Nuclear Theory·nucl-th

Tuesday·October 17, 2017

11 papers—5 primary·6 cross-listed

01
Light nuclei production in Pb+Pb collisions at $s_{N N} = 2.76$ TeV
Lilin Zhu🇨🇳 · Hua Zheng🇮🇹 · Che Ming Ko🇺🇸 · Yifeng Sun🇺🇸
Using the coalescence model based on the phase-space distribution of nucleons from an extended blast-wave model that includes the space-momentum correlation of high momentum nucleons, we study the transverse momentum spectra and elliptic flows of deuteron and helium-3 in Pb+Pb collisions at the energy $s_{N N} = 2.76$ TeV. We find that the measured elliptic flows of deuteron can be satisfactorily described if nucleons of large transverse momenta are more spread in space when their momenta are more aligned along the reaction plane.
nucl-thnucl-exEPJA(2018)·22 citations
02
Kinetics of the chiral phase transition in a linear $σ$ model
C. Wesp🇩🇪 · H. van Hees🇩🇪 · A. Meistrenko🇩🇪 · C. Greiner🇩🇪
We study the dynamics of the chiral phase transition in a linear quark-meson $σ$ model using a novel approach based on semiclassical wave-particle duality. The quarks are treated as test particles in a Monte-Carlo simulation of elastic collisions and the coupling to the $σ$ meson, which is treated as a classical field. The exchange of energy and momentum between particles and fields is described in terms of appropriate Gaussian wave packets. It has been demonstrated that energy-momentum conservation and the principle of detailed balance are fulfilled, and that the dynamics leads to the correct equilibrium limit. First schematic studies of the dynamics of matter produced in heavy-ion collisions are presented.
nucl-thhep-phEPJA(2018)·6 citations
03
Examinations of the consistency of the quasiparticle random-phase approximation approach to double- $β$ decay of $^{48}$ Ca
J. Terasaki🇨🇿
The nuclear matrix elements (NMEs) of the neutrinoless and two-neutrino double- $β$ decays of $^{48}$ Ca are calculated by the quasiparticle random-phase approximation (QRPA) with emphasis on the consistency examinations of this calculation method. The main new examination points are the consistency of two ways to treat the intermediate-state energies in the two-neutrino double- $β$ NME and comparison with the experimental charge-exchange strength functions obtained from $^{48}$ Ca $(p, n)$ and $^{48}$ Ti $(n, p)$ reactions. No decisive problem preventing the QRPA approach is found. The obtained neutrinoless double- $β$ NME adjusted by the ratio of the effective and bare axial-vector current couplings is lowest in those calculated by several groups and close to one of the QRPA values obtained by another group.
nucl-thnucl-exPRC(2018)·16 citations
04
Nuclear density-functional theory and fission of super-heavy elements
P.-G. Reinhard
We review the prediction of fission properties of super-heavy elements (SHE) by self-consistent mean-field models thereby concentrating on the widely used Skyrme-Hartree-Fock (SHF) approach. We explain briefly the theoretical tools: the SHF model, the calibration of model parameters together with statistical analysis of uncertainties and correlations, and the involved computation of fission lifetimes. We present an overview of fission stability in comparison to other decay channels over the whole landscape of SHE reaching deep into the $r$ -process domain. The main emphasis lies on a detailed discussion of the various ingredients determining eventually the fission properties. The main result is that fission is an involved process which explores many different influences with almost equal share, basic bulk properties (also known as liquid-drop model parameters), pairing strengths, and shell effects. %
nucl-thEPJA(2018)·9 citations
05
Non-trivial effect for the large radius at the dripline of Oxygen isotopes
N. Itagaki · A. Tohsaki
The anomalous large radii are exotic phenomena observed around the neutron dripline. Around the neutron dripline, the weak binding of the last bound neutron(s) causes the drastic increase of the radius, which is called neutron halo structure. Although the nucleus $^{24}$ O is located at the dripline of Oxygen isotopes, the separation energies of one and two neutron(s) are 4.19 MeV and 6.92 MeV, respectively. In spite of this enough binding, the enhancement of the matter radius is observed. In this study, we microscopically describe the structure change of $^{22}$ O core in $^{24}$ O and explain the observed large radius based on the cluster model. Two degrees of freedom for the large radius; the relative distances among four $α$ clusters and size of each $α$ cluster are examined, where Tohsaki interaction, which has finite range three-body terms is employed. The nucleus $^{24}$ O has the almost the same amount of the clusterization compared with $^{22}$ O, but the expansion of each $α$ cluster plays an important role. When two neutrons are added to $^{22}$ O at the center, the expansion of each $α$ clusters is energetically more favored than enhancing the clustering for reducing the kinetic energy of the neutrons. The calculated rms matter radius of $^{22}$ O and $^{24}$ O are 2.75 fm and 2.92 fm, respectively. Although these are slightly smaller than the experimental values, the jump at $^{24}$ O from $^{22}$ O is reproduced.
nucl-thnucl-exPRC(2018)·19 citations
06
An effective field theory for warm QCD
Sourendu Gupta🇮🇳 · Rishi Sharma🇮🇳
Using only global symmetries of QCD, we set up an effective model of quarks at finite temperature near the cross over, including all possible terms up to dimension 6. We first treat this in mean field theory. Then we investigate low-energy fluctuations around it up to one-loop order in fermions below the cross over. Static correlation functions of pions and the cross over temperature, both measured on the lattice, completely suffice to fix all parameters of the theory. We examine predictions of this theory, including those for thermodynamic quantities. The results are encouraging.
↳ hep-phhep-latnucl-thPRD(2018)·13 citations
07
The effect of quantum fluctuations in compact star observables
Péter Pósfay🇭🇺 · Gergely Gábor Barnaföldi🇭🇺 · Antal Jakovác🇭🇺
Astrophysical measurements regarding compact stars are just ahead of a big evolution jump, since the NICER experiment deployed on ISS on 14 June 2017. This will soon provide data that would enable the determination of compact star radius with less than 10% error. This poses new challenges for nuclear models aiming to explain the structure of super dense nuclear matter found in neutron stars. Detailed studies of the QCD phase diagram shows the importance of bosonic quantum fluctuations in the cold dense matter equation of state. Here, we using a demonstrative model to show the effect of bosonic quantum fluctuations on compact star observables such as mass, radius, and compactness. We have also calculated the difference in the value of compressibility which is caused by quantum fluctuations. The above mentioned quantities are calculated in mean field, one-loop and in high order many-loop approximation. The results show that the magnitude of these effects is ~5%, which place it into the region where forthcoming high-accuracy measurements may detect it.
↳ hep-phastro-ph.HEgr-qcnucl-thPubl.Astron.Soc.Austral.(2018)·4 citations
08
$Λ_{c} N$ interaction from lattice QCD and its application to $Λ_{c}$ hypernuclei
Takaya Miyamoto🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Shinya Gongyo🇯🇵 · Tetsuo Hatsuda🇯🇵 · Yoichi Ikeda🇯🇵 · Takashi Inoue🇯🇵 · Takumi Iritani🇯🇵 · Noriyoshi Ishii🇯🇵 · Daisuke Kawai🇯🇵 · Keiko Murano🇯🇵 · Hidekatsu Nemura🇯🇵 · Kenji Sasaki🇯🇵
The interaction between $Λ_{c}$ and a nucleon ( $N$ ) is investigated by employing the HAL QCD method in the (2+1)-flavor lattice QCD on a $(2.9 fm)^{3}$ volume at $m_{π} ≃ 410, 570, 700$ MeV. We study the central potential in $^{1} S_{0}$ channel as well as central and tensor potentials in $^{3} S_{1} -$ $^{3} D_{1}$ channel, and find that the tensor potential for $Λ_{c} N$ is negligibly weak and central potentials in both $^{1} S_{0}$ and $^{3} S_{1} -$ $^{3} D_{1}$ channels are almost identical with each other except at short distances. Phase shifts and scattering lengths calculated with these potentials show that the interaction of $Λ_{c} N$ system is attractive and has a similar strength in $^{1} S_{0}$ and $^{3} S_{1}$ channels at low energies (i.e. the kinetic energy less than about $40$ MeV). While the attractions are not strong enough to form two-body bound states, our results lead to a possibility to form $Λ_{c}$ hypernuclei for sufficiently large atomic numbers ( $A$ ). To demonstrate this, we derive a single-folding potential for $Λ_{c}$ hypernuclei from the $Λ_{c}$ -nucleon potential obtained in lattice QCD, and find that $Λ_{c}$ hypernuclei can exist for $A \geq 12$ with the binding energies of a few MeV. We also estimate the Coulomb effect for the $Λ_{c}$ hypernuclei.
↳ hep-lathep-phnucl-thNPA(2018)·57 citations
09
Calm Multi-Baryon Operators
Evan Berkowitz🇩🇪 · Amy Nicholson🇺🇸 · Chia Cheng Chang🇺🇸 · Enrico Rinaldi🇺🇸 · M.A. Clark🇺🇸 · Bálint Joó🇺🇸 · Thorsten Kurth🇺🇸 · Pavlos Vranas🇺🇸 · André Walker-Loud🇺🇸
Outstanding problems in nuclear physics require input and guidance from lattice QCD calculations of few baryons systems. However, these calculations suffer from an exponentially bad signal-to-noise problem which has prevented a controlled extrapolation to the physical point. The variational method has been applied very successfully to two-meson systems, allowing for the extraction of the two-meson states very early in Euclidean time through the use of improved single hadron operators. The sheer numerical cost of using the same techniques in two-baryon systems has been prohibitive. We present an alternate strategy which offers some of the same advantages as the variational method while being significantly less numerically expensive. We first use the Matrix Prony method to form an optimal linear combination of single baryon interpolating fields generated from the same source and different sink interpolators. Very early in Euclidean time this linear combination is numerically free of excited state contamination, so we coin it a calm baryon. This calm baryon operator is then used in the construction of the two-baryon correlation functions. To test this method, we perform calculations on the WM/JLab iso-clover gauge configurations at the SU(3) flavor symmetric point with m{\pi} $\sim$ 800 MeV --- the same configurations we have previously used for the calculation of two-nucleon correlation functions. We observe the calm baryon removes the excited state contamination from the two-nucleon correlation function to as early a time as the single-nucleon is improved, provided non-local (displaced nucleon) sources are used. For the local two-nucleon correlation function (where both nucleons are created from the same space-time location) there is still improvement, but there is significant excited state contamination in the region the single calm baryon displays no excited state contamination.
↳ hep-latnucl-thEPJ Web Conf.(2018)·8 citations
10
Study of spin-dependent structure functions of $^{3} He$ and $^{3} H$ at NNLO approximation and corresponding nuclear corrections
Hamzeh Khanpour🇮🇷 · S. Taheri Monfared🇮🇷 · S. Atashbar Tehrani🇮🇷
We determine polarized parton distribution functions (PPDFs) and structure functions from recent experimental data of polarized deep inelastic scattering (DIS) on nuleons at next-to-next-to-leading order (NNLO) approximation in perturbative quantum chromodynamic (pQCD). The nucleon polarized structure functions are computed using the Jacobi polynomial approach while target mass corrections (TMCs) are included in our fitting procedure. Having extracted the polarized spin structure functions, we extend our study to describe $^{3} H e$ and $^{3} H$ polarized structure functions, as well as the Bjorken sum rule. We also explore the importance of the nuclear corrections on the polarized nuclear structure functions at small and large values of $x$ . Our results are compared with the recent available and high precision polarized $^{3} H e$ and $^{3} H$ experimental data.
↳ hep-phhep-exnucl-thPRD(2017)·24 citations
11
Exact evolution equation for the effective potential
Christof Wetterich🇩🇪
We derive a new exact evolution equation for the scale dependence of an effective action. The corresponding equation for the effective potential permits a useful truncation. This allows one to deal with the infrared problems of theories with massless modes in less than four dimensions which are relevant for the high temperature phase transition in particle physics or the computation of critical exponents in statistical mechanics.
↳ hep-thcond-mat.quant-gascond-mat.str-elgr-qc+1PLB(1993)·2294 citations

Affiliations

first authorsco-authorsvia INSPIRE