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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Preparation of the SU(3) lattice Yang-Mills vacuum with variational quantum methods

Studying QCD and other gauge theories on quantum hardware requires the preparation of physically interesting states. The variational quantum eigensolver provides a way of performing vacuum state preparation on quantum hardware. Here in this work, variational quantum eigensolver is applied to pure SU(3) lattice Yang-Mills on a single plaquette and one dimensional plaquette chains. Bayesian optimization and gradient descent were investigated for performing the classical optimization. Ansatz states for plaquette chains are constructed in a scalable manner from smaller systems using domain decomposition and a stitching procedure analogous to the density matrix renormalization group. Small examples are performed on IBM’s superconducting Manila processor.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Mirror neutron stars

The fundamental nature of dark matter is entirely unknown. A compelling candidate is twin Higgs mirror matter, invisible hidden-sector cousins of the Standard Model particles and forces. This predicts mirror neutron stars made entirely of mirror nuclear matter. Here we find their structure using realistic equations of state, robustly modified based on first-principle quantum chromodynamic calculations, for the first time. This allows us to predict their gravitational wave signals, demonstrating an impressive discovery potential and ability to probe dark sectors connected to the hierarchy problem.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Reverse phase transitions in binary neutron-star systems with exotic-matter cores

Multimessenger observations of binary neutron-star mergers provide a unique opportunity to constrain the dense-matter equation of state. Although it is known from quantum chromodynamics that hadronic matter will undergo a phase transition to exotic forms of matter—e.g., quark matter—the onset density of such a phase transition cannot be computed from first principles. Hence, it remains an open question if such phase transitions occur inside isolated neutron stars or during binary neutron-star mergers, or if they appear at even higher densities that are not realized in the cosmos. Here, in this article, we perform numerical relativity simulations of neutron-star mergers and investigate scenarios in which the onset density of such a phase transition is exceeded in at least one inspiraling binary component. Our simulations reveal that shortly before the merger, it is possible that such stars undergo a “reverse phase transition”—i.e., densities decrease and the quark core inside the star disappears, leaving a purely hadronic star at merger. After the merger, when densities increase once more, the phase transition occurs again and leads, in the cases considered in this work, to the rapid formation of a black hole. We compute the gravitational-wave signal and the mass ejection for our simulations of such scenarios and find clear signatures that are related to the postmerger phase transition—e.g., smaller ejecta masses due to the softening of the equation of state through the quark core formation. Unfortunately, we do not find measurable imprints of the reverse phase transition.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Spin polarization and correlation of quarks from the glasma

We investigate the interaction of strong color fields in the glasma stage of high-energy nuclear collisions with the spins of quarks and antiquarks. We employ the perturbative solution of the quantum kinetic theory for the spin transport of (massive) quarks in a background color field governed by the linearized Yang-Mills equation and derive expressions for the quark-spin polarization and quark-antiquark spin correlation at small momentum in terms of field correlators. For the Golec-Biernat–Wusthoff dipole distribution the quark-spin polarization vanishes, but the out-of-plane spin correlation of quarks and antiquarks is nonzero. Our order-of-magnitude estimate of the correlation far exceeds that caused by vorticity effects, but does not fully explain the data for vector meson alignment. We identify possible mechanisms that could further increase the predicted spin correlation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Measurement of cross sections for production of a $Z$ boson in association with a flavor-inclusive or doubly $b$-tagged large-radius jet in proton-proton collisions at $\sqrt{s}$ = $13$ $\mathrm{TeV}$ with the ATLAS experiment

We present measurements of cross sections for production of a leptonically decaying $Z$ boson in association with a large-radius jet in 13 TeV proton-proton collisions at the LHC, using 36 fb –1 of data from the ATLAS detector. Integrated and differential cross sections are measured at particle level in both a flavor inclusive and a doubly $b$-tagged fiducial phase space. The large-radius jet mass and transverse momentum, its kinematic relationship to the Z boson, and the angular separation of $b$-tagged small-radius track jets within the large-radius jet are measured. This measurement constitutes an important test of perturbative quantum chromodynamics in kinematic and flavor configurations relevant to several Higgs boson and beyond-Standard-Model physics analyses. The results highlight issues with modeling of additional hadronic activity in the flavor-inclusive selection, and a distinction between flavor-number schemes in the $b$-tagged phase space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗