Fri·Jul 20, 2018Friday·July 20, 2018

1. 01*

   High-resolution $(p,t)$ study of low-spin states in ${}^{240}$Pu: Octupole excitations, $\alpha$ clustering, and other structure features

   M. Spieker🇺🇸 · S. Pascu🇷🇴 · D. Bucurescu🇷🇴 · T. M. Shneidman🇷🇺 · T. Faestermann🇩🇪 · R. Hertenberger🇩🇪 · H.-F. Wirth🇩🇪 · N.-V. Zamfir🇷🇴 · A. Zilges🇩🇪

   A high-resolution $(p,t)$ experiment at $E_p$= 24 MeV was performed to populate low-spin states in the actinide nucleus ${}^{240}$Pu. The Q3D magnetic spectrograph of the Maier-Leibnitz Laboratory (MLL) in Munich (Germany) was used to identify the ejected tritons via $dE/E$ particle identification with its focal-plane detection system. Angular distributions were measured at nine different Q3D angles to assign spin and parity to the excited states based on a comparison with coupled-channels DWBA calculations. In total, 209 states have been excited in ${}^{240}$Pu up to an excitation energy of 3 MeV. Many previously known states have also been observed and their spin-parity assignments were confirmed. However, many of the populated states have been seen for the first time. The low-spin one-octupole phonon excitations, i.e. $K^{\pi }=0^{-},1^{-},2^{-},3^{-}$, could be observed and a new candidate for the $K=3$ projection is proposed. Furthermore, the double-octupole or $\alpha$-cluster structure of the $0_2^{+}$ state in ${}^{240}$Pu has been studied in more detail. It is shown that the $0_2^{+}$ state in ${}^{230}$Th has a distinctly different structure. In addition, strongly excited $1^{-}$ states have been observed at 1.5\,MeV and 1.8\,MeV in ${}^{240}$Pu. The present study suggests that similar states might be observed in ${}^{230}$Th. At least two different and distinct structures for $J^{\pi }=0^{+}$ states are present in the actinides. These are pairing states and states with enhanced octupole correlations. We have shown that it is crucial to consider negative-parity single-particle states being admixed to some $K^{\pi }=0_2^{+}$ rotational bands to understand the $\alpha$-decay hindrance factors and enhanced $E1$-decay rates. Based on our analysis, we have identified the double-octupole or $\alpha$-cluster $K^{\pi }=0^{+}$ candidates from ${}^{224}$Ra to ${}^{240}$Pu.

   nucl-exnucl-thPRC(2018)·25 citations
2. 02*

   Shape coexisistence and collective low-spin states in ${}^{112,114}$Sn studied with the $(p,p^{\prime }\gamma )$ DSA coincidence technique

   M. Spieker🇺🇸 · P. Petkov · E. Litvinova🇺🇸 · C. Müller-Gatermann🇩🇪 · S.G. Pickstone · S. Prill · P. Scholz · A. Zilges🇩🇪

   Proton-scattering experiments followed by the coincident spectroscopy of $\gamma$ rays have been performed at the Institute for Nuclear Physics of the University of Cologne to excite low-spin states in ${}^{112}$Sn and ${}^{114}$Sn, to determine their lifetimes and extract reduced transitions strengths $B(\Pi L)$. The combined spectroscopy setup SONIC@HORUS has been used to detect the scattered protons and the emitted $\gamma$ rays of excited states in coincidence. The novel $(p,p^{\prime }\gamma )$ DSA coincidence technique was employed to measure sub-ps nuclear level lifetimes. 74 level lifetimes $\tau$ of states with $J=0-6$ were determined. In addition, branching ratios were deduced which allowed the investigation of the intruder configuration in both nuclei. Here, $sd$ IBM-2 mixing calculations were added which support the coexistence of the two configurations. Furthermore, members of the expected QOC quintuplet are proposed in ${}^{114}$Sn for the first time. The $1^{-}$ candidate in ${}^{114}$Sn fits perfectly into the systematics observed for the other stable Sn isotopes. The $E2$ transition strengths observed for the low-spin members of the so-called intruder band support the existence of shape coexistence in ${}^{112,114}$Sn. The collectivity in this configuration is comparable to the one observed in the Pd nuclei, i.e. the 0p-4h nuclei. Strong mixing between the $0^{+}$ states of the normal and intruder configuration might be observed in ${}^{114}$Sn. The general existence of QOC states in ${}^{112,114}$Sn is supported by the observation of QOC candidates with $J\ne 1$.

   nucl-exPRC(2018)·28 citations
3. 03*

   Non-strange and strange D-meson and charm-baryon production in heavy-ion collisions measured with ALICE at the LHC

   Xinye Peng (for the ALICE collaboration)🇨🇳

   We present recent result on strange and non-strange D-meson production measured with ALICE in Pb--Pb collisions at the LHC. In addition, the measurements of the ${\Lambda }_{\mathrm{c}}^{+}$-baryon production and of the ${\Lambda }_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ ratio in pp, p--Pb, and, for the first time ever, Pb--Pb collisions are reported.

   nucl-exNPA(2019)·4 citations
4. 04*

   Distributions of the largest fragment size in multifragmentation: Traces of a phase transition

   J. Brzychczyk🇵🇱 · T. Pietrzak🇵🇱 · A. Wieloch🇵🇱 · W. Trautmann🇩🇪

   Distributions of the largest fragment charge are studied using the ALADIN data on fragmentation of ${}^{197}$Au projectiles at relativistic energies. The statistical measures skewness and kurtosis of higher-order fluctuations provide a robust indication of the transition point, linked to a phase transition in the thermodynamic limit. Extensive comparisons with predictions of a bond percolation model corroborate the high accuracy of this model in reproducing the distributions as well as the whole fragmentation pattern as represented by the measured charge correlations. In analogy to percolation, the pseudocritical and critical points are identified in the fragmentation data. Questions concerning the distinction between different models and between first- and second-order phase transitions are discussed.

   nucl-exnucl-thPRC(2018)·6 citations
5. 05*

   Multiplicity dependence of strangeness and hadronic resonance production in pp and p-Pb collisions with ALICE at the LHC

   Ajay Kumar Dash (For the ALICE collaboration)🇮🇳

   One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 7 and 5.02 TeV, respectively. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. A smooth increase of strange particle yields relative to the non-strange ones with event multiplicity has been observed in such systems. We report the latest results on multiplicity dependence of strange and multi-strange hadron production in pp collisions at $\sqrt{s}=$ 13 TeV with ALICE. We also presented recent measurements of mesonic and baryonic resonances in small collision systems like pp and p--Pb at $\sqrt{s_{\mathrm{NN}}}$ = 13 and 8.16 TeV, respectively. The system size dependent studies in pp and p-Pb collisions have been used to investigate how the hadronic scattering processes affect measured resonance yields and to better understand the interplay between canonical suppression and strangeness enhancement. The measurement of the $\varphi (1020)$ meson as a function of multiplicity provides crucial constraints in this context.

   ↳ hep-exnucl-exNPA(2019)·18 citations
6. 06*

   Gamma-gamma angular correlation analysis techniques with the GRIFFIN spectrometer

   J.K. Smith🇨🇦 · A.D. MacLean🇨🇦 · W. Ashfield · A. Chester🇨🇦 · A.B. Garnsworthy🇨🇦 · C.E. Svensson🇨🇦

   Gamma-gamma angular correlation measurements are a powerful tool for identifying the angular momentum (spin) of excited nuclear states involved in a $\gamma$-ray cascade, and for measuring the multipole orders and mixing ratios of transitions. Though the physical angular correlations are fully calculable from first principles, experimental effects can make the extraction of coefficients and thus conclusions about spins and mixing ratios difficult. In this article we present data analysis techniques developed for the clover detectors of the GRIFFIN spectrometer at TRIUMF-ISAC combined with GEANT4 simulations in order to extract accurate experimental results.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2019)·28 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.