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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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Higher order and anisotropic hydrodynamics for Bjorken and Gubser flows
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Dynamical model calculation to reconcile the nuclear fission lifetime from different measurement techniques
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Effective operators in two-nucleon systems
Effective Hamiltonians and effective electroweak operators are calculated with the Okubo-Lee-Suzuki formalism for two-nucleon systems. Working within a harmonic oscillator basis, first without and then with a confining harmonic oscillator trap, we demonstrate the effects of renormalization on observables calculated for truncated basis spaces. We illustrate the renormalization effects for the root-mean-square point-proton radius, electric quadrupole moment, magnetic dipole moment, Gamow-Teller transition and neutrinoless double-beta decay operator using nucleon-nucleon interactions from chiral Effective Field Theory. Renormalization effects tend to be larger in the weaker traps and smaller basis spaces suggesting applications to heavier nuclei with transitions dominated by weakly-bound nucleons would be subject to more significant renormalization effects within achievable basis spaces.
Supersymmetric S U ( 5 ) × U ( 1 ) χ and the weak gravity conjecture
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Data-Driven Modeling of Electron Recoil Nucleation in PICO C$_3$F$_8$ Bubble Chambers
The primary advantage of moderately superheated bubble chamber detectors is their simultaneous sensitivity to nuclear recoils from weakly interacting massive particle (WIMP) dark matter and insensitivity to electron recoil backgrounds. A comprehensive analysis of PICO gamma calibration data demonstrates for the first time that electron recoils in C3F8 scale in accordance with a new nucleation mechanism, rather than one driven by a hot spike as previously supposed. Using this semiempirical model, bubble chamber nucleation thresholds may be tuned to be sensitive to lower energy nuclear recoils while maintaining excellent electron recoil rejection. The PICO-40L detector will exploit this model to achieve thermodynamic thresholds as low as 2.8 keV while being dominated by single-scatter events from coherent elastic neutrino-nucleus scattering of solar neutrinos. In one year of operation, PICO-40L can improve existing leading limits from PICO on spin-dependent WIMP-proton coupling by nearly an order of magnitude for WIMP masses greater than 3 GeV c-2 and will have the ability to surpass all existing non-xenon bounds on spin-independent WIMP-nucleon coupling for WIMP masses from 3 to 40 GeV c-2.
Azimuthal asymmetries of back-to-back π ± - ( π 0 , η , π ± ) pairs in e + e - annihilation
This work reports the first observation of azimuthal asymmetries around the thrust axis in e + e – annihilation of pairs of back-to-back charged pions in one hemisphere, and π 0 and η mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π 0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function $H$ $^{1}_{⊥}$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of $H$ $^{1}_{⊥}$. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb –1 collected by the Belle experiment at or near a center- of-mass energy of 10.58 GeV.
Bounds on the density of states and the spectral gap in CFT 2
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Physics reach of a low threshold scintillating argon bubble chamber in coherent elastic neutrino-nucleus scattering reactor experiments
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Results on photon-mediated dark-matter–nucleus interactions from the PICO-60 C 3 F 8 bubble chamber
Many compelling models predict dark matter coupling to the electromagnetic current through higher multipole interactions, while remaining electrically neutral. Different multipole couplings have been studied, among them anapole moment, electric and magnetic dipole moments, and millicharge. This study sets limits on the couplings for these photon-mediated interactions using nonrelativistic contact operators in an effective field theory framework. Using data from the PICO-60 bubble chamber leading limits for dark matter masses between 2.7 and 24 GeV/c 2 and above 265 GeV/c 2 (anapole moment), 2.7 and 11.7 GeV/c 2 (electric moment), 3 and 9.5 GeV/c 2 (magnetic moment), and 2.7 and 12 GeV/c 2 (millicharged) are reported for the coupling of these photon-mediated dark matter-nucleus interactions. The detector was filled with 52 kg of C 3 F 8 operating at thermodynamic thresholds of 2.45 keV and 3.29 keV, reaching exposures of 1404 kg-day and 1167 kg-day, respectively.
Wormholes and half wormholes under irrelevant deformation
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Determining the bubble nucleation efficiency of low-energy nuclear recoils in superheated C 3 F 8 dark matter detectors
The bubble nucleation efficiency of low-energy nuclear recoils in superheated liquids plays a crucial role in interpreting results from direct searches for weakly interacting massive particle (WIMP) dark matter. Here, the PICO collaboration presents the results of the efficiencies for bubble nucleation from carbon and fluorine recoils in superheated C 3 F 8 from calibration data taken with five distinct neutron spectra at various thermodynamic thresholds ranging from 2.1 to 3.9 keV. Instead of assuming any particular functional forms for the nuclear recoil efficiency, a generalized piecewise linear model is proposed with systematic errors included as nuisance parameters to minimize model-introduced uncertainties. A Markov chain Monte Carlo routine is applied to sample the nuclear recoil efficiency for fluorine and carbon at 2.45 and 3.29 keV thermodynamic thresholds simultaneously. The nucleation efficiency for fluorine was found to be ≥ 50% for nuclear recoils of 3.3 keV (3.7 keV) at a thermodynamic Seitz threshold of 2.45 keV (3.29 keV), and for carbon the efficiency was found to be ≥ 50% for recoils of 10.6 keV (11.1 keV) at a threshold of 2.45 keV (3.29 keV). Simulated datasets are used to calculate a p value for the fit, confirming that the model used is compatible with the data. The fit paradigm is also assessed for potential systematic biases, which although small, are corrected for. Additional steps are performed to calculate the expected interaction rates of WIMPs in the PICO-60 detector, a requirement for calculating WIMP exclusion limits.
Reappraisal of spontaneous R-parity violation
In this short reappraisal of spontaneous lepton number violation in a supersymmetric scenario implemented through singlet sneutrino vacuum expectation value (VEV), we contribute two new things in the context where the lepton number symmetry is global: (i) provide explicit expressions of R-parity violating couplings in terms of the neutrino Yukawa couplings and the singlet sneutrino VEV, and (ii) estimate the limit on this VEV using the current knowledge of the light neutrino mass and the astrophysical constraint on the Majoron-electron coupling. Besides, we put updated constraints on the VEV and Yukawa coupling of the singlet superfield when the lepton number is gauged.
Quantum phase transition in a Dp-Dq system
Using the top-down approach, we study intersecting Dp-Dq brane configuration in string theory and find examples, where there can be a quantum phase transition at zero temperature induced by the violation of the Breitenlohner-Freedman bound at IR, which is done essentially by a combination of charge density and magnetic fields. In particular, there exists a Berezinskii-Kosterlitz-Thouless (BKT) type of transition for D3-D5 and D5-D5 systems. The study of the BKT type of transition is initiated by Jensen et al.[Phys. Rev. Lett. 105, 041601 (2010)] for a D3-D5 system with nonzero charge density and a magnetic field. Here, we show that one can have the BKT transition for a D3-D5 system even in the absence of charge density but requires multiple magnetic fields. In this case the field theory lives in 2+1 dimensions, whereas for the D5-D5 type, the transition requires the presence of both the charge density and magnetic fields and the dual field theory lives on a 3+1 dimensional spacetime. We also study the D3-D7 system but it does not show the BKT type of transition.
Search for the decay B 0 → Φ γ
We have searched for the decay B 0 → Φγ using the full Belle data set of 772 × 10 6 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB e+e– collider. No signal is observed, and we set an upper limit on the branching fraction of B(B 0 → Φγ) < 1.0 × 10 –7 at the 90% confidence level. Here, this is the most stringent limit on this decay mode to date.
Study of excited Ξ c states decaying into Ξ c 0 and Ξ c + baryons
Here, with a data sample of 980 fb - 1 of e + e - annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy e + e - collider, we discuss the results of a study of excited Ξ c states that decay, via the emission of photons and/or charged pions, into Ξ c 0 or Ξ c + ground state charmed-strange baryons. We present new measurements of the masses of all members of the Ξ c ' , Ξ c ( 2645 ) , Ξ c ( 2790 ) , Ξ c ( 2815 ) , and Ξ c ( 2980 ) isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.
Search for Λ c + → φ p π 0 and branching fraction measurement of Λ c + → K - π + p π 0
We have investigated the Cabibbo-suppressed decay Λ c + → φ p π 0 in e + e - collisions using a data sample corresponding to an integrated luminosity of 915 fb - 1 . The data were collected by the Belle experiment at the KEKB e + e - asymmetric-energy collider running at or near the Υ ( 4 S ) and Υ ( 5 S ) resonances. No significant signal is observed, and we set an upper limit on the branching fraction of B ( Λ c + → φ p π 0 ) < 15.3 × 10 - 5 at 90% confidence level. The contribution of nonresonant Λ c + → K + K - p π 0 decays is found to be consistent with zero, and the corresponding upper limit on its branching fraction is set to be B ( Λ c + → K + K - p π 0 ) NR < 6.3 × 10 - 5 at 90% confidence level. We also search for an intermediate hidden-strangeness pentaquark decay P s + → φ p . We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of B ( Λ c + → P s + π 0 ) × B ( P s + → φ p ) < 8.3 × 10 - 5 at 90% confidence level. Finally, we measure the branching fraction for the Cabibbo-favored decay Λ c + → K - π + p π 0 ; the result is B ( Λ c + → K - π + p π 0 ) = ( 4.42 ± 0.05 ( stat ) ± 0.12 ( syst ) ± 0.16 ( norm ) ) % , which is the most decisive measurement to date.
Measurement of the decays B → η ℓ ν ℓ and B → η ' ℓ ν ℓ in fully reconstructed events at Belle
We report branching fraction measurements of the decays B + → ηℓ + νℓ and B + → η'ℓ + νℓ based on 711 fb –1 of data collected near the Υ(4S) resonance with the Belle experiment at the KEKB asymmetric-energy e + e – collider. This data sample contains 772 million BB¯ events. One of the two B mesons is fully reconstructed in a hadronic decay mode. Among the remaining (“signal-B”) daughters, we search for the η meson in two decay channels, η → γγ and η → π + π – π 0 , and reconstruct the η' meson in η' → ηπ + π – with subsequent decay of the η into γγ. Combining the two η modes and using an extended maximum likelihood, the B + → ηℓ + νℓ branching fraction is measured to be (4.2 ± 1.1(stat.) ± 0.3(syst.)) × 10 –5 . For B + → η'ℓ + νℓ, we observe no significant signal and set an upper limit of 0.72 × 10 –4 at 90% confidence level.