Nuclear Theory·nucl-th

Tuesday·March 10, 2020

9 papers—5 primary·4 cross-listed

01
[Submitted on 7 Mar 2020]
Physical features of strength of isoscalar pairing interaction determined by relation between double charge change and double pair transfer
J. Terasaki🇨🇿
A new method has been proposed to determine the strength of the isoscalar proton-neutron pairing interaction applicable to many nuclei. The principle is the equivalence between the double charge change and the double transfer of like-particle pair, and a constraint is derived to the effective interactions used in approximations. This method was applied to the quasiparticle random-phase approximation for determining that interaction strength. In this paper, detail of this method is explained thoroughly, and applications are made to nuclei of several instances of the double- $β$ decays. The systematics of the strengths determined for those nuclei is understood in terms of a midshell effect. The effect of the new interaction strength is examined in two examples of the Gamow-Teller strength function with comparisons with the experimental data. The nuclear matrix elements of the neutrinoless double- $β$ decay are also calculated.
Comments:
18 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2003.03542 [pdf]
PRC(2020)·41 citations
02
[Submitted on 8 Mar 2020]
A microscopic model for spontaneous fission: validity of the adiabatic approximation
K. Hagino · G.F. Bertsch
We investigate microscopically the tunneling dynamics in spontaneous fission of atomic nuclei. To this end, we employ a schematic solvable model with a pairing-plus-quadrupole interaction. The spontaneous decay of a system is simulated by introducing a small imaginary part to the energy of a fission doorway state. We show that the many-body Hamiltonian can be reduced to an effective 2 $\times$ 2 Hamiltonian, from which one can derive a simple approximate formula for the decay width. We particularly investigate the applicability of the adiabatic approximation, which has often been used in the literature. With typical value of the parameters, we find that the adiabatic approximation works within a factor of around 5 for the decay width.
Comments:
9 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2003.03702 [pdf]
PRC(2020)·6 citations
03
[Submitted on 8 Mar 2020]
Chiral phase transition in a rotating sphere
Zheng Zhang🇨🇳 · Chao Shi🇨🇳 · Xiaofeng Luo🇨🇳 · Hong-Shi Zong🇨🇳
We study the chiral phase transition of the two-flavor Nambu-Jona-Lasinio (NJL) model in a rotating sphere, which includes both rotation and finite size effects. We find that rotation leads to a suppression of the chiral condensate at a finite temperature, while its effects are smaller than the finite size effects. Our work can be helpful to study the effects relevant to rotation in heavy-ion collisions in a more realistic way.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2003.03765 [pdf]
PRD(2020)·13 citations
04
[Submitted on 9 Mar 2020]
Nuclear matrix elements for $λ$ mechanism of $0 ν β β$ of $^{48}$ Ca in nuclear shell-model: Closure versus nonclosure approach
Shahariar Sarkar🇮🇳 · Y. Iwata🇯🇵 · P.K. Raina🇮🇳
The $λ$ and $m_{β β}$ mechanisms of neutrinoless double beta decay ( $0 ν β β$ ) occur with light neutrino exchange via $W_{L} - W_{R}$ , and $W_{L} - W_{L}$ mediation, respectively. In the present study, we calculate the nuclear matrix elements (NMEs) for the $m_{β β}$ and $λ$ mechanisms of $0 ν β β$ , which has origin in the left-right symmetric model with right-handed gauge boson at TeV scale. The NMEs are calculated for one of the $0 ν β β$ decaying isotope $^{48}$ Ca in the interacting nuclear shell-model using the GXPF1A effective interaction of $p f$ -shell. The NMEs are calculated in both closure and nonclosure approaches using four different methods: closure, running closure, running nonclosure, and mixed methods. All the NMEs are calculated incorporating the effects of the finite size of nucleons and the revisited higher order terms such as isoscalar and weak magnetism terms of the nucleon currents. Inclusion of the short-range nature of nucleon-nucleon interaction in Miller-Spencer, CD-Bonn, and AV18 parametrizations is also taken care of. The comparative dependence of the running closure and running nonclosure NMEs with the spin-parity of the allowed states of intermediate nucleus $^{48}$ Sc, the coupled spin-parity of the two initial decaying neutrons and the final two protons, the cutoff excitation energy of $^{48}$ Sc, the cutoff number of states of $^{48}$ Sc are also examined. Results show that there are about 2-20\% enhancements in different types of total NMEs, calculated in the nonclosure approach as compared to the closure approach. The significant enhancements are found in the $M_{q GT}$ and $M_{q T}$ type NMEs for the inclusion of the higher-order terms of the nucleon currents.
Comments:
13 pages, 6 figures, to be submitted in PHYSICAL REV. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2003.04002 [pdf]
PRC(2020)·14 citations
05
[Submitted on 9 Mar 2020]
Effective field theory for triaxially deformed odd-mass nuclei
Q. B. Chen🇩🇪 · N. Kaiser🇩🇪 · Ulf-G. Meißner🇩🇪 · J. Meng🇨🇳
The effective field theory for collective rotations of triaxially deformed nuclei is generalized to odd-mass nuclei by including the angular momentum of the valence nucleon as an additional degree of freedom. The Hamiltonian is constructed up to next-to-leading order within the effective field theory formalism. The applicability of this Hamiltonian is examined by describing the wobbling bands observed in the lutetium isotopes $^{161, 163, 165, 167}$ Lu. It is found that by taking into account the next-to-leading order corrections, quartic in the rotor angular momentum, the wobbling energies $E_{wob}$ and spin-rotational frequency relations $ω (I)$ are better described than with the leading order Hamiltonian.
Comments:
19 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2003.04065 [pdf]
7 citations
06
[Submitted on 7 Mar 2020] (cross-list from nucl-ex)
Polarization and Vorticity in the Quark Gluon Plasma
Francesco Becattini🇮🇹 · Michael Lisa🇺🇸
The quark-gluon plasma produced by collisions between ultra-relativistic heavy nuclei is well described in the language of hydrodynamics. Non-central collisions are characterized by very large angular momentum, which in a fluid system manifests as flow vorticity. This rotational structure can lead to a spin polarization of the hadrons that eventually emerge from the plasma, providing experimental access to flow substructure at unprecedented detail. Recently, first observations of $Λ$ hyperon polarization along the direction of collisional angular momentum have been reported. These measurements are in broad agreement with hydrodynamic and transport-based calculations and reveal that the QGP is the most vortical fluid ever observed. However, there remain important tensions between theory and observation which might be fundamental in nature. In the relatively mature field of heavy ion physics, the discovery of global hyperon polarization and three-dimensional simulations of the collision have opened an entirely new direction of research. We discuss the current status of this rapidly developing area and directions for future research.
Comments:
30 pages, 6 figures; Invited review article for Annual Review of Nuclear and Particle Science; Comments to the authors are welcome! When citing this paper, please use the following: Becattini F, Lisa M. 2020. Title. Annu. Rev. Nucl. Part. Sci: Submitted. DOI: 10.1146/annurev-nucl-021920-095245
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.03640 [pdf]
Ann.Rev.Nucl.Part.Sci.(2020)·292 citations
07
[Submitted on 8 Mar 2020] (cross-list from hep-ph)
Semi-Inclusive Jet Functions and Jet Substructure in $J_{E_{T}}^{(I)}$ and $J_{E_{T}}^{(I I)}$ Algorithms
Lei Wang🇨🇳 · Zhong-Bo Kang🇺🇸 · Hongxi Xing🇨🇳 · Ben-Wei Zhang🇨🇳
Within the framework of Soft Collinear Effective Theory, we present calculations of semi-inclusive jet functions and fragmenting jet functions at next-to-leading order (NLO) for both quark- and gluon-initiated jets, for jet algorithms of $J_{E_{T}}^{(I)}$ and $J_{E_{T}}^{(I I)}$ where one maximizes a suitable jet function. We demonstrate the consistency of the obtained results with the standard perturbative QCD calculations for $J_{E_{T}}^{(I)}$ algorithm, while the results for fragmenting jet functions with the $J_{E_{T}}^{(I I)}$ algorithm are new. The renormalization group (RG) equation for both semi-inclusive jet functions and fragmenting jet functions are derived and shown to follow the time-like DGLAP evolution equations, independent of specific jet algorithms. The RG equation can be used to resum single logarithms of the jet size parameter $β$ for highly collimated jets in these algorithms where $β ≫ 1$ .
Comments:
16 pages, 2 figures, typos corrected, some analytical results updated
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.03796 [pdf]
PRD(2021)·3 citations
08
[Submitted on 6 Mar 2020] (cross-list from hep-ph)
$Y (4260)$ as four-quark state
Anna Zuzana Dubnickova🇸🇰 · Stanislav Dubnicka🇸🇰 · Aidos Issadykov🇷🇺 · Mikhail Alekseevich Ivanov🇷🇺 · Andrej Liptaj🇸🇰
We treat the $Y (4260)$ resonance as a four-quark state in the framework of the covariant confining quark model. We study two choices of the interpolating current, either the molecular-type current which effectively corresponds to the product of $D$ and $D ˉ_{1}$ quark currents or tetraquark one. In both cases we calculate the widths of decays $Y (4260) \to Z_{c} (3900) + π$ and $Y (4260) \to D^{(*)} + D ˉ^{(*)}$ . It is found that in both approches the mode $Y \to Z_{c}^{+} + π^{-}$ is enhanced compared with the open charm modes. However the absolute value of the $Y \to Z_{c}^{+} + π^{-}$ decay width obtained in molecular picture is arguably too large. On the other hand the value obtained in tetraquark picture is reasonable.
Comments:
12 pages, 1 figure
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.04142 [pdf]
PRD(2020)·17 citations
09
[Submitted on 9 Mar 2020] (cross-list from hep-ph)
Nuclear shadowing in DIS at electron-ion colliders
Michal Krelina🇨🇱 · Jan Nemchik🇨🇿
We present a revision of predictions for nuclear shadowing in deep-inelastic scattering at small Bjorken $x_{B j}$ corresponding to kinematic regions accessible by the future experiments at electron-ion colliders. The nuclear shadowing is treated within the color dipole formalism based on the rigorous Green function technique. This allows incorporating naturally color transparency and coherence length effects, which are not consistently and properly included in present calculations. For the lowest $∣ q q ˉ ⟩$ Fock component of the photon, our calculations are based on an exact numerical solution of the evolution equation for the Green function. Here the magnitude of shadowing is tested using a realistic form for the nuclear density function, as well as various phenomenological models for the dipole cross section. The corresponding variation of the transverse size of the $q q ˉ$ photon fluctuations is important for $x_{B j} ≳ 1 0^{- 4}$ , on the contrary with the most of other models, which use frequently only the eikonal approximation with the "frozen" transverse size. At $x_{B j} ≲ 0.01$ we calculate within the same formalism also a shadowing correction for the higher Fock component of the photon containing gluons. The corresponding magnitudes of gluon shadowing correction are compared adopting different phenomenological dipole models. Our results are tested by available data from the E665 and NMC collaborations. Finally, the magnitude of nuclear shadowing is predicted for various kinematic regions that should be scanned by the future experiments at electron-ion colliders.
Comments:
Datasets at https://zenodo.org/record/3470138 , fixed figure and misprints
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2003.04156 [pdf]
Eur.Phys.J.Plus(2020)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE