Mon·Jan 29, 2018Monday·January 29, 2018

1. 01*

   Centrality dependent Lévy-stable two-pion Bose-Einstein correlations at the PHENIX experiment

   Sándor Lökös (for PHENIX Collaboration)🇭🇺

   Investigation of femtoscopic correlation functions in relativistic heavy ion reactions is an important tool to access the space-time structure of particle production in the sQGP. The shape of the correlation functions is often assumed to be Gaussian, but a detailed analysis reveals that the statistically correct assumption could be the so-called Lévy distribution. The detailed analysis of correlation functions in various systems may shed light on the location of the critical endpoint on the QCD phase diagram. It could also reveal if there is partially coherent pion production or could indicate the possible in-medium mass modification of the ${\eta }^{\prime }$ meson due to the (partial) restoration of the $U_A(1)$ axial symmetry. In this paper we present the status of the centrality dependent measurements of two-pion Lévy Bose-Einstein correlation functions in Au+Au collisions at PHENIX.

   nucl-exhep-exUniverse(2018)·14 citations
2. 02*

   Precision mass measurements on neutron-rich rare-earth isotopes at JYFLTRAP - reduced neutron pairing and implications for the $r$-process calculations

   M. Vilen🇫🇮 · J.M. Kelly🇺🇸 · A. Kankainen🇫🇮 · M. Brodeur🇺🇸 · A. Aprahamian🇺🇸 · L. Canete · T. Eronen🇫🇮 · A. Jokinen🇫🇮 · T. Kuta · I.D. Moore🇫🇮 · M.R. Mumpower🇺🇸 · D.A. Nesterenko🇫🇮 and 7 other authors

   The rare-earth peak in the $r$-process abundance pattern depends sensitively on both the astrophysical conditions and subtle changes in nuclear structure in the region. This work takes an important step elucidating the nuclear structure and reducing the uncertainties in $r$-process calculations via precise atomic mass measurements at the JYFLTRAP double Penning trap. ${}^{158}$Nd, ${}^{160}$Pm, ${}^{162}$Sm, and ${}^{164-166}$Gd have been measured for the first time and the precisions for ${}^{156}$Nd, ${}^{158}$Pm, ${}^{162,163}$Eu, ${}^{163}$Gd, and ${}^{164}$Tb have been improved considerably. Nuclear structure has been probed via two-neutron separation energies $S_{2n}$ and neutron pairing energy metrics $D_n$. The data do not support the existence of a subshell closure at $N=100$. Neutron pairing has been found to be weaker than predicted by theoretical mass models. The impact on the calculated $r$-process abundances has been studied. Substantial changes resulting in a smoother abundance distribution and a better agreement with the solar $r$-process abundances are observed.

   nucl-exastro-ph.HEastro-ph.SRnucl-thPRL(2018)·57 citations
3. 03*

   N* Structure and Strong QCD

   Craig D. Roberts🇺🇸

   In attempting to match QCD with Nature, it is necessary to confront the many complexities of strong, nonlinear dynamics in relativistic quantum field theory, e.g. the loss of particle number conservation, the frame and scale dependence of the explanations and interpretations of observable processes, and the evolving character of the relevant degrees-of-freedom. The peculiarities of QCD ensure that it is also the only known fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, gluons and quarks; and yet gluons and quarks are predicted to acquire mass dynamically so that the only massless systems in QCD are its composite Nambu-Goldstone bosons. All other everyday bound states possess nuclear-size masses, far in excess of anything that can directly be tied to the Higgs boson. These observations highlight fundamental questions within the Standard Model: what is the source of the mass for the vast bulk of visible matter in the Universe, how is its appearance connected with confinement; how is this mass distributed within hadrons and does the distribution differ from one hadron to another? This contribution sketches insights drawn using modern methods for the continuum bound-state problem in QCD, and how they have been informed by empirical information on the hadron spectrum and nucleon-to-resonance transition form factors.

   ↳ nucl-thhep-lathep-phnucl-exFew Body Syst.(2018)·23 citations
4. 04*

   Microscopically-based energy density functionals for nuclei using the density matrix expansion: Full optimization and validation

   R. Navarro Perez🇺🇸 · N. Schunck🇺🇸 · A. Dyhdalo🇺🇸 · R.J. Furnstahl🇺🇸 · S.K. Bogner🇺🇸

   We seek to obtain a usable form of the nuclear energy density functional that is rooted in the modern theory of nuclear forces. We thus consider a functional obtained from the density matrix expansion of local nuclear potentials from chiral effective field theory. We propose a parametrization of this functional carefully calibrated and validated on selected ground-state properties that is suitable for large-scale calculations of nuclear properties. The first component of this functional is a non-local functional of the density and corresponds to the direct part (Hartree term) of the expectation value of local chiral potentials on a Slater determinant. A second component is a local functional of the density and is obtained by applying the density matrix expansion to the exchange part (Fock term) of the expectation value of the local chiral potential. We apply the UNEDF2 optimization protocol to determine the coupling constants of this energy functional. We obtain a set of microscopically-constrained functionals for local chiral potentials from leading-order up to next-to-next-to-leading order with and without three-body forces and contributions from $\Delta$ excitations. These functionals are validated on the calculation of nuclear and neutron matter, nuclear mass tables, single-particle shell structure in closed-shell nuclei and the fission barrier of ${}^{240}$Pu. Quantitatively, they perform noticeable better than the more phenomenological Skyrme functionals. The inclusion of higher-order terms in the chiral perturbation expansion seems to produce a systematic improvement in predicting nuclear binding energies. This result is especially promising since all the fits have been performed at the single reference level of the energy density functional approach, where important collective correlations such as center-of-mass correction have not been taken into account yet.

   ↳ nucl-thhep-phnucl-exPRC(2018)·47 citations
5. 05*

   Beyond the neutron-drip line: two-neutron decay of unbound nuclei

   K. Hagino🇯🇵 · H. Sagawa🇯🇵

   We discuss a decay of unbound nuclei beyond the neutron drip-line using a three-body model with a core nucleus and two valence neutrons. We particularly discuss the role of dineutron correlation between the valence neutrons in the two-neutron emission from the ground state of ${}^{26}$O and ${}^{10}$He nuclei. Our calculations clearly indicate that the emission of the two neutrons in the back-to-back direction is enhanced due to the dineutron correlation.

   ↳ nucl-thnucl-exJPS Conf.Proc.(2018)·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.