Session K01: Poster Session II (14:00-17:00)

EOS-BPM: A new diagnostic for PWFA experiments.

A beam driven plasma wakefield accelerator (PWFA) utilizes two electron bunches. A "drive" beam creates a wake in the PWFA plasma source, blowing out plasma electrons and leaving behind a stationary ion column. A “witness” beam is injected behind the drive bunch and feels a high accelerating gradient throughout the PWFA. The energy gain in a PWFA depends on the longitudinal displacement of the witness beam from the drive bunch. Additionally, to avert hosing instability the beams must be well aligned transversely. Diagnostics providing information on relative beam positions will be an integral tool in future PWFA research. One design for such a diagnostic is the electro-optic sampling beam position monitor (EOS-BPM). The setup consists of two EO crystals positioned on either side of the beamline. The EO signal from each crystal measures same beam current profile, and the relative strength of the signal is correlated with the nearness of each bunch to either crystal. From the combined temporally resolved signals of the crystals, the transverse position of each bunch can be independently determined. Simulations of an EOS-BPM using beam parameters for upcoming experiments at the SLAC linac are presented.   

GeFiCa–Germanium detector Field Calculator(GEMADARC Student Education Package)

Germanium detector Field Calculator (GeFiCa) is used to calculate electrostatic potentials and fields inside high-purity germanium detectors with various geometries. It provides generic numerical calculations based on the successive over-relaxation method. GeFiCa is written in C++ , it is provided as an extension to the ROOT libraries widely used in the particle physics community. Calculation codes for individual detectors are provided as ROOT macros and python scripts distributed along with the GeFiCa core library, serving as both examples showing the usage of GeFiCa and starting points for customized calculations. The numerical results are saved in a ROOT tree, making full use of the I/O optimization and plotting functionalities in ROOT. The speed and precision of the calculation are comparable to other commonly used packages, which qualifies GeFiCa as a scientific research tool. However, the main focus of GeFiCa is to clearly explain and demonstrate the analytic and numeric methods to solve Poisson's equation, practical coding considerations as well as visualization methods, with intensive documentation and example macros. It serves as a one-stop resource for people who want to understand the operating mechanism of such a package under the hood   

NOvA Neutron Test Beam

The Fermilab Test Beam Facility is dedicated to detector research, and in our
case: The NOvA detectors. The goal of R&D on a test beam is to further
calibrate and understand how the particles we are ultimately studying behave
inside the detector (protons, pions, kaons, etc.). Results from NOvA heavily rely
upon electrically charged particles emitting energy. However, there is no known
experimental set up that allows us to explore neutron interactions in the
detector, due to a neutron’s neutral charge. The purpose of this experiment is to
build a tagged neutron beam inside a particle simulator: G4beamline, with the
goal of being able to use charged particles to infer the momentum of the
neutrons.   

Design and Production of the CMS High Granularity Calorimeter Mockup Modules

During the LHC long shutdown 3 (2024-2026), the Compact Muon Solenoid (CMS) experiment will replace its current endcaps with a high granularity calorimeter (HGCAL) that comprises ~6M silicon cells and ~400K scintillator tiles. HGCAL will operate at -30 C in order to keep electronics noise low and charge collection efficiency as high as possible to maintain MIP calibration capability. A mock-up program for silicon-based modules is underway to optimize materials and construction techniques to meet the challenges of cold operation. We present the current design, material choices, assembly process, and results of thermal and mechanical studies to date.   

Exploring the timing capabilities of the High Granularity Calorimeter

The CMS High Granularity Calorimeter (HGCAL) will replace the present endcap Electromagnetic (ECAL) and Hadron calorimeters (HCAL) for the High Luminosity LHC (HL-LHC). One of the unique features of the HGCAL is its ability to measure the time of fight of showers precisely. We will present results on the timing performance of the HGCAL with respect to electromagnetic and hadronic showers. We will also explore the timing performance of the detector in 140 and 200 pile-up scenarios.   

Simulating Liquid Xenon Interactions with the Noble Element Scintillation Technique (NEST)

I will be presenting the latest release of the Noble Element Scintillation Technique (NEST). Noble element target media have become common in rare event searches, and an accurate comparison model is critical for understanding and predicting signals and unwanted backgrounds. Like its predecessors, NESTv2.0 is a simulation tool written in C++ and is based heavily on  experimental data, taking into account most existing ionization and scintillation data for solid, liquid, and gaseous xenon. Due to the large amount of data for liquid xenon, most theoretical models in NEST have been replaced with simple, well-behaved, empirical formulas, such as sigmoids and power laws. NESTv2.0 incorporates an empirical, non-binomial, recombination fluctuations model. In addition, NESTv2.0 simulates S1 and S2 scintillation signals with correct energy resolutions in dual-phase xenon time-projection chambers, and this is done without using an external package. While NEST can be used with GEANT, NESTv2.0 is fully capable of operating as a stand-alone command-line tool.

LBECA -- a dual-phase xenon ionization chamber for hidden-sector dark matter search

Noble liquid dual-phase time projection chambers (TPCs), when treated as low-threshold ionization detectors, have demonstrated exceptional sensitivities to both low-mass WIMPs and certain hidden-sector dark-matter candidates. However, current xenon TPCs were not designed for optimal performance in the ionization-only search mode, and consequently exhibited excessive electron backgrounds, which limit their applications in this dark-matter search channel. The Low Background Electron Counting Apparatus (LBECA) is a newly proposed compact xenon TPC experiment, specifically designed to achieve extremely low ionization-only background rates down to the single-electron level. It aims to exploit the ultimate sensitivity of the xenon TPC technology.  The technical challenges and the potential scientific reach of this experiment in both dark matter and neutrino detection will be discussed.
  

Recent results and R&D of the Generation-2 Axion Dark Matter Experiment

 The Axion Dark Matter eXperiment (ADMX) is a search for the dark matter axion. The axion, if discovered, solves both the strong CP problem and the dark matter problem. ADMX seeks to detect axions by the resonant conversion of axions into microwave photons in a high Q cavity in the presence of a strong magnetic field. Because the expected signal is of yocto-watt order, Generation-2 ADMX (G2) employs a dilution refrigerator and quantum noise limited SQUID amplifiers to achieve its necessary sub-kelvin cavity temperature and low noise sensitivity. This poster highlights axion exclusion limits from previous runs, future run plans, and the R&D work to achieve them.   

On Novel Superfluids Inside Of Dark Matter Halos

We study dark matter models admitting phase transitions to novel superfluid states. We demonstrate that this can occur in broad classes of both fermionic and bosonic dark models, and focus on axion dark matter with higher derivative interactions. These higher derivative terms impact the symmetry breaking phase transition, and are encoded in physical properties of dark matter halos (e.g. the density profile). We identify observable signatures from both the late and early universe, providing a suite of complimentary observable to probe the superfluid nature of dark matter.   

Superconducting resonant cavity R&D for dark matter axion experiment at CAPP

The IBS Center for Axion and Precision Physics Research (CAPP) in Korea is searching for axions using a tunable resonant cavity and conducting an R&D to enhance axion to photon conversion rates to a detectable level. The deposition of superconducting thin films on the inner surface of the cavity increases the Q factor and thereby enhances the conversion power significantly. However, in order to make superconducting cavity works in the experimental condition, especially in high DC magnetic field (> 8 T), we have to exploit the magnetic property of type II superconductors. Type II superconductors have a relatively high critical field (> 1 T) due to its magnetic vortex formation rather than type I superconductor. Still, we have to solve other problems due to vortex vibration and field penetration into the substrate by the resonant mode. They are the main factors to decrease Q factor. In this work, we will present various RF characteristics related to NbTi film and YBCO film on the inner wall of the sample cavities at the various temperature and the varied DC magnetic field, and describe the behavior of vortex loss and penetration length. From the result, we will discuss the way to make better performance.   

Neutrino Event Reconstruction with Machine Learning on NOvA

The NOvA experiment has detected the disappearance of muon (anti-)neutrinos and the appearance of electron (anti-)neutrinos in the NuMI beam at Fermilab and have made measurements of parameters related to neutrino oscillations including the neutrino mass hierarchy and the CP violating phase. Key to these measurements is the identification of neutrino events and the reconstruction of their energies, for which NOvA has developed some of the first machine learning implementations in the field. Further applications of machine learning are possible using new algorithms in semantic segmentation, a technique for classification of individual elements of an image, which are also applicable to neutrino events. I will present an application of machine learning for doing full neutrino event reconstruction utilizing instance aware semantic segmentation.   

Cherenkov Light in Liquid Scintillator at the NOvA Experiment

NOvA is a long-baseline neutrino experiment. Its physics goal is to measure $\theta_{23}$ and $\delta_{CP}$ values and to determine the mass hierarchy of neutrinos. NOvA has two functionally identical detectors, both of which are fine segmented and filled by liquid scintillator. In NOvA oscillation analyses, the systematic uncertainty contributed from scintillator response is one of the significant systematic contributions. There are two main models in NOvA detectors light response simulation. One is Birks suppression, which is optimized to improve the data and Monte-Carlo (MC) agreement for energy loss along particle tracks. The other one is Cherenkov model, which corrects the radiation response of NOvA detectors by capturing the Cherenkov radiation emitted when a charged particle passes through the detectors at a speed greater than the velocity of light in that medium. In general, Cherenkov effect will compensate with Birks model. Introducing these two models and performing a joint fit gives us a better agreement between our observed data and simulated MC events. In this poster, I will present the details of the data-driven tuning of the Cherenkov model and the impact of the new scintillator model on oscillation results.   

FLUKA Simulation of sFLASH Experiment

The Telescope Array (TA) is the largest cosmic ray detector in the Northern Hemisphere. It consists of a surface detector of plastic scintillation counters overlooked by 3 fluorescence detector sites. TA measures cosmic rays from 1 PeV to 100 EeV and higher by observing extensive air showers in the atmosphere. To determine the shower energy, it is important to understand the fluorescence yield (FY), which is a conversion factor from the energy deposition in air to the fluorescence light. sFLASH is an auxiliary experiment of TA that measures FY in air produced by high energy electrons in an air volume called the active region. In this work, we report the results of a FLUKA simulation of sFLASH to gauge our understanding of the energy deposition in the experiment. We compare our FLUKA simulation results with an alternative simulation that uses Geant4 software, implemented by a different team within the sFLASH collaboration. Preliminary results show that both results agree to within 3%. The sFLASH FY systematic uncertainty will be reduced using the energy deposition of our sFLASH FLUKA simulation. This will improve the energy estimation of the high energy cosmic rays by the experiments such as TA and Auger.

Data Quality Control for the Muon g-2 Experiment

In the Muon g-2 experiment, parameters such as the voltages applied to the focusing electric quadrupoles can affect the recorded time spectrum of positrons from muon decay. When a spark occurs in the quadrupole system, the voltages must be reduced and brought back up before collection of valid data resumes. A data quality control process eliminates these intervals of unstable quadrupole voltages to produce a usable time spectrum for analysis of the muon spin precession frequency. Using Python libraries numpy, scipy, and matplotlib to interact with a PostgreSQL database, optimal settings for the parameters in the selected timeframe are found from a histogram and a time series plot. The data set is divided into time intervals on the order of 10 seconds, known as subruns. The data quality algorithm determines if each subrun is acceptable for use based on the optimal settings that were found.  This process can be used on any parameter that may introduce a systematic error into the physics result.   

Spacetime Discretization Methods for Numerical Relativity

Conventional approaches to numerical relativity (NR) rely on a 3+1 decomposition of spacetime that requires choosing a particular gauge which fixes the foliation of the spacetime. While the 3+1 approach has been known to work very well, e.g., for computing gravitational waveforms, it is not well-suited for a study of the strong field region near singularities. We investigate a different approach towards discretizing spacetime using spacetime volume elements that do not require an a priori choice of the foliation and are easier to adapt to complex geometries, e.g., in a binary black hole merger. We also explore spacetime elements with null or space-like boundaries that lead to a significant reduction in the communication overhead in parallel calculations, compared to conventional 3+1 NR codes which—due to the presence of time-like boundaries between grid components—require nearest-neighbour communication at every time step.
  

Reconciliation of quantum theory and general relativity via redefinition of time in a non-discrete compressible fluid model of the universe with interactions governed by the Wheeler-Feynman transactional framework.

This work proposes that the philosophical assumptions concerning the concept time as constituting the major barrier in reconciling quantum theory and general relativity. The suggestive idea is proposed that time should be redefined as a measure of the magnitude of change in the location of a demarcated physical structure (a clock), within a non-discrete compressible fluid physical universe, that is an enclosed structure (a closed ball). Consequently, time and length are not just related, but are in fact one and the same. Matter and vacuum, along with other components of the universe are manifestations of differential “specific energy” densities due to compressions and rarefactions. Demarcation (detection/interaction) and analysis of the dynamics of said demarcated physical structures is governed by the framework of the Wheeler-Feynman transactional (quantum handshake) theory, wherein energy exchange is restricted to supersymmetric partner-wavefunctions (fermions-compressions and bosons-rarefactions). The dynamics of demarcated physical structures within the universe is termed an emergent equilibrium state, which is model one-dimensionally as a longitudinal wave and analyzed using the wave equation and perturbation theory in a novel framework, termed equilibrium theory.   

Qualitative dynamics of quantum cosmology from loop quantum gravity

In this talk, I shall present our recent studies on qualitative dynamics of three different quantizations of the flat FLRW universe in loop quantum gravity (LQG) from an effective description of the quantum spacetime derived by using the geometric quantum mechanics of
coherent states.  These include the standard loop quantum cosmology (LQC) and its two recently-revived modifications, referred to as mLQC-I and mLQC-II, respectively.  Various features of LQC, including quantum bounce and pre-inflationary dynamics, are found to be 
shared with the mLQC-I and mLQC-II models. I shall present universal properties of the evolution of the FLRW universe with, respectively, the chaotic, fractional monodromy, Starobinsky, non-minimal Higgs, and exponential potentials, and show various qualitative similarities in the post-bounce phase for all these models. The pre-bounce qualitative dynamics of LQC and mLQC-II turns out to be very similar, but is strikingly different from that of mLQC-I.   For all these potentials, non-perturbative quantum gravitational effects always result generically in a slow-roll inflationary phase. Between it and the quantum bounce a phase of super-inflation always exists.   

Quasi-Particle Production During Gravitational Collapse of a Reissner-Nordtrom-AdS Domain Wall

The of investigation quasi-particle creation during gravitational collapse is essential for understanding the thermal nature of the radiation and the information loss paradox. In this poster we investigate the gravitational collapse of a Reissner-Norstrom-AdS domain wall for both a non-extremal and overcharged case. In the overcharged case, the domain wall oscillates about a radius outside of the naked singularity, abiding by the cosmic censorship conjecture, due to the competition between the Coulomb repulsion and the gravitational attraction. Due to the periodic behavior of the collapsing domain wall, the quasi-particle production acquires a Berry Phase, which is a real, measurable phase.   

Rotational superconducting gravitational wave detectors based on Cooper-pair electronic transducers

We report here on experimental and theoretical developments of a new method for gravitational wave (GW) detection.  It's principal steps are: 1) conversion of the GW action into rotational motion and 2) conversion of the rotational motion into an electric current.  The ability to detect extremely tiny currents via superconducting electronics empowers this approach.  Preliminary experiments confirm the theoretical expectations and suggest that gravitational waves far beyond the reach of LIGO can be detected.  We came to the conclusion that very efficient all-solid-state detectors may be achieved utilizing Cooper pairs as transducers.  The advantage of superconductivity is in the exponential reduction of noise, which will require relatively low, operating temperatures.  Besides superior sensitivity, the devices will have very moderate, meter-range sizes, which will make it possible to place them on orbital platforms and orient so as to maximize the signal from selected sources.  As our room-temperature experiments have demonstrated, having duplicate detectors or duplicate elements in one detector, in close vicinity to each other, yields effective suppression of the seismic noise, as well as the stray field pick-up, thus achieving sensitivity close to the theoretical limits.   

A Realistic Analytic Model for Complete Gravitational Wave Templates

Gravitational waves are produced by orbiting massive binary objects, such as black holes and neutron stars.
Their detection depends on simple, accurate, and efficient analytic templates tuned to numerical simulations of Einstein's equations of General Relativity.
Recently we developed a simple and cohesive matching method for the analytic calculation of gravitational waves by using the post-Newtonian (PN) theory for the inspiral phase and the Implicit Rotating Source (IRS) toy model for the merger phase of the binary evolution, then combined them into one complete waveform.
We extend previous work by introducing eccentricity in the inspiral model and by employing a more realistic analytic model for the merger -- the Backwards One Body (BOB) method proposed by S. McWilliams. 
We test the performance of the BOB method by comparing the produced waveforms with the IRS model and the numerical results from the Simulating eXtreme Spacetimes (SXS) collaboration.   
After building the inspiral and merger waveforms, we will reconstruct our matching method and validate it by comparing our results with the waveforms for the first detection, GW150914, available as open-source. 
This is a rich and timely topic, and our approach is accessible and easily reproducible.   

Testing Einstein-Aether Theory by Gravitational Wave Observations

Gravitationally bound hierarchies containing three or more components are very common, and many of them should be detected by the advanced LIGO/Virgo, KAGRA and LISA. In this talk, I present our recent  studies on the emissions of periodic gravitational waves (GWs) in Einstein-aether theory, which violates the Lorentz symmetry, yet satisfies all the theoretical and observational constraints carried out so far. 

In particular, I shall first show that, in the weak-field approximations and with the current  constraints,  the strong-field effects for a binary system of neutron stars are about six orders lower than that of GR. Ignoring these effects I present  the general formulas of the theory to  the lowest post-Newtonian order, by taking the coupling of the aether field with matter into account. Then, I shall show that the scalar breather  and longitudinal modes are all suppressed by a factor of $10^{-5}$ with respect to the transverse-traceless modes, while the vectorial modes are suppressed by a factor of $10^{-15}$. Applying the general formulas to a triple system, I shall show that the corresponding GW forms, response functions, and their Fourier transforms all depend sensitively on the configurations of the triple systems and binding energies of the 3-bodies.    

Computation of highly eccentric EMRIs to characterize background confusion noise in LISA

Extreme mass ratio inspirals (EMRIs) result when stellar mass compact objects orbiting a supermassive black hole (SMBH) undergo radiation damping. Such systems are prime sources for the proposed space-based gravitational wave detector LISA. However, highly eccentric EMRIs produce significant gravitational radiation only when the orbiting body is at closest approach to the SMBH. While a single source is not likely to be detectable, an ensemble of many such sources may cause background confusion noise that could mask sources that LISA would otherwise detect. We solve the Teukolsky equation using a frequency domain hypergeometric approach to probe the gravitational radiation produced by highly eccentric EMRIs in hopes of characterizing this signal confusion background. This code is programmed in a new programming language called Julia which is syntactically similar to Python but comes close to the speeds of C or Fortran for numerical computation. Additionally, we discuss possible methods of skipping evaluation of small modes to speed up computation times.   

Numerical Simulation Infrastructure For Gravitational Wave Data Analysis

The first gravitational waves from a merger of a binary neutron star system were detected less than a year ago, on August 17th 2017. This is still the only detection of gravitational waves involving neutron stars to date. Like binary black holes (BBH), investigations of binary neutron stars (BNS) rely on numerical simulations for the most accurate understanding of waveform dynamics at merger. Driven by several BBH detections to date, infrastructure for this analysis has been developed primarily for BBH. Meanwhile, infrastructure for BNS waveforms have not yet been fully incorporated. Using a standalone Python script, numerical binary neutron star mergers from third parties can now be converted into a format that can be uploaded and used inside the collaborative LALSuite/PyCBC projects to analyze the effects of numerical merger on searches and parameter estimation. The first examples of hybrid waveforms have also been generated using this system.   

Parameter Estimation of Gravitational Waves of Binary Neutron Star Mergers Using LALInference

The first gravitational waves emitted by a neutron star binary coalescence was detected on August 17, 2017. Being able to estimate the parameters of such a system including mass, and tidal deformation is an important factor in understanding the physics of neutron stars. LALInference is a parameter estimation tool used to estimate parameters from gravitational wave signals. By using other computational methods to create fake gravitational wave signals we can test the capability of LALInference to predict the correct parameters of these gravitational waves for some given noise spectrum. In my project, I ran LALInference parameter estimation on several fake gravitational wave signals and compared the predicted parameters with the ones used to create the fake signals. This research can be used to predict the scientific capabilities of future observing runs for advanced interferometers.   

Investigation of Noise Transients in the Advanced LIGO Calibration Model

LIGO searches for gravitational waves in calibrated data using time-dependent calibration parameters. In this project, we looked for significant fluctuations in these parameters during the second observing run. Large fluctuations in these parameters may indicate a significant error in the Advanced LIGO strain calculations during a gravitational wave measurement, which would impact the determination of the astrophysical source that produced the gravitational wave signal.    

Diamonds in the Rough: Characterizing the Effect of Noise Transients on Gravitational-Wave Data

During its first two observing runs, LIGO detected gravitational waves from the merging of binary black holes and neutron stars. The collaboration operates two detectors and has multiple methods used to locate signals in the detector data, but this presentation will focus on one search known as PyCBC, which identifies potential signals and produces triggers to flag them. While it finds signals, it also sometimes flags noise transients. The LIGO detector characterization group works to distinguish these transients, called glitches, from real signals. Glitches can be separated into categories, as is done in the GravitySpy web-based citizen science project. In my research, I analyzed the PyCBC triggers produced by GravitySpy glitch categories. I first compared glitches to real signal models. I then identified the astrophysical system that would produce a signal most closely resembling a glitch of a given type and plotted the characteristics of the systems to look for commonalities in the triggers produced by each glitch class. I lastly produced plots showing the probability that a certain glitch type will produce a trigger resembling a signal of certain characteristics. Such numbers will help LIGO determine whether a trigger is a glitch or a real signal.
  

Optical followup of gravitational wave events with the Dark Energy Camera during LIGO O1/O2

We present a summary of the DES-GW program to search for electromagnetic counterparts of gravitational wave events during the first two LIGO observing runs from 2015 to 2017. We will describe the decision-making process of whether or not to follow up.a given event, formulation of the observing plan for followup, the image processing pipeline, and lessons learned from followup of four binary black hole mergers and one binary neutron star merger, including how we plan to apply them during the next LIGO observing run.   

A Two-Charge Theory of Gravity

Our current standard theory of gravity is unable to fully explain the accelerating expansion of the universe. This expansion seems to imply a repulsive force associated with gravitational interaction. We propose a 2-charge theory of gravity based on the Quantum Field Theory applied to a second rank tensor field that allows for an attractive force between like charges and a repulsive force between opposite charges. This model could partly explain matter-antimatter asymmetry, the smallness of the cosmological constant, and the accelerating expansion of the universe. Our calculations of a lattice model with a billion points show that a net gravitational force at any spacetime point would be slightly repulsive. This new model is also consistent with the local physics described by the standard theory of gravity. Our theory may be experimentally supported by results from the ALPHA Collaboration.
  

Modeling Black-Hole/Neutron-Star Binaries with Rapid Black-Hole Spins

LIGO and Virgo have observed gravitational waves---ripples of curved spacetime---from binary black holes and from binary neutron stars. Looking forward, we hope to observe black hole-neutron star mergers, which (like binary neutron stars) are potential multi-messenger sources, emitting both electromagnetic and gravitational waves. Highly accurate models of these waves are important for helping to detect as many gravitational waves from merging black holes and neutron stars as possible while learning as much as possible about the waves' sources. I will discuss the progress of new simulations, using the Spectral Einstein Code, of black hole-neutron star mergers with rapidly rotating black holes, an astrophysically interesting but technically challenging case.   

Exotic Spacetime Topology as an Alternative to Dark Matter and Energy

Dark matter and energy are widely accepted features of the current cosmological standard model, but they suffer from troubling questions of theoretical interpretation and a lack of direct experimental support. The standard model is based on Einstein’s general relativity, which implicitly assumes that spacetime in locally inertial frames is Euclidean. It may instead be smooth, but topologically exotic (homeomorphic, but not diffeomorphic to Euclidean spacetime). Since gravity is the physical manifestation of spacetime curvature, such a change could mimic the effects of dark matter and/or energy (Brans conjecture). Exotic versions of Euclidean space exist in the case of four dimensions, where there are uncountably many of them. If this is a coincidence, it is surely a remarkable one. Recently, C. Duston has used techniques pioneered by C.H. Taubes to derive metrics for two such exotic smooth manifolds. We revisit the classical light deflection test of general relativity with one of these metrics and use observational data on gravitational lensing by galaxy clusters in an attempt to put quantitative constraints on exotic topology as an alternative to dark matter.   

Gravitational ponderomotive forces and linear gravitational waves in matter

Recent detection of electromagnetic waves accompanying gravitational-wave (GW) emission by astrophysical sources has reinvigorated interest in the problem of GW coupling with plasma surrounding the sources. Existing theories of such coupling are cumbersome and not directly applicable to the GWs of interest that are inhomogeneous in space and have more general polarization than in vacuum. We propose an alternative, variational formulation of this problem, which also leads to the prediction of the nonlinear ponderomotive force that a GW pulse exerts on massive particles. This force is calculated explicitly for the first time. Developing on our variational method, we also propose a geometrical-optics theory for collective matter oscillations in self-consistent metric with general polarization. Electromagnetic interactions can be added similarly, leading to a generalized theory of plasma waves in astrophysical context.   

The Effect of Gravitational Waves on a Ring of Test Masses from Inspiraling Compact Binary System

Objects in orbit produce gravitational waves; however, waves are only large enough to measure when they are produced from a sufficiently large system. A system of two massive objects spiraling in toward each other, such as neutron stars, produce large enough waves that they can be measured. Our Vpython simulation demonstrates the effect of this wave on a ring of test masses, scaling up the effect so that the ring is visibly distorted.   

Short-range gravity search with optically-levitated nanoparticles

 Optically levitated dielectric particles are a promising tool for use in precision experiments. Since they are decoupled mechanically from the environment optically levitated particles can have very large quality factors enabling ultrasensitive force detection.  We describe progress on an experiment using silica nanospheres trapped in an optical lattice to search for deviations from Newton’s inverse square law at the micron scale where we have achieved zeptonewton force sensitivity. Recent modifications to the experiment include a fiber based dipole trap, and solid invar cavity.   

Test of Violation of Einstein's Equivalence Principle By Galactic Dark Matter

We report here the results of operation of a torsion balance with a period of ∼ 1.27 x 10⁴ s.  The analysis of data collected over a period of ∼ 115 days shows that the difference in acceleration towards the Galactic Center of test bodies made of aluminum and quartz was (0.8 ± 1.3) x 10^-15 ms^-2.  This sets a bound on the violation of the equivalence principle by forces exerted by Galactic dark matter, expressed as an Eötvös parameter η_DM = (1.7 ± 2.8) x 10^-5, and improves upon the earlier bounds significantly.  We also present preliminary results on the violation of the equivalence principle by forces exerted by the sun.
  

Suppression of tilt-induced low frequency noise at Ligo Livingston Observatory

A well known fact is that horizontal seismometers are have sensitivity to ground rotation at low frequencies. Conventional tiltmeters and seismometers cannot discern between rotation of the ground and horizontal acceleration. This is especially problematic for seismic isolation in current gravitational wave detectors, such as Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO), where rotation noise poses limits to duty cycle of the detectors. Earthquakes, High Wind and High Microseism cause significant down-time of both detectors. All are primarily related to the problem of tilt-horizontal coupling producing too much ISI motion.

To address this problem we use a rotation-sensor to get a tilt-free ground translation signal and use it for sensor-correction at LIGO Livingston Observatory as well as at Hanford. I will describe the system in general and present our latest improvement of controls and suppression of low-frequency noise using this system. This should give us a substantial increase of duty cycle of the detectors at O3 during tilt-noise dominated periods.