Mon·Mar 16, 2020Monday·March 16, 2020

1. 01*

   High precision mass measurements of the isomeric and ground states of ${}^{44}$V: improving constraints on the IMME parameters of the A=44, ${\text{0}}^{\text{+}}$ quintet

   D. Puentes🇺🇸 · G. Bollen🇺🇸 · M. Brodeur🇺🇸 · M. Eibach🇩🇪 · K. Gulyuz🇺🇸 · A. Hamaker🇺🇸 · C. Izzo🇺🇸 · S. M. Lenzi🇮🇹 · M. MacCormick🇫🇷 · M. Redshaw🇺🇸 · R. Ringle🇺🇸 · R. Sandler🇺🇸 and 7 other authors

   The Isobaric Multiplet Mass Equation (IMME) has been successful at predicting the masses of isobaric analogue states in the same multiplet, while its coefficients are known to follow trends as functions of mass number. The Atomic Mass Evaluation 2016 [Chin. Phys. C 41, 030003 (2017)] ${}^{44}$V mass value results in an negative $c$ coefficient for the IMME quadratic term. The $b$ and $c$ coefficients can provide constraints for construction of the isospin-nonconserving (INC) Hamiltonians for the $pf$ shell. The excitation energy of the $0^{+},T=2$ level in ${}^{44}$V is currently unknown and can be used to constrain the ${}^{44}$Cr mass. The aim of the experiment was to perform high-precision mass measurements to resolve the difference between ${}^{44}$V isomeric and ground states, to test the IMME, and to provide ingredients for identifying the $0^{+}$, $T=2$ state in ${}^{44}$V. High-precision Penning trap mass spectrometry was performed at LEBIT, to measure the cyclotron frequency ratios of [${}^{44g,m}$VO]${}^{+}$ versus [${}^{32}$SCO]${}^{+}$, a reference mass, to extract both the isomeric and ground state masses of ${}^{44}$V. The mass excess of the ground and isomeric states in ${}^{44}$V were measured to be $-23804.9(80)$ keV/${\text{c}}^2$ and $-23537.0(55)$ keV/${\text{c}}^2$. This yielded a new proton separation energy of $S_p$ = 1\ 773(10) keV. The new mass values of ${}^{44}$V have been used to deduce the IMME $b$ and $c$ coefficients of the lowest $2^{+}$ and $6^{+}$ triplets in $A=44$. The $2^{+}$ $c$ coefficient is verified with the IMME trend and agrees with the shell-model predictions using charge-dependent Hamiltonians. The mirror energy differences were determined between ${}^{44}$V and ${}^{44}$Sc, in line with isospin-symmetry. The new value of the proton separation energy determined will be important for the determination of the $0^{+}$, $T=2$ state in ${}^{44}$V and for prediction of the mass of ${}^{44}$Cr.

   nucl-exPRC(2020)·14 citations
2. 02*

   Measurement of nuclear effects on $\psi (2S)$ production in p-Pb collisions at $\sqrt{{\text{s}}_{\mathrm{NN}}}=8.16$ TeV

   ALICE Collaboration

   Inclusive $\psi$(2S) production is measured in p-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{\mathrm{NN}}}=8.16$ TeV, using the ALICE detector at the CERN LHC. The production of $\psi$(2S) is studied at forward ($2.03<y_{\mathrm{cms}}<3.53$) and backward ($-4.46<y_{\mathrm{cms}}<-2.96$) centre-of-mass rapidity and for transverse momentum $p_{\mathrm{T}}$ $<$ 12 GeV/$c$ via the decay to muon pairs. In this paper, we report the integrated as well as the $y_{\mathrm{cms}}$- and $p_{\mathrm{T}}$-differential inclusive production cross sections. Nuclear effects on $\psi$(2S) production are studied via the determination of the nuclear modification factor that shows a strong suppression at both forward and backward centre-of-mass rapidities. Comparisons with corresponding results for inclusive J/$\psi$ show a similar suppression for the two states at forward rapidity (p-going direction), but a stronger suppression for $\psi$(2S) at backward rapidity (Pb-going direction). As a function of $p_{\mathrm{T}}$, no clear dependence of the nuclear modification factor is found. The relative size of nuclear effects on $\psi$(2S) production compared to J/$\psi$ is also studied via the double ratio of production cross sections $[{\sigma }_{\psi (2S)}/{\sigma }_{J/\psi }{]}_{\mathrm{pPb}}/[{\sigma }_{\psi (2S)}/{\sigma }_{J/\psi }{]}_{\mathrm{pp}}$ between p-Pb and pp collisions. The results are compared with theoretical models that include various effects related to the initial and final state of the collision system and also with previous measurements at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV.

   nucl-exhep-exJHEP(2020)·40 citations
3. 03*

   Charge radius of the short-lived ${}^{68}$Ni and correlation with the dipole polarizability

   S. Kaufmann🇩🇪 · J. Simonis🇩🇪 · S. Bacca🇩🇪 · J. Billowes🇬🇧 · M. L. Bissell🇬🇧 · K. Blaum🇩🇪 · B. Cheal🇬🇧 · R. F. Garcia Ruiz🇨🇭 · W. Gins🇧🇪 · C. Gorges🇩🇪 · G. Hagen🇺🇸 · H. Heylen🇩🇪 and 17 other authors

   We present the first laser spectroscopic measurement of the neutron-rich nucleus ${}^{68}$Ni at the \mbox{$N=40$} subshell closure and extract its nuclear charge radius. Since this is the only short-lived isotope for which the dipole polarizability ${\alpha }_{\mathrm{D}}$ has been measured, the combination of these observables provides a benchmark for nuclear structure theory. We compare them to novel coupled-cluster calculations based on different chiral two- and three-nucleon interactions, for which a strong correlation between the charge radius and dipole polarizability is observed, similar to the stable nucleus ${}^{48}$Ca. Three-particle--three-hole correlations in coupled-cluster theory substantially improve the description of the experimental data, which allows to constrain the neutron radius and neutron skin of ${}^{68}$Ni.

   nucl-exnucl-thPRL(2020)·50 citations
4. 04*

   Signature dependent triaxiality for shape evolution from superdeformation in rapidly rotating ${}^{40}$Ca and ${}^{41}$Ca

   Shinkuro Sakai · Kenichi Yoshida🇯🇵 · Masayuki Matsuo🇯🇵

   We investigate the possible occurrence of the highly-elongated shapes near the yrast line in ${}^{40}$Ca and ${}^{41}$Ca at high spins on the basis of the nuclear energy-density functional method. Not only the superdeformed (SD) yrast configuration but the yrare configurations on top of the SD band are described by solving the cranked Skyme-Kohn-Sham equation in the three-dimensional coordinate-space representation. It is suggested that some of the excited SD bands undergo band crossings and develop to the hyperdeformation (HD) beyond $J\simeq 25\hslash$ in ${}^{40}$Ca. We find that the change of triaxiality in response to rotation plays a decisive role for the shape evolution towards HD, and that this is governed by the signature quantum number of the last occupied orbital at low spins. This mechanism can be verified in an experimental observation of the positive-parity SD yrast signature-partner bands in ${}^{41}$Ca, one of which ($\alpha =+1/2$) undergoes crossings with the HD band while the other ($\alpha =-1/2$) shows the smooth evolution from the collective rotation at low spins to the non-collective rotation with oblate shape at the termination.

   ↳ nucl-thnucl-exPTEP(2020)·10 citations
5. 05*

   TDHF and a macroscopic aspect of low-energy nuclear reactions

   Kouhei Washiyama · Kazuyuki Sekizawa🇯🇵

   Time-dependent Hartree--Fock (TDHF) method has been applied to various low-energy nuclear reactions, such as fusion, fission, and multinucleon transfer reactions. In this Mini Review, we summarize recent attempts to bridge a microscopic nuclear reaction theory, TDHF, and a macroscopic aspect of nuclear reactions through nucleus--nucleus potentials and energy dissipation from macroscopic degrees of freedom to microscopic ones obtained from TDHF in various colliding systems from light to heavy mass regions.

   ↳ nucl-thnucl-exFront.in Phys.(2020)·9 citations
6. 06*

   Momentum Anisotropy of Leptons from Two Photon Processes in Heavy Ion Collisions

   Bo-Wen Xiao🇨🇳 · Feng Yuan🇺🇸 · Jian Zhou🇨🇳

   We investigate the azimuthal angular correlation between the lepton transverse momentum $P_{\perp }$ and the impact parameter $b_{\perp }$ in non-central heavy-ion collisions, where the leptons are produced through two-photon scattering. Among the Fourier harmonic coefficients, a significant $v_4$ asymmetry is found for the typical kinematics at RHIC and LHC with a mild dependence on the $P_{\perp }$, whereas $v_2$ is power suppressed by the lepton mass over $P_{\perp }$. This unique prediction, if confirmed from the experiments, shall provide crucial information on the production mechanism for the dilepton in two-photon processes.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2020)·38 citations

* 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.