Nuclear Theory·nucl-th

Thursday·May 10, 2018

8 papers—5 primary·3 cross-listed

01
Nuclear surface diffuseness revealed in nucleon-nucleus diffraction
S. Hatakeyama · W. Horiuchi · A. Kohama
Nuclear surface provides useful information on nuclear radius, nuclear structure as well as properties of nuclear matter. We discuss the relationship between the nuclear surface diffuseness and elastic scattering differential cross section at the first diffraction peak of high-energy nucleon-nucleus scattering as an efficient tool in order to extract the nuclear surface information from limited experimental data involving short-lived unstable nuclei. The high-energy reaction is described by a reliable microscopic reaction theory, the Glauber model. Extending the idea of the black sphere model, we find one-to-one correspondence between the nuclear bulk structure information and proton elastic scattering diffraction peak. This implies that we can extract both the nuclear radius and diffuseness simultaneously, using the position of the first diffraction peak and its magnitude of the elastic scattering differential cross section. We confirm the reliability of this approach by using realistic density distributions obtained by a mean-field model.
nucl-thnucl-exPRC(2018)·32 citations
02
Role of hexadecapole deformation of projectile $^{28}$ Si in heavy-ion fusion reactions near the Coulomb barrier
Gurpreet Kaur🇮🇳 · K. Hagino🇯🇵 · N. Rowley🇫🇷
The vast knowledge of strong influence of quadrupole deformation $β_{2}$ of colliding nuclei on heavy-ion subbarrier fusion reactions inspires a desire to quest the sensitivity of fusion dynamics to higher order deformations, such as $β_{4}$ and $β_{6}$ deformations. However, such studies have rarely been carried out, especially for deformation of projectile nuclei. In this article, we investigated the role of $β_{4}$ of the projectile nucleus in fusion of the $^{28}$ Si + $^{92}$ Zr system. We demonstrated that the fusion barrier distribution is sensitive to the sign and the value of the $β_{4}$ parameter of the projectile, $^{28}$ Si, and confirmed that the $^{28}$ Si nucleus has a large positive $β_{4}$ . This study opens an indirect way to estimate deformation parameters of radioactive nuclei using fusion reactions, which is otherwise difficult due to experimental constraints.
nucl-thPRC(2018)·15 citations
03
Nuclear structure in Parity Doublet Model
Myeong-Hwan Mun🇰🇷 · Ik Jae Shin🇰🇷 · Won-Gi Paeng🇰🇷 · Masayasu Harada🇯🇵 · Youngman Kim🇰🇷
Using an extended parity doublet model with the hidden local symmetry, we study some properties of nuclei in the mean field approximation to see if the parity doublet model could reproduce nuclear properties and also to estimate the value of the chiral invariant nucleon mass $m_{0}$ preferred by nuclear structure. We first determine our model parameters using the inputs from free space and from nuclear matter properties. Then, we study some basic nuclear properties such as the nuclear binding energy with several different choices of the chiral invariant mass. We observe that our results approach the experimental values as $m_{0}$ is increased until $m_{0} = 700$ MeV and start to deviate more from the experiments afterwards with $m_{0}$ larger than $m_{0} = 700$ MeV. From this observation, we conclude that $m_{0} = 700$ MeV is preferred by nuclear properties. We then calculate some properties of several selected nuclei with $m_{0} = 700$ MeV and compare them with experiments. Finally, we study the neutron-proton mass difference in some nuclei.
nucl-thEPJA(2023)·16 citations
04
Joint $R_{AA}$ and $v_{2}$ predictions for $P b + P b$ collisions at the LHC within DREENA-C framework
Dusan Zigic🇷🇸 · Igor Salom🇷🇸 · Jussi Auvinen🇷🇸 · Marko Djordjevic🇷🇸 · Magdalena Djordjevic🇷🇸
In this paper, we presented our recently developed DREENA-C framework, which is a fully optimized computational suppression procedure based on our state-of-the-art dynamical energy loss formalism in constant temperature finite size QCD medium. With this framework, we for the first time, generated joint $R_{AA}$ and $v_{2}$ predictions within our dynamical energy loss formalism. The predictions are generated for both light and heavy flavor probes, and different centrality regions in $P b + P b$ collisions at the LHC, and compared with the available experimental data. Despite the fact that DREENA-C does not contain medium evolution (to which $v_{2}$ is largely sensitive) and the fact that other approaches faced difficulties in explaining $v_{2}$ data, we find that DREENA-C leads to qualitatively good agreement with this data, though quantitatively, the predictions are visibly above the experimental data. Intuitive explanation behind such results is presented, supporting the validity of our model, and it is expected that introduction of evolution in the ongoing improvement of DREENA framework, will lead to better joint agreement with $R_{AA}$ and $v_{2}$ data, and allow better understanding of the underlying QCD medium.
nucl-thhep-phJ.Phys.G(2019)·38 citations
05
Behavior of the collective rotor in wobbling motion
E. Streck · Q. B. Chen · N. Kaiser · Ulf-G. Meißner
The behavior of the collective rotor in wobbling motion is investigated within the particle-rotor model for the nucleus $^{135}$ Pr by transforming the wave functions from the $K$ -representation to the $R$ -representation. After reproducing the experimental energy spectra and wobbling frequencies, the evolution of the wobbling mode in $^{135}$ Pr, from transverse at low spins to longitudinal at high spins, is illustrated by the distributions of the total angular momentum in the intrinsic reference frame (azimuthal plot). Finally, the coupling schemes of the angular momenta of the rotor and the high- $j$ particle for transverse and longitudinal wobbling are obtained from the analysis of the probability distributions of the rotor angular momentum ( $R$ -plots) and their projections onto the three principal axes ( $K_{R}$ -plots).
nucl-thnucl-exPRC(2018)·54 citations
06
Kinetic freeze-out properties from transverse momentum spectra of pions in high energy proton-proton collisions
Li-Li Li🇨🇳 · Fu-Hu Liu🇨🇳
Transverse momentum spectra of negative and positive pions produced at mid-(pseudo)rapidity in inelastic or non-single-diffractive proton-proton collisions over a center-of-mass energy, $s$ , range from a few GeV to above 10 TeV are analyzed by the blast-wave fit with Boltzmann (Tsallis) distribution. The blast-wave fit results are well fitting to the experimental data measured by several collaborations. In a particular superposition with Hagedorn function, both the excitation functions of kinetic freeze-out temperature ( $T_{0}$ ) of emission source and transverse flow velocity ( $β_{T}$ ) of produced particles obtained from a given selection in the blast-wave fit with Boltzmann distribution have a hill at $s \approx 10$ GeV, a drop at dozens of GeV, and then an increase from dozens of GeV to above 10 TeV. However, both the excitation functions of $T_{0}$ and $β_{T}$ obtained in the blast-wave fit with Tsallis distribution do not show such a complex structure, but a very low hill. In another selection for the parameters or in the superposition with the usual step function, $T_{0}$ and $β_{T}$ increase generally quickly from a few GeV to about 10 GeV and then slightly at above 10 GeV, there is no such the complex structure, when also studying nucleus-nucleus collisions.
↳ hep-phhep-exnucl-exnucl-thMDPI Physics(2020)·17 citations
07
Electromagnetic couplings of radially excited light vector mesons from QCD sum rules
S. S. Afonin🇷🇺 · T. D. Solomko🇷🇺
The couplings of unflavored vector mesons to the $e^{+} e^{-}$ annihilation are an important source of information on the nature and structure of these resonances which play a prominent role in the hadron phenomenology. The couplings of many radially excited heavy vector mesons are measured, while the corresponding couplings for light vector mesons are not known. We propose a phenomenological method allowing to estimate these unknown couplings. The method is suggested by our observation that the electromagnetic coupling of the $n$ -th radial excitation of $S$ -wave heavy vector meson decouples from the $e^{+} e^{-}$ annihilation with nearly exponential rate with $n$ . It becomes natural to assume that the same effect takes place in the light vector mesons and this would allow to estimate the unknown couplings. We tested this assumption with the help of a generalized version of borelized QCD spectral sum rules saturated by a linear radial trajectory of meson states taken from the phenomenology. This leads to a consistent setup which is able to predict the decoupling rate. The calculated rate turned out to be almost the same as in the heavy vector mesons. Our result may be interpreted as an effective account for non-trivial electromagnetic formfactor in meson decays to $e^{+} e^{-}$ , thus looking beyond the large- $N_{c}$ limit. On the one hand, we argue that the given decoupling does not necessary contradict to the previous large- $N_{c}$ results for the Regge like meson spectra.
↳ hep-phnucl-thEur.Phys.J.Plus(2019)·4 citations
08
Vacuum stabilized by anomalous magnetic moment
Stefan Evans🇺🇸 · Johann Rafelski (Arizona)🇺🇸
An analytical result for Euler-Heisenberg effective action, valid for electron spin $g -$ factor $∣ g ∣ < 2$ , was extended to the domain $∣ g ∣ > 2$ via discovered periodicity of the effective action. This allows for a simplified computation of vacuum instability modified by the electrons measured $g = 2.002319$ . We find a strong suppression of vacuum decay into electron positron pairs when magnetic fields are dominant. The result is reminiscent of mass catalysis by magnetic fields.
↳ hep-phnucl-thPRD(2018)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE