Fall 2017 Joint High Energy Physics and Astrophysics Seminar Schedule

Talks are on Wednesdays at 3:35pm in Nielsen 512. Please plan for a 45 minute talk with 15 minutes of questions. For updates and changes, contact Andrew W. Steiner. Graduate students signed up for credit, see instructions here.

 Date Speaker Title Aug. 23 Xiao Luo (Yale) Liquid Argon Time Projection Chamber for Neutrino Physics Abstract: The Time Projection Chamber (TPC) is a widely used detector technology in particle physics. As neutrino physics enters the era of precision measurement of oscillation parameters, Liquid Argon TPC (LArTPC) is chosen as the main detector technology for the future DUNE experiment - an international mega-science project seeking answers to the fundamental questions such as CP violation, neutrino mass hierarchy, and proton decay. In this talk, I will discuss the working principle of LArTPC, as well as advantages and challenges from the experiences of several existing LArTPC experiments. Sep. 6 Wei Tang (UTK) Data Unfolding with the Wiener-SVD Method Abstract: Data unfolding is a common analysis technique used in HEP data analysis. Inspired by the deconvolution technique in the digital signal processing, a new unfolding technique based on the SVD technique and the well-known Wiener filter is introduced. The Wiener-SVD unfolding approach achieves the unfolding by maximizing the signal to noise ratios in the effective frequency domain given expectations of signal and noise and is free from regularization parameter. Through a couple examples, the pros and cons of the Wiener-SVD approach as well as the nature of the unfolded results are discussed. Sep. 13 Sophia Han (UTK) Thermal states of transiently accreting neutron stars Abstract: The standard picture for the composition of neutron stars assumes that they are composed of neutrons and protons, embedded in a gas of electrons and muons. Current observations of neutron star masses and radii are yet not fully convincing to rule out possibilities of exotic phases such as hyperonic or quark matter in their densest cores. In this talk, I will report on our recent efforts in discerning compositions of neutron star interiors. Confining the study within nucleons-only framework, we analyze the thermal states of accreting neutron stars in quiescence, taking into account variations in e.g. the equations of state, superfluidity gaps, and deep crustal heating. We find that the stringent limitation imposed by the hottest and coldest sources observed disfavors the scenario without exotic matter. Sep. 20 Andrew W. Steiner (UTK) Using qLMXBs to Determine the Nature of Dense Matter In this talk, I will report on our recent work determining the mass and radius of neutron stars in globular clusters. The principal challenge which this paper tackles is how to address the potential systematic uncertainties which have plagued the analysis of observations of quiescent low-mass X-ray binary systems. Some of the systematics can be handled by properly rescaling the data, so I will outline this formalism. Then, I will apply the Bayesian inference machinery we have previously developed to obtain final results on the neutron star mass-radius curve and the equation of state of dense matter. Sep. 27 Leah Broussard (ORNL) New Search for Mirror Neutrons at HFIR The observation of neutron oscillations into an invisible neutron state would indicate the existence of a new form of matter which could explain some or all of dark matter. Neutron oscillations are predicted by some models which contain Mirror Matter, which is an identical copy of Standard Model particles and interactions, but opposite Parity. Direct searches for neutron oscillations to mirror neutrons in a controlled magnetic field have previously been performed using ultracold neutrons in storage/disappearance measurements, with some inconclusive results for oscillation times of $\tau\sim$ 10 s. I will describe a proposed disappearance and regeneration experiment in which the neutron oscillates to and from a mirror neutron state. An experiment performed using the existing General Purpose-Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor at Oak Ridge National Laboratory could have the sensitivity to exclude up to $\tau<$ 15 s with short beamtime and low cost. Oct. 4 (Fall break) (Fall break) Oct. 11 Yuri Kamyshkov (UTK) The Magnetic Moment of Mirror Neutrons This is a work in progress. Together with collaborators Z. Berezhiani and L. Varriano we are studying the role of the magnetic moment in the transformations of neutrons to mirror neutrons and the possible observable effects it might create. Oct. 18 Josh Barrow Studies Toward the Search for Neutron-Antineutron Oscillation The baryon asymmetry of the universe (BAU) remains a conundrum for the Standard Model (SM), as no SM process has been able to adequately theoretically explain the vast asymmetry between matter and antimatter we easily see across the universe. Theoretical extensions have been proposed to go beyond the Standard Model (BSM), adding higher order operators to the SM Lagrangian; these include proton decay, but the addition of many of these new operators to the SM does not explain the BAU. Post-sphaleron baryogenesis (PSB) via neutron-antineutron oscillation is the leading candidates to explain the BAU, predicting observable oscillation phenomena at high-energy scales. A review of this physics, along with experimental techniques to search for oscillations, will be presented to the seminar. Further details will be given as to the progress toward accurate simulation of the oscillation, analysis of generated data, and observation viability within multiple future experiments. Oct. 25 Ryan Landfield (UTK) Sensitivity of Core Collapse Supernovae to the Nuclear Equation of State Core Collapse Supernovae (CCSN) result from the rapid gravitational collapse and ensuing cataclysmic explosion of massive stars. The modeling of such events is a unique challenge given the breadth of the physics involved; weak force interactions, radiation transport, nuclear force microphysics, hydrodynamics, general relativity, etc. all need to be taken into account to provide an accurate model of the event. Developments in the fields of nuclear theory and astronomical observation have allowed for the production of improved modern Equations of State (EOS) taking into account neutron star observations and constraints; we have implemented these new tabular EOS’s into our supernova simulations to examine the effects of new EOS's on collapse, the formation and evolution of the PNS, and the dynamics of explosion, so as to better constrain and characterize our understanding of the CCSN problem. Nov. 1 Zurab Berezhiani (University L'Aquila and LNGS/INFN) Cosmological implications of neutron - mirror neutron transformations Observation of neutron-mirror neutron transformation will imply possible existence of mirror world where Dark Matter is Mirror Matter. Implications for high-energy cosmic rays phenomena, neutron stars, black holes, etc. will be discussed. Nov. 8 Jordi Bustamante (ORNL) Multi-dimensional stellar explosions: from classical nova to core-collapse supernovae I will talk about the current status of multi-dimensional nova explosions, and the work in progress at ORNL on the effect of turbulence in core-collapse supernovae. Nov. 15 Andrew Mogan (UTK) and Gray Yarbrough (UTK) "Measuring Longitudinal Electron Diffusion in MicroBooNE" and "Studies of Proton Production and Beam Target scans to Improve BNB Flux Prediction at MicroBooNE" Mogan's abstract: Liquid Argon Time Projection Chambers (LArTPCs) are a rising technology in the field of experimental neutrino physics. LArTPCs use ionization electrons and scintillation light to reconstruct neutrino interactions with exceptional calorimetric and position resolution. Furthermore, understanding how ionization electrons diffuse as they traverse the detector can help to improve the timing resolution. However, current measurements of electron diffusion in liquid argon are sparse and inconsistent. In this talk, we outline a Monte Carlo method to extract the diffusion constant based on the signal pulse spread in time of the ionization electrons. We present this in the context of the MicroBooNE experiment, a 170-ton LArTPC located on Fermilab's Booster neutrino beamline. This analysis is highly sensitive to low-level effects (electronics noise, detector response, etc.), so we start by simulating a sample with physics effects turned off in order to first correct for these low-level effects. We then show more recent results using samples with physics effects turned on. Once the method is solidified in Monte Carlo, we plan to apply it to MicroBooNE data in order to extract a diffusion measurement at various E-fields. Yarbrough's abstract: Measurements of neutrino oscillations and cross-sections require a thorough understanding of the neutrino flux. Flux uncertainties in the Booster Neutrino Beam (BNB) currently form the dominant systematics for these measurements in the MicroBooNE detector. My project is a two-part approach to improving the BNB flux prediction and related systematics for the MicroBooNE experiment at Fermilab: 1. Analyze BNB target scan data to accurately measure the delivery of protons on target (POT) along with optimizing the beam optics to minimize POT losses, and 2. Incorporate the long target and proton production data from the HARP experiment into the MicroBooNE BNB flux prediction and validate it. Nov. 29 Charles Hughes The Search for B mode Polarization in the Cosmic Microwave Background Abstract: The current “best-candidate” cosmological model is the big-bang theory. In summation, the big bang provides a model which accounts for the history of the universe from its early high density, high temperature state through its expansion and large scale evolution. The success of the big bang theory is evident in its comprehensive explanation for a broad range of physical and astronomical observables, including the cosmological abundance of light elements (Deuterium, Helium-3, and Helium-4), observed expansion of the universe (measured linear relationship between cosmological redshift and distance), and the existence of the Cosmic Microwave Background Radiation (CMB). However, the Big Bang theory is not able to provide an explanation for all observed phenomena, and as such necessitates modification to account for the incongruous observations. One possible solution to both of these problems, is the modification to the standard big-bang cosmology via the addition of the theory of inflation. Broadly stated, inflation posits a period in the early history of the observable universe, in which the universe was uniform (within quantum fluctuations) until the scale-factor (observed today as the distance between galaxy clusters) grew exponentially for a brief time period. While inflation is not directly observable, the gravitational waves resulting from the exponential expansion of space, may in fact be possible to measure. If the exponential growth of the scale factor was slightly asymmetric (via quantum fluctuations in the inflaton field), then gravitational waves may have been produced. These gravitational waves would give rise to a specific polarization pattern in the CMB; a curl-free component (E-mode) and curl component (B-mode). The physics for these B-mode polarizations in the CMB will be discussed, along with the BICEP2 experiments attempt to measure them.