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Nuclear Theory·nucl-th

Friday·March 27, 2015

7 papers—2 primary·5 cross-listed

All7Primary2Cross-lists5
  1. 01

    [Submitted on 26 Mar 2015]

    On the Wong cross section and fusion oscillations

    N. Rowley · K. Hagino

    We re-examine the well-known Wong formula for heavy-ion fusion cross sections. Although this celebrated formula yields almost exact results for single-channel calculations for relatively heavy systems such as O+Sm, it tends to overestimate the cross section for light systems such as C+C. We generalise the formula to take account of the energy dependence of the barrier parameters and show that the energy-dependent version gives results practically indistinguishable from a full quantal calculation. We then examine the deviations arising from the discrete nature of the intervening angular momenta, whose effect can lead to an oscillatory contribution to the excitation function. We recall some compact, analytic expressions for these oscillations, and highlight the important physical parameters that give rise to them. Oscillations in symmetric systems are discussed, as are systems where the target and projectile identities can be exchanged via a strong transfer channel.

    Comments:
    14 pages, 14 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1503.07608 [pdf]
    0 citations
  2. 02

    [Submitted on 26 Mar 2015]

    Fusion Probability in Dinuclear System

    Juhee Hong

    Fusion can be described by the time evolution of a dinuclear system with two degrees of freedom, the relative motion and transfer of nucleons. In the presence of the coupling between two collective modes, we solve the Fokker-Planck equation in a locally harmonic approximation. The potential of a dinuclear system has the quasifission barrier and the inner fusion barrier, and the escape rates can be calculated by the Kramers' model. To estimate the fusion probability, we calculate the quasifission rate and the fusion rate. We investigate the coupling effects on the fusion probability and the cross section of evaporation residue.

    Comments:
    18 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1503.07729 [pdf]
    0 citations
  3. 03

    [Submitted on 25 Mar 2015] (cross-list from astro-ph.SR)

    A two-parameter criterion for classifying the explodability of massive stars by the neutrino-driven mechanism

    T. Ertl (1,2) · H.-Th. Janka (1) · S.E. Woosley (3) · T. Sukhbold (3) · M. Ugliano (4) ((1) MPI Astrophysics, Garching, (2) Physik Dept., TUM, Garching, (3) UC Santa Cruz, (4) TU Darmstadt)

    Thus far, judging the fate of a massive star (either a neutron star (NS) or a black hole) solely by its structure prior to core collapse has been ambiguous. Our work and previous attempts find a non-monotonic variation of successful and failed supernovae with zero-age main-sequence mass, for which no single structural parameter can serve as a good predictive measure. However, we identify two parameters computed from the pre-collapse structure of the progenitor, which in combination allow for a clear separation of exploding and non-exploding cases with only few exceptions (~1-2.5%) in our set of 621 investigated stellar models. One parameter is M4, defining the normalized enclosed mass for a dimensionless entropy per nucleon of s=4, and the other is mu4 = d(m/M_sun)/d(r/1000 km) at s=4, being the normalized mass-derivative at this location. The two parameters mu4 and M4*mu4 can be directly linked to the mass-infall rate, Mdot, of the collapsing star and the electron-type neutrino luminosity of the accreting proto-NS, L_nue ~ M_ns*Mdot, which play a crucial role in the "critical luminosity" concept for the theoretical description of neutrino-driven explosions as runaway phenomenon of the stalled accretion shock. All models were evolved employing the approach of Ugliano et al. for simulating neutrino-driven explosions in spherical symmetry. The neutrino emission of the accretion layer is approximated by a gray transport solver, while the uncertain neutrino emission of the 1.1 M_sun proto-NS core is parametrized by an analytic model. The free parameters connected to the core-boundary prescription are calibrated to reproduce the observables of Supernova 1987A for five different progenitor models.

    Comments:
    23 pages, 12 figures; accepted by ApJ; revised version considerably enlarged (Fig. 7 and Sect.3.6 added)
    Subjects:
    Solar and Stellar Astrophysics (astro-ph.SR); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    1503.07522 [pdf]
    ApJ(2016)·388 citations
  4. 04

    [Submitted on 26 Mar 2015] (cross-list from hep-ph)

    Sensitivity of Pion versus Parton-Jet Nuclear Modification Factors to the Path-Length Dependence of Jet-Energy Loss at RHIC and LHC

    Barbara Betz🇩🇪 · Miklos Gyulassy🇺🇸

    We compare the jet-path length and beam-energy dependence of the pion nuclear modification factor and a parton-jet nuclear modification factor at RHIC and LHC. We contrast predictions based on a linear pQCD and a highly non-linear hybrid-AdS holographic model of jet-energy loss. We find that both models require a reduction of the jet-medium coupling from RHIC to LHC to account for the measured pion nuclear modification factor. In case of the parton-jet nuclear modification factor, however, which serves as a lower bound for the LO jet nuclear modification factor of reconstructed jets, the extracted data can be characterized without a reduced jet-medium coupling at LHC energies. We conclude that while reconstructed jets are sensitive to both quarks and gluons and thus provide more information than the pion nuclear modification factor, their information regarding the jet-medium coupling is limited due to the superimposition with NLO and medium effects. Hence, a detailed description of the underlying physics requires both the leading hadron and the reconstructed jet nuclear modification factor. Unfortunately, the results for both the pion and the parton-jet nuclear modification factor are insensitive to the jet-path dependence of the models considered.

    Comments:
    5 pages, 1 figure
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    1503.07671 [pdf]
    Chin.Phys.Lett.(2015)·6 citations
  5. 05

    [Submitted on 26 Mar 2015] (cross-list from hep-ph)

    Physics Opportunities with Meson Beams

    William J. Briscoe (GW)🇺🇸 · Michael Döring (GW)🇺🇸 · Helmut Haberzettl (GW)🇺🇸 · D. Mark Manley (KSU)🇺🇸 · Megumi Naruki (Kyoto Univ.)🇯🇵 · Igor I. Strakovsky (GW)🇺🇸 · Eric S. Swanson (Univ. of Pittsburgh)🇺🇸

    Over the past two decades, meson photo- and electro-production data of unprecedented quality and quantity have been measured at electromagnetic facilities worldwide. By contrast, the meson-beam data for the same hadronic final states are mostly outdated and largely of poor quality, or even nonexistent, and thus provide inadequate input to help interpret, analyze, and exploit the full potential of the new electromagnetic data. To reap the full benefit of the high-precision electromagnetic data, new high-statistics data from measurements with meson beams, with good angle and energy coverage for a wide range of reactions, are critically needed to advance our knowledge in baryon and meson spectroscopy and other related areas of hadron physics. To address this situation, a state of-the-art meson-beam facility needs to be constructed. The present paper summarizes unresolved issues in hadron physics and outlines the vast opportunities and advances that only become possible with such a facility.

    Comments:
    46 pages, 10 figures, 4 tables
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1503.07763 [pdf]
    EPJA(2015)·55 citations
  6. 06

    [Submitted on 26 Mar 2015] (cross-list from hep-ph)

    production and suppression in high energy proton-nucleus collisions

    Yan-Qing Ma🇺🇸 · Raju Venugopalan🇺🇸 · Hong-Fei Zhang🇨🇳

    We apply a Color Glass Condensate+Non-Relativistic QCD (CGC+NRQCD) framework to compute production in deuteron-nucleus collisions at RHIC and proton-nucleus collisions at the LHC. Our results match smoothly at high to a next-to-leading order perturbative QCD + NRQCD computation. Excellent agreement is obtained for spectra at RHIC and LHC for central and forward rapidities, as well as for the normalized ratio of these results to spectra in proton-proton collisions. In particular, we observe that the data is strongly bounded by our computations of the same for each of the individual NRQCD channels; this result provides strong evidence that our description is robust against uncertainties in initial conditions and hadronization mechanisms.

    Comments:
    7 pages, 4 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1503.07772 [pdf]
    PRD(2015)·101 citations
  7. 07

    [Submitted on 26 Mar 2015] (cross-list from astro-ph.HE)

    Reconciling Nuclear and Astrophysical Constraints

    V. Dexheimer🇺🇸 · R. Negreiros🇧🇷 · S. Schramm🇩🇪

    In view of new constraints put forth by recent observations and measurements in the realm of astrophysics and nuclear physics, we update the non-linear realization of the sigma model as to reflect such constraints. By doing this, we obtain new equations of state that may be used to describe neutron stars. Such equations of state are obtained by investigating different ways by which the vector mesons self-interact. Furthermore, we also investigate the role played by the delta mesons in the model. As a result, we are able to develop equations of state that are in better agreement with data, such as nuclear compressibility and slope of the symmetry energy at saturation, star masses, radii, and cooling profiles.

    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
    arXiv:
    1503.07785 [pdf]
    PRC(2015)·44 citations

Affiliations

first authorsco-authorsvia INSPIRE