Nuclear Theory·nucl-th

Wednesday·December 12, 2018

8 papers—5 primary·3 cross-listed

01
[Submitted on 11 Dec 2018]
$γ W$ -box Inside-Out: Nuclear Polarizabilities Distort the Beta Decay Spectrum
Mikhail Gorchtein🇩🇪
I consider the $γ W$ -box correction to superallowed nuclear $β$ -decays in the framework of dispersion relations. I address a novel effect of a distortion of the emitted electron energy spectrum by nuclear polarizabilities and show that this effect, while neglected in the literature, is sizable. I estimate its size in the approximation of a linear energy dependence, and using two models that are expected to give the lower and the upper bound. The respective correction to the $β^{+}$ spectrum is estimated to be $Δ_{R} (E) = (1.6 \pm 1.6) \times 1 0^{- 4} E / MeV$ assuming a conservative 100\% uncertainty. The effect is positive-definite and can be observed if a high-precision measurement of the positron spectrum is viable. If only the full rate is observed, it should be included in the calculated $F t$ -values of nuclear decays. I argue that this novel effect should be evaluated in state-of-the-art nuclear models and included in the analyses of nuclear beta decay experiments to ensure the correct extraction of $V_{u d}$ from decay rates, and of the Fierz interference term from precision measurements of decay spectra.
Comments:
5 pages, 2 figures, 1 table; version accepted to Phys.Rev.Lett
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1812.04229 [pdf]
PRL(2019)·109 citations
02
[Submitted on 11 Dec 2018]
Search for the QCD Critical Point by Transverse Velocity Dependence of Anti-deuteron to Deuteron Ratio
Ning Yu🇨🇳 · Dingwei Zhang🇨🇳 · Xiaofeng Luo🇨🇳
We propose the transverse velocity ( $β_{T}$ ) dependence of the anti-deuteron to deuteron ratio as a new observable to search for the QCD critical point in heavy-ion collisions. The QCD critical point can attract the system evolution trajectory in the QCD phase diagram, which is known as focusing effect. To quantify this effect, we employ thermal model and hadronic transport model to simulate the dynamical particle emission along a hypothetical focusing trajectory near critical point. We found the focusing effect can lead to anomalous $β_{T}$ dependence of $p ˉ / p$ , $d ˉ / d$ and $^{3} He /^{3} He$ ratios. We examined the $β_{T}$ dependence of $p ˉ / p$ and $d ˉ / d$ ratios of central Au+Au collisions at $s_{N N}$ = 7.7 to 200 GeV measured by the STAR experiment at RHIC. Surprisingly, we only observe a negative slope in $β_{T}$ dependence of $d ˉ / d$ ratio at $s_{N N}$ = 19.6 GeV, which indicates the trajectory evolution has passed through the critical region. In the future, we could constrain the location of the critical point and/or width of the critical region by making precise measurements on the $β_{T}$ dependence of $d ˉ / d$ ratio at different energies and rapidity.
Comments:
4 pages, 5 figures, To be published in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1812.04291 [pdf]
CPC(2020)·26 citations
03
[Submitted on 11 Dec 2018]
Renormalization of the GT operator within the realistic shell model
L. Coraggio🇮🇹 · L. De Angelis🇮🇹 · T. Fukui🇮🇹 · A. Gargano🇮🇹 · N. Itaco🇮🇹 · F. Nowacki🇫🇷
In nuclear structure calculations, the choice of a limited model space, due to computational needs, leads to the necessity to renormalize the Hamiltonian as well as any transition operator. Here, we present a study of the renormalization procedure and effects of the Gamow-Teller operator within the framework of the realistic shell model. Our effective shell-model operators are obtained, starting from a realistic nucleon-nucleon potential, by way of the many-body perturbation theory in order to take into account the degrees of freedom that are not explicitly included in the chosen model space. The theoretical effective shell-model Hamiltonian and transition operators are then employed in shell-model calculations, whose results are compared with data of Gamow-Teller transition strengths and double-beta half-lives for nuclei which are currently of interest for the detection of the neutrinoless double-beta decay process, in a mass interval ranging from A=48 up to A=136. We show that effective operators are able to reproduce quantitatively the spectroscopic and decay properties without resorting to an empirical quenching neither of the axial coupling constant gA, nor of the spin and orbital gyromagnetic factors. This should assess the reliability of applying present theoretical tools to this problematic.
Comments:
16 pages, 15 figures, to be published in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1812.04292 [pdf]
PRC(2019)·61 citations
04
[Submitted on 11 Dec 2018]
Nuclear Astrophysics in the Multimessenger Era: A Partnership Made in Heaven
J. Piekarewicz🇺🇸
On August 17, 2017 the LIGO-Virgo collaboration detected for the first time gravitational waves from the binary merger of two neutron stars (GW170817). Unlike the merger of two black holes, the associated electromagnetic radiation was also detected by a host of telescopes operating over a wide range of frequencies---opening a brand new era of multimessenger astronomy. This historical detection is providing fundamental new insights into the astrophysical site for the r-process and on the nature of dense matter. In this contribution we examine the impact of GW170817 on the equation of state of neutron rich matter, particularly on the density dependence of the symmetry energy. Limits on the tidal polarizability extracted from GW170817 seem to suggest that the symmetry energy is soft, thereby excluding models that predict overly large stellar radii.
Comments:
16 pages, 4 figures, Invited Lecture presented at the Zakopane Conference on Nuclear Physics "Extremes of the Nuclear Landscape", Zakopane, Poland, August 26-September 2, 2018. To be published in ACTA PHYSICA POLONICA B Volume 50
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
arXiv:
1812.04438 [pdf]
Acta Phys.Polon.B(2019)·4 citations
05
[Submitted on 7 Dec 2018]
Sensitivity of the elastic electron-proton cross section to the proton radius
Simone Pacetti🇮🇹 · Egle Tomasi-Gustafsson🇫🇷
The precise determination of the proton radius from recent elastic scattering electron-proton data is discussed. The necessary precision on the elastic cross section to discriminate among the values coming from atomic spectroscopy is scrutinized in terms of the relevant quantity, i.e., the derivative of the form factor. It is shown that such precision is two orders of magnitude higher than the precision on the cross section, that is the measured observable. Different fits on the available data and of their discrete derivative, with analytical constraints are shown. The systematic error associated to the radius is evaluated taking into account the uncertainties from different sources, as the extrapolation to the static point, the choice of the class of fitting functions and the range of the data sample. This error is shown to be even orders of magnitude larger than commonly assumed.
Comments:
18 pages, 10 figures, 1 table
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1812.04444 [pdf]
EPJA(2020)·10 citations

Affiliations

first authorsco-authorsvia INSPIRE

γW-box Inside-Out: Nuclear Polarizabilities Distort the Beta Decay Spectrum

Search for the QCD Critical Point by Transverse Velocity Dependence of Anti-deuteron to Deuteron Ratio

Renormalization of the GT operator within the realistic shell model

Nuclear Astrophysics in the Multimessenger Era: A Partnership Made in Heaven

Sensitivity of the elastic electron-proton cross section to the proton radius

Affiliations

$γ W$ -box Inside-Out: Nuclear Polarizabilities Distort the Beta Decay Spectrum