Nuclear Theory·nucl-th

Thursday·November 26, 2015

10 papers—7 primary·3 cross-listed

01
Further evidence for a dynamically generated secondary bow in $^{13}$ C+ $^{12}$ C rainbow scattering
S. Ohkubo · Y. Hirabayashi · A. A. Ogloblin
The existence of a secondary bow is confirmed for 13C+12C nuclear rainbow scattering in addition to the 16O+12C system. This is found by studying the experimental angular distribution of 13C+12C scattering at the incident 13C energy $E_{L}$ =250 MeV with an extended double folding (EDF) model that describes all the diagonal and off-diagonal coupling potentials derived from the microscopic wave functions for 12C using a density-dependent nucleon-nucleon force. The Airy minimum at \theta\approx $70$ ^\circ$, which is not reproduced by a conventional folding potential, is revealed to be a secondary bow generated dynamically by a coupling to the excited state 2+ (4.44 MeV) of 12C. The essential importance of the quadruple {\it Y2} term (reorientation term) of potential of the excited state 2+ of 12C for the emergence of a secondary bow is found. The mechanism of the secondary bow is intuitively explained by showing how the trajectories are refracted dynamically into the classically forbidden angular region beyond the rainbow angle of the primary rainbow.
nucl-thnucl-exPRC(2015)·13 citations
02
Nonrelativistic nucleon effective masses in nuclear matter: BHF versus RHF
A. Li🇨🇳 · J. N. Hu🇨🇳 · X. L. Shang🇨🇳 · W. Zuo🇨🇳
The density and isospin dependences of the nonrelativistic nucleon effective mass ( $m^{*}$ ) are studied, which is a measure of the nonlocality of the single particle (s.p.) potential. We decouple it further into the so called k-mass ( $m_{k}^{*}$ , i.e., the nonlocality in space) and E-mass ( $m_{E}^{*}$ , i.e., the nonlocality in time). Both masses are determined and compared from the latest versions of the nonrelativistic Brueckner-Hartree Fock (BHF) model and the relativistic Hartree-Fock (RHF) model. The latter are achieved based on the corresponding Schrödinger equivalent s.p. potential in a relativistic framework. We demonstrate the origins of different effective masses and discuss also their neutron-proton splitting in the asymmetric matter in different models. We find that the neutron-proton splittings of both the k-mass and the E-mass have the same asymmetry dependences at considered densities, namely $m_{k, n}^{*} > m_{k, p}^{*}$ and $m_{E, p}^{*} > m_{E, n}^{*}$ . However, the resulting splittings of nucleon effective masses could have different asymmetry dependences in the two models, because they could be dominated either by that of the k-mass (then we have $m_{n}^{*} > m_{p}^{*}$ in the BHF model) or by that of the E-mass (then we have $m_{p}^{*} > m_{n}^{*}$ in the RHF model).
nucl-thastro-ph.SRPRC(2016)·23 citations
03
Freeze-out conditions for production of resonances, hadronic molecules, and light nuclei
Sungtae Cho🇰🇷 · Taesoo Song🇩🇪 · Su Houng Lee🇰🇷
We investigate the freeze-out conditions of a particle in an expanding system of interacting particles in order to understand the productions of resonances, hadronic molecules and light nuclei in heavy ion collisions. Applying the kinetic freeze-out condition with explicit hydrodynamic calculations for the expanding hadronic phase to the daughter particles of $K^{*}$ mesons, we find that the larger suppression of the yield ratio of $K^{*} / K$ at LHC than at RHIC compared to the expectations from the statistical hadronization model based on chemical freeze-out parameters reflects the lower kinetic freeze-out temperature at LHC than at RHIC. Furthermore, we point out that for the light nuclei or hadronic molecules that are bound, the yields are affected by the freeze-out condition of the respective particle in the hadronic matter, which leads to the observation that the deuteron production yields are independent of the size of deuteron, and depend only on the number of ground state constituents.
nucl-thhep-exhep-phPRC(2018)·13 citations
04
Phonon-particle coupling effects in odd-even double mass differences of magic nuclei
E.E. Saperstein · M. Baldo · N.V. Gnezdilov · S.V. Tolokonnikov
A method is developed to consider the particle-phonon coupling (PC) effects in the problem of finding odd-even double mass differences (DMD) of magic nuclei within the approach starting from the free $N N$ -potential. Three PC effects are taken into account, the phonon induced interaction, the renormalization of the "ends" due to the $Z$ -factors and the change of the single-particle energies. We use the perturbation theory in $g_{L}^{2}$ , where $g_{L}$ is the vertex of the $L$ -phonon creation. PC corrections to single-particle energies are found self-consistently with an approximate account for the so-called tadpole diagram. Results for double-magic $^{132}$ Sn and $^{208}$ Pb nuclei show that the PC corrections make agreement with the experimental data better.
nucl-thJETP Lett.(2016)·5 citations
05
A Hydrodynamical Study on the Conversion of Hadronic Matter to Quark Matter: I. Shock-Induced Conversion
Shun Furusawa🇯🇵 · Takahiro Sanada🇯🇵 · Shoichi Yamada🇯🇵
We study transitions of hadronic matter (HM) to 3-flavor quark matter (3QM) locally, regarding the conversion processes as combustion and describing them hydrodynamically. Not only the jump condition on both sides of the conversion front but the structures inside the front are also considered by taking into account what happens during the conversion processes on the time scale of weak interactions as well as equations of state (EOS's) in the mixed phase. Under the assumption that HM is metastable with their free energies being larger than those of 3QM but smaller than those of 2-flavor quark matter (2QM), we consider the transition via 2QM triggered by a rapid density rise in a shock wave. Based on the results, we discuss which combustion modes (strong/weak detonation) may be realized. HM is described by an EOS based on the relativistic mean field theory and 2, 3QM's are approximated by the MIT bag model. We demonstrate for a wide range of bag constant and strong coupling constant in this combination of EOS's that the combustion may occur in the so-called endothermic regime, in which the Hugoniot curve for combustion runs below the one for the shock wave in P-V plane, and which has no terrestrial counter part. We find that strong detonation always occurs. Depending on the EOS of quark matter (QM) as well as the density of HM and the Mach number of the detonation front, deconfinement from HM to 2QM is either completed or not completed in the shock wave. In the latter case, which is more likely if the EOS of QM ensures that deconfinement occurs above the nuclear saturation density and that the maximum mass of cold quark stars is larger than two solar mass, the conversion continues further via the mixing state of HM and 3QM on the time scale of weak interactions.
nucl-thastro-ph.SRPRD(2016)·11 citations
06
Energy Dependence of exotic nuclei production cross sections by photofission reaction in GDR range
Debasis Bhowmick🇮🇳 · F. A. Khan🇮🇳 · Debasis Atta🇮🇳 · D. N. Basu🇮🇳 · Alok Chakrabarti🇮🇳
Photofission of actinides is studied in the region of nuclear excitation energies that covers the entire giant dipole resonance (GDR) region. The mass distributions of $^{238}$ U photofission fragments have been explored theoretically for eight different endpoint bremsstrahlung energies from 11.5 MeV to 67.7 MeV which correspond to average photon energy of 9.09 MeV to 15.90 MeV. Among these energies, the 29.1 MeV corresponds to the average photon energy of 13.7 $\pm$ 0.3 MeV which coincides with GDR peak for $^{238}$ U photofission. The integrated yield of $^{238}$ U photofission as well as charge distribution of photofission products are calculated and its role in producing nuclei and their neutron-richness is investigated.
nucl-thCan.J.Phys.(2016)·2 citations
07
A Hydrodynamical Study on the Conversion of Hadronic Matter to Quark Matter: II. Diffusion-Induced Conversion
Shun Furusawa🇯🇵 · Takahiro Sanada🇯🇵 · Shoichi Yamada🇯🇵
We study transitions of hadronic matter (HM) to 3-flavor quark matter (3QM), regarding the conversion processes as combustion and describing them hydrodynamically. Under the assumption that HM is metastable with their free energies being larger than those of 3QM but smaller than those of 2-flavor quark matter (2QM), we consider in this paper the conversion induced by diffusions of seed 3QM. This is a sequel to our previous paper, in which the shock-induced conversion was studied in the same frame work. We not only pay attention to the jump condition on both sides of the conversion front but the structures inside the front are also considered by taking into account what happens during the conversion processes on the time scale of weak interactions. We employ for HM the Shen's EOS, which is based on the relativistic mean field theory, and the bag model-based EOS for QM just as in the previous paper. We demonstrated in that paper that in this combination of EOS's the combustion will occur for a wide range of the bag constant and strong coupling constant in the so-called endothermic regime, in which the Hugoniot curve for combustion runs below the initial state. We find that weak deflagration nearly always occurs and that weak detonation is possible only when the diffusion constant is (unrealistically) large and the critical strange fraction is small. The velocities of the conversion front are ~ $1 0^{3} - 1 0^{7}$ cm/s depending on the initial temperature and density as well as the parameters in the QM EOS and become particularly small when the final state is in the mixed phase. Finally we study linear stability of the laminar weak-deflagration front and find that it is unstable in the exothermic regime (Darrius-Landau instability) but stable in the endothermic regime, which is quite contrary to the ordinary combustions.
nucl-thastro-ph.HEPRD(2016)·10 citations
08
Spectral properties of the Goldstino in supersymmetric Bose-Fermi mixtures
Jean-Paul Blaizot🇫🇷 · Yoshimasa Hidaka🇯🇵 · Daisuke Satow🇮🇹
We evaluate the spectral properties of the Goldstino in a Bose-Fermi mixture of cold atoms and molecules whose dynamics is governed by a supersymmetric hamiltonian. Model independent results are obtained from sum rules obeyed by the spectral function. We carry out specific calculations, at zero and finite temperature, using the Random Phase Approximation, and obtain in particular analytic expressions for the dispersion relation at small momentum. These explicit calculations allow us to pin down more precisely the features of the Goldstino that can be attributed to the supersymmetry alone, together with its spontaneous breaking. The anomalous large effect of the Fermi sea at moderate and large momenta is emphasized.
↳ cond-mat.quant-gashep-phnucl-thPRA(2015)·17 citations
09
Progenitor-dependent Explosion Dynamics in Self-consistent, Axisymmetric Simulations of Neutrino-driven Core-collapse Supernovae
Alexander Summa (1) · Florian Hanke (1,2) · Hans-Thomas Janka (1) · Tobias Melson (1,2) · Andreas Marek (3) · Bernhard Müller (4,5) ((1) MPI Astrophysics, Garching, (2) TUM, Garching, (3) MPCDF, Garching, (4) Queen's Univ. Belfast, (5) Monash Univ., Victoria)
We present self-consistent, axisymmetric core-collapse supernova simulations performed with the Prometheus-Vertex code for 18 pre-supernova models in the range of 11-28 solar masses, including progenitors recently investigated by other groups. All models develop explosions, but depending on the progenitor structure, they can be divided into two classes. With a steep density decline at the Si/Si-O interface, the arrival of this interface at the shock front leads to a sudden drop of the mass-accretion rate, triggering a rapid approach to explosion. With a more gradually decreasing accretion rate, it takes longer for the neutrino heating to overcome the accretion ram pressure and explosions set in later. Early explosions are facilitated by high mass-accretion rates after bounce and correspondingly high neutrino luminosities combined with a pronounced drop of the accretion rate and ram pressure at the Si/Si-O interface. Because of rapidly shrinking neutron star radii and receding shock fronts after the passage through their maxima, our models exhibit short advection time scales, which favor the efficient growth of the standing accretion-shock instability. The latter plays a supportive role at least for the initiation of the re-expansion of the stalled shock before runaway. Taking into account the effects of turbulent pressure in the gain layer, we derive a generalized condition for the critical neutrino luminosity that captures the explosion behavior of all models very well. We validate the robustness of our findings by testing the influence of stochasticity, numerical resolution, and approximations in some aspects of the microphysics.
↳ astro-ph.SRastro-ph.HEnucl-thApJ(2016)·128 citations
10
Consistency check of charged hadron multiplicities and fragmentation functions in SIDIS
Dong-Jing Yang🇹🇼 · Fu-Jiun Jiang🇹🇼 · Wen-Chen Chang🇹🇼 · Chung-Wen Kao🇹🇼 · Seung-il Nam🇰🇷
We derived the conditions on certain combinations of integrals of the fragmentation functions of pion using HERMES data of the sum for the charged pion multiplicities from semi-inclusive deep-inelastic scattering (SIDIS) off the deuteron target. In our derivation the nucleon parton distribution functions (PDFs) are assumed to be isospin SU(2) symmetric. Similar conditions have also been obtained for the fragmentation functions (FFs) of kaon by the sum of charged kaon multiplicities as well. We have chosen several FFs to study the impact of those conditions we have derived. Among those FFs, only that produced in the nonlocal chiral-quark model (NL $χ$ QM) constantly satisfy the conditions. Furthermore, the ratios of the strange PDFs $S (x)$ and the nonstrange PDFs $Q (x, Q^{2})$ extracted from the charged pion and kaon multiplicities differ from each other significantly. Finally, we demonstrate that the HERMES pion multiplicity data is unlikely to be compatible with the two widely-used PDFs, namely CTEQ6M and NNPDF3.0.
↳ hep-phhep-exnucl-thPLB(2016)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE