Tue·Apr 30, 2019Tuesday·April 30, 2019

1. 01*

   Direct determination of the ${}^{138}$La $\beta$-decay $Q$ value using Penning trap mass spectrometry

   R. Sandler🇺🇸 · G. Bollen🇺🇸 · J. Dissanayake🇺🇸 · M. Eibach🇺🇸 · K. Gulyuz🇺🇸 · A. Hamaker🇺🇸 · C. Izzo🇨🇦 · X. Mougeot🇫🇷 · D. Puentes🇺🇸 · F. G. A. Quarati🇳🇱 · M. Redshaw🇺🇸 · R. Ringle🇺🇸 · I. Yandow🇺🇸

   Background: The understanding and description of forbidden decays provides interesting challenges for nuclear theory. These calculations could help to test underlying nuclear models and interpret experimental data. Purpose: Compare a direct measurement of the ${}^{138}$La $\beta$-decay $Q$ value with the $\beta$-decay spectrum end-point energy measured by Quarati et al. using LaBr${}_3$ detectors [Appl. Radiat. Isot. 108, 30 (2016)]. Use new precise measurements of the ${}^{138}$La $\beta$-decay and electron capture (EC) $Q$ values to improve theoretical calculations of the $\beta$-decay spectrum and EC probabilities. Method: High-precision Penning trap mass spectrometry was used to measure cyclotron frequency ratios of ${}^{138}$La, ${}^{138}$Ce and ${}^{138}$Ba ions from which $\beta$-decay and EC $Q$ values for ${}^{138}$La were obtained. Results: The ${}^{138}$La $\beta$-decay and EC $Q$ values were measured to be $Q$ = 1052.42(41) keV and $Q_{EC}$ = 1748.41(34) keV, improving the precision compared to the values obtained in the most recent atomic mass evaluation [Wang, et al., Chin. Phys. C 41, 030003 (2017)] by an order of magnitude. These results are used for improved calculations of the ${}^{138}$La $\beta$-decay shape factor and EC probabilities. New determinations for the ${}^{138}$Ce 2EC $Q$ value and the atomic masses of ${}^{138}$La, ${}^{138}$Ce, and ${}^{138}$Ba are also reported. Conclusion: The ${}^{138}$La $\beta$-decay $Q$ value measured by Quarati et al. is in excellent agreement with our new result, which is an order of magnitude more precise. Uncertainties in the shape factor calculations for ${}^{138}$La beta-decay using our new $Q$ value are reduced by an order of magnitude. Uncertainties in the EC probability ratios are also reduced and show improved agreement with experimental data.

   nucl-exPRC(2019)·11 citations
2. 02*

   First observation of an attractive interaction between a proton and a multi-strange baryon

   ALICE Collaboration

   This work presents the first experimental observation of the attractive strong interaction between a proton and a multi-strange baryon (hyperon) ${\Xi }^{-}$. The result is extracted from two-particle correlations of combined $\mathrm{p}-{\mathrm{\Xi }}^{-}$$\oplus$$\bar{\mathrm{p}}-{\bar{\mathrm{\Xi }}}^{+}$ pairs measured in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV at the LHC with ALICE. The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a standard deviation in the range $[3.6,5.3]$ is found. Since the measured $\mathrm{p}-{\mathrm{\Xi }}^{-}$$\oplus$$\bar{\mathrm{p}}-{\bar{\mathrm{\Xi }}}^{+}$ correlation is significantly enhanced with respect to the Coulomb prediction, the presence of an additional, strong, attractive interaction is evident. The data are compatible with recent lattice calculations by the HAL-QCD Collaboration, with a standard deviation in the range $[1.8,3.7]$. The lattice potential predicts a shallow repulsive ${\Xi }^{-}$ interaction within pure neutron matter at saturation densities and this implies stiffer equations of state for neutron-rich matter including hyperons. Implications of the strong interaction for the modeling of neutron stars are discussed.

   nucl-exhep-exPRL(2019)·175 citations
3. 03*

   Neutron skins of atomic nuclei: per aspera ad astra

   M. Thiel🇩🇪 · C. Sfienti🇩🇪 · J. Piekarewicz🇺🇸 · C.J. Horowitz🇺🇸 · M. Vanderhaeghen🇩🇪

   The complex nature of the nuclear forces generates a broad range and diversity of observational phenomena. Heavy nuclei, though orders of magnitude less massive than neutron stars, are governed by the same underlying physics, which is enshrined in the nuclear equation of state. Heavy nuclei are expected to develop a neutron-rich skin where many neutrons collect near the surface. Such a skin thickness is strongly sensitive to the poorly-known density dependence of the symmetry energy near saturation density. An accurate and model-independent determination of the neutron-skin thickness of heavy nuclei would provide a significant first constraint on the density dependence of the nuclear symmetry energy. The determination of the neutron-skin thickness of heavy nuclei has far reaching consequences in many areas of physics as diverse as heavy-ion collisions, polarized electron and proton scattering off nuclei, precision tests of the standard model using atomic parity violation, and nuclear astrophysics. While a systematic and concerted experimental effort has been made to measure the neutron-skin thickness of heavy nuclei, a precise and model-independent determination remains elusive. How to move forward at a time when many new facilities are being commissioned and how to strengthen the synergy with other areas of physics are primary goals of this review.

   nucl-exastro-ph.HEnucl-thJ.Phys.G(2019)·150 citations
4. 04*

   Constraining the symmetry energy with heavy-ion collisions and Bayesian analyses

   P. Morfouace🇫🇷 · C.Y. Tsang🇺🇸 · Y. Zhang🇨🇳 · W.G. Lynch🇺🇸 · M.B. Tsang🇺🇸 · D.D.S Coupland · M. Youngs · Z. Chajecki🇺🇸 · M.A. Famiano🇺🇸 · T.K. Ghosh🇮🇳 · G. Jhang🇺🇸 · Jenny Lee🇨🇳 and 4 other authors

   Efficiency corrected single ratios of neutron and proton spectra in central ${}^{112}$Sn+${}^{112}$Sn and ${}^{124}$Sn+${}^{124}$Sn collisions at 120 MeV/u are combined with double ratios to provide constraints on the density and momentum dependencies of the isovector mean-field potential. Bayesian analyses of these data reveal that the isoscalar and isovector nucleon effective masses, $m_s^{\ast }-m_v^{\ast }$ are strongly correlated. The linear correlation observed in $m_s^{\ast }-m_v^{\ast }$ yields a nearly independent constraint on the effective mass splitting $\Delta m_{np}^{\ast }=(m_n^{\ast }-m_p^{\ast })/m_N=-0.05_{-0.09}^{+0.09}\delta$. The correlated constraint on the standard symmetry energy, $S_0$ and the slope, $L$ at saturation density yields the values of symmetry energy $S({\rho }_s)=16.8_{-1.2}^{+1.2}$ MeV at a sensitive density of ${\rho }_s/{\rho }_0=0.43_{-0.05}^{+0.05}$.

   nucl-exnucl-thPLB(2019)·88 citations
5. 05*

   Measurement of the Helicity Asymmetry $E$ for the reaction $\gamma p\to {\pi }^{0}p$

   CBELSA/TAPS collaboration: M. Gottschall🇩🇪 · F. Afzal🇩🇪 · A.V. Anisovich🇩🇪 · D. Bayadilov🇩🇪 · R. Beck🇩🇪 · M. Bichow🇩🇪 · K.-Th. Brinkmann🇩🇪 · V. Crede🇺🇸 · M. Dieterle🇨🇭 · F. Dietz🇩🇪 · H. Dutz🇩🇪 · H. Eberhardt🇩🇪 and 56 other authors

   A measurement of the double-polarization observable $E$ for the reaction $\gamma p\to {\pi }^{0}p$ is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C${}_4$H${}_9$OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from $E_{\gamma }=600$~MeV to $E_{\gamma }=2310$~MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.

   nucl-exEPJA(2021)·20 citations
6. 06*

   High density matter physics at J-PARC-HI

   Takao Sakaguchi (for the J-PARC-HI collaboration)🇺🇸

   Physics prospective of the high density matter using heavy ions collisions is presented. The J-PARC-HI project which is a unique lab to tackle the high density matter physics is described. The world highest rate of heavy ion beam of 10${}^{11}$ Hz is aimed at J-PARC-HI which enables us to perform measurements of hadrons, fluctuation of conserved quantities, dileptons, multi-strange hypernuclei. New event selections are also discussed to reach a highest baryon density on the ground.

   nucl-exhep-exPoS(2019)·9 citations
7. 07*

   Possible chiral doublets in ${}^{60}$Ni

   J. Peng🇨🇳 · Q. B. Chen🇩🇪

   The open problem on whether or not the chirality exists in doublet bands M1 and M4 in light-mass even-even nucleus ${}^{60}$Ni is studied by adopting the recently developed fully quantal four-$j$ shells triaxial particle rotor model. The corresponding experimental energy spectra, energy differences between doublet bands, and the available $B(M1)/B(E2)$ values are successfully reproduced. The analyses on the basis of the angular momentum components, the azimuthal plots, and the $K$-plots suggest that the chiral modes exist at $I\ge 12\hslash$ in doublet bands M1 and M4.

   ↳ nucl-thnucl-exPLB(2019)·20 citations
8. 08*

   Review of recent forward physics results from the CMS experiment

   Ralf Ulrich (for the CMS Collaboration)🇩🇪

   There is a rich program of forward physics measurements within the CMS Collaboration covering a wide range of topics. In many cases there is a connection to quantities and effects relevant for very high energy cosmic ray interaction. Some of the recent measurements in the fields of exclusive final states, low-pT inclusive and diffractive cross sections, underlying event, multi parton interactions, double parton scattering, final state particle correlations and minimum bias results are briefly summarized here.

   ↳ hep-exnucl-exEPJ Web Conf.(2019)·0 citations
9. 09*

   A background estimator for jet studies in p+p and A+A collisions

   Yacine Mehtar-Tani🇺🇸 · Alba Soto-Ontoso🇺🇸 · Marta Verweij🇺🇸

   Experimentally, jet physics studies face an unavoidable task: distinguishing, at the detector level, the particles produced in the hard partonic scattering from the ones created in unrelated soft processes such as pileup interactions in high-luminosity proton-proton scattering or the underlying event in heavy-ion collisions. The fluctuating nature of the background constitutes the main source of uncertainty for any subtraction algorithm. Aiming at mitigating the effect of such fluctuations, we present a new method to estimate the background contribution to the transverse momentum on a jet-by-jet basis. Our approach is based on estimating the median background momentum density stored above a $p_{\mathrm{T}}$-cut applied at the constituent level and an experimentally accessible correction term related to the signal contribution below the cut. This allows to trade part of the uncertainty due to background contamination for that of the signal below the cut, similarly to SoftKiller method. We propose to reduce the fluctuations of the latter by exploiting intrinsic correlations among the soft and hard sectors of QCD jets. Our data-driven approach is tested against PYTHIA8 and JEWEL di-jet events embedded in a thermal background and compared to the area-median and SoftKiller methods. The main result of this study is a $\sim 5-40\%$ improvement on the resolution of the reconstructed jet $p_T$ compared to previous methods in a high-luminosity proton-proton scenario. Its applicability in a heavy-ion context is also discussed.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2019)·3 citations
10. 10*

    Results from a Prototype Combination TPC Cherenkov Detector with GEM Readout

    B. Azmoun🇺🇸 · K. Dehmelt🇺🇸 · T. K. Hemmick🇺🇸 · R. Majka🇺🇸 · H. N. Nguyen🇺🇸 · M. Phipps🇺🇸 · M. L. Purschke🇺🇸 · N. Ram🇺🇸 · W. Roh🇺🇸 · D. Shangase🇺🇸 · N. Smirnov🇺🇸 · C. Woody🇺🇸 · A. Zhang🇺🇸

    A combination Time Projection Chamber-Cherenkov prototype detector has been developed as part of the Detector R&D Program for a future Electron Ion Collider. The prototype was tested at the Fermilab test beam facility to provide a proof of principle to demonstrate that the detector is able to measure particle tracks and provide particle identification information within a common detector volume. The TPC portion consists of a 10x10x10cm3 field cage, which delivers charge from tracks to a 10x10cm2 quadruple GEM readout. Tracks are reconstructed by interpolating the hit position of clusters on an array of 2x10mm2 zigzag pads The Cherenkov component consists of a 10x10cm2 readout plane segmented into 3x3 square pads, also coupled to a quadruple GEM. As tracks pass though the drift volume of the TPC, the generated Cherenkov light is able to escape through sparsely arranged wires making up one side of the field cage, facing the CsI photocathode of the Cherenkov detector. The Cherenkov detector is thus operated in a windowless, proximity focused configuration for high efficiency. Pure CF4 is used as the working gas for both detector components, mainly due to its transparency into the deep UV, as well as its high N0. Results from the beam test, as well as results on its particle id capabilities will be discussed.

    ↳ physics.ins-dethep-exnucl-exIEEE Trans.Nucl.Sci.(2019)·6 citations
11. 11*

    A new software implementation of the Oslo method with rigorous statistical uncertainty propagation

    Jørgen E. Midtbø🇳🇴 · Fabio Zeiser🇳🇴 · Erlend Lima · Ann-Cecilie Larsen🇳🇴 · Gry M. Tveten🇳🇴 · Magne Guttormsen🇳🇴 · Frank L. Bello Garrote🇳🇴 · Anders Kvellestad🇬🇧 · Therese Renstrøm🇳🇴

    The Oslo method comprises a set of analysis techniques designed to extract nuclear level density and average $\gamma$-decay strength function from a set of excitation-energy tagged $\gamma$-ray spectra. Here we present a new software implementation of the entire Oslo method, called OMpy. We provide a summary of the theoretical basis and derive the essential equations used in the Oslo method. In addition to the functionality of the original analysis code, the new implementation includes novel components such as a rigorous method to propagate uncertainties throughout all steps of the Oslo method using a Monte Carlo approach. The resulting level density and $\gamma$-ray strength function have to be normalized to auxiliary data. The normalization is performed simultaneously for both quantities, thus preserving all correlations. The software is verified by the analysis of a synthetic spectrum and compared to the results of the previous implementation, the oslo-method-software.

    ↳ physics.comp-phnucl-exphysics.data-anComput.Phys.Commun.(2021)·20 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.