Nuclear Theory·nucl-th

Friday·May 6, 2016

6 papers—4 primary·2 cross-listed

01
[Submitted on 5 May 2016]
Improvement in a phenomenological formula for ground state binding energies
G. Gangopadhyay
The phenomenological formula for ground state binding energy derived earlier (International Journal of Modern Physics E {\bf 20} (2011) 179) has been modified. The parameters have been obtained by fitting the latest available tabulation of experimental values. The major modifications include a new term for pairing and introduction of a new neutron magic number at $N = 160$ . The new formula reduced the root mean square deviation to 363 keV, a substantial improvement over the previous version of the formula.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.01476 [pdf]
IJMPE(2016)·1 citation
02
[Submitted on 5 May 2016]
Structure of $^{78}$ Ni from first principles computations
G. Hagen🇺🇸 · G. R. Jansen🇺🇸 · T. Papenbrock🇺🇸
Doubly magic nuclei have a simple structure and are the cornerstones for entire regions of the nuclear chart. Theoretical insights into the supposedly doubly magic $^{78}$ Ni and its neighbors are challenging because of the extreme neutron-to-proton ratio and the proximity of the continuum. We predict the $J^{π} = 2_{1}^{+}$ state in $^{78}$ Ni from a correlation with the $J^{π} = 2_{1}^{+}$ state in $^{48}$ Ca using chiral nucleon-nucleon and three-nucleon interactions. Our results confirm that $^{78}$ Ni is doubly magic, and the predicted low-lying states of $^{79, 80}$ Ni open the way for shell-model studies of many more rare isotopes.
Comments:
8 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1605.01477 [pdf]
PRL(2016)·141 citations
03
[Submitted on 5 May 2016]
Geometrical scaling of inclusive charged hadron $p_{T}$ spectra in Pb-Pb collsions at 2.76 TeV
W. C. Zhang🇨🇳
In Pb-Pb collisions at $s_{NN}$ = 2.76 TeV, we report on a geometrical scaling in the transverse momentum ( $p_{T}$ ) spectra of inclusive charged hadrons at 0-5 $%$ , 5-10 $%$ , 10-20 $%$ , 20-30 $%$ , 30-40 $%$ , 40-50 $%$ , 50-60 $%$ , 60-70 $%$ and 70-80 $%$ centralities. This geometrical scaling is exhibited when these spectra are expressed in terms of a new scaling variable, $p_{T}^{'} = p_{T} (191.5/ N_{A})^{1/ (3 λ + 6)}$ , where $N_{A}$ is the number of participating nucleon pairs, $λ$ is the scaling parameter. With the method of ratios, this scaling parameter is determined to be 1.68. We then use a single Tsallis distribution to parameterize the spectra at different centralities, and find that the Tsallis temperature $T$ is proportional to $N_{A}^{1/ (3 λ + 6)}$ , which is exactly the prediction of the geometrical scaling. The geometrical scaling also predicts that the charged-particle density per participating nucleon pair ( $(d N_{ch} / d η) / N_{A}$ ) grows as a power of $N_{A}$ , $N_{A}^{2/ (3 λ + 6)}$ , which is confirmed by the data collected by the ALICE collaboration.
Comments:
6 pages, 5 EPS figures included. In v2, another table is added, and the fifth reference has been changed
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.01541 [pdf]
0 citations
04
[Submitted on 5 May 2016]
Tritium $β$ -decay in chiral effective field theory
A. Baroni🇺🇸 · L. Girlanda🇮🇹 · A. Kievsky🇮🇹 · L.E. Marcucci🇮🇹 · R. Schiavilla🇺🇸 · M. Viviani🇮🇹
We evaluate the Fermi and Gamow-Teller (GT) matrix elements in tritium $β$ -decay by including in the charge-changing weak current the corrections up to one loop recently derived in nuclear chiral effective field theory ( $χ$ EFT). The trinucleon wave functions are obtained from hyperspherical-harmonics solutions of the Schrodinger equation with two- and three-nucleon potentials corresponding to either $χ$ EFT (the N3LO/N2LO combination) or meson-exchange phenomenology (the AV18/UIX combination). We find that contributions due to loop corrections in the axial current are, in relative terms, as large as (and in some cases, dominate) those from one-pion exchange, which nominally occur at lower order in the power counting. We also provide values for the low-energy constants multiplying the contact axial current and three-nucleon potential, required to reproduce the experimental GT matrix element and trinucleon binding energies in the N3LO/N2LO and AV18/UIX calculations.
Comments:
19 pages,6 figures, corrections to Text as suggested by Referee added; Erratum: 4 pages, 3 figures, corrections to Eq.(20), Tables I, II, III, Figures 4, 5, conclusions unchanged
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1605.01620 [pdf]
PRC(2016)·72 citations

Affiliations

first authorsco-authorsvia INSPIRE

Improvement in a phenomenological formula for ground state binding energies

Structure of 78Ni from first principles computations

Geometrical scaling of inclusive charged hadron pT​ spectra in Pb-Pb collsions at 2.76 TeV

Tritium β-decay in chiral effective field theory

Affiliations

Structure of $^{78}$ Ni from first principles computations

Geometrical scaling of inclusive charged hadron $p_{T}$ spectra in Pb-Pb collsions at 2.76 TeV

Tritium $β$ -decay in chiral effective field theory