Nuclear Theory·nucl-th

Monday·December 24, 2018

12 papers—5 primary·7 cross-listed

01
The effect of the neutron and proton numbers ratio in colliding nuclei at formation of the evaporation residues in the $^{34}$ S+ $^{208}$ Pb and $^{36}$ S+ $^{206}$ Pb reactions
A.K. Nasirov (1,2) · B.M. Kayumov (2) · G. Mandaglio (3,4) · G. Giardina (5) · K. Kim (6) · Y. Kim (6)((1) BLTP, Joint Institute for Nuclear Research, Dubna, Russia, (2) Institute of Nuclear Physics, Ulugbek, Tashkent, Uzbekistan,(3) Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, University of Messina, Messina, Italy, (4) INFN Sezione di Catania, Catania, Italy, (5) Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, University of Messina, Messina, Italy, (6) Rare Isotope Science Project, Institute for Basic Science, Daejeon, Republic of Korea)
The difference between observed cross sections of the evaporation residues (ER) of the $^{34}$ S+ $^{208}$ Pb and $^{36}$ S+ $^{206}$ Pb reactions formed in the 2n and 3n channels has been explained by two reasons related with the entrance channel characteristics of these reactions. The first reason is that the capture cross section of the latter reaction is larger than the one of the $^{34}$ S+ $^{208}$ Pb reaction since the nucleus-nucleus potential is more attractive in the $^{36}$ S+ $^{206}$ Pb reaction due to two more neutrons in isotope $^{36}$ S. The second reason is the difference in the heights of the intrinsic fusion barrier $B_{fus}^{*}$ appearing on the fusion trajectory by nucleon transfer between nuclei of the DNS formed after the capture. The value of $B_{fus}^{*}$ calculated for the $^{34}$ S+ $^{208}$ Pb reaction is higher than the one obtained for the $^{36}$ S+ $^{206}$ Pb reaction. This fact has been caused by the difference between the $N / Z$ -ratios in the light fragments of the DNS formed during the capture in these reactions. The $N / Z$ -ratio has been found by solution of the transport master equations for the proton and neutron distributions between fragments of the DNS formed at capture with the different initial neutron numbers $N = 18$ and $N = 20$ for the reactions with the $^{34}$ S and $^{36}$ S, respectively.
nucl-thnucl-exEPJA(2019)·18 citations
02
Possible non-prompt photons in $pp$ collisions and their effects in $AA$ analyses
Akihiko Monnai🇯🇵
Direct photons are a powerful tool for elucidating the properties of the hot QCD matter in heavy-ion collisions. They are conventionally estimated by assuming prompt photon contributions in proton-proton collisions and thermal and prompt photon contributions in heavy-ion collisions. On the other hand, there could also be other sources of photons such as pre-equilibrium photons. I investigate prompt, pre-equilibrium and thermal photons and their effects on the direct photon $p_{T}$ spectra at CERN Large Hadron Collider energies.
nucl-thhep-phnucl-exPoS(2019)·8 citations
03
Structure of resonances in a simple quantum-mechanical model
Peter C. Bruns
We study the structure of resonances derived from the solution of an exactly solvable Lippmann-Schwinger equation. Within this framework, we discuss the concept of "resonance form factors", and the description of the resonant amplitudes in terms of effective energy-dependent potentials.
nucl-th1 citation
04
Neutron transfer reactions in halo effective field theory
M. Schmidt · L. Platter · H.-W. Hammer
Direct reaction experiments provide a powerful tool to probe the structure of neutron-rich nuclei like beryllium-11. We use halo effective field theory to calculate the cross section of the deuteron-induced neutron transfer reaction $^{10} Be (d, p)^{11} Be$ . The effective theory contains dynamical fields for the beryllium-10 core, the neutron, and the proton. In contrast, the deuteron and the beryllium-11 halo nucleus are generated dynamically from contact interactions using experimental and ab initio input. The reaction amplitude is constructed up to next-to-leading order in an expansion in the ratio of the length scales characterizing the core and the halo. The Coulomb repulsion between core and proton is treated perturbatively. Finally, we compare our results to cross-section data and other calculations.
nucl-thPRC(2019)·7 citations
05
Energy dependence of fission-fragment neutron multiplicity in $^{235} U (n, f)$
M. Albertsson🇸🇪
A consistent framework for treating the energy dependence of fission-fragment neutron multiplicities is presented. The shape evolution of the compound nucleus towards scission is treated in the strong damping limit using the Metropolis walk method. The available excitation energy at scission is then divided statistically between the two fragments using microscopic level densities. Deformation energies, which contribute to the excitation energy when the fragments relax to their ground-state shapes, are also computed. From the total fragment excitation energies, the number of emitted neutrons is obtained and illustrated for neutron-induced fission of $^{235} U$ .
nucl-thActa Phys.Polon.Supp.(2019)·1 citation
06
Chiral crossover in QCD at zero and non-zero chemical potentials
A. Bazavov🇺🇸 · H.-T. Ding🇨🇳 · P. Hegde🇮🇳 · O. Kaczmarek🇨🇳 · F. Karsch🇩🇪 · N. Karthik🇺🇸 · E. Laermann🇩🇪 · Anirban Lahiri🇩🇪 · R. Larsen🇺🇸 · S.-T. Li🇨🇳 · Swagato Mukherjee🇺🇸 · H. Ohno🇯🇵 and 5 other authors
We present results for pseudo-critical temperatures of QCD chiral crossovers at zero and non-zero values of baryon ( $B$ ), strangeness ( $S$ ), electric charge ( $Q$ ), and isospin ( $I$ ) chemical potentials $μ_{X = B, Q, S, I}$ . The results were obtained using lattice QCD calculations carried out with two degenerate up and down dynamical quarks and a dynamical strange quark, with quark masses corresponding to physical values of pion and kaon masses in the continuum limit. By parameterizing pseudo-critical temperatures as $T_{c} (μ_{X}) = T_{c} (0) [1 - κ_{2}^{X} (μ_{X} / T_{c} (0))^{2} - κ_{4}^{X} (μ_{X} / T_{c} (0))^{4}]$ , we determined $κ_{2}^{X}$ and $κ_{4}^{X}$ from Taylor expansions of chiral observables in $μ_{X}$ . We obtained a precise result for $T_{c} (0) = (156.5 \pm 1.5) MeV$ . For analogous thermal conditions at the chemical freeze-out of relativistic heavy-ion collisions, i.e., $μ_{S} (T, μ_{B})$ and $μ_{Q} (T, μ_{B})$ fixed from strangeness-neutrality and isospin-imbalance, we found $κ_{2}^{B} = 0.012 (4)$ and $κ_{4}^{B} = 0.000 (4)$ . For $μ_{B} ≲ 300 MeV$ , the chemical freeze-out takes place in the vicinity of the QCD phase boundary, which coincides with the lines of constant energy density of $0.42 (6) GeV/fm^{3}$ and constant entropy density of $3.7 (5) fm^{- 3}$ .
↳ hep-lathep-phhep-thnucl-ex+1PLB(2019)·878 citations
07
First observation of unbound $^{11}$ O, the mirror of the halo nucleus $^{11}$ Li
T.B. Webb · S.M. Wang · K.W. Brown · R.J. Charity · J.M. Elson · J. Barney · G. Cerizza · Z. Chajecki · J. Estee · D.E.M. Hoff · S.A. Kuvin · W.G. Lynch and 14 other authors
The structure of the extremely proton-rich nucleus $_{8}^{11}$ O $_{3}$ , the mirror of the two-neutron halo nucleus $_{3}^{11}$ Li $_{8}$ , has been studied experimentally for the first time. Following two-neutron knockout reactions with a $^{13}$ O beam, the $^{11}$ O decay products were detected after two-proton emission and used to construct an invariant-mass spectrum. A broad peak of width $\sim$ 3\,MeV was observed. Within the Gamow coupled-channel approach, it was concluded that this peak is a multiplet with contributions from the four-lowest $^{11}$ O resonant states: $J^{π}$ =3/2 $_{1}^{-}$ , 3/2 $_{2}^{-}$ , 5/2 $_{1}^{+}$ , and 5/2 $_{2}^{+}$ . The widths and configurations of these states show strong, non-monotonic dependencies on the depth of the $p$ - $^{9}$ C potential. This unusual behavior is due to the presence of a broad threshold resonant state in $^{10}$ N, which is an analog of the virtual state in $^{10}$ Li in the presence of the Coulomb potential. After optimizing the model to the data, only a moderate isospin asymmetry between ground states of $^{11}$ O and $^{11}$ Li was found.
↳ nucl-exnucl-thPRL(2019)·45 citations
08
Fine structure of giant resonances: What can be learned
Peter von Neumann-Cosel🇩🇪
Fine structure of giant resonances (GR) has been established in recent years as a global phenomenon across the nuclear chart and for different types of resonances. A quantitative description of the fine structure in terms of characteristic scales derived by wavelet techniques is discussed. By comparison with microscpic calculations of GR strength distributions one can extract information on the role of different decay mechanisms contributing to the width of GRs. The observed cross-section fluctuations contain information on the level density (LD) of states with a given spin and parity defined by the multipolarity of the GR.
↳ nucl-exnucl-thActa Phys.Polon.B(2019)·1 citation
09
Gamma strength functions and the Brink-Axel hypothesis
Peter von Neumann-Cosel
Experimental tests of the Brink-Axel hypothesis relating gamma strength functions (GSF) deduced from absorption and emission experiments are discussed. High-resolution inelastic proton scattering at energies of a few hundred MeV and at very forwrd angles including $0^{\circ}$ presents a new approach to test the validity of the BA hypothesis in the energy region of the pygmy dipole resonance. Such data not only provide the GSF but also the level density and thus permit an independent test of their model-dependent decomposition in the Oslo method.
↳ nucl-exnucl-thSpringer Proc.Phys.(2020)·0 citations
10
Improvement of functionals in density functional theory by the inverse Kohn--Sham method and density functional perturbation theory
Tomoya Naito · Daisuke Ohashi · Haozhao Liang
We propose a way to improve energy density functionals (EDFs) in the density functional theory based on the combination of the inverse Kohn--Sham method and the density functional perturbation theory. Difference between the known EDF and the exact one is treated as the first-order perturbation. As benchmark calculations, we reproduce the theoretical exchange and correlation functionals in the local density approximation. Systems of noble-gas atoms are used for benchmark calculations, and the ground-state energies and densities, as well as the functionals, are reproduced with good accuracies.
↳ physics.chem-phcond-mat.str-elnucl-thphysics.atom-ph+1J.Phys.B(2019)·7 citations
11
Adding new branches to the "Christmas tree" of the quasinormal spectrum of black branes
Sašo Grozdanov🇺🇸 · Andrei O. Starinets🇬🇧
In holography, quasinormal spectra of black branes coincide with the poles of retarded finite-temperature correlation functions of a dual quantum field theory in the limit of infinite number of relevant degrees of freedom such as colours. For asymptotically anti-de Sitter backgrounds, the spectra form a characteristic pattern in the complex frequency plane, colloquially known as the "Christmas tree". At infinite coupling, the tree has only one pair of branches. At large but finite coupling, the branches become more dense and lift up towards the real axis, consistent with the expectation of forming a branch cut in the limit of zero coupling. However, it is known that at zero coupling, the corresponding correlators generically have not one but multiple branch cuts separated by intervals proportional to the Matsubara frequency. This suggests the existence of multiple branches of the "Christmas tree" spectrum in dual gravity. In this note, we show numerically how these additional branches of the spectrum can emerge from the dual gravitational action with higher-derivative terms. This phenomenon appears to be robust, yet, reproducing the expected weak coupling behaviour of the correlators quantitatively implies the existence of certain constraints on the coefficients of the higher-derivative terms of the dual gravity theory.
↳ hep-thcond-mat.str-elnucl-thJHEP(2019)·28 citations
12
Probing Generalized Parton Distributions through the photoproduction of a $γ π$ pair
G. Duplančić🇭🇷 · K. Passek-Kumerički🇭🇷 · B. Pire🇫🇷 · L. Szymanowski🇵🇱 · S. Wallon🇫🇷
We study in the framework of collinear QCD factorization the photoproduction of a $γ π$ pair with a large invariant mass and a small transverse momentum, as a new way to access generalized parton distributions. In the kinematics of JLab 12-GeV, we demonstrate the feasibility of this measurement and show the extreme sensitivity of the unpolarized cross section to the axial quark GPDs.
↳ hep-phhep-exnucl-exnucl-thActa Phys.Polon.Supp.(2019)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE