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1. Constraints on bosonic dark matter from ultralow-field nuclear magnetic resonance

   https://doi.org/10.1126/sciadv.aax4539  

   Garcon, Antoine ; Blanchard, John W. ; Centers, Gary P. ; Figueroa, Nataniel L. ; Graham, Peter W. ; Jackson Kimball, Derek F. ; Rajendran, Surjeet ; Sushkov, Alexander O. ; Stadnik, Yevgeny V. ; Wickenbrock, Arne ; et al ( October 2019 , Science Advances)

   The nature of dark matter, the invisible substance making up over 80% of the matter in the universe, is one of the most fundamental mysteries of modern physics. Ultralight bosons such as axions, axion-like particles, or dark photons could make up most of the dark matter. Couplings between such bosons and nuclear spins may enable their direct detection via nuclear magnetic resonance (NMR) spectroscopy: As nuclear spins move through the galactic dark-matter halo, they couple to dark matter and behave as if they were in an oscillating magnetic field, generating a dark-matter–driven NMR signal. As part of the cosmic axion spin precession experiment (CASPEr), an NMR-based dark-matter search, we use ultralow-field NMR to probe the axion-fermion “wind” coupling and dark-photon couplings to nuclear spins. No dark matter signal was detected above background, establishing new experimental bounds for dark matter bosons with masses ranging from 1.8 × 10 −16 to 7.8 × 10 −14 eV.
2. A method for controlling the magnetic field near a superconducting boundary in the ARIADNE axion experiment

   https://doi.org/10.1088/2058-9565/abf1cc  

   Fosbinder-Elkins, H. ; Kim, Y. ; Dargert, J. ; Harkness, M. ; Geraci, A. A. ; Levenson-Falk, E. ; Mumford, S. ; Fang, A. ; Kapitulnik, A. ; Matlashov, A. ; et al ( January 2022 , Quantum Science and Technology)

   The QCD axion is a particle postulated to exist since the 1970s to explain the strong-CP problem in particle physics. It could also account for all of the observed dark matter in the Universe. The axion resonant interaction detection experiment (ARIADNE) intends to detect the QCD axion by sensing the fictitious ‘magnetic field’ created by its coupling to spin. Short-range axion-mediated interactions can occur between a sample of laser-polarized³He nuclear spins and an unpolarized source-mass sprocket. The experiment must be sensitive to magnetic fields below the 10⁻¹⁹T level to achieve its design sensitivity, necessitating tight control of the experiment’s magnetic environment. We describe a method for controlling three aspects of that environment which would otherwise limit the experimental sensitivity. Firstly, a system of superconducting magnetic shielding is described to screen ordinary magnetic noise from the sample volume at the 10⁸level, which should be sufficient to reduce the contribution of Johnson noise in the sprocket-shaped source mass, expected to be at the 10⁻¹²T$/\sqrt{\mathrm{H}\mathrm{z}}$level, to below the threshold for signal detection. Secondly, a method for reducing magnetic field gradients within the sample up to 10²times is described, using a simple and cost-effective design geometry. Thirdly,more »a novel coil design is introduced which allows the generation of fields similar to those produced by Helmholtz coils in regions directly abutting superconducting boundaries. This method allows the nuclear Larmor frequency of the sample to be tuned to match the axion field modulation frequency set by the sprocket rotation. Finally, we experimentally investigate the magnetic shielding factor of sputtered thin-film superconducting niobium on quartz substrates for various geometries and film thicknesses relevant for the ARIADNE axion experiment using SQUID magnetometry. The methods may be generally useful for magnetic field control near superconducting boundaries in other experiments where similar considerations apply.

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3. Search for heavy resonances decaying to ZZ or ZW and axion-like particles mediating nonresonant ZZ or ZH production at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP04(2022)087  

   Tumasyan, A. ; Adam, W. ; Andrejkovic, J. W. ; Bergauer, T. ; Chatterjee, S. ; Damanakis, K. ; Dragicevic, M. ; Escalante Del Valle, A. ; Frühwirth, R. ; Jeitler, M. ; et al ( April 2022 , Journal of High Energy Physics)

   A bstract A search has been performed for heavy resonances decaying to ZZ or ZW and for axion-like particles (ALPs) mediating nonresonant ZZ or ZH production, in final states with two charged leptons ( ℓ = e , μ) produced by the decay of a Z boson, and two quarks produced by the decay of a Z, W, or Higgs boson H. The analysis is sensitive to resonances with masses in the range 450 to 2000 GeV. Two categories are defined corresponding to the merged or resolved reconstruction of the hadronically decaying boson. The search is based on data collected during 2016–2018 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . No significant excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-2 and spin-1 resonances are derived as functions of the resonance mass, and exclusion limits on the production of bulk graviton particles and W′ bosons are calculated in the framework of the warped extra dimensions and heavy vector triplet models, respectively. In addition, upper limits onmore »the ALP-mediated diboson production cross section and ALP couplings to standard model particles are obtained in the framework of linear and chiral effective field theories. These are the first limits on nonresonant ALP-mediated ZZ and ZH production obtained by the LHC experiments.« less
4. Source Mass Characterization in the ARIADNE Axion Experiment

   https://doi.org/10.1007/978-3-030-43761-9_9  

   Lohmeyer, C. ; Aggarwal, N. ; Arvanitaki, A. ; Brown, A. ; Fang, A. ; Geraci, A. ; Kapitulnik, A. ; Kim, D. ; Kim, Y ; . Lee, I ; et al ( January 2020 , Springer proceedings in physics)

   The Axion Resonant InterAction Detection Experiment (ARIADNE) is a collaborative effort to search for the QCD axion using nuclear magnetic resonance (NMR), where the axion acts as a mediator of spin-dependent forces between an unpolarized tungsten source mass and a sample of polarized helium-3 gas. Since the experiment involves precision measurement of a small magnetization, it relies on limiting ordinary magnetic noise with superconducting magnetic shielding. In addition to the shielding, proper characterization of the noise level from other sources is crucial.We investigate one such noise source in detail: the magnetic noise due to impurities and Johnson noise in the tungsten source mass.
5. LigninGraphs: lignin structure determination with multiscale graph modeling

   https://doi.org/10.1186/s13321-022-00627-2  

   Wang, Yifan ; Kalscheur, Jake ; Ebikade, Elvis ; Li, Qiang ; Vlachos, Dionisios G. ( July 2022 , Journal of Cheminformatics)

   Lignin is an aromatic biopolymer found in ubiquitous sources of woody biomass. Designing and optimizing lignin valorization processes requires a fundamental understanding of lignin structures. Experimental characterization techniques, such as 2D-heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) spectra, could elucidate the global properties of the polymer molecules. Computer models could extend the resolution of experiments by representing structures at the molecular and atomistic scales. We introduce a graph-based multiscale modeling framework for lignin structure generation and visualization. The framework employs accelerated rejection-free polymerization and hierarchical Metropolis Monte Carlo optimization algorithms. We obtain structure libraries for various lignin feedstocks based on literature and new experimental NMR data for poplar wood, pinewood, and herbaceous lignin. The framework could guide researchers towards feasible lignin structures, efficient space exploration, and future kinetics modeling. Its software implementation in Python, LigninGraphs, is open-source and available on GitHub.

   Graphical abstract