Bulletin of the American Physical Society
APS April Meeting 2023
Volume 68, Number 6
Minneapolis, Minnesota (Apr 15-18)
Virtual (Apr 24-26); Time Zone: Central Time
Session B14: Precision Measurements for Gravity, Dark Matter, and Dark Energy |
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Sponsoring Units: GPMFC Chair: William Snow, Indiana University Bloomington Room: Marquette V - 2nd Floor |
Saturday, April 15, 2023 10:45AM - 10:57AM |
B14.00001: Spectral method for computing gravitational quasinormal-mode frequencies of black hole Chung Ka Wai, Nicolas Yunes, Pratik K Wagle Since the first direct detection of gravitational waves, the black-hole ringdown phase has been subjected to extensive analyses because of its novel application to probe fundamental physics in the strong-field regime. To thoroughly understand the detected ringdown signals, we need to calculate the gravitational quasinormal-mode frequencies of a black hole under various conditions. However, most existing methods are adequate to study quasinormal modes at sufficient accuracy only for some limited black-hole models. In this talk, I will describe a novel technique to solve the linearized Einstein equations for the quasinormal-mode frequencies of a perturbed black hole using spectral decompositions. Our method works directly with the metric perturbations, and in particular, it does not require simplifying the linearized field equations into master equations through special master functions. Moreover, our method turns the resulting, coupled and partial differential equations into a linear algebra problem, without requiring the decoupling of the radial and angular coordinates. All of this makes this new method extremely powerful in the study of black hole ringdown because, as a consequence, it can be applied to a general black hole background. Applying the method to the Kerr black hole background, we can accurately and efficiently calculate the 022-mode frequency with a relative error in the real and imaginary parts smaller than 1e-3 and we can easily calculate the 033 and 132 modes with similar accuracy. |
Saturday, April 15, 2023 10:57AM - 11:09AM |
B14.00002: Neutron grating interferometry evaluation of test masses Daniel S Hussey, Kofi T Assumin-Gyimah, Dipangkar Dutta, William M Snow, Chloe Langlois, Vincent D Lee Newton’s gravitational constant, G, remains the least well-known of the fundamental constants. Multiple precision measurements are highly discrepant, differing up to 10-sigma. This suggests a lack of understanding of all measurement systematic effects. One possible systematic is mass density gradients which are difficult to measure in general. One solution is to employ optically transparent test masses whose mass gradients can be assessed by laser interferometry. A candidate test mass material is PbWO4, with density 8.28 g cm-3. Given the use of PbWO4 as a scintillator, large quantities of single crystal are available. Another solution, and the focus of this presentation, is to employ penetrating radiation, such as neutrons. For example, whether in elemental form or in a chemical compound, Pb and Bi have negligible absorption cross sections, allowing slow neutrons to pass through several cm of material. Neutron grating interferometry, whose signal depends on the coherent rather than absorption cross section, is a sensitive method for measuring density gradients. We report on recently published measurements of PbWO4 crystals using a neutron Talbot-Lau interferometer in which mass gradients < 5×10-7 cm-1 were measured. We also provide estimates on future measurement possibilities. |
Saturday, April 15, 2023 11:09AM - 11:21AM |
B14.00003: Towards high precision measurements of dynamic gravity Tobias Brack, Jürg Dual, Fadoua Balabdaoui, Bernhard Zybach, Jonas Fankhauser, Stephan Kaufmann, Stefan Blunier, Donat Scheiwiller, Francesco Palmegiano, Pavel Trtik, Laura De Lorenzis, Helge C Hille, Jean-Claude Tomasina, Michael Meyer With advances in gravitational physics, especially in the field of gravitational wave (GW) research, fully controlled laboratory experiments on dynamic gravitation become more and more important (Astone et al., 1991, 1998; The LIGO Scientific Collaboration et al., 2015; Ross et al., 2021). Such new experiments can provide new insights into potential dynamic effects and might contribute to bringing light into the mystery still surrounding gravity. Usually, such experiments consist of a transmitter system, that is, a periodically moving mass distribution, and a detector system, which transforms the produced periodically changing gravitational forces into measurable signals. Two such systems have been described recently (Brack et al., 2022, 2023), where the transmitter system consists of either a vibrating bending beam or two rotating bars, both made of tungsten. In both cases, the detector consists of a high Q (1E4), 42 Hz resonant bending beam. Its motion is analyzed using three laser Doppler vibrometers and multichannel lock-in amplifiers. Of paramount importance is the vibration isolation of the detector from ambient noise and crosstalk from the transmitter. Here we present progress on several fronts: High precision gravitational interaction modeling, quantitative crosstalk assessment and transmitter characterization using neutron imaging. The laser interferometers are calibrated at the measurement frequency specifically for the extremely small displacements in the pm range. This results in an estimated measurement uncertainty of around 0.1%. |
Saturday, April 15, 2023 11:21AM - 11:33AM |
B14.00004: Generating an Array of Levitated Microspheres and its Applications to Precision Searches for Dark Matter Benjamin Siegel, Gadi Afek, Thomas Penny, Yu-Han Tseng, Jiaxiang Wang, Molly Watts, David C Moore Optically levitated micron-sized spheres offer ~aN/√Hz force and ~ng/√Hz acceleration sensitivities for conducting precision measurements. The high mechanical, electrical and thermal isolation allows these force sensitivities, and has permitted ground state cooling for smaller nanometer sized objects. As such, levitated spheres have been utilized in millicharge particle searches, tests probing gravity at short ranges, and searches for impulses of imparted momentum from dark matter particles. Arrays of levitated microspheres can lead to improvements in many of these studies by increasing the mass available and filtering out background and noise via correlated motion of the spheres. Such arrays will be utilized to boost the cross section of dark matter scattering events and increase the sample size in millicharged particle searches. We present a system using an acousto-optic deflector to levitate a two dimensional array of microspheres in vacuum. This array is composed of time-shared traps with independent control of each sphere's position and feedback. We detail the methodology in creating, loading and monitoring an array, and we study optically and electrically mediated intersphere interactions to better understand backgrounds inherent with this new tool. |
Saturday, April 15, 2023 11:33AM - 11:45AM |
B14.00005: Dark Matter search in the Muon g-2 experiment at Fermilab Byungchul Yu, On Kim, Baisakhi Mitra, Breese Quinn Dark matter (DM) is one of the most interesting research topics in physics. Many particle physicists are trying to identify if because we know that dark matter could be a major component of a complete fundamental description of nature. The Muon g-2 experiment at Fermilab measures the anomalous spin precession frequency of the muon. Oscillations of this precession frequency could be produced by dark matter coupling to muons. This talk will describe how we could observe DM signals in the Muon g-2 data. I will explain how we determine the Muon g-2 DM mass range sensitivity, and analysis strategies throughout the mass range. Finally, I will present the expected Muon g-2 experiment discovery/exclusion research in selected DM model-dependent scenarios. |
Saturday, April 15, 2023 11:45AM - 11:57AM |
B14.00006: Measurement of the Gravitational Constant at NIST Stephan Schlamminger, David B Newell, Clive C Speake, Leon S Chao, Vincent D Lee In 2001, researchers at the International Bureau of Weights and Measures (BIPM) published a measurement for the gravitational constant G, determined with a torsion balance using two independent modes, the Cavendish (free deflection) and servo (electrostatic) [1]. While the results obtained with both methods agreed, they were significantly higher than the results obtained by other researchers. In the following years, researchers at the BIPM built a second-generation torsion balance, MARK-2, and published it in 2013[2,3]. The 2001 and 2013 results were also in agreement. To further understand both the large discrepancy between the BIPM measurements and those of the rest of the world, as well as the inconsistent results produced by all 16 of these G experiments, MARK-2 was shipped to NIST in 2016. The experiment is currently being finalized at NIST, and we will provide the findings and results at the meeting. |
Saturday, April 15, 2023 11:57AM - 12:09PM |
B14.00007: Towards a Better Determination of Big G Using a Multi-Mode Apparatus Emily Ord, Muchuan Hua, Ricardo S Decca, C. D. Hoyle, Alexandra Papesh, Evan Liang, Marvin Q Jones, Grace C Mattingly, Hilde F Isachsen, Rutuj Gavankar, Nicholas Fuller, Ian S Guerrero, William M Snow, Stefan W Ballmer The Newtonian gravitational constant, G, is a fundamental constant in nature not linked by any complete theories to other forces of nature. Compared to all other fundamental constants, G is known with the least precision. Over the last 200 years, its value has been repeatedly measured, and leading experiments across the globe have produced values which are incompatible with one another. In fact, compared to the most precise experiment, some measured values differ by up to 50 times the experimental uncertainty. Recently, two experiments have measured consistent results at the 12 ppm level. After examination of the methodology used in previous measurements, the research group at IUPUI, in collaboration with Humboldt State University, will use multiple approaches to determine G within a singular torsion pendulum apparatus. We expect to obtain a measurement at the 2 ppm level using these new methods. By continuing the use of a torsion pendulum apparatus, we also hope to better understand the current discrepancies among previous experimental results. This talk will be focused on the characterization of noise measurements of our experimental system as well as an update on the overall status of the project. |
Saturday, April 15, 2023 12:09PM - 12:21PM |
B14.00008: Realization of a complete Stern-Gerlach interferometer: Towards a test of quantum gravity Ron Folman
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Saturday, April 15, 2023 12:21PM - 12:33PM |
B14.00009: Potential for definitive discovery of a 70 GeV dark matter WIMP with only second-order gauge couplings Roland E Allen Assuming a dark matter fraction $Omega_{DM} = 0.27$ and a reduced Hubble constant $h = 0.73$, we obtain a value of 70 GeV/c$^2$ for the mass of the dark matter WIMP we have previously proposed~[1-4]. We also obtain a value for the annihilation cross section given by $langle sigma_{ann} v angle = 1.19 imes 10^{-26} $ cm$^3$/s in the present universe, consistent with the current limits for dwarf spheroidal galaxies. Both the mass and cross-section are consistent with analyses of the Galactic-center gamma rays observed by Fermi-LAT and the antiprotons observed by AMS-02 if these data are interpreted as resulting from dark matter annihilation. The spin-independent cross-section for direct detection in Xe-based experiments is estimated to be slightly above $10^{-48}$ cm$^2$, presumably just within reach of the LZ and XENONnT experiments with $gtrsim 1000$ days of data taking. The cross-section for production in high-energy proton collisions via vector boson fusion is estimated to be $sim 1$ femtobarn, possibly within reach of the high-luminosity LHC, with $ge 140$ GeV of missing energy accompanied by two jets. |
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