Nuclear Experiment·nucl-ex
4 papers—1 primary·3 cross-listed·reconstructed*
A summary of the QM19 conference is given by highlighting a few selected results. These are discussed as examples to illustrate the exciting future of heavy-ion collisions and the need for further instrumentation. (The arXiv version is significantly longer than the printed proceedings, with more figures.)
Patrick Carzon🇺🇸 · Skandaprasad Rao🇺🇸 · Matthew Luzum🇧🇷 · Matthew Sievert🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
Recent measurements have established the sensitivity of ultracentral heavy-ion collisions to the deformation parameters of non-spherical nuclei. In the case of Xe collisions, a quadrupole deformation of the nuclear profile led to an enhancement of elliptic flow in the most central collisions. In Pb collisions a discrepancy exists in similar centralities, where either elliptic flow is over-predicted or triangular flow is under-predicted by hydrodynamic models; this is known as the -to- puzzle in ultracentral collisions. Motivated by low-energy nuclear structure calculations, we consider the possibility that Pb nuclei could have a pear shape deformation (octupole), which has the effect of increasing triangular flow in central PbPb collisions. Using the recent data from ALICE and ATLAS, we revisit the -to- puzzle in ultracentral collisions, including new constraints from recent measurements of the triangular cumulant ratio and comparing two different hydrodynamic models. We find that, while an octupole deformation would slightly improve the ratio between and , it is at the expense of a significantly worse triangular flow cumulant ratio. In fact, the latter observable prefers no octupole deformation, with for Pb, and is therefore consistent with the expectation for a doubly-magic nucleus even at top collider energies. The -to- puzzle remains a challenge for hydrodynamic models.
Muhammad Waqas🇨🇳 · Fu-Hu Liu🇨🇳 · Rui-Qin Wang🇨🇳 · Irfan Siddique🇨🇳
The transverse momentum (mass) spectra of the multi-strange and non-multi-strange (i.e. other identified) particles in central gold-gold (Au-Au), lead-lead (Pb-Pb), argon-muriate (Ar-KCl) and nickel-nickel (Ni-Ni) collisions over a wide energy range have been studied in this work. The experimental data measured by various collaborations have been analyzed. The blast-wave fit with Tsallis statistics is used to extract the kinetic freeze-out temperature and transverse flow velocity from the experimental data of transverse momentum (mass) spectra. The extracted parameters increase with the increase of collision energy and appear with the trend of saturation at the Beam Energy Scan (BES) energies at the Relativistic Heavy Ion Collider (RHIC). This saturation implies that the onset energy of phase transition of partial deconfinement is 7.7 GeV and that of whole deconfinement is 39 GeV. Furthermore, the energy scan/dependence of kinetic freeze-out scenarios are observed for the multi-strange and other identified particles, though the multiple freeze-out scenarios are also observed for various particles.
Sota Kimura🇯🇵 · Daiya Kaji🇯🇵 · Yuta Ito🇯🇵 · Hiroari Miyatake🇯🇵 · Kouji Morimoto🇯🇵 · Peter Schury🇯🇵 · Michiharu Wada
Two independent beam stoppers have been developed for improving the beam separation of the gas-filled recoil ion separator GARIS-II. Performance evaluation of these supplemental beam stoppers was performed by using the 208Pb (18O,3n)223Th reaction. A160-fold enhancement of the signal-to-noise ratio at the GARIS-II focal plane was observed.
* 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.