Fri·Nov 2, 2018Friday·November 2, 2018

1. 01*

   The $\gamma$-ray strength function for Thallium isotopes relevant to the ${}^{205}$Pb - ${}^{205}$Tl chronometry

   H. Utsunomiya🇯🇵 · T. Renstrøm🇳🇴 · G. M. Tveten🇳🇴 · S. Goriely🇧🇪 · T. Ari-izumi🇯🇵 · D. Filipescu🇷🇴 · J. Kaur🇷🇴 · Y.-W. Lui🇺🇸 · W. Luo🇨🇳 · S. Miyamoto🇯🇵 · A. C. Larsen🇳🇴 · S. Hilaire🇫🇷 · S. Péru🇫🇷 · A. J. Koning🇦🇹

   Photoneutron cross sections were measured for ${}^{203}$Tl and ${}^{205}$Tl at energies between the one- and two-neutron thresholds using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. Our new measurement results in cross sections significantly different from the previously reported bremsstrahlung experiment, leading to rather different GDR parameters, in particular to lower GDR peak energies and higher peak cross sections. The photoneutron data are used to constrain the $\gamma$-ray strength function on the basis of the Hartree-Fock-Bogolyubov plus quasi-particle random phase approximation using the Gogny D1M interaction. Supplementing the experimentally constrained $\gamma$-ray strength function with the zero-limit E1 and M1 contributions for the de-excitation mode, we estimate the Maxwellian-averaged cross section for the s-process branching-point nucleus ${}^{204}$Tl in the context of the ${}^{205}$Pb - ${}^{205}$Tl chronometry.

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

   Excited states of ${}^{39}$Ca and their significance in nova nucleosynthesis

   Kiana Setoodehnia · Caleb Marshall🇺🇸 · Richard Longland🇺🇸 · John H. Kelley🇺🇸 · Johnson Liang · Federico Portillo Chaves

   Background: Discrepancies exist between the observed abundances of argon and calcium in oxygen-neon nova ejecta and those predicted by nova models. An improved characterization of the ${}^{38}$K($p,\gamma$)${}^{39}$Ca reaction rate over the nova temperature regime ($\sim$ 0.1 -- 0.4 GK), and thus the nuclear structure of ${}^{39}$Ca above the proton threshold (5770.92(63) keV), is necessary to resolve these contradictions. Purpose: The present study was performed to search for low-spin proton resonances in the ${}^{38}$K $+$ $p$ system, and to improve the uncertainties in energies of the known astrophysically significant proton resonances in ${}^{39}$Ca. Method: The level structure of ${}^{39}$Ca was investigated via high-resolution charged-particle spectroscopy with an Enge split-pole spectrograph using the ${}^{40}$Ca(${}^3$He, $\alpha$)${}^{39}$Ca reaction. Differential cross sections were measured over 6 laboratory angles at 21 MeV. Distorted-wave Born approximation calculations were performed to constrain the spin-parity assignments of observed levels with special attention to those significant in determination of the ${}^{38}$K($p,\gamma$)${}^{39}$Ca reaction rate over the nova temperature regime. Results: The resonance energies corresponding to two out of three astrophysically important states at 6154(5) and 6472.2(24) keV are measured with better precision than previous charged-particle spectroscopy measurements. A tentatively new state is discovered at 5908(3) keV. The spin-parity assignments of a few of the astrophysically important resonances are determined. Conclusions: The present ${}^{38}$K($p,\gamma$)${}^{39}$Ca upper limit thermonuclear reaction rate at 0.1 -- 0.4 GK is higher than that determined in [Physical Review C 97 (2018) 025802] by at most a factor of 1.4 at 0.1 GK.

   nucl-exPRC(2018)·4 citations
3. 03*

   Tests of Lorentz invariance at the Sudbury Neutrino Observatory

   SNO Collaboration: B. Aharmim🇨🇦 · S. N. Ahmed🇨🇦 · A. E. Anthony🇺🇸 · N. Barros🇵🇹 · E. W. Beier🇺🇸 · A. Bellerive🇨🇦 · B. Beltran🇨🇦 · M. Bergevin🇺🇸 · S. D. Biller🇬🇧 · E. Blucher🇺🇸 · R. Bonventre🇺🇸 · K. Boudjemline🇨🇦 and 121 other authors

   Experimental tests of Lorentz symmetry in systems of all types are critical for ensuring that the basic assumptions of physics are well-founded. Data from all phases of the Sudbury Neutrino Observatory, a kiloton-scale heavy water Cherenkov detector, are analyzed for possible violations of Lorentz symmetry in the neutrino sector. Such violations would appear as one of eight possible signal types in the detector: six seasonal variations in the solar electron neutrino survival probability differing in energy and time dependence, and two shape changes to the oscillated solar neutrino energy spectrum. No evidence for such signals is observed, and limits on the size of such effects are established in the framework of the Standard Model Extension, including 40 limits on perviously unconstrained operators and improved limits on 15 additional operators. This makes limits on all minimal, Dirac-type Lorentz violating operators in the neutrino sector available for the first time.

   ↳ hep-exnucl-exPRD(2018)·28 citations
4. 04*

   Old and New in Strangeness Nuclear Physics

   Avraham Gal🇮🇱

   Several persistent problems in strangeness nuclear physics are discussed in this opening talk at HYP2018, Portsmouth-Norfolk VA, June 2018: (i) the ${}_{\Lambda }^3$H and ${}_{\Lambda }^3$n (if existing) lifetimes; (ii) charge symmetry breaking in $\Lambda$ hypernuclei; (iii) the overbinding of ${}_{\Lambda }^5$He which might be related to the hyperon puzzle in neutron stars; and (iv) does ${\Lambda }^{\ast }$(1405) survive in strange hadronic matter?

   ↳ nucl-thhep-phnucl-exAIP Conf.Proc.(2019)·2 citations
5. 05*

   Lambda polarization in heavy ion collisions: from RHIC BES to LHC energies

   Iurii Karpenko🇫🇷 · Francesco Becattini🇮🇹

   STAR collaboration at RHIC has recently measured the polarization of $\Lambda$ hyperons in non-central heavy ion collisions in the RHIC Beam Energy Scan (BES) program. The magnitude of the polarization was found to decrease from few percents at the lowest BES energies to $\approx 0.2$% at the top RHIC energy. The polarization signal has been reproduced in different hydrodynamic calculations assuming a thermodynamic spin-vorticity coupling mechanism at the Cooper-Frye hypersurface. In this work an extension of our existing calculations of the $\Lambda$ polarization in the RHIC BES program to the top RHIC and 2.76 TeV LHC energies is presented. The longitudinal component of the $\Lambda$ polarization, which is the dominant component of the polarization at the LHC energies, is discussed. Finally we show that the global polarization of $\Lambda$ originates dominantly from the relativistic analogue of the classical vorticity, whereas the quadrupole longitudinal component originates from the gradients of temperature and acceleration of the medium when the $\Lambda$s are produced out of the fluid.

   ↳ nucl-thhep-phnucl-exNPA(2019)·31 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.