Nuclear Theory·nucl-th

Wednesday·January 17, 2018

5 papers—3 primary·2 cross-listed

01
Poisson baseline of net-charge fluctuations in the relativistic heavy ion collisions
Xue Pan🇨🇳 · Yufu Lin🇨🇳 · Lizhu Chen🇨🇳 · Mingmei Xu🇨🇳 · Yuanfang Wu🇨🇳
Taking doubly charged particles, positive-negative charge pair production and the effects of volume fluctuations into account, the Poisson baseline of the fluctuations of net-charge is studied. Within the Poisson baseline, the cumulants of net-charge are derived. Comparing to the Skellam baseline of net-charge, we infer that doubly charged particles broaden the distributions of net-charge, while positive-negative charge pairs narrow the distributions. Using the ratios of doubly charged particles and positive-negative charge pairs from neutral resonance decays to the total positive charges from THERMINATOR 2, the first four orders of moments and the corresponding moment products are calculated in the Poisson baseline for Au + Au collisions at $s_{N N}$ = 200 GeV at RHIC/STAR. We find that the standard deviation is mainly influenced by the resonance decay, while the third and fourth order moments and corresponding moment products are mainly modified and fit the data of RHIC/STAR much better after including the effects of volume fluctuations.
nucl-thhep-exhep-phCPC(2018)·1 citation
02
Neutron Anomalous Magnetic Moment in Dense Magnetized Systems
Zeinab Rezaei🇮🇷
In this work, we calculate the neutron anomalous magnetic moment supposing that this value can depend on the density and magnetic field of system. We employ the lowest order constraint variation (LOCV) method and $A V_{18}$ nuclear potential to calculate the medium dependency of the neutron anomalous magnetic moment. It is confirmed that the neutron anomalous magnetic moment increases by increasing the density, while it decreases as the magnetic field grows. The energy and equation of state for the system have also been investigated.
nucl-thastro-ph.HEastro-ph.SRIJMPE(2018)·2 citations
03
Characteristic \alpha and ^{6}He decays of the linear-chains in ^{16}C
Tomoyuki Baba · Masaaki Kimura
The linear-chain states of $^{16}$ C and their decay modes are theoretically investigated by using the antisymmetrized molecular dynamics. It is found that the positive-parity linear-chain states have the $(3/ 2_{π}^{-})^{2} (1/ 2_{σ}^{-})^{2}$ configuration and primary decay to the $^{12}$ Be( $2_{1}^{+}$ ) as well as to the $^{12}$ Be(g.s.) by the $α$ particle emission. Moreover, we show that they also decay to the $^{6} He +^{10} Be$ channel. In the negative-parity states, it is found that two types of the linear-chains exist. One has the valence neutrons occupying the molecular-orbits $(3/ 2_{π}^{-})^{2} (1/ 2_{σ}^{-}) (3/ 2_{π}^{+})$ , while the other's configuration cannot be explained in terms of the molecular orbits because of the strong parity mixing. Both configurations constitute the rotational bands with large moment of inertia and intra-bands $E 2$ transitions. Their $α$ and $^{6} He$ reduced widths are sufficiently large to be distinguished from other non-cluster states although they are smaller than those of the positive-parity linear-chain.
nucl-thPRC(2018)·19 citations
04
Reorientation-effect measurement of the first 2 $^{+}$ state in $^{12}$ C: confirmation of oblate deformation
M. Kumar Raju · J. N. Orce · P. Navratil · G. C. Ball · T. E. Drake · S. Triambak · G. Hackman · C. J. Pearson · the TIGRESS/UWC Collaboration
A Coulomb-excitation reorientation-effect measurement using the TIGRESS $γ -$ ray spectrometer at the TRIUMF/ISAC II facility has permitted the first determination of the $⟨ 2_{1}^{+} ∣∣ E 2^∣∣ 2_{1}^{+} ⟩$ diagonal matrix element in $^{12}$ C from particle $- γ$ coincidence data. Required state-of-the-art no-core shell model calculations of the nuclear polarizability for the ground and first-excited (2 $_{1}^{+}$ ) states in $^{12}$ C using chiral NN N $^{4}$ LO500 and NN+3NF350 interactions have been performed. Consistent predictions show a larger polarizability than previously anticipated. The polarizability of the 2 $_{1}^{+}$ state is introduced into the current and previous Coulomb-excitation reorientation-effect analysis of $^{12}$ C. Spectroscopic quadrupole moments of $Q_{_{S}} (2_{1}^{+}) = + 0.053 (44)$ eb and $Q_{_{S}} (2_{1}^{+}) = + 0.08 (3)$ eb are determined, respectively, yielding a weighted average of $Q_{_{S}} (2_{1}^{+}) = + 0.071 (25)$ eb, in agreement with recent ab initio calculations. The present measurement confirms that the 2 $_{1}^{+}$ state of $^{12}$ C is oblate and emphasizes the important role played by the nuclear polarizability in Coulomb-excitation studies of light nuclei.
↳ nucl-exnucl-thPLB(2018)·25 citations
05
Dark Matter Interpretation of the Neutron Decay Anomaly
Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸
There is a long-standing discrepancy between the neutron lifetime measured in beam and bottle experiments. We propose to explain this anomaly by a dark decay channel for the neutron, involving one or more dark sector particles in the final state. If any of these particles are stable, they can be the dark matter. We construct representative particle physics models consistent with all experimental constraints.
↳ hep-phnucl-exnucl-thPRL(2018)·262 citations

Affiliations

first authorsco-authorsvia INSPIRE

Poisson baseline of net-charge fluctuations in the relativistic heavy ion collisions

Neutron Anomalous Magnetic Moment in Dense Magnetized Systems

Characteristic \alpha and ^{6}He decays of the linear-chains in ^{16}C

Reorientation-effect measurement of the first 2+ state in 12C: confirmation of oblate deformation

Dark Matter Interpretation of the Neutron Decay Anomaly

Affiliations

Reorientation-effect measurement of the first 2 $^{+}$ state in $^{12}$ C: confirmation of oblate deformation