Nuclear Theory·nucl-th

Wednesday·December 23, 2020

7 papers—3 primary·4 cross-listed

01
[Submitted on 21 Dec 2020]
Towards complete leading-order predictions for neutrinoless double $β$ decay
Vincenzo Cirigliano🇺🇸 · Wouter Dekens🇺🇸 · Jordy de Vries🇺🇸 · Martin Hoferichter🇨🇭 · Emanuele Mereghetti🇺🇸
The amplitude for the neutrinoless double $β$ ( $0 ν β β$ ) decay of the two-neutron system, $nn \to pp e^{-} e^{-}$ , constitutes a key building block for nuclear-structure calculations of heavy nuclei employed in large-scale $0 ν β β$ searches. Assuming that the $0 ν β β$ process is mediated by a light-Majorana-neutrino exchange, a systematic analysis in chiral effective field theory shows that already at leading order a contact operator is required to ensure renormalizability. In this work, we develop a method to estimate the numerical value of its coefficient in analogy to the Cottingham formula and validate the result by reproducing the charge-independence-breaking contribution to the nucleon-nucleon scattering lengths. Our central result, while derived in the $MS$ scheme, is given in terms of the renormalized amplitude $A_{ν} (∣ p ∣, ∣ p^{'} ∣)$ , matching to which will allow one to determine the contact-term contribution in regularization schemes employed in nuclear-structure calculations. Our results thus greatly reduce a crucial uncertainty in the interpretation of searches for $0 ν β β$ decay.
Comments:
7 pages, 3 figures; journal version. See arXiv:2102.03371 for an extended version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2012.11602 [pdf]
PRL(2021)·103 citations
02
[Submitted on 22 Dec 2020]
Nuclear charge-exchange excitations based on relativistic density-dependent point-coupling model
D. Vale · Y. F. Niu · N. Paar
Spin-isospin transitions in nuclei away from the valley of stability are essential for the description of astrophysically relevant weak interaction processes. While they remain mainly beyond the reach of experiment, theoretical modeling provides important insight into their properties. In order to describe the spin-isospin response,vcthe proton-neutron relativistic quasiparticle random phase approximation (PN-RQRPA) is formulated using the relativistic density-dependent point coupling interaction, and separable pairing interaction in both the $T = 1$ and $T = 0$ pairing channels. By implementing recently established DD-PCX interaction with improved isovector properties relevant for the description of nuclei with neutron-to-proton number asymmetry, the isobaric analog resonances (IAR) and Gamow-Teller resonances (GTR) have been investigated. In contrast to other models that usually underestimate the IAR excitation energies in Sn isotope chain, the present model accurately reproduces the experimental data, while the GTR properties depend on the isoscalar pairing interaction strength. This framework provides not only an improved description of the spin-isospin response in nuclei, but it also allows future large scale calculations of charge-exchange excitations and weak interaction processes in stellar environment.
Comments:
40 pages, 6 figures, revised version
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2012.11977 [pdf]
PRC(2021)·22 citations
03
[Submitted on 22 Dec 2020]
Structure of double pionic atoms
Akari Tani🇯🇵 · Natsumi Ikeno🇯🇵 · Daisuke Jido🇯🇵 · Hideko Nagahiro🇯🇵 · Hiroyuki Fujioka🇯🇵 · Kenta Itahashi🇯🇵 · Satoru Hirenzaki🇯🇵
We study theoretically the structure of double pionic atoms, in which two negatively charged pions ( $π^{-}$ ) are bound in the atomic orbits. The double pionic atom is considered to be an interesting system from the point of view of the multi bosonic systems. In addition, it could be possible to deduce valuable information on the isospin $I = 2$ $π π$ interaction and the pion-nucleus strong interaction. In this paper, we take into account the $π π$ strong and electromagnetic interactions, and evaluate the effects on the binding energies by perturbation theory for the double pionic atoms in heavy nuclei. We investigate several combinations of two pionic states and find that the order of magnitude of the energy shifts due to the $π π$ interaction is around 10 keV for the strong interaction and around 100 keV for the electromagnetic interaction for the ground states.
Comments:
16 pages, 6 figures, 5 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2012.12236 [pdf]
PTEP(2021)·4 citations
04
[Submitted on 21 Dec 2020] (cross-list from hep-ph)
Electromagnetic form factors of the $Ω^{-}$ baryon in the spacelike and timelike regions
G. Ramalho🇧🇷
We present complete calculations of the electromagnetic form factors of the $Ω^{-}$ in the spacelike region and in the timelike region. The four elastic form factors: electric charge ( $G_{E 0}$ ), magnetic dipole ( $G_{M 1}$ ), electric quadrupole ( $G_{E 2}$ ) and magnetic octupole ( $G_{M 3}$ ), are estimated within the covariant spectator quark model, in terms of the square momentum transfer $q^{2}$ . The free parameters of the $Ω^{-}$ wave function, including a $S$ -wave state and two independent $D$ -wave states radial wave functions and the admixture coefficients are fixed by the comparison with the lattice QCD data in the spacelike region ( $Q^{2} = - q^{2} \leq 0$ ) and with the recent $e^{+} e^{-} \to Ω^{-} Ω ˉ^{+}$ data from CLEO in the timelike region ( $q^{2} > 0$ ). The estimates in the timelike region for square momentum transfer $q^{2} \geq 4 M_{Ω}^{2}$ are based on large- $q^{2}$ asymptotic relations ( $M_{Ω}$ is the $Ω^{-}$ mass). We examine also the impact of the large- $Q^{2}$ correlations between different form factors and analyze the possible solutions. The electric quadrupole and the magnetic octupole moments of the $Ω^{-}$ , and the $e^{+} e^{-} \to Ω^{-} Ω ˉ^{+}$ integrated cross sections for very large $q^{2}$ are estimated based on the model results.
Comments:
Published version. 22 pages, 5 figures and 6 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2012.11710 [pdf]
PRD(2021)·22 citations
05
[Submitted on 21 Dec 2020] (cross-list from hep-ph)
Kinematic Azimuthal Asymmetries and Lam-Tung Relation
O.V. Teryaev🇷🇺
The origin of Lam-Tung relation for the angular asymmetry of Drell-Yan dileptons is analyzed. The asymmetry constrained by this relation is shown to belongto the class of kinematic azimuthal asymmetries, emerging due to the deviation of the reference axis from the natural physical one. The validity and violation of Lam-Tung relation due to radiative and power QCD corrections is discussed. The relation is generalized to the case when the virtual photon is not the transverse oneand the possible applications are suggested.
Comments:
3 pages, Published in Proceedings of XI WORKSHOP ON HIGH ENERGY SPIN PHYSICS (SPIN-05, Dubna, September 27 - October 1, 2005, http://theor.jinr.ru/meetings/2005/spin2005/ ), p.171-174
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2012.11720 [pdf]
4 citations
06
[Submitted on 22 Dec 2020] (cross-list from nucl-ex)
Comprehensive test of the Brink-Axel hypothesis in the energy region of the pygmy dipole resonance
M. Markova (1) · P. von Neumann-Cosel (2) · A. C. Larsen (1) · S. Bassauer (2) · A. Görgen (2) · M. Guttormsen (1) · F. L. Bello Garrote (1) · H. C. Berg (1) · M. M. Bjørøen (1) · T. Dahl-Jacobsen (1) · T. K. Eriksen (1) · D. Gjestvang (1) and 13 other authors
The validity of the Brink-Axel hypothesis, which is especially important for numerous astrophysical calculations, is addressed for 116,120,124Sn below the neutron separation energy by means of three independent experimental methods. The $γ$ -ray strength functions (GSFs) extracted from primary $γ$ -decay spectra following charged-particle reactions with the Oslo method and with the Shape method demonstrate excellent agreement with those deduced from forward-angle inelastic proton scattering at relativistic beam energies. In addition, the GSFs are shown to be independent of excitation energies and spins of the initial and final states. The results provide a critical test of the generalized Brink-Axel hypothesis in heavy nuclei, demonstrating its applicability in the energy region of the pygmy dipole resonance.
Comments:
6 pages, 4 figures, Phys. Rev. Lett. (in press)
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2012.11956 [pdf]
PRL(2021)·27 citations
07
[Submitted on 22 Dec 2020] (cross-list from hep-ph)
Formation of light (anti)nuclei
J. Tjemsland🇳🇴
The production mechanism of light nuclei, such as deuteron, helium-3, tritium and their antiparticles, has recently attracted an increased attention from the astroparticle and heavy ion communities. The expected low astrophysical background of light antinulei makes them ideal probes for exotic astrophysical processes, such as dark matter annihilations. At the same time, they can be used to measure two-nucleon correlations and density fluctuations in heavy ion collisions, which may shed light on the QCD phase diagram. Motivated by the importance of light antinuclei in cosmic ray studies, we developed a new coalescence model for light (anti)nuclei that includes both the size of the formation region, which is process dependent, and momentum correlations in a semi-classical picture. We have employed the model as an afterburner to the event generators Pythia 8 and QGSJET II, and find that the model agrees well with experimental data on antideuteron and antihelium-3 production in $e^{+} e^{-}$ , $pp$ , $p$ Be and $p$ Al collisions at various energies. In this paper, we review this model and update existing fits to experimental data based on new insights.
Comments:
12 pages, 4 pdf figures. Contribution to Tools for High Energy Physics and Cosmology - TOOLS2020 2-6 Nov. 2020
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2012.12252 [pdf]
PoS(2021)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE

Towards complete leading-order predictions for neutrinoless double β decay

Nuclear charge-exchange excitations based on relativistic density-dependent point-coupling model

Structure of double pionic atoms

Electromagnetic form factors of the Ω− baryon in the spacelike and timelike regions

Kinematic Azimuthal Asymmetries and Lam-Tung Relation

Comprehensive test of the Brink-Axel hypothesis in the energy region of the pygmy dipole resonance

Formation of light (anti)nuclei

Affiliations

Towards complete leading-order predictions for neutrinoless double $β$ decay

Electromagnetic form factors of the $Ω^{-}$ baryon in the spacelike and timelike regions