Nuclear Theory·nucl-th

Thursday·May 13, 2021

6 papers—4 primary·2 cross-listed

01
[Submitted on 11 May 2021]
Density matrix renormalization group description of the island of inversion isotopes $^{28 - 33}$ F
K. Fossez🇺🇸 · J. Rotureau🇸🇪
Recent experiments have confirmed that the neutron-rich isotopes $^{28, 29}$ F belong to the so-called island of inversion (IOI), a region of the nuclear chart around $Z = 10$ and $N = 20$ where nuclear structure deviates from the standard shell model predictions due to deformation and continuum effects. However, while the general principles leading to the IOI are relatively well understood, the details of the low-lying structure of the exotic fluorine isotopes $^{28 - 33}$ F are basically unknown. In this work, we perform large-scale shell model calculations including continuum states to investigate the properties of the neutron-rich isotopes $^{25 - 33}$ F, using a core of $^{24}$ O and an effective two-body interaction with only three adjustable parameters. We adjust the core potential and interaction on experimentally confirmed states in $^{25, 26}$ O and $^{25 - 27}$ F and solve the many-body problem using the density matrix renormalization group method for open quantum systems in a $s d$ - $f p$ model space. We obtain the first detailed spectroscopy of $^{25 - 33}$ F in the continuum and show how the interplay between continuum effects and deformation explains the recent data on $^{28, 29}$ F, and produces an inversion of the $5/2^{+}$ and $1/2^{+}$ states in $^{29, 31, 33}$ F. Several deformed one- and two-neutron halo states are predicted in $^{29, 31}$ F, and we predict the ground state of $^{30}$ F to have a structure similar to that of the first $5/2^{+}$ state of $^{29}$ F. We also suggest several experimental studies to constraint models and test the present predictions. The complex structure of neutron-rich fluorine isotopes offers a trove of information about the formation of the southern shore of the IOI through a subtle interplay of deformation and continuum couplings driven by the occupation of the quasi-degenerate neutron shells $0 d_{3/2}$ and $1 p_{3/2}$ .
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2105.05287 [pdf]
PRC(2022)·23 citations
02
[Submitted on 12 May 2021]
Ab initio calculation of the contact operator contribution in the standard mechanism for neutrinoless double beta decay
R. Wirth🇺🇸 · J. M. Yao🇨🇳 · H. Hergert🇺🇸
Starting from chiral nuclear interactions, we evaluate the contribution of the leading-order contact transition operator to the nuclear matrix element (NME) of neutrinoless double-beta decay, assuming a light Majorana neutrino-exchange mechanism. The corresponding low-energy constant (LEC) is determined by fitting the transition amplitude of the $nn \to pp e^{-} e^{-}$ process to a recently proposed synthetic datum. We examine the dependence of the amplitude on similarity renormalization group (SRG) scale and chiral expansion order of the nuclear interaction, finding that both dependences can be compensated to a large extent by readjusting the LEC. We evaluate the contribution of both the leading-order contact operator and standard long-range operator to the neutrinoless double-beta decays in the light nuclei $^{6, 8}$ He and the candidate nucleus $^{48}$ Ca. Our results provide the first clear demonstration that the contact term enhances the NME by 43(7)% in $^{48}$ Ca, where the uncertainty is propagated from the synthetic datum.
Comments:
6 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.05415 [pdf]
PRL(2021)·85 citations
03
[Submitted on 12 May 2021]
Probing nuclear quadrupole deformation from correlation of elliptic flow and transverse momentum in heavy ion collisions
Jiangyong Jia🇺🇸 · Shengli Huang🇺🇸 · Chunjian Zhang🇺🇸
In heavy ion collisions, elliptic flow $v_{2}$ and radial flow, characterized by event-wise average transverse momentum $[p_{T}]$ , are related to the shape and size of the overlap region, which are sensitive to the shape of colliding atomic nuclei. The Pearson correlation coefficient between $v_{2}$ and $[p_{T}]$ , $ρ_{2}$ , was found to be particularly sensitive to the quadrupole deformation parameter $β$ that is traditionally measured in low energy experiments. Built on earlier insight that the prolate deformation $β > 0$ reduces the $ρ_{2}$ in ultra-central collisions (UCC), we show that the prolate deformation $β < 0$ enhances the value of $ρ_{2}$ . As $β > 0$ and $β < 0$ are the two extremes of triaxiality, the strength and sign of $v_{2}^{2} - [p_{T}]$ correlation can be used to provide valuable information on the triaxiality of the nucleus. Our study provide further arguments for using the hydrodynamic flow as a precision tool to directly image the deformation of the atomic nuclei at extremely short time scale ( $< 1 0^{- 24}$ s).
Comments:
13 pages, 10 figures, update to the Accepted version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Atomic Physics (physics.atom-ph)
arXiv:
2105.05713 [pdf]
PRC(2022)·57 citations
04
[Submitted on 12 May 2021]
Nucleon decay in the deuteron
F. Oosterhof🇳🇱 · J. de Vries🇳🇱 · R. G. E. Timmermans🇳🇱 · U. van Kolck🇫🇷
We calculate the lifetime of the deuteron from dimension-six quark operators that violate baryon number by one unit. We construct an effective field theory for $∣Δ B ∣ = 1$ interactions that give rise to nucleon and $Δ B = 1$ deuteron decay in a systematic expansion. We show that up to and including next-to-leading order the deuteron decay rate is given by the sum of the decay rates of the free proton and neutron. The first nuclear correction is expected to contribute at the few-percent level and comes with an undetermined low-energy constant. We discuss its relation to earlier potential-model calculations.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2105.05715 [pdf]
PLB(2021)·5 citations
05
[Submitted on 11 May 2021] (cross-list from hep-ph)
Neutron star structure with a new force between quarks
Jeffrey M. Berryman🇺🇸 · Susan Gardner🇺🇸
The discovery of nondiffuse sources of gravitational waves through compact-object mergers opens new prospects for the study of physics beyond the Standard Model. In this paper, we study the effects of a new force between quarks, suggested by the gauging of baryon number, on pure neutron matter at supranuclear densities. This leads to a stiffening of the equation of state, allowing neutron stars to be both larger and heavier and possibly accommodating the light progenitor of GW190814 as a neutron star. The role of conventional three-body forces in neutron star structure is still poorly understood, though they can act in a similar way, implying that the mass and radius do not in themselves resolve whether new physics is coming into play. However, a crucial feature of the scenario we propose is that the regions of the new physics parameter space that induce observable changes to neutron star structure are testable at low-energy accelerator facilities. This testability distinguishes our scenario from other classes of new phenomena in dense matter.
Comments:
9 pages, 3 figures; updated to match journal version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
arXiv:
2105.05254 [pdf]
PRC(2021)·11 citations
06
[Submitted on 11 May 2021] (cross-list from cond-mat.quant-gas)
Dissipative superfluid hydrodynamics for the unitary Fermi gas
Jiaxun Hou🇺🇸 · Thomas Schaefer🇺🇸
In this work we establish constraints on the temperature dependence of the shear viscosity $η$ in the superfluid phase of a dilute Fermi gas in the unitary limit. Our results are based on analyzing experiments that measure the aspect ratio of a deformed cloud after release from an optical trap. We discuss how to apply the two-fluid formalism to the unitary gas, and provide a suitable parametrization of the equation of state. We show that in expansion experiments the difference between the normal and superfluid velocities remains small, and can be treated as a perturbation. We find that expansion experiments favor a shear viscosity that decreases significantly in the superfluid regime. Using an exponential parametrization we find $η (T_{c} / (2 T_{F})) < 0.37 η (T_{c} / T_{F})$ , where $T_{c}$ is the critical temperature, $T_{F}$ is the local Fermi temperature of the gas.
Comments:
30 pages, 11 figures. To appear in Phys Rev A
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2105.05284 [pdf]
PRA(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE

Density matrix renormalization group description of the island of inversion isotopes 28−33F

Ab initio calculation of the contact operator contribution in the standard mechanism for neutrinoless double beta decay

Probing nuclear quadrupole deformation from correlation of elliptic flow and transverse momentum in heavy ion collisions

Nucleon decay in the deuteron

Neutron star structure with a new force between quarks

Dissipative superfluid hydrodynamics for the unitary Fermi gas

Affiliations

Density matrix renormalization group description of the island of inversion isotopes $^{28 - 33}$ F