Fri·Nov 23, 2018Friday·November 23, 2018

1. 01*

   Isochronous mass measurements of $T_z=-1$ $fp$-shell nuclei from projectile fragmentation of ${}^{58}$Ni

   Y. H. Zhang🇨🇳 · P. Zhang🇨🇳 · X. H. Zhou🇨🇳 · M. Wang🇨🇳 · Yu. A. Litvinov🇩🇪 · H. S. Xu🇨🇳 · X. Xu🇨🇳 · P. Shuai🇨🇳 · Y. H. Lam🇨🇳 · R. J. Chen🇨🇳 · X. L. Yan🇨🇳 · T. Bao🇨🇳 and 24 other authors

   Atomic masses of seven $T_z=-1$, $fp$-shell nuclei from ${}^{44}$V to ${}^{56}$Cu and two low-lying isomers, ${}^{44m}$V ($J^{\pi }=6^{+}$) and ${}^{52m}$Co ($J^{\pi }=2^{+}$), have been measured with relative precisions of $1-4\times 10^{-7}$ with Isochronous Mass Spectrometry (IMS) at CSRe. The masses of ${}^{56}$Cu, ${}^{52g,52m}$Co, and ${}^{44m}$V were measured for the first time in this experiment. The Mass Excesses ($M{E}^{\prime }$s) of ${}^{44}$V, ${}^{48}$Mn, ${}^{50}$Fe, and ${}^{54}$Ni are determined with an order of magnitude improved precision compared to the literature values. ${}^{52g,52m}$Co and ${}^{56}$Cu are found to be $370$~keV and $400$~keV more bound, respectively, while ${}^{44g,44m}$V are $\sim 300$~keV less bound than the extrapolations in the Atomic-Mass Evaluation 2012 (AME${}^{\prime }$12). The masses of the four $T_z=-1/2$ nuclei ${}^{45}$V, ${}^{47}$Cr, ${}^{49}$Mn, and ${}^{51}$Fe are re-determined to be in agreement, within the experimental errors, with the recent JYFLTRAP measurements or with the previous IMS measurements in CSRe. Details of the measurements and data analysis are described, and the impact of the new $ME$ values on different aspects in nuclear structure are investigated and discussed.

   nucl-exPRC(2018)·48 citations
2. 02*

   Non-linear flow modes of identified particles in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector

   Naghmeh Mohammadi🇨🇭

   The non-linear flow modes, $v_{4,22}$, $v_{5,32}$ and $v_{6,33}$ as a function of transverse momentum ($p_{\mathrm{T}}$) have been measured for the first time in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV for identified particles, i.e. charged pions, kaons and (anti-)protons. These observables probe the contribution of the second and third initial anisotropy coefficients to the higher order flow harmonics. Interestingly, all the characteristic features observed in previous $p_{\mathrm{T}}$-differential as well as $p_{\mathrm{T}}$-integrated measurements (e.g. $v_2$ and $v_3$) for various particle species are present in these measurements, i.e. increase of magnitude with increasing centrality percentile, a mass ordering in the low $p_{\mathrm{T}}$ region and a particle type grouping in the intermediate $p_{\mathrm{T}}$ region. The results cover 0--1\% (ultra-central collisions), 10--20\% (mid-central collisions) and 40--50\% (mid-peripheral collisions) centrality intervals and allow to test models that attempt to describe initial conditions and the mode-coupling of different harmonics.

   nucl-exNPA(2019)·0 citations
3. 03*

   A method to measure the transition energy ${\gamma }_t$ of the isochronously tuned storage ring

   R. J. Chen🇨🇳 · X. L. Yan🇨🇳 · W. W. Ge🇨🇳 · Y. J. Yuan🇨🇳 · M. Wang🇨🇳 · M. Z. Sun🇨🇳 · Y. M. Xing🇨🇳 · P. Zhang🇨🇳 · C. Y. Fu🇨🇳 · P. Shuai🇨🇳 · X. Xu🇨🇳 · Y. H. Zhang🇨🇳 and 18 other authors

   The Isochronous Mass Spectrometry (IMS) is a powerful technique developed in heavy-ion storage rings for measuring masses of very short-lived exotic nuclei. The IMS is based on the isochronous setting of the ring. One of the main parameters of this setting is the transition energy ${\gamma }_t$. %The transition energy ${\gamma }_t$ plays an important role in the isochronous mass spectrometry (IMS). It has been a challenge to determine the ${\gamma }_t$ and especially to monitor the variation of ${\gamma }_t$ during experiments. In this paper we introduce a method to measure the ${\gamma }_t$ online during IMS experiments by using the acquired experimental data. Furthermore, since the storage ring has (in our context) a relatively large momentum acceptance, the variation of the ${\gamma }_t$ across the ring acceptance is a source of systematic uncertainty of measured masses. With the installation of two time-of-flight (TOF) detectors, the velocity of each stored ion and its revolution time are simultaneously available for the analysis. These quantities enabled us to determine the ${\gamma }_t$ as a function of orbital length in the ring. The presented method is especially important for future IMS experiments planned at the new-generation storage ring facilities FAIR in Germany and HIAF in China.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2018)·14 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.