanne Hawley, 026 JHN 3:45 PM to 5:15 PM

* Note: Titles in order of presentation.

Revising the Properties of Low-Mass Stars to Better Detection of Transiting using Kepler Determine the Habitability of Their Lightcurves Justin Brenton, Senior, Physics: Comprehensive Physics, John Mark (John) Mehlhaff, Junior, Computer Science, Astronomy Physics: Comprehensive Physics Mary Gates Scholar NASA Space Grant Scholar Mentor: Sarah Ballard, Astronomy Nancy Helen (Nancy) Thomas, Senior, Astronomy, Physics Mary Gates Scholar, NASA Space Grant Scholar, Extrasolar planets are being discovered at an incredible rate Undergraduate Research Conference Travel Awardee, UW today. We have yet to discover another that can sup- Honors Program port life as we know it, but that will very likely change soon. Christopher James Martin, Senior, Astronomy, Physics Currently, most exoplanets are discovered indirectly by the Mentor: , Astronomy influence they have on their host stars. Therefore, we only Mentor: Andrew Becker, Astronomy know the temperature and size of an as well as we Mentor: Benjamin Vega-Westhoff, Astronomy know the temperature and size of the star it orbits. For low- mass stars in the spectral range between K5 and M2, models Exoplanets are planets outside our solar system, and the cur- do not provide the desired accuracy for these parameters. I rent explosion in exoplanet discoveries is revolutionizing our improve this accuracy for a sample of planet candidates dis- understanding of the potential for extraterrestrial life. This covered by the by using a technique prolific era of detections has stemmed largely from the un- that assigns the parameters of nearby and well studied ”stel- precedented observing capabilities of NASA’s Kepler Space lar twins” to the planet hosting stars. I find these stellar twins Telescope. The Kepler Spacecraft collects high precision by comparing the spectra of planet hosting stars to the spec- time-series photometric data on a fixed group of approxi- tra of similar nearby stars. By assigning the parameters of mately 160,000 stars. The data are represented by temporal the nearby stellar twins to the planet hosting stars, I reduce lightcurves (i.e. brightness vs. time) that can be used to detect the uncertainties in size and temperature for the planet host- transiting exoplanets, the topic of our research. Transits are ing stars. This will also reduce the uncertainties in the size events where an orbiting planet partially eclipses its host star, and temperature of the exoplanets, and thus allow for a better casting a small shadow on the telescope. To detect transit sig- determination of their habitability. nals, we rely on the Quasi-Periodic Automated Transit Search Algorithm (QATS). As an automated tool, QATS provides a crucial means to reduce the Kepler dataset to a manageable size. However, since the algorithm is sensitive to stellar vari- ability, eclipsing binary stars, and systematic artifacts of the spacecraft, additional analysis is required to separate true de- tections from false positives. Determining the best way to do this is the present focus of our work. Concurrently, we are ex- ploring the potential for QATS not only to determine orbital period, but also to constrain transit depth and duration (prop- erties related to the size of the exoplanet and to the density of the stellar host). While this increases the complexity of the QATS algorithm and the amount of output to manage, it

Undergraduate Research Program 1 exp.washington.edu/urp provides greater potential for a fully automated transit search ber of satellites to determine their line-of-sight velocities. We process with results that are more descriptive of the exoplanet will use these results and a Jeans equation approximation to systems detected. infer the mass of NGC 2841, and by comparing this value to the amount of visible mass, we will estimate the mass of its Experimental Verification of Gor’kov Theory of Acoustic dark matter halo. Levitation David Graham, Junior, Physics, Edmonds Community Search for Flavor Violation in Higgs Decays with the College ATLAS Detector at the LHC Muhammad Osama, Sophomore, Electrical Engineering, William Joseph (Will) Johnson, Senior, Physics, Mathematics Computer Science, Edmonds Community College Mary Gates Scholar Mentor: Tom Fleming, Department of Physics, Edmonds Mentor: Shih-Chieh Hsu, Physics Community College The discovery of a new particle, which we suspect is the long- Acoustic levitation is a method of levitating matter against sought-after Higgs boson, has opened a wide range of oppor- the influence of gravity using sound waves. Small droplets of tunities to explore new physics at the Large Hadron Collider fluid can, for example, be suspended in standing wave fields (LHC). One particularly promising direction is the search for produced by high-power ultrasonic transducers at locations ”flavor violation” in Higgs decays, where a Higgs decays to a where the gradients of the sound field potentials counterbal- non-matching pair of particles. We focus particularly on de- ance the gravitational forces acting on the droplets, creating cays into a tau and a mu lepton (both of which are heavier a simulated microgravity environment. These environments relatives of the electron). At present, indirect data from low- could be useful in simulating and studying how chemical and energy experiments allows these Higgs-to-tau-mu decays to biochemical reactions might take place in space. Our research make up up to 10% of all Higgs decays, while the current builds on earlier work by J.Santa Cruz and J. Griffith who Standard Model of particle physics does not expect them to successfully achieved acoustic levitation at EdCC in 2011. happen at all. The goal of my research is to develop a method Santa Cruz and Griffith were able to experimentally demon- for separating these decays out of the other billions of colli- strate rough preliminary agreement with Bjerknes theory for sions that happen every second in the ATLAS detector, and levitation stability points in a planar field approximation, but analyzing them in such a way to make flavor violating de- they also observed stable particle orbits completely beyond cays stand out against background events (which look similar explanation by the planar theory. Here, we compare our ex- but have different origins). This will allow us to put much perimental findings to the more general Gor’kov theory of stricter limits on the rate at which these decays occur, and if levitation to explain both one- and two-dimensional levitation any do occur we will have made a big step into previously- stability subspaces. unexplored physics territory.

Satellite Galaxies as Dynamical Tracers for NGC 2841 Analysis of Silicon Photomultiplier Characteristics Denise Marie (Denise) Schmitz, Senior, Mathematics towards Calorimeter Development for the New Muon (Comprehensive), Physics: Comprehensive Physics, (g-2) Experiment at Fermilab Astronomy Kazimir Baiame (Kazimir) Wall, Senior, Physics: Mary Gates Scholar Comprehensive Physics Mentor: Peter Yoachim, Astronomy Mentor: David Hertzog, Physics Mentor: Loreto Alonzi, Physics Research on galaxy dynamics indicates that visible matter cannot account for all of a galaxy’s mass; the prevailing the- The goal of the New Muon (g-2) Experiment at Fermilab is a ory is that each galaxy is surrounded by a halo of dark matter. fourfold precision increase of the measurement of the anoma- Dark matter can be studied by observing its gravitational in- lous magnetic dipole moment of the muon, with the hope fluence on luminous matter, a technique known as dynamical of achieving a 5σ deviation from theory. Such a discovery tracing. We measure the orbital velocities of dwarf satellite would provide a basis for the exploration of new physics be- galaxies as dynamical tracers for a central galaxy. Using data yond the Standard Model. Many candidates exist for explain- from the Sloan Digital Sky Survey (SDSS) DR8 and Hyper- ing this discrepancy, such as supersymmetry, dark photons, Leda databases we have identified massive, isolated galax- or lepton substructure. My work involves the characterization ies as potential targets and selected NGC 2841, a nearby and analysis of Silicon Photomultipliers (SiPM’s) in support large spiral galaxy. We also used SDSS to identify potential of the development of the (g-2) calorimeters — the central satellite galaxies and prioritize them for observation. Using detector systems required to make the measurement. These the DIS spectrograph on the Apache Point Observatory 3.5m avalanche photodiode arrays are a significant change from telescope, we have performed optical spectrosopy on a num- the previously used vacuum photomultiplier tubes (PMT’s). SiPM’s are extremely compact and can be mounted directly

2 inside the magnetic field of the muon storage ring; character- istics such as these them a distinct advantage over PMT’s. A thorough study of pulse resolution, temperature dependence, gain, rate, and other properties is necessary to understand how SiPM’s may be most effectively utilized in the (g-2) experi- ment. Analyzing pulse resolution and gain involves exciting the SiPM with two laser pulses spaced 2 to 100 nanoseconds apart and determining how closely the pulses can overlap be- fore a significant amount of information contained in the out- put of the SiPM is lost. Variations in the size and strength of each pulse have also been introduced in the study, such as saturating the SiPM circuit with a blast of laser light and studying how long it takes the device to recover.

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