Nuclear Theory·nucl-th

Friday·September 25, 2020

14 papers—8 primary·6 cross-listed

01
[Submitted on 23 Sept 2020]
Consistent description of angular correlations in $β$ decay for Beyond Standard Model physics searches
Leendert Hayen🇺🇸 · Albert R. Young🇺🇸
Measurements of angular correlations between initial and final particles in $β$ decay remain one of the most promising ways of probing the Standard Model and looking for new physics. As experiments reach unprecedented precision well into the per-mille regime, proper extraction of results requires one to take into account a great number of nuclear structure and radiative corrections in a procedure which becomes dependent upon the experimental geometry. We provide here a compilation and update of theoretical results which describe all corrections in the same conceptual framework, point out pitfalls and review the influence of the experimental geometry. Finally, we summarize the potential for new physics reach.
Comments:
23 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2009.11364 [pdf]
22 citations
02
[Submitted on 24 Sept 2020]
Proximity effect of pair correlation in the inner crust of neutron stars
Toshiyuki Okihashi · Masayuki Matsuo
We study proximity effect of pair correlation in the inner crust of neutron stars by means of the Skyrme-Hartree-Fock-Bogoliubov theory formulated in the coordinate space. We describe a system composed of a nuclear cluster immersed in neutron superfluid, which is confined in a spherical box. Using a density-dependent effective pairing interaction which reproduces both the pair gap of neutron matter obtained in ab initio calculations and that of finite nuclei, we analyze how the pair condensate in neutron superfluid is affected by the presence of the nuclear cluster. It is found that the proximity effect is characterized by the coherence length of neutron superfluid measured from the edge position of the nuclear cluster. The calculation predicts that the proximity effect has a strong density dependence. In the middle layers of the inner crust with baryon density $5 \times 1 0^{- 4}$ fm $^{- 3} < ρ_{b} < 2 \times 1 0^{- 2}$ fm $^{- 3}$ , the proximity effect is well limited in the vicinity of the nuclear cluster, i.e. in a sufficiently smaller area than the Wigner-Seitz cell. On the contrary, the proximity effect is predicted to extend to the whole volume of the Wigner-Seitz cell in shallow layers of the inner crust with $ρ_{b} < 2 \times 1 0^{- 4}$ fm $^{- 3}$ , and in deep layers with $ρ_{b} > 5 \times 1 0^{- 2}$ fm $^{- 3}$ .
Comments:
23 pages, 8 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.11505 [pdf]
PTEP(2021)·8 citations
03
[Submitted on 24 Sept 2020]
Magnetic field effect on pion superfluid
Shijun Mao🇨🇳
Magnetic field effect on pion superfluid phase transition is investigated in frame of a Pauli-Villars regularized NJL model. Instead of directly dealing with charged pion condensate, we apply the Goldstone's theorem (massless Goldstone boson $π^{+}$ ) to determine the onset of pion superfluid phase, and obtain the phase diagram in magnetic field, temperature, isospin and baryon chemical potential space. At weak magnetic field, it is analytically proved that the critical isospin chemical potential of pion superfluid phase transition is equal to the mass of $π^{+}$ meson in magnetic field. The pion superfluid phase is retarded to higher isospin chemical potential, and can survive at higher temperature and higher baryon chemical potential under external magnetic field.
Comments:
5 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2009.11550 [pdf]
PRD(2020)·6 citations
04
[Submitted on 24 Sept 2020]
Dynamical energy loss formalism: from describing suppression patterns to implications for future experiments
Magdalena Djordjevic🇷🇸 · Dusan Zigic🇷🇸 · Bojana Blagojevic🇷🇸 · Jussi Auvinen🇷🇸 · Igor Salom🇷🇸 · Marko Djordjevic🇷🇸
Understanding properties of Quark-Gluon Plasma requires an unbiased comparison of experimental data with theoretical predictions. To that end, we developed the dynamical energy loss formalism which, in distinction to most other methods, takes into account a realistic medium composed of dynamical scattering centers. The formalism also allows making numerical predictions for a wide number of observables with the same parameter set fixed to standard literature values. In this proceedings, we overview our recently developed DREENA-C and DREENA-B frameworks, where DREENA is a computational implementation of the dynamical energy loss formalism, and where C stands for constant temperature QCD medium, while B stands for the medium modeled by 1+1D Bjorken expansion. At constant temperature our predictions overestimate $v_{2}$ , in contrast to other models, but consistent with simple analytical estimates. With Bjorken expansion, we have a good agreement of the predictions with both $R_{AA}$ and $v_{2}$ measurements. We find that introducing medium evolution has a larger effect on $v_{2}$ predictions, but for precision predictions it has to be taken into account in $R_{AA}$ predictions as well. Based on numerical calculations and simple analytical derivations, we also propose a new observable, which we call path length sensitive suppression ratio, for which we argue that the path length dependence can be assessed in a straightforward manner. We also argue that $P b + P b$ vs. $X e + X e$ measurements make a good system to assess the path length dependence. As an outlook, we expect that introduction of more complex medium evolution (beyond Bjorken expansion) in the dynamical energy loss formalism can provide a basis for a state of the art QGP tomography tool - e.g. to jointly constrain the medium properties from the point of both high pt and low pt data.
Comments:
Proceedings of the XXVIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions(Quark Matter 2018)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2009.11579 [pdf]
NPA(2019)·3 citations
05
[Submitted on 24 Sept 2020]
Structure of the quartetting ground state of $N = Z$ nuclei
A. G. Serban · D. R. Nichita · D. Negrea · V. V. Baran
The formal equivalence between the quartetting picture and the symmetry restored BCS picture is established for the ground state correlations induced by the general isovector-isoscalar pairing interaction. Multiple ground state structures compatible with the particle number and isospin symmetries are evaluated. The competition of isovector and isoscalar correlations is discussed for the $N = Z$ nuclei above $^{100}$ Sn.
Comments:
5 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.11588 [pdf]
EPJA(2021)·2 citations
06
[Submitted on 24 Sept 2020]
Complete experiments in pseudoscalar meson photoproduction
Yannick Wunderlich
The problem of extracting photoproduction amplitudes uniquely from so called complete experiments is discussed. This problem can be considered either for the extraction of full production amplitudes, or for the determination of multipoles. Both cases are treated briefly. Preliminary results for the fitting of multipoles, as well as the determination of their error, from recent polarization measurements in the $Δ$ -region are described in more detail.
Comments:
9 pages, 2 figures, 2 tables; This article was originally published as part of the Proceedings of the Mini-Workshop "Exploring Hadron Resonances" held in Bled, Slovenia, in July 2015
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.11613 [pdf]
Bled Workshops Phys.(2015)·0 citations
07
[Submitted on 24 Sept 2020]
Mathematical aspects of phase rotation ambiguities in partial wave analyses
Yannick Wunderlich
The observables in a single-channel $2$ -body scattering problem remain invariant once the amplitude is multiplied by an overall energy- and angle-dependent phase. This invariance is known as the continuum ambiguity. Also, mostly in truncated partial wave analyses (TPWAs), discrete ambiguities originating from complex conjugation of roots are known to occur. In this note, it is shown that the general continuum ambiguity mixes partial waves and that for scalar particles, discrete ambiguities are just a subset of continuum ambiguities with a specific phase. A numerical method is outlined briefly, which can determine the relevant connecting phases.
Comments:
11 pages, 3 figures; This article was originally published as part of the Proceedings of the Mini-Workshop "Advances in Hadronic Resonances" held in Bled, Slovenia, in July 2017
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2009.11625 [pdf]
Bled Workshops Phys.(2017)·0 citations
08
[Submitted on 24 Sept 2020]
Dilepton production in microscopic transport theory with in-medium $ρ$ -meson spectral function
A.B. Larionov🇩🇪 · U. Mosel🇩🇪 · L. von Smekal🇩🇪
We use the microscopic GiBUU transport model to calculate dilepton ( $e^{+} e^{-}$ ) production in heavy-ion collisions at SIS18 energies focusing on the effect of collisional broadening of the $ρ$ -meson. The collisional width of the $ρ$ -meson at finite temperature and baryon density in nuclear matter is calculated on the basis of the collision integral of the GiBUU model. A systematic comparison with HADES data on dilepton production in heavy-ion collisions is performed. The collisional broadening of the $ρ$ improves the agreement between theory and experiment for the dilepton invariant-mass distributions near the $ρ$ pole mass and for the excess radiation in Au+Au at $1.23 A$ GeV. We furthermore show that some remaining underprediction of the experimental dilepton spectra in C+C at $1 A$ GeV and Au+Au at $1.23 A$ GeV at intermediate invariant masses $0.2 - 0.4$ GeV can be accounted for by adjusting the $p n$ bremsstrahlung cross section in a way to agree with the inclusive dilepton spectrum from $d p$ collisions at $1.25 A$ GeV.
Comments:
Relevant result figures replaced, correcting small bug in pion propagation, Conclusions unchanged
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2009.11702 [pdf]
PRC(2021)·20 citations

Affiliations

first authorsco-authorsvia INSPIRE