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  • arXiv  (412)
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  • 1
    Language: English
    In: The European Physical Journal C, 2011, Vol.71(9), pp.1-11
    Description: We extend a known method to integrate out the strange quark in three flavour chiral perturbation theory to the context of an arbitrary number of flavours. As an application, we present the explicit formulæ to one-loop accuracy for the heavy quark mass dependency of the low-energy constants after decreasing the number of flavours by one while integrating out the heaviest quark in N -flavour chiral perturbation theory.
    Keywords: High Energy Physics - Phenomenology ; High Energy Physics - Lattice;
    ISSN: 1434-6044
    E-ISSN: 1434-6052
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  • 2
    Description: The treatment of nuclear effects in neutrino-nucleus interactions is one of the main sources of systematic uncertainty for the analysis and interpretation of data of neutrino oscillation experiments. Neutrinos interact with nuclei via charged or neutral currents and both cases must be studied to obtain a complete information. We give an overview of the theoretical work that has been done to describe nuclear effects in neutral-current neutrin onucleus scattering in the kinematic region ranging between beam energies of a few hundreds MeV to a few GeV, which is typical of most ongoing and future accelerator-based neutrino experiments, and where quasielastic scattering is the main interaction mechanism. We review the current status and challenges of the theoretical models, the role and relevance of the contributions of different nuclear effects, and the present status of the comparison between the numerical predictions of the models as well as the available experimental data. We discuss also the sensitivity to the strange form factors of the nucleon and the methods and observables that can allow one to obtain evidence for a possible strange quark contribution from measurements of neutrino and antineutrino-nucleus scattering. Comment: 62 pages, 34 figures, JPG focus issue on Neutrino-Nucleus Interactions
    Keywords: High Energy Physics - Phenomenology ; Nuclear Experiment ; Nuclear Theory
    Source: Cornell University
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  • 3
    Language: English
    In: Scientific reports, 06 September 2016, Vol.6, pp.32653
    Description: Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schrödinger equation for and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process.
    Keywords: Physics - Atomic Physics;
    E-ISSN: 2045-2322
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  • 4
    Language: English
    In: Journal of Magnetic Resonance, December 2016, Vol.273, pp.56-64
    Description: We propose a robust and highly efficient NMR technique to create singlet spin order from longitudinal spin magnetization in coupled spin-½ pairs and to perform backward conversion (singlet order) → magnetization. In this method we exploit adiabatic ramping of an RF-field in order to drive transitions between the singlet state and the triplet states of a spin pair under study. We demonstrate that the method works perfectly for both strongly and weakly coupled spin pairs, providing a conversion efficiency between the singlet spin order and magnetization, which is equal to the theoretical maximum. We anticipate that the proposed technique is useful for generating long-lived singlet order, for preserving spin hyperpolarization and for analyzing singlet spin order in nearly equivalent spin pairs in specially designed molecules and in low-field NMR studies.
    Keywords: Spin Relaxation ; Long-Lived States ; Spin Pairs ; Adiabatic Transitions ; Chemistry ; Physics
    ISSN: 1090-7807
    E-ISSN: 1096-0856
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  • 5
    In: 15, pages 145-154. World Scientific, 2014
    Description: This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2 m long Halbach-octupole array of permanent magnets with an inner bore radius of 47 mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.
    Keywords: Physics - Instrumentation And Detectors ; Nuclear Experiment
    Source: Cornell University
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  • 6
    Language: English
    In: Deep-Sea Research Part II, February 2019, Vol.160, pp.25-31
    Description: The propagation of surface water waves interacting with a current and an uneven bottom is studied. Such a situation is typical for ocean waves where the winds generate currents in the top layer of the ocean. The role of the bottom topography is taken into account since it also influences the local wave and current patterns. Specific scaling of the variables is selected which leads to approximations of Boussinesq and KdV types. The arising KdV equation with variable coefficients, dependent on the bottom topography, is studied numerically when the initial condition is in the form of the one soliton solution for the initial depth. Emergence of new solitons is observed as a result of the wave interaction with the uneven bottom.
    Keywords: Oceanography
    ISSN: 0967-0645
    E-ISSN: 1879-0100
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  • 7
    Language: English
    In: Faraday Discussions, 2016, Vol.194, pp.509-524
    Description: An autoionizing resonance in molecular N$_2$ is excited by an ultrashort XUV pulse and probed by a subsequent weak IR pulse, which ionizes the contributing Rydberg states. Time- and angular-resolved photoelectron spectra recorded with a velocity map imaging spectrometer reveal two electronic contributions with different angular distributions. One of them has an exponential decay rate of $20\pm5$ fs, while the other one is shorter than 10 fs. This observation is interpreted as a manifestation of interference stabilization involving the two overlapping discrete Rydberg states. A formalism of interference stabilization for molecular ionization is developed and applied to describe the autoionizing resonance. The results of calculations reveal, that the effect of the interference stabilization is facilitated by rotationally-induced couplings of electronic states with different symmetry. Comment: 8 pages, 6 figures
    Keywords: Physics - Atomic Physics ; Physics - Optics;
    ISBN: 9781782624790
    ISSN: 1359-6640
    E-ISSN: 1364-5498
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  • 8
    Language: English
    In: Applied Surface Science, 2006, Vol. 252(15), pp. 5615-5618
    Description: X-ray absorption and resonant X-ray emission measurements at the O 1s edge of the uranium oxides UO2, U3O8 and UO3 are presented. The spectral shapes of the O Kα X-ray emission spectra of UO3 exhibit significant excitation energy dependence, from an asymmetric to a symmetric form, which differs from those of UO2 and U3O8. This energy dependence is attributed to a significant difference in the oxygen–uranium hybridization between two different sites in the crystal structure of UO3. The spectral shapes of UO2 and U3O8 are also found to be different but without significant energy dependence. The experimental spectra of the valence and conduction bands of the uranium oxides are compared to the results of electronic structure calculations available in the literature.
    Keywords: Natural Sciences ; Physical Sciences ; Naturvetenskap ; Fysik
    ISSN: 0169-4332
    E-ISSN: 18735584
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  • 9
    Description: We present the results of the chi2 minimization model fitting technique applied to optical and near-infrared photometric and radial velocity data for a sample of 9 fundamental and 3 first overtone classical Cepheids in the Small Magellanic Cloud (SMC). The near- infrared photometry (JK filters) was obtained by the European Southern Observatory (ESO) public survey "VISTA near-infrared Y; J;Ks survey of the Magellanic Clouds system"(VMC). For each pulsator isoperiodic model sequences have been computed by adopting a nonlinear convective hydrodynamical code in order to reproduce the multi- filter light and (when available) radial velocity curve amplitudes and morphological details. The inferred individual distances provide an intrinsic mean value for the SMC distance modulus of 19.01 mag and a standard deviation of 0.08 mag, in agreement with the literature. Moreover the instrinsic masses and luminosities of the best fitting model show that all these pulsators are brighter than the canonical evolutionary Mass- Luminosity relation (MLR), suggesting a significant efficiency of core overshooting and/or mass loss. Assuming that the inferred deviation from the canonical MLR is only due to mass loss, we derive the expected distribution of percentage mass loss as a function of both the pulsation period and of the canonical stellar mass. Finally, a good agreement is found between the predicted mean radii and current Period-Radius (PR) relations in the SMC available in the literature. The results of this investigation support the predictive capabilities of the adopted theoretical scenario and pave the way to the application to other extensive databases at various chemical compositions, including the VMC Large Magellanic Cloud pulsators and Galactic Cepheids with Gaia parallaxes. Comment: 14 pages, 11 figures, accepted for publication on MNRAS
    Keywords: Astrophysics - Solar And Stellar Astrophysics ; Astrophysics - Astrophysics Of Galaxies
    Source: Cornell University
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  • 10
    In: Nature Photonics, 2016
    Description: As a fundamental property of the electron, the spin plays a decisive role in the electronic structure of matter, from solids to molecules and atoms, for example, by causing magnetism. Yet, despite its importance, the spin dynamics of the electrons released during the interaction of atoms with strong ultrashort laser pulses has remained experimentally unexplored1, 2. Here, we report the experimental detection of electron spin polarization by the strong-field ionization of xenon atoms and support our results with theoretical analysis. We found up to 30% spin polarization changing its sign with electron energy. This work opens the new dimension of spin to strong-field physics. It paves the way to the production of sub-femtosecond spin-polarized electron pulses with applications ranging from probing the magnetic properties of matter at ultrafast timescales3 to testing chiral molecular systems with sub-femtosecond temporal and sub-ångström spatial resolutions.
    Keywords: Applied Sciences;
    ISSN: 1749-4885
    E-ISSN: 17494893
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