Nuclear Theory·nucl-th

Friday·October 19, 2018

12 papers—11 primary·1 cross-listed

01
[Submitted on 17 Oct 2018]
Large violation of the flavour SU(3) symmetry in $η$ MAID2018 isobar model
V. A. Kuznetsov🇷🇺 · M.V. Polyakov🇷🇺
We demonstrate that the explanation of the neutron anomaly around $W \sim 1685$ MeV in $γ N \to η N$ reactions provided by the $η$ MAID2018 isobar model is based on large violation of the flavour SU(3) symmetry in hadron interactions. This is yet another example of how conventional explanation (without invoking exotic narrow nucleon resonance) of the neutron anomaly metamorphoses into unconventional physics picture of hadron interactions. A possibility to mend the flavour SU(3) symmetry for some of resonances in $η$ MAID model is discussed.
Comments:
5 pages
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1810.07713 [pdf]
1 citation
02
[Submitted on 17 Oct 2018]
Recent developments in radioactive charged-particle emissions and related phenomena
Chong Qi · Roberto Liotta · Ramon Wyss
The advent and intensive use of new detector technologies as well as radioactive ion beam facilities have opened up possibilities to investigate alpha, proton and cluster decays of highly unstable nuclei. This article provides a review of the current status of our understanding of clustering and the corresponding radioactive particle decay process in atomic nuclei. We put alpha decay in the context of charged-particle emissions which also include one- and two-proton emissions as well as heavy cluster decay. The experimental as well as the theoretical advances achieved recently in these fields are presented. Emphasis is given to the recent discoveries of charged-particle decays from proton-rich nuclei around the proton drip line. Those decay measurements have shown to provide an important probe for studying the structure of the nuclei involved. Developments on the theoretical side in nuclear many-body theories and supercomputing facilities have also made substantial progress, enabling one to study the nuclear clusterization and decays within a microscopic and consistent framework. We report on properties induced by the nuclear interaction acting in the nuclear medium, like the pairing interaction, which have been uncovered by studying the microscopic structure of clusters. The competition between cluster formations as compared to the corresponding alpha-particle formation are included. In the review we also describe the search for super-heavy nuclei connected by chains of alpha and other radioactive particle decays.
Comments:
58 pages, submitted to Prog. Part. Nucl. Phys
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.07745 [pdf]
PPNP(2019)·119 citations
03
[Submitted on 17 Oct 2018]
Partial conservation of seniority and its unexpected influence on E2 transitions in $g_{9/2}$ nuclei
Chong Qi
There exist two uniquely defined $v = 4$ states in systems within a $j = 9/2$ subshell, which automatically conserve seniority and do not mix with other states. Here I show that the partial conservation of seniority plays an essential role in our understanding of the electric quadrupole transitions of the semimagic nuclei involving $j = 9/2$ subshells, including the long-lived $8^{+}$ isomer in $^{94}$ Ru. The effects of configuration mixing from neighboring subshells on the structure of those unique states are analysed. It is shown that a sharp transition from pure seniority coupling to a significant mixture between the $v = 2$ and $v = 4$ states may be induced by the cross-orbital non-diagonal interaction matrix elements. Such strong mixture is essential to explain the observed E2 transition properties of $N = 50$ isotones $^{96}$ Pd and $^{94}$ Ru.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.07747 [pdf]
PLB(2017)·25 citations
04
[Submitted on 17 Oct 2018]
QCD Processes in Few Nucleon Systems
Dhiraj Maheswari🇺🇸
One of the important issues of Quantum Chromodynamics (QCD) - the fundamental theory of strong interaction, is the understanding of the role of the quark-gluon interactions in the processes involving nuclear targets. One direction in such studies is to explore the onset of the quark gluon degrees of freedom in nuclear dynamics. The other direction is using the nuclear targets as a `micro-labs' in studies of the QCD processes involving protons and neutrons bound in the nucleus. In the proposed research, we work in both directions considering high energy photo- and electro-production reactions involving deuteron and $^{3}$ He nuclei. In the first half of the research, we study the high energy break-up of the $^{3}$ He nucleus, caused by a incoming photon, into a proton-deuteron pair at the large center of mass scattering angle. The main motivation of the research is the theoretical interpretation of recent experimental data which revealed the unprecedentedly large exponent $s^{- 17}$ , for the energy dependence of the differential cross section. In the present research, we extend the theoretical formalism of the hard QCD rescattering model to calculate energy and angular dependences of the absolute cross section of the $γ^{3} He \to p d$ reaction in high momentum transfer limit. The second half of the research explores the deep-inelastic scattering of a polarized electron off the polarized deuteron and $^{3}$ He nuclei, to explore the quark-gluon structure of polarized neutron. In this work, we developed a comprehensive theoretical framework for calculation of the all relevant nuclear effects that will allow the accurate extraction of the neutron data from deep-inelastic scattering involving deuteron and $^{3}$ He targets.
Comments:
125 pages, PhD dissertation
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.07835 [pdf]
0 citations
05
[Submitted on 18 Oct 2018]
Effect of energy conservation on in-medium $\mbox N N \to \mbox N Δ$ cross section in isospin-asymmetric nuclear matter
Ying Cui🇨🇳 · Yingxun Zhang🇨🇳 · Zhuxia Li🇨🇳
In this paper, the in-medium $N N \to N Δ$ cross section is calculated in the framework of the one-boson exchange model by including the isovector mesons, i.e. $δ$ and $ρ$ mesons. Due to the isospin exchange in the $N N \to N Δ$ process, the vector self-energies of the outgoing particles are modified relative to the incoming particles in isospin asymmetric nuclear matter, and it leads to the effective energies of the incoming $N N$ pair being different from the outgoing $N Δ$ pair. This effect is investigated in the calculation of the in-medium $N N \to N Δ$ cross section. With the corrected energy conservation, the cross sections of the $Δ^{++}$ and $Δ^{+}$ channels are suppressed, and the cross sections of the $Δ^{0}$ and $Δ^{-}$ channels are enhanced relative to the results obtained without properly considering the potential energy changes. Our results further confirm the dependence of medium correction factor, $R = σ_{N N \to N Δ}^{*} / σ_{N N \to N Δ}^{free}$ , on the charge state of $N N \to N Δ$ especially around the threshold energy, but the isospin splitting of medium correction factor $R$ becomes weak at high beam energies.
Comments:
8 pages, 5 figures, accepted by Phys.Rev.c
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.07854 [pdf]
PRC(2018)·14 citations
06
[Submitted on 18 Oct 2018]
Elliptic flow of transported and non-transported proton in Au+Au collisions within the UrQMD model
Biao Tu🇨🇳 · Shusu Shi🇨🇳 · Feng Liu🇨🇳
With the framework of UrQMD model, by tracing the number of initial quarks in protons, we study the elliptic flow of transported protons, poduced protons and anti-protons in Au+Au collisions at $s_{N N}$ = 7.7, 11.5, 39, 200 GeV. The difference of elliptic flow between transported protons and anti-protons is observed. The results of UrQMD model show a good agreement with the STAR results at low energies, but are deviate at high energies. It partly explains the $v_{2}$ difference between proton and anti-proton observed in the Beam Energy Scan program in Relativistic Heavy Ion Collider~(RHIC).
Comments:
5 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.07869 [pdf]
CPC(2019)·9 citations
07
[Submitted on 18 Oct 2018]
Consistent mean-field description of the $^{12}$ C+ $^{12}$ C optical potential at low energies and the astrophysical $S$ factor
Le Hoang Chien · Dao T. Khoa · Do Cong Cuong · Nguyen Hoang Phuc
The nuclear mean-field potential built up by the $^{12}$ C+ $^{12}$ C interaction at energies relevant for the carbon burning process is calculated in the double-folding model (DFM) using the realistic ground-state density of $^{12}$ C and the CDM3Y3 density dependent nucleon-nucleon (NN) interaction, with the rearrangement term properly included. To validate the use of a density dependent NN interaction in the DFM calculation in the low-energy regime, an adiabatic approximation is suggested for the nucleus-nucleus overlap density. The reliability of the nuclear mean-field potential predicted by this low-energy version of the DFM is tested in a detailed optical model analysis of the elastic $^{12}$ C+ $^{12}$ C scattering data at energies below 10 MeV/nucleon. The folded mean-field potential is then used to study the astrophysical $S$ factor of the $^{12}$ C+ $^{12}$ C fusion in the barrier penetration model. Without any adjustment of the potential strength, our results reproduce very well the non-resonant behavior of the $S$ factor of the $^{12}$ C+ $^{12}$ C fusion over a wide range of energies.
Comments:
Version published in Physical Review C 98, 064604 (2018)
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.07887 [pdf]
PRC(2018)·24 citations
08
[Submitted on 18 Oct 2018]
Low-energy Bremsstrahlung photon in relativistic nucleon+nucleon collisions
Taesoo Song🇩🇪 · Pierre Moreau🇩🇪
We study the production of Bremsstrahlung photon in relativistic nucleon+nucleon collisions by introducing a deceleration time of electromagnetic currents. It is found that Bremsstrahlung photon spectrum at low energy does not depend on the deceleration time but solely on the amount of reduced electromagnetic current in collision. On the other hand, the photon spectrum becomes soft with increasing deceleration time. We also find that Bremsstrahlung photon spectrum in p+n collisions is considerably different from that in p+p collisions at low energy.
Comments:
11 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.08013 [pdf]
PRD(2018)·4 citations
09
[Submitted on 16 Oct 2018]
A New Effective Potential for Deuteron
Taha Koohrokhi🇮🇷 · Sehban Kartal🇹🇷
We calculate for the first time the static properties of the deuteron, within the framework of supersymmetric quantum mechanics, analytically. A new effective potential and its partner are derived from a superpotential so that all parameters are fitted by the experimental data. An analytical expression is obtained for the deuteron wave function and contributions of the orthogonal $^{13} S_{1}$ and $^{13} D_{1}$ states are determined, explicitly. Compared to one pion exchange, the superpotential produces an electrostatic as well as two pion exchange terms for the potential. The saddle point radius of the potential and the maximum of the wave function are linearly proportional.
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1810.08053 [pdf]
Commun.Theor.Phys.(2022)·5 citations
10
[Submitted on 18 Oct 2018]
Using excitation-energy dependent fission yields to identify key fissioning nuclei in r-process nucleosynthesis
Nicole Vassh · Ramona Vogt · Rebecca Surman · Jorgen Randrup · Trevor Sprouse · Matthew Mumpower · Patrick Jaffke · David Shaw · Erika Holmbeck · Yonglin Zhu · Gail McLaughlin
We evaluate the impact of using sets of fission yields given by the GEF code for spontaneous (sf), neutron-induced ((n,f)), and beta-delayed (betadf) fission processes which take into account the approximate initial excitation energy of the fissioning compound nucleus. We further explore energy-dependent fission dynamics in the r process by considering the sensitivity of our results to the treatment of the energy sharing and de-excitation of the fission fragments using the FREYA code. We show that the asymmetric-to-symmetric yield trends predicted by GEF can reproduce the high-mass edge of the second r-process peak seen in solar data and examine the sensitivity of this result to the mass model and astrophysical conditions applied. We consider the effect of fission yields and barrier heights on the nuclear heating rates used to predict kilonova light curves. We find that fission barriers influence the contribution of 254Cf spontaneous fission to the heating at ~100 days, such that a light curve observation consistent with such late-time heating would both confirm that actinides were produced in the event and imply the fission barriers are relatively high along the 254Cf beta-feeding path. We lastly determine the key nuclei responsible for setting the r-process abundance pattern by averaging over thirty trajectories from a 1.2--1.4 M_odot neutron star merger simulation. We show it is largely the odd-N nuclei undergoing (Z,N)(n,f) and (Z,N)betadf that control the relative abundances near the second peak. We find the "hot spots" for beta-delayed and neutron-induced fission given all mass models considered and show most of these nuclei lie between the predicted N=184 shell closure and the location of currently available experimental decay data.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.08133 [pdf]
J.Phys.G(2019)·83 citations
11
[Submitted on 18 Oct 2018]
A modified-Boltzmann approach for modeling the hot QCD medium-induce splitting vertices in the deep LPM region
Weiyao Ke🇺🇸 · Yingru Xu🇺🇸 · Steffen A. Bass🇺🇸
Hard probes produced in perturbative processes are excellent probes for the study of the hot and dense QCD matter created in relativistic heavy-ion collisions. Transport theory, allowing for coupling to an evolving medium with fluctuating initial conditions, has become a powerful tool in this endeavor. However, the implementation of the Landau-Pomeranchuk-Migdal (LPM) effect for medium-induced parton bremsstrahlung and pair production, poses a challenge to semi-classical transport models based on Boltzmann-type transport equations. In this work, we investigate a possible solution to approximate the LPM effect in a "modified Boltzmann transport" approach, including a prescription for the running coupling constant. By fixing a numerical parameter, this approach quantitatively reproduces the rates of medium-induced parton splitting predicted by the next-to-lead-log solution of the AMY equation which is valid in the deep-LPM regime of an infinite medium. We also find qualitative agreement of our implementation with calculations in a finite and expanding medium, but future improvements are needed for added precision at small path length. This work benefits transport model-based studies and the usage of these models in the phenomenological extraction of the jet transport coefficient.
Comments:
15 pages, 9 figures, heavily modified for re-submission
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.08177 [pdf]
PRC(2019)·83 citations
12
[Submitted on 18 Oct 2018] (cross-list from hep-ph)
On the Existence of $N^{*} (890)$ Resonance in $S_{11}$ Channel of $π N$ Scatterings
Yu-Fei Wang🇨🇳 · De-Liang Yao🇪🇸 · Han-Qing Zheng🇨🇳
Low-energy partial-wave $π N$ scattering data is reexamined with the help of the production representation of partial-wave $S$ matrix, where branch cuts and poles are thoroughly under consideration. The left-hand cut contribution to the phase shift is determined, with controlled systematic error estimates, by using the results of $O (p^{3})$ chiral perturbative amplitudes obtained in the extended-on-mass-shell scheme. In $S_{11}$ and $P_{11}$ channels, severe discrepancies are observed between the phase shift data and the sum of all known contributions. Statistically satisfactory fits to the data can only be achieved by adding extra poles in the two channels. We find that a $S_{11}$ resonance pole locates at $z_{r} = (0.895 \pm 0.081) - (0.164 \pm 0.023) i$ GeV, on the complex $s$ -plane. On the other hand, a $P_{11}$ virtual pole, as an accompanying partner of the nucleon bound-state pole, locates at $z_{v} = (0.966 \pm 0.018)$ GeV, slightly above the nucleon pole on the real axis below threshold. Physical origin of the two newly established poles is explored to the best of our knowledge. It is emphasized that the $O (p^{3})$ calculation greatly improves the fit quality comparing with the previous $O (p^{2})$ one.
Comments:
7 Pages
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1810.07958 [pdf]
Front.Phys.(Beijing)(2019)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE