Nuclear Theory·nucl-th

Wednesday·February 3, 2016

10 papers—5 primary·5 cross-listed

01
Neutrino Interactions with Nucleons and Nuclei: Importance for Long-Baseline Experiments
Ulrich Mosel🇩🇪
This article reviews our present knowledge of neutrino interactions with nucleons and discusses the interactions with nuclei, the target material of all presently running and planned long-baseline experiments. I emphasize descriptions of semi-inclusive reactions and full descriptions of the final state; the latter are needed to reconstruct the incoming neutrino energy from final-state observations. I then discuss Monte Carlo generator and more advanced transport theoretical approaches in connection with experimental results on various reaction mechanisms. Finally, I describe the effects of uncertainties in the reconstruction of the incoming neutrino energy on oscillation parameters. The review argues that the precision era of neutrino physics also needs precision-era generators.
nucl-thhep-exhep-phnucl-exAnn.Rev.Nucl.Part.Sci.(2016)·128 citations
02
Causal hydrodynamic fluctuation in Bjorken expansion
Kenichi Nagai · Ryuichi Kurita · Koichi Murase · Tetsufumi Hirano
We investigate effects of causal hydrodynamic fluctuations in the longitudinally expanding quark gluon plasma on final entropy distributions in high-energy nuclear collisions.
nucl-thNPA(2016)·16 citations
03
Nonclassical Particle Transport in 1-D Random Periodic Media
Richard Vasques · Kai Krycki · Rachel N. Slaybaugh
We investigate the accuracy of the recently proposed nonclassical transport equation. This equation contains an extra independent variable compared to the classical transport equation (the path-length $s$ ), and models particle transport taking place in homogenized random media in which a particle's distance-to-collision is not exponentially distributed. To solve the nonclassical equation one needs to know the $s$ -dependent ensemble-averaged total cross section, $Σ_{t} (μ, s)$ , or its corresponding path-length distribution function, $p (μ, s)$ . We consider a 1-D spatially periodic system consisting of alternating solid and void layers, randomly placed in the $x$ -axis. We obtain an analytical expression for $p (μ, s)$ and use this result to compute the corresponding $Σ_{t} (μ, s)$ . Then, we proceed to numerically solve the nonclassical equation for different test problems in rod geometry; that is, particles can move only in the directions $μ = \pm 1$ . To assess the accuracy of these solutions, we produce "benchmark" results obtained by (i) generating a large number of physical realizations of the system, (ii) numerically solving the transport equation in each realization, and (iii) ensemble-averaging the solutions over all physical realizations. We show that the numerical results validate the nonclassical model; the solutions obtained with the nonclassical equation accurately estimate the ensemble-averaged scalar flux in this 1-D random periodic system, greatly outperforming the widely-used atomic mix model in most problems.
nucl-thNucl.Sci.Eng.(2017)·3 citations
04
Bimodality emerges from transport model calculations of heavy ion collisions at intermediate energy
S. Mallik · S. Das Gupta · G. Chaudhuri
This work is a continuation of our effort [Phys. Rev. C 91, 034616 (2015)] to examine if signatures of a phase transition can be extracted from transport model calculations of heavy ion collisions at intermediate energy. A signature of first order phase transition is the appearance of a bimodal distribution in $P_{m} (k)$ in finite systems. Here P_m(k) is the probability that the maximum of the multiplicity distribution occurs at mass number k. Using a well-known model for event generation (BUU plus fluctuation), we do two cases of central collision: mass 40 on mass 40 and mass 120 on mass 120. Bimodality is seen in both the cases. The results are quite similar to those obtained in statistical model calculations. An intriguing feature is seen. We observe that at the energy where bimodality occurs. other phase transition like signatures appear. There are breaks in certain first order derivatives. We then examine if such breaks appear in standard Botzmann-Uehling-Uhlenbeck (BUU) calculations without fluctuations. They do. The implication is interesting. If first order phase transition occurs, it may be possible to recognise that from ordinary BUU calculation. Probably the reason this was not seen already is because this aspect was not investigated before.
nucl-thnucl-exPRC(2016)·11 citations
05
The phonon-coupling model for Skyrme forces
N. Lyutorovich · V. Tselyaev · J. Speth · S. Krewald · P.-G. Reinhard
A short review on the self-consistent RPA based on a energy-density functional of the Skyrme type is given. We also present an extension of the RPA where the coupling of phonons to the single-particle states is considered. Within this approach we present numerical results which are compared with data. The self-consistent approach is compared with the Landau-Migdal theory. Here we derive from the self-consistent $p h$ interaction, the Landau-Migdal parameters as well as their density dependence. In the Appendix a new derivation of the reduced matrix elements of the $p h$ interaction is presented.
nucl-thPhys.Atom.Nucl.(2016)·16 citations
06
CPT, CP, and C transformations of fermions, and their consequences, in theories with B-L violation
Susan Gardner🇺🇸 · Xinshuai Yan🇺🇸
We consider the transformation properties of fermions under the discrete symmetries CPT, CP, and C in the presence of B-L violation. We thus generalize the analysis of the known properties of Majorana neutrinos, probed via neutrinoless double beta decay, to include the case of Dirac fermions with B-L violation, which can be probed via neutron-antineutron oscillations. We show that the resulting CPT phase has implications for the interplay of neutron-antineutron oscillations with external fields and sources and consider the differences in the Majorana dynamics of neutrinos and neutrons in the context of theories with self-conjugate isospin I=0 and I=1/2 fields.
↳ hep-phnucl-thPRD(2016)·25 citations
07
The radius of the rho meson determined from its decay constant
A.F. Krutov🇷🇺 · R.G. Polezhaev🇷🇺 · V.E. Troitsky🇷🇺
We present a unified model describing electroweak properties of the pi and rho mesons. Using a general method of relativistic parametrization of matrix elements of local operators, adjusted for the nondiagonal in total angular momentum case, we calculate the rho-meson lepton-decay constant f_rho using the same parameters of free constituent quarks that have ensured exclusively good results for the pi meson previously. The only free parameter, characterizing quark interactions, which include additional spin-spin contribution and hence differ from the $π$ -meson case, is fixed by matching the decay constant to its experimental value. The mean square charge radius is calculated, <r^2_rho>=(0.56+-0.04) fm^2. This result verifies, for the rho-meson case, the conjecture of equality between electromagnetic and strong radii of hadrons tested previously for proton, pi and K mesons.
↳ hep-phnucl-thPRD(2016)·43 citations
08
Interplay of quark and meson degrees of freedom in near-threshold states: A practical parametrisation for line shapes
F.-K. Guo🇨🇳 · C. Hanhart🇩🇪 · Yu.S. Kalashnikova🇷🇺 · P. Matuschek🇩🇪 · R.V. Mizuk🇷🇺 · A.V. Nefediev🇷🇺 · Q. Wang🇩🇪 · J.-L. Wynen🇩🇪
We propose a practical parametrisation for the line shapes of near-threshold states compatible with all requirements of unitarity and analyticity. The coupled-channel system underlying the proposed parametrisation includes bare poles and an arbitrary number of elastic and inelastic channels treated fully nonperturbatively. The resulting formulae are general enough to be used for a simultaneous analysis of the data in all available production and decay channels of the (system of) state(s) under consideration for a quite wide class of reactions. As an example, we fit the experimental data currently available for several decay channels for the charged $Z_{b}^{(')}$ states in the spectrum of bottomonia and find a good overall description of the data. We find the present data to be consistent with the $Z_{b} (10610)$ as a virtual state and with the $Z_{b} (10650)$ as a resonance, both residing very close to the $B B ˉ^{*}$ and $B^{*} B ˉ^{*}$ threshold, respectively.
↳ hep-phhep-exhep-latnucl-thPRD(2016)·93 citations
09
Theoretical Developments in QCD Jet Energy Loss
Yacine Mehtar-Tani🇺🇸
We review the recent developments in the theory of jet-quenching. First, we analyze the coherent vacuum cascade and incoherent medium-induced cascade separately. We then discuss the interplay between the two kinds of cascade and the resulting partial decoherence of the inner jet structure. Finally, we report on recent calculations of higher-order corrections. In particular, the dominant radiative corrections to jet observables that yield the renormalization of the jet-quenching parameter are addressed.
↳ hep-phnucl-thNPA(2016)·5 citations
10
Measuring the neutron star equation of state using X-ray timing
Anna L. Watts · Nils Andersson · Deepto Chakrabarty · Marco Feroci · Kai Hebeler · Gianluca Israel · Frederick K. Lamb · M. Coleman Miller · Sharon Morsink · Feryal Özel · Alessandro Patruno · Juri Poutanen and 6 other authors
One of the primary science goals of the next generation of hard X-ray timing instruments is to determine the equation of state of the matter at supranuclear densities inside neutron stars, by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modelling. The flux we observe from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, giving rise to a pulsation. Information about mass and radius is encoded into the pulse profile via relativistic effects, and tight constraints on mass and radius can be obtained. The second technique involves characterising the spin distribution of accreting neutron stars. The most rapidly rotating stars provide a very clean constraint, since the mass-shedding limit is a function of mass and radius. However the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasi-periodic oscillations in X-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state. We illustrate how these complementary X-ray timing techniques can be used to constrain the dense matter equation of state, and discuss the results that might be expected from a 10m $^{2}$ instrument. We also discuss how the results from such a facility would compare to other astronomical investigations of neutron star properties. [Modified for arXiv]
↳ astro-ph.HEastro-ph.SRnucl-thRMP(2016)·393 citations

Affiliations

first authorsco-authorsvia INSPIRE