Tue·Apr 21, 2020Tuesday·April 21, 2020

1. 01*

   Locating the freeze-out curve in heavy-ion collisions

   Marcus Bluhm (SUBATECH, Nantes and Darmstadt, EMMI)🇫🇷 · Marlene Nahrgang (SUBATECH, Nantes and Darmstadt, EMMI)🇫🇷 · Jan M. Pawlowski (Heidelberg U. and Darmstadt, EMMI)🇩🇪

   Based on transport equations we argue that the chiral dynamics in heavy-ion collisions at high collision energies effectively decouples from the thermal physics of the fireball. With full decoupling at LHC energies the chiral condensate relaxes to its vacuum expectation value on a much shorter time scale than the typical evolution time of the fluid dynamical fields and their fluctuations. In particular, the net-baryon density remains coupled to the bulk evolution at all collision energies. As the mass scales of the hadrons are controlled by the chiral condensate, it is reasonable to employ vacuum masses in the statistical description of the hadron production at the chemical freeze-out for high collision energies. We predict that at lower collision energies the coupling of the chiral condensate to the thermal medium gradually increases with consequences for the related hadronic masses. A new estimate for the location of the freeze-out curve takes these effects into account.

   ↳ nucl-thhep-phnucl-ex8 citations
2. 02*

   Geometry optimisation of a transparent axisymmetric ion trap for the MORA project

   M. Benali (1)🇫🇷 · G. Quéméner (1)🇫🇷 · P. Delahaye (2)🇫🇷 · X. Fléchard (1)🇫🇷 · E. Liénard (1)🇫🇷 · B. M. Retailleau (2) ((1) Normandie Univ, ENSICAEN, UNICAEN, CNRS/IN2P3, LPC Caen, Caen, France, (2) GANIL, CEA/DSM-CNRS/IN2P3, Bd Henri Becquerel, France)🇫🇷

   In the frame of the project MORA (Matter's Origin from the Radio Activity of trapped and oriented ions), a transparent axially symmetric radio-frequency ion trap (MORATrap) was designed in order to measure the triple correlation parameter $D$ in nuclear $\beta -$decay of laser-polarised ions. The trap design was inspired from the LPCTrap geometry, operated at GANIL from 2005 to 2013. In a real (non-ideal) Paul trap, the quadrupole electric potential is not perfect leading to instabilities in ion motion and therefore affecting the overall trapping efficiency. This paper presents a numerical method aiming to optimise the geometry of a trap. It is applied to MORATrap in order to improve the trapping efficiency and to enlarge the axial transparent solid angle compared to LPCTrap. In the whole optimisation process, numerical computation of electric potential and field was carried out using an electrostatic solver based on boundary element method (BEM). The optimisation consisted in minimising an objective function (fitness function) depending on higher order multipoles of the potential. Finally, systematic changes of trap dimensions and electrode displacements were applied to investigate geometrical effects on the potential quality.

   ↳ physics.ins-detnucl-exEPJA(2020)·5 citations
3. 03*

   Heavy ${\Omega }_c$ and ${\Omega }_b$ baryons in the quark model

   E. Ortiz-Pacheco🇲🇽 · R. Bijker🇲🇽 · A. Giachino🇮🇹 · E. Santopinto🇮🇹

   In this contribution, we present a study of ground- and excited-state ${\Omega }_c$ and ${\Omega }_b$ baryons consisting of two strange quarks and a heavy charm or bottom quark. An analysis in the quark model shows that the recently observed excited ${\Omega }_c$ and ${\Omega }_b$ states can be interpreted in terms of $\lambda$-mode excitations.

   ↳ nucl-thhep-exhep-phnucl-exJ.Phys.Conf.Ser.(2020)·17 citations
4. 04*

   Time-dependent generator coordinate method study of fission: mass parameters

   Jie Zhao🇺🇸 · Tamara Nikšić🇭🇷 · Dario Vretenar🇭🇷 · Shan-Gui Zhou🇨🇳

   Collective mass tensors derived in the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (ATDHFB) method are employed in a study of induced fission dynamics. Together with a collective potential determined in deformation-constrained self-consistent mean-field calculations based on nuclear energy density functionals, the mass tensors specify the collective Hamiltonian that governs the time evolution of the nuclear wave function from an initial state at equilibrium deformation, up to scission and the formation of fission fragments. In an illustrative calculation of low-energy induced fission of ${}^{228}$Th, ${}^{230}$Th, ${}^{234}$U, and ${}^{240}$Pu, we compare the non-perturbative and perturbative cranking ATDHFB mass tensors in the plane of axially-symmetric quadrupole and octupole deformations, as well as the resulting charge yields.

   ↳ nucl-thnucl-exPRC(2020)·20 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.