Nuclear Theory·nucl-th

Friday·April 29, 2016

8 papers—6 primary·2 cross-listed

01
Relation between (e,e') sum rules in 6,7Li and 4He nuclei.Experiment and cluster model
V. D. Efros · I. S. Timchenko · A. Yu. Buki
The sums over (e,e') spectra of 6Li and 7Li nuclei which correspond to the longitudinal sum rule are studied. It is suggested that due to the cluster structure of the lithium isotopes these sums may approximately be expressed in terms of such a sum pertaining to the alpha-particle. Calculation of these sums is performed in the framework of cluster models with antisymmetrization done with respect to all the nucleons. At momentum transfers higher than 0.8 fm^{-1} the relations expressing the A=6 or 7 sum in terms of the A=4 sum prove to be valid with rather high accuracy. In the region of momentum transfers around 1 fm^{-1} the longitudinal correlation functions of 6Li and 7Li nuclei are found to be close to that of the alpha-particle. The experimental longitudinal sums in the range between 0.450 and 1.625 fm^{-1} are employed to perform comparison with those calculated in the framework of cluster models. Out of the mentioned experimental sums, those in the range between 0.750 and 1.000 fm^{-1} in the 6Li case and between 0.750 and 1.125 fm^{-1} in the 7Li case are obtained in the present work. In the 6Li case a complete agreement is found while in the 7Li case an agreement only at a qualitative level is observed.
nucl-thnucl-exEPJA(2016)·0 citations
02
Relativistic model of 2p-2h meson exchange currents in (anti)neutrino scattering
I. Ruiz Simo🇪🇸 · J.E. Amaro🇪🇸 · M.B. Barbaro🇮🇹 · A. De Pace🇮🇹 · J.A. Caballero🇪🇸 · T.W. Donnelly🇺🇸
We develop a model of relativistic, charged meson-exchange currents (MEC) for neutrino-nucleus interactions. The two-body current is the sum of seagull, pion-in-flight, pion-pole and $Δ$ -pole operators. These operators are obtained from the weak pion-production amplitudes for the nucleon derived in the non-linear $σ$ -model together with weak excitation of the $Δ (1232)$ resonance and its subsequent decay into $N π$ . With these currents we compute the five 2p-2h response functions contributing to $(ν_{l}, l^{-})$ and $(ν_{l}, l^{+})$ reactions in the relativistic Fermi gas model. The total current is the sum of vector and axial two-body currents. The vector current is related to the electromagnetic MEC operator that contributes to electron scattering. This allows one to check our model by comparison with the results of De Pace {\em et al.,} Nuclear Physics A 726 (2003) 303. Thus our model is a natural extension of that model to the weak sector with the addition of the axial MEC operator. The dependences of the response functions on several ingredients of the approach are analyzed. Specifically we discuss relativistic effects, quantify the size of the direct-exchange interferences, and the relative importance of the axial versus vector current.
nucl-thhep-phJ.Phys.G(2017)·121 citations
03
Critical endpoint in the presence of a chiral chemical potential
Zhu-Fang Cui🇨🇳 · Ian C. Cloet🇺🇸 · Ya Lu🇨🇳 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪 · Shu-Sheng Xu🇨🇳 · Hong-Shi Zong🇨🇳
A class of Polyakov-loop-modified Nambu--Jona-Lasinio (PNJL) models have been used to support a conjecture that numerical simulations of lattice-regularized quantum chromodynamics (QCD) defined with a chiral chemical potential can provide information about the existence and location of a critical endpoint in the QCD phase diagram drawn in the plane spanned by baryon chemical potential and temperature. That conjecture is challenged by conflicts between the model results and analyses of the same problem using simulations of lattice-regularized QCD (lQCD) and well-constrained Dyson-Schwinger equation (DSE) studies. We find the conflict is resolved in favor of the lQCD and DSE predictions when both a physically-motivated regularization is employed to suppress the contribution of high-momentum quark modes in the definition of the effective potential connected with the PNJL models and the four-fermion coupling in those models does not react strongly to changes in the mean-field that is assumed to mock-up Polyakov loop dynamics. With the lQCD and DSE predictions thus confirmed, it seems unlikely that simulations of lQCD with $μ_{5} > 0$ can shed any light on a critical endpoint in the regular QCD phase diagram.
nucl-thhep-lathep-phnucl-exPRD(2016)·53 citations
04
Asymptotics of three-body bound state radial wave functions of halo nuclei involving two charged particles
R. Yarmukhamedov
Asymptotic expressions for the radial and full wave functions of a three{body bound halo nuclear system with two charged particles in relative coordinates are obtained in explicit form, when the relative distance between two particles tends to infinity. The obtained asymptotic forms are applied to the analysis of the asymptotic behavior of the three-body (pn?) wave functions for the halo ( $E^{*} = 3.562$ MeV, $J^{π} = 0^{+}$ , $T = 1$ ) state of $^{6}$ Li derived by D. Baye within the Lagrange-mesh method for two forms of the $α N$ -potential. The agreement between the calculated wave function and the asymptotic formula is excellent for distances up to 30 fm. Information about the values of the three-body asymptotic normalization functions is extracted. It is shown that the extracted values of the three-body asymptotic normalization function are sensitive to the form of the $α N$ -potential. The mirror symmetry is revealed for the three-body asymptotic normalization functions derived for the isobaric ( $^{6}$ He, $^{6}$ Li) pair.
nucl-thNPA(2017)·0 citations
05
High Baryon Densities in Heavy Ion Collisions at Energies Attainable at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider
Ming Li🇺🇸 · Joseph I. Kapusta🇺🇸
In very high energy collisions nuclei are practically transparent to each other but produce very hot, nearly baryon-free, matter in the so-called central rapidity region. The energy in the central rapidity region comes from the kinetic energy of the colliding nuclei. We calculate the energy and rapidity loss of the nuclei using the color glass condensate model. This model also predicts the excitation energy of the nuclear fragments. Using a space-time picture of the collision we calculate the baryon and energy densities of the receding baryonic fireballs. For central collisions of gold nuclei at the highest energy attainable at the Relativistic Heavy Ion Collider, for example, we find baryon densities more than ten times that of atomic nuclei over a large volume.
nucl-thPRC(2017)·23 citations
06
Universal symmetry energy contribution to the neutron star equation of state
D. Blaschke🇵🇱 · D. E. Alvarez-Castillo🇷🇺 · T. Klahn🇵🇱
We discuss the observation that under neutron star conditions of charge neutrality and $β -$ equilibrium the contribution from the symmetry energy to the equation of state (EoS) follows a universal behaviour. We call this behaviour the conjecture of a Universal Symmetry Energy Contribution (USEC). We find that an USEC holds provided the density dependence of the symmetry energy $E_{s} (n)$ follows a behaviour that limits the proton fraction $x (n)$ to values below the threshold for the direct Urca (DU) cooling process. The absence of DU cooling in typical mass neutron stars appears to be supported by the phenomenology of neutron star cooling data and allows to constrain the behaviour of $E_{s} (n)$ at high densities. Two classes of symmetry energy functions are investigated more in detail to elucidate the USEC. We derive an analytic formula for the USEC to the neutron star EoS based on the result for the symmetry energy extracted from isobaric analog states of nuclei.
nucl-thastro-ph.HEhep-ph17 citations
07
A Fast Algorithm for Lattice Hyperonic Potentials
Hidekatsu Nemura🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Takumi Iritani🇯🇵 · Noriyoshi Ishii🇯🇵 · Takaya Miyamoto🇯🇵 · Keiko Murano🇯🇵 · Kenji Sasaki🇯🇵
We describe an efficient algorithm to compute a large number of baryon-baryon interactions from $N N$ to $ΞΞ$ by means of HAL QCD method, which lays the groundwork for the nearly physical point lattice QCD calculation with volume $(96 a)^{4} \approx$ ( $8.2$ fm) $^{4}$ . Preliminary results of $Λ N$ potential calculated with quark masses corresponding to ( $m_{π}$ , $m_{K}$ ) $\approx$ (146,525)MeV are presented.
↳ hep-latnucl-thJPS Conf.Proc.(2017)·6 citations
08
Scoping of material response under DEMO neutron irradiation: comparison with fission and influence of nuclear library selection
M.R. Gilbert · J.-Ch. Sublet
Predictions of material activation inventories will be a key input to virtually all aspects of the operation, safety and environmental assessment of future fusion nuclear plants. Additionally, the neutron-induced transmutation (change) of material composition (inventory) with time, and the creation and evolution of configurational damage from atomic displacements, require precise quantification because they can lead to significant changes in material properties, and thus influence reactor-component lifetime. A comprehensive scoping study has been performed to quantify the activation, transmutation (depletion and build-up) and immediate damage response under neutron irradiation for all naturally occurring elements from hydrogen to bismuth. The resulting database provides a global picture of the response of a material, covering the majority of nuclear technological space, but focussing specifically on typical conditions expected for a demonstration fusion power plant (DEMO). Results from fusion are compared against typical fission conditions for selected fusion relevant materials, demonstrating that the latter cannot be relied upon to give accurate scalable experimental predictions of material response in a future fusion reactor. Results from different nuclear data libraries are also compared, highlighting the variations and deficiencies.
↳ cond-mat.mtrl-scinucl-thphysics.ins-detFusion Eng.Des.(2017)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE