Fri·Mar 1, 2019Friday·March 1, 2019

1. 01*

   A Novel Method for the Measurement of Half-Lives and Decay Branching Ratios of Exotic Nuclei

   Ivan Miskun (1) · Timo Dickel (1 and 2)🇩🇪 · Israel Mardor (3 and 4)🇮🇱 · Christine Hornung (1) · Daler Amanbayev (1) · Samuel Ayet San Andrés (1 and 2)🇩🇪 · Julian Bergmann (1)🇩🇪 · Jens Ebert (1) · Hans Geissel (1 and 2)🇩🇪 · Magdalena Górska (2) · Florian Greiner (1) · Emma Haettner (2)🇩🇪 and 19 other authors

   A novel method for simultaneous measurement of masses, Q-values, isomer excitation energies, half-lives and decay branching ratios of exotic nuclei has been demonstrated. The method includes first use of a stopping cell as an ion trap, combining containment of precursors and decay-recoils for variable durations in a cryogenic stopping cell (CSC), and afterwards the identification and counting of them by a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). Feasibility has been established by recording the decay and growth of ${}^{216}$Po and ${}^{212}$Pb (alpha decay) and of ${}^{119m2}$Sb (t${}_{1/2}$ = 850$\pm$90 ms) and ${}^{119g}$Sb (isomer transition), obtaining half-lives and branching ratios consistent with literature values. Hardly any non-nuclear-decay losses have been observed in the CSC for up to $\sim$10 seconds, which exhibits its extraordinary cleanliness. For ${}^{119}$Sb, this is the first direct measurement of the ground and second isomeric state masses, resolving the discrepancies in previous excitation energy data. These results pave the way for the measurement of branching ratios of exotic nuclei with multiple decay channels.

   nucl-exEPJA(2019)·10 citations
2. 02*

   Shape staggering of mid-shell mercury isotopes from in-source laser spectroscopy compared with Density Functional Theory and Monte Carlo Shell Model calculations

   S. Sels🇧🇪 · T. Day Goodacre🇨🇭 · B. A. Marsh🇨🇭 · A. Pastore🇬🇧 · W. Ryssens🇫🇷 · Y. Tsunoda🇯🇵 · N. Althubiti🇬🇧 · B. Andel🇸🇰 · A. N. Andreyev🇬🇧 · D. Atanasov🇩🇪 · A. E. Barzakh🇷🇺 · M. Bender🇫🇷 and 36 other authors

   Neutron-deficient ${}^{177-185}$Hg isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility, in an experiment combining different detection methods tailored to the studied isotopes. These include either alpha-decay tagging or Multi-reflection Time-of-Flight gating to identify the isotopes of interest. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring for the first time the isotope shifts and hyperfine structures of ${}^{177-180}$Hg. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole and electric quadrupole moments of the odd-A isotopes and arguments in favor of $I=7/2$ spin assignment for ${}^{177,179}$Hg were deduced. Experimental results are compared with Density Functional Theory (DFT) and Monte-Carlo Shell Model (MCSM) calculations. DFT calculations with several Skyrme parameterizations predict a large jump in the charge radius around the neutron $N=104$ mid shell, with an odd-even staggering pattern related to the coexistence of nearly-degenerate oblate and prolate minima. This near-degeneracy is highly sensitive to many aspects of the effective interaction, a fact that renders perfect agreement with experiment out of reach for current functionals. Despite this inherent diffculty, the SLy5s1 and a modified UNEDF1^{SO} parameterization predict a qualitatively correct staggering that is off by two neutron numbers. MCSM calculations of states with the experimental spins and parities show good agreement for both electromagnetic moments and the observed charge radii. A clear mechanism for the origin of shape staggering within this context is identified: a substantial change in occupancy of the proton $\pi h_{9/2}$ and neutron $\nu i_{13/2}$ orbitals.

   nucl-exnucl-thPRC(2019)·65 citations
3. 03*

   Novel Method for Precisely Measuring the $X(3872)$ Mass

   Feng-Kun Guo🇨🇳

   The $X(3872)$ is the first and the most interesting one amongst the abundant $XYZ$ states. Its mass coincides exactly with the $D^0{\bar{D}}^{\ast 0}$ threshold with an uncertainty of 180 keV. Precise knowledge of its mass is crucial to understand the $X(3872)$. However, whether it is above or below the $D^0{\bar{D}}^{\ast 0}$ threshold is still unknown. We propose a completely new method to measure the $X(3872)$ mass precisely by measuring the $X(3872)\gamma$ line shape between 4010 and 4020 MeV, which is strongly sensitive to the $X(3872)$ mass relative to the $D^0{\bar{D}}^{\ast 0}$ threshold due to a triangle singularity. This method can be applied to experiments which produce copious $D^{\ast 0}{\bar{D}}^{\ast 0}$ pairs, such as electron-positron, proton-antiproton and other experiments, and may lead to much more precise knowledge about the $X(3872)$ mass.

   ↳ hep-phhep-exnucl-exnucl-thPRL(2019)·77 citations
4. 04*

   Charm baryon production in pp, p-Pb and Pb-Pb collisions with ALICE at the LHC

   Elisa Meninno (on behalf of the ALICE Collaboration)🇮🇹

   In this contribution, the latest ALICE results on charmed baryon production are presented. In particular the measurements of ${\Lambda }_{\mathrm{c}}^{+}$-baryon production in pp collisions at $\sqrt{\mathrm{s}}$ = 5.02 TeV and in p-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 5.02 TeV are shown and compared with previous measurements performed using pp and p-Pb data samples collected during LHC Run 1. At mid-rapidity charmed baryons are reconstructed via their hadronic decay and semileptonic decay channels, exploiting the high precision tracking, excellent vertexing and particle identification capabilities offered by the ALICE detector. The first measurement of ${\Lambda }_{\mathrm{c}}^{+}$-baryon production in Pb-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 5.02 TeV is also shown. Results are compared with theoretical expectations.

   ↳ hep-exnucl-exPoS(2019)·2 citations
5. 05*

   Examination of Flow and Non-Flow Factorization Methods in Small Collision Systems

   S.H. Lim🇺🇸 · Q. Hu🇺🇸 · R. Belmont🇺🇸 · K.K. Hill🇺🇸 · J.L. Nagle🇺🇸 · D.V. Perepelitsa🇺🇸

   Two particle correlations have been used extensively to study hydrodynamic flow patterns in heavy-ion collisions. In small collision systems, such as $p$$+$$p$ and $p$$+$$A$, where particle multiplicities are much smaller than in $A$$+$$A$ collisions, non-flow effects from jet correlations, momentum conservation, particle decays, etc. can be significant, even when imposing a large pseudorapidity gap between the particles. A number of techniques to subtract the non-flow contribution in two particle correlations have been developed by experiments at the Large Hadron Collider (LHC) and then used to measure particle flow in $p$$+$$p$ and $p$$+$Pb collisions. Recently, experiments at the Relativistic Heavy Ion Collider (RHIC) have explored the possibility of adopting these techniques for small collision systems at lower energies. In this paper, we test these techniques using Monte Carlo generators PYTHIA and HIJING, which do not include any collective flow, and AMPT, which does. We find that it is crucial to examine the results of such tests both for correlations integrated over particle transverse momentum $p_T$ and differentially as a function of $p_T$. Our results indicate reasonable non-flow subtraction for $p$$+$$p$ collisions at the highest LHC energies, while failing if applied to $p$$+$$p$ collisions at RHIC. In the case of $p$$+$Au collisions at RHIC, both HIJING and AMPT results indicate a substantial over-subtraction of non-flow for $p_T\gtrsim 1\mathrm{GeV}/c$ and hence an underestimate of elliptic flow.

   ↳ nucl-thnucl-exPRC(2019)·33 citations
6. 06*

   A novel ppm-precise absolute calibration method for precision high-voltage dividers

   O. Rest (1)🇩🇪 · D. Winzen (1)🇩🇪 · S. Bauer (2) · R. Berendes (1)🇩🇪 · J. Meisner (2) · T. Thümmler (3)🇩🇪 · S. Wüstling (4)🇩🇪 · C. Weinheimer (1) ((1) Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, Germany, (2) Physikalisch-Technische Bundesanstalt Braunschweig, Germany, (3) Karlsruhe Institute of Technology (KIT), Institute for Nuclear Physics (IKP), Karlsruhe, Germany, (4) Karlsruhe Institute of Technology (KIT), Institute for Data Processing and Electronics (IPE), Karlsruhe, Germany)🇩🇪

   The most common method to measure direct current high voltage (HV) down to the ppm-level is to use resistive high-voltage dividers. Such devices scale the HV into a range where it can be compared with precision digital voltmeters to reference voltages sources, which can be traced back to Josephson voltage standards. So far the calibration of the scale factors of HV dividers for voltages above 1~kV could only be done at metrology institutes and sometimes involves round-robin tests among several institutions to get reliable results. Here we present a novel absolute calibration method based on the measurement of a differential scale factor, which can be performed with commercial equipment and outside metrology institutes. We demonstrate that reproducible measurements up to 35~kV can be performed with relative uncertainties below $1\cdot 10^{-6}$. This method is not restricted to metrology institutes and offers the possibility to determine the linearity of high-voltage dividers for a wide range of applications.

   ↳ physics.ins-detnucl-exMetrologia(2019)·18 citations
7. 07*

   A boron-coated CCD camera for direct detection of Ultracold Neutrons (UCN)

   K. Kuk · C. Cude-Woods · C. R. Chavez · J. H. Choi · J. Estrada · M. Hoffbauer · M. Makela · P. Merkel · C. L. Morris · E. Ramberg · Z. Wang · T. Bailey and 40 other authors

   A new boron-coated CCD camera is described for direct detection of ultracold neutrons (UCN) through the capture reactions ${}^{10}$B (n,$\alpha$0$\gamma$)${}^7$Li (6%) and ${}^{10}$B(n,$\alpha$1$\gamma$)${}^7$Li (94%). The experiments, which extend earlier works using a boron-coated ZnS:Ag scintillator, are based on direct detections of the neutron-capture byproducts in silicon. The high position resolution, energy resolution and particle ID performance of a scientific CCD allows for observation and identification of all the byproducts $\alpha$, ${}^7$Li and $\gamma$ (electron recoils). A signal-to-noise improvement on the order of 10${}^4$ over the indirect method has been achieved. Sub-pixel position resolution of a few microns is demonstrated. The technology can also be used to build UCN detectors with an area on the order of 1 m${}^2$. The combination of micrometer scale spatial resolution, few electrons ionization thresholds and large area paves the way to new research avenues including quantum physics of UCN and high-resolution neutron imaging and spectroscopy.

   ↳ physics.ins-detnucl-exNuclear Instruments and Methods in Physic…·1 citation

* 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.