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Nuclear Theory·nucl-th

Wednesday·August 5, 2015

9 papers—3 primary·6 cross-listed

All9Primary3Cross-lists6
  1. 04

    [Submitted on 16 Jul 2015] (cross-list from astro-ph.CO)

    Dark Matter Velocity Spectroscopy

    Eric G. Speckhard🇺🇸 · Kenny C. Y. Ng🇺🇸 · John F. Beacom🇺🇸 · Ranjan Laha🇺🇸

    Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will reach the required 0.1% level. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

    Comments:
    9 pages, 6 figures, supplemental materials and references added, minor numerical error fixed, conclusions unchanged
    Subjects:
    Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1507.04744 [pdf]
    PRL(2016)·44 citations
  2. 05

    [Submitted on 4 Aug 2015] (cross-list from nucl-ex)

    Toward precision mass measurements of neutron-rich nuclei relevant to -process nucleosynthesis

    B. H. Sun🇨🇳 · Yu.A. Litvinov🇨🇳 · I. Tanihata🇨🇳 · Y. H. Zhang🇨🇳

    The open question of where, when, and how the heavy elements beyond iron enrich our Universe has triggered a new era in nuclear physics studies.\ Of all the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is a key quantity for revealing the origin of heavy elements beyond iron.\ Although the precise determination of this property is a great challenge, enormous progress has been made in recent decades, and it has contributed significantly to both nuclear structure and astrophysical nucleosynthesis studies.\ In this review, we first survey our present knowledge of the nuclear mass surface, emphasizing the importance of nuclear mass precision in -process calculations.\ We then discuss recent progress in various methods of nuclear mass measurement with a few selected examples.\ For each method, we focus on recent breakthroughs and discuss possible ways of improving the weighing of -process nuclides.

    Comments:
    10 figures, review articles in Frontiers of Physics
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1508.00695 [pdf]
    Front.Phys.(Beijing)(2015)·20 citations
  3. 06

    [Submitted on 4 Aug 2015] (cross-list from nucl-ex)

    Breaking of axial symmetry in excited heavy nuclei as identified in Giant Dipole Resonance data

    Eckart Grosse · Arnd R. Junghans · Ralph Massarczyk

    A recent theoretical prediction of a breaking of axial symmetry in quasi all heavy nuclei is confronted to a new critical analysis of photon strength functions of nuclei in the valley of stability. For the photon strength in the isovector giant dipole resonance (IVGDR) regime a parameterization of GDR shapes by the sum of three Lorentzians (TLO) is extrapolated to energies below and above the IVGDR. The impact of non-GDR modes adding to the low energy slope of photon strength is discussed including recent data on photon scattering and other radiative processes. These are shown to be concentrated in energy regions where various model calculations predict intermediate collective strength; thus they are obviously separate from the IVGDR tail. The triple Lorentzian (TLO) ansatz for giant dipole resonances is normalized in accordance to the dipole sum rule. The nuclear droplet model with surface dissipation accounts well for positions and widths without local, nuclide specific, parameters. Very few and only global parameters are needed when a breaking of axial symmetry already in the valley of stability is admitted and hence a reliable prediction for electric dipole strength functions also outside of it is expected.

    Comments:
    21 pages, 21 figures, PACS: 26.50.+x, 25.20.Dc,27.60.+j Accepted by Europ. Phys. Journal A
    Subjects:
    Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1508.00740 [pdf]
    EPJA(2017)·16 citations
  4. 07

    [Submitted on 4 Aug 2015] (cross-list from hep-ph)

    Goldstone's Theorem on a Light-Like Plane

    Silas R. Beane🇺🇸

    I review various aspects of chiral symmetry and its spontaneous breaking on null planes, including the interesting manner in which Goldstone's theorem is realized and the constraints that chiral symmetry imposes on the null-plane Hamiltonians. Specializing to QCD with N massless flavors, I show that there is an interesting limit in which the chiral constraints on the null-plane Hamiltonians can be solved to give the spin-flavor algebra SU(2N), recovering a result originally found by Weinberg using different methods.

    Comments:
    6 pages, written version of talk presented at the Light Cone 2014 Conference held at North Carolina State Univ. May 26-30
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    1508.00800 [pdf]
    Few Body Syst.(2015)·1 citation
  5. 08

    [Submitted on 4 Aug 2015] (cross-list from hep-ph)

    Predictions for Boson-Jet Observables and Fragmentation Function Ratios from a Hybrid Strong/Weak Coupling Model for Jet Quenching

    Jorge Casalderrey-Solana🇪🇸 · Doga Can Gulhan🇺🇸 · José Guilherme Milhano🇨🇭 · Daniel Pablos🇪🇸 · Krishna Rajagopal🇺🇸

    We have previously introduced a hybrid strong/weak coupling model for jet quenching in heavy ion collisions that describes the production and fragmentation of jets at weak coupling, using PYTHIA, and describes the rate at which each parton in the jet shower loses energy as it propagates through the strongly coupled plasma, dE/dx, using an expression computed holographically at strong coupling. The model has a single free parameter that we fit to a single experimental measurement. We then confront our model with experimental data on many other jet observables, focusing here on boson-jet observables, finding that it provides a good description of present jet data. Next, we provide the predictions of our hybrid model for many measurements to come, including those for inclusive jet, dijet, photon-jet and Z-jet observables in heavy ion collisions with energy ATeV coming soon at the LHC. As the statistical uncertainties on near-future measurements of photon-jet observables are expected to be much smaller than those in present data, with about an order of magnitude more photon-jet events expected, predictions for these observables are particularly important. We find that most of our pre- and post-dictions do not depend sensitively on the form we choose for the rate of energy loss dE/dx of the partons in the shower. This gives our predictions considerable robustness. To better discriminate between possible forms for the rate of energy loss, though, we must turn to intrajet observables. Here, we focus on ratios of fragmentation functions. We close with a suggestion for a particular ratio, between the fragmentation functions of inclusive and associated jets with the same kinematics in the same collisions, which is particularly sensitive to the x- and E-dependence of dE/dx, and hence may be used to learn which mechanism of parton energy loss best describes the quenching of jets.

    Comments:
    59 pages, 24 figures. v2: minor changes, typos corrected and references added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1508.00815 [pdf]
    JHEP(2016)·125 citations
  6. 09

    [Submitted on 4 Aug 2015] (cross-list from hep-lat)

    Two-Nucleon Higher Partial-Wave Scattering from Lattice QCD

    Evan Berkowitz🇺🇸 · Thorsten Kurth🇺🇸 · Amy Nicholson🇺🇸 · Balint Joo🇺🇸 · Enrico Rinaldi🇺🇸 · Mark Strother🇺🇸 · Pavlos M. Vranas🇺🇸 · Andre Walker-Loud🇺🇸

    We present a determination of nucleon-nucleon scattering phase shifts for l >= 0. The S, P, D and F phase shifts for both the spin-triplet and spin-singlet channels are computed with lattice Quantum ChromoDynamics. For l > 0, this is the first lattice QCD calculation using the Luscher finite-volume formalism. This required the design and implementation of novel lattice methods involving displaced sources and momentum-space cubic sinks. To demonstrate the utility of our approach, the calculations were performed in the SU(3)-flavor limit where the light quark masses have been tuned to the physical strange quark mass, corresponding to m_pi = m_K ~ 800 MeV. In this work, we have assumed that only the lowest partial waves contribute to each channel, ignoring the unphysical partial wave mixing that arises within the finite-volume formalism. This assumption is only valid for sufficiently low energies; we present evidence that it holds for our study using two different channels. Two spatial volumes of V ~ (3.5 fm)^3 and V ~ (4.6 fm)^3 were used. The finite-volume spectrum is extracted from the exponential falloff of the correlation functions. Said spectrum is mapped onto the infinite volume phase shifts using the generalization of the Luscher formalism for two-nucleon systems.

    Comments:
    Added plots and expanded text to clarify discussions, particularly for extraction of the energies. Published version
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1508.00886 [pdf]
    PLB(2017)·135 citations

Affiliations

first authorsco-authorsvia INSPIRE