Tue·Jan 7, 2020Tuesday·January 7, 2020

1. 01*

   First Exploration of Neutron Shell Structure Below Lead and Beyond $\mathbf{N}=126$

   T. L. Tang🇺🇸 · B. P. Kay🇺🇸 · C. R. Hoffman🇺🇸 · J. P. Schiffer🇺🇸 · D. K. Sharp🇬🇧 · L. P. Gaffney🇨🇭 · S. J. Freeman🇬🇧 · M. R. Mumpower🇺🇸 · A. Arokiaraj · E. F. Baader🇨🇭 · P. A. Butler🇬🇧 · W. N. Catford🇬🇧 and 17 other authors

   The nuclei below lead but with more than 126 neutrons are crucial to an understanding of the astrophysical $r$-process in producing nuclei heavier than $A\sim 190$. Despite their importance, the structure and properties of these nuclei remain experimentally untested as they are difficult to produce in nuclear reactions with stable beams. In a first exploration of the shell structure of this region, neutron excitations in ${}^{207}$Hg have been probed using the neutron-adding ($d$,$p$) reaction in inverse kinematics. The radioactive beam of ${}^{206}$Hg was delivered to the new ISOLDE Solenoidal Spectrometer at an energy above the Coulomb barrier. The spectroscopy of ${}^{207}$Hg marks a first step in improving our understanding of the relevant structural properties of nuclei involved in a key part of the path of the $r$-process.

   nucl-exnucl-thPRL(2020)·28 citations
2. 02*

   Possible Formation of a Perfect Fluid in $pp$, $p$-Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider Energies: A Color String Percolation Approach

   Dushmanta Sahu🇮🇳 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳 · Swatantra Kumar Tiwari🇮🇳

   Isothermal compressibility (${\kappa }_{\mathrm{T}}$) is an important thermodynamic observable which gives information about the deviation of a system from perfect fluid behavior. In this work, for the first time we have estimated the isothermal compressibility of QCD matter formed in high energy hadronic and nuclear collisions using color string percolation model (CSPM), where we investigate the change in ${\kappa }_{\mathrm{T}}$ as a function of final state charged particle multiplicity and initial percolation temperature across various collision species. The estimated initial percolation temperature for different collision systems at different collision energies helps us to have a better understanding of the system at the initial phase of evolution. The comparison of the CSPM results for isothermal compressibility with that for the well known fluids, indicates that the matter formed in heavy-ion collisions might be the {\it closest perfect fluid} found in nature. This estimation complements the well-known observation of minimum shear viscosity to entropy density ratio for a possible QGP medium created in heavy-ion collision experiments. A threshold of pseudorapidity density of charged particles, $⟨d{N}_{\mathrm{ch}}/d\eta ⟩\ge 20$ in the final state event multiplicity is observed, after which one may look for a possible QGP formation at the LHC energies.

   ↳ hep-phhep-exnucl-exnucl-thEPJA(2022)·17 citations
3. 03*

   Vorticity in low-energy heavy-ion collisions

   Xian-Gai Deng🇨🇳 · Xu-Guang Huang🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

   We study the kinematic and thermal vorticities in low-energy heavy-ion collisions by using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. We explore their time evolution and spatial distribution. We find that the initial vorticities have a non-monotonic dependence on the collision energy $\sqrt{s_{\mathrm{NN}}}$: as $\sqrt{s_{\mathrm{NN}}}$ grows the vorticities first increase steeply and then decrease with the turning point around $\sqrt{s_{\mathrm{NN}}}\sim 3-5$ GeV depending on the centrality.

   ↳ nucl-thhep-phnucl-exPRC(2020)·104 citations
4. 04*

   Approach to thermalization and hydrodynamics

   Yukinao Akamatsu🇯🇵

   I review recent progress in thermalization in heavy-ion collisions, with particular emphasis on hydrodynamic attractor, and also report recent progress in hydrodynamic fluctuations.

   ↳ nucl-thhep-phhep-thnucl-exNPA(2021)·4 citations
5. 05*

   Front-end-Electronics for the SiPM-readout gaseous TPC for neutrinoless double beta decay search

   K. Z. Nakamura🇯🇵 · S. Ban🇯🇵 · A. K. Ichikawa🇯🇵 · M. Ikeno🇯🇵 · K. D. Nakamura🇯🇵 · T. Nakaya🇯🇵 · S. Obara🇯🇵 · S. Tanaka🇯🇵 · T. Uchida🇯🇵 · M. Yoshida (for the AXEL collaboration)🇯🇵

   We have developed a dedicated front-end-electronics board for a high-pressure xenon gas time projection chamber for a neutrinoless double-beta decay search. The ionization signal is readout by detecting electroluminescence photons with SiPM's. The board readout the signal from 56~SiPM's through the DC-coupling and record the waveforms at 5 MS/s with a wide dynamic range up to 7,000 photons/200 ns. The SiPM bias voltages are provided by the board and can be adjusted for each SiPM. In order to calibrate and monitor the SiPM gain, additional auxiliary ADC measures 1 photon-equivalent dark current. The obtained performance satisfies the requirement for a neutrinoless double-beta decay search.

   ↳ physics.ins-dethep-exnucl-exIEEE Trans.Nucl.Sci.(2020)·6 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.