Mon·Jun 17, 2019Monday·June 17, 2019

1. 01*

   Experimental Constraint on Stellar Electron-Capture Rates from the ${}^{88}\text{Sr}(t,{}^3\text{He}+\gamma ){}^{88}\text{Rb}$ reaction at 115 MeV/u

   J. C. Zamora🇧🇷 · R.G.T. Zegers🇺🇸 · Sam M. Austin · D. Bazin🇺🇸 · B. A. Brown🇺🇸 · P.C. Bender🇨🇦 · H.L. Crawford🇺🇸 · J. Engel🇺🇸 · A. Falduto · A. Gade🇺🇸 · P. Gastis · B. Gao and 13 other authors

   The Gamow-Teller strength distribution from ${}^{88}$Sr was extracted from a $(t,{}^3\text{He}+\gamma )$ experiment at 115 MeV/$u$ to constrain estimates for the electron-capture rates on nuclei around $N=50$, between and including ${}^{78}$Ni and ${}^{88}$Sr, which are important for the late evolution of core-collapse supernovae. The observed strength below an excitation energy of 8 MeV was consistent with zero and below 10 MeV amounted to $0.1\pm 0.05$. Except for a very-weak transition that could come from the 2.231-MeV $1^{+}$ state, no $\gamma$ lines that could be associated with the decay of known $1^{+}$ states were identified. The derived electron-capture rate from the measured strength distribution is more than an order of magnitude smaller than rates based on the single-state approximation presently used in astrophysical simulations for most nuclei near $N=50$. Rates based on shell-model and quasiparticle random-phase approximation calculations that account for Pauli blocking and core-polarization effects provide better estimates than the single-state approximation, although a relatively strong transition to the first $1^{+}$ state in ${}^{88}$Rb is not observed in the data. Pauli unblocking effects due to high stellar temperatures could partially counter the low electron-capture rates. The new data serves as a zero-temperature benchmark for constraining models used to estimate such effects.

   nucl-exastro-ph.SRPRC(2019)·11 citations
2. 02*

   Levy HBT results at NA61/SHINE

   Barnabas Porfy (for the NA61/SHINE collaboration)🇭🇺

   Bose-Einstein (or HBT) momentum correlations reveal the space-time structure of the particle emitting source created in high energy nucleus-nucleus collisions. In this paper we present the latest NA61/SHINE measurements of Bose-Einstein correlations of identified pion pairs and their description based on Levy distributed sources in Be+Be collisions at 150A GeV/c. We investigate the transverse mass dependence of the Levy source parameters and discuss their possible interpretations.

   nucl-exhep-exUniverse(2019)·6 citations
3. 03*

   Constraining the Neutron Star Compactness: Extraction of the ${}^{23}$Al($p,\gamma$) Reaction Rate for the $rp$-Process

   C. Wolf🇩🇪 · C. Langer🇩🇪 · F. Montes🇺🇸 · J. Pereira · W.-J. Ong🇺🇸 · T. Poxon-Pearson · S. Ahn🇺🇸 · S. Ayoub · T. Baumann · D. Bazin🇺🇸 · P.C. Bender🇨🇦 · B.A. Brown🇺🇸 and 24 other authors

   The ${}^{23}$Al($p,\gamma$)${}^{24}$Si reaction is among the most important reactions driving the energy generation in Type-I X-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The ${}^{23}$Al($d,n$) reaction was used to populate the astrophysically important states in ${}^{24}$Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2${}_2^{+}$ and (4${}_1^{+}$,0${}_2^{+}$) state in ${}^{24}$Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.

   nucl-exastro-ph.IMastro-ph.SRnucl-thPRL(2019)·21 citations
4. 04*

   Calculation of resonance energies from Q-values

   Christian Iliadis🇺🇸

   Resonance energies are frequently derived from precisely measured excitation energies and reaction Q-values. The latter quantities are usually calculated from atomic instead of nuclear mass differences. This procedure disregards the energy shift caused by the difference in the total electron binding energies before and after the interaction. Assuming that the interacting nuclei in a stellar plasma are fully ionized, this energy shift can have a significant effect, considering that the resonance energy enters exponentially into the expression for the narrow-resonance thermonuclear reaction rates. As an example, the rate of the ${}^{36}$Ar(p,$\gamma$)${}^{37}$K reaction is discussed, which, at temperatures below 1 GK, depends only on the contributions of a single resonance and direct capture. In this case, disregarding the energy shift caused by the total electron binding energy difference erroneously enhances the rate by $\approx$40\% near temperatures of 70 MK.

   nucl-exastro-ph.GAnucl-thPRC(2019)·10 citations
5. 05*

   $\gamma$-ray Strength Function for Barium Isotopes

   H. Utsunomiya🇯🇵 · T. Renstrøm🇳🇴 · G. M. Tveten🇳🇴 · S. Goriely🇧🇪 · T. Ari-izumi🇯🇵 · V.W. Ingeberg🇳🇴 · B. V. Kheswa🇿🇦 · Y.-W. Lui🇺🇸 · S. Miyamoto🇯🇵 · S. Hilaire🇫🇷 · S. Péru🇫🇷 · A. J. Koning🇦🇹

   Photoneutron cross sections were measured for ${}^{137}$Ba and ${}^{138}$Ba at energies below two-neutron threshold using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. 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 which are unique to the deexcitation mode, we discuss radiative neutron capture cross sections relevant to the s-process nucleosynthesis of barium isotopes in the vicinity of the neutron magic number 82.

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

   Viscosity calculations from Hadron Resonance Gas model: Finite size effect

   Snigdha Ghosh🇮🇳 · Subhasis Samanta🇮🇳 · Sabyasachi Ghosh🇮🇳 · Hiranmaya Mishra🇮🇳

   We have attempted to review on microscopic calculation of transport coefficients like shear and bulk viscosities in the framework of hadron resonance gas model, where a special attention is explored on the effect of finite system size. The standard expressions of transport coefficients, obtained from relaxation time approximation of kinetic theory or diagrammatic Kubo-type formalism, carry mainly two temperature dependent components -- thermodynamical phase space and relaxation time of medium constituent. Owing to quantum effect of finite system size, thermodynamical phase space can be reduced as its momentum distribution will be started from some finite lower momentum cut-off instead of zero momentum. On the other hand, relaxation time of hadrons can also face finite size effect by considering only those relaxation scales, which are lower than the system size. Owing to these phenomenological issues, we have proposed a system size dependent upper bound of transport coefficients for ideal HRG model, whose qualitative technique may also be applicable in other models. This finite size prescription may guide to shorten the broad numerical band, within which earlier estimated values of transport coefficients for hadronic matter are located. It is also suspected that the hadronic matter may not be far from the (nearly) perfect fluid nature like the quark gluon plasma.

   ↳ nucl-thhep-phnucl-exIJMPE(2019)·8 citations
7. 07*

   Deuteron-like heavy dibaryons from Lattice QCD

   Parikshit Junnarkar🇮🇳 · Nilmani Mathur🇮🇳

   We report the first lattice quantum chromodynamics (QCD) study of deuteron($np$)-like dibaryons with heavy quark flavours. These include particles with following dibaryon structures and valence quark contents: ${\Sigma }_c{\Xi }_{cc}(uucucc)$, ${\Omega }_c{\Omega }_{cc}(sscscc)$, ${\Sigma }_b{\Xi }_{bb}(uububb)$, ${\Omega }_b{\Omega }_{bb}(ssbsbb)$ and ${\Omega }_{ccb}{\Omega }_{cbb}(ccbcbb)$, and with spin ($J$)-parity ($P$), $J^P\equiv 1^{+}$. Using a state-of-the art lattice QCD calculation, after controlling relevant systematic errors, we unambiguously find that the ground state masses of dibaryons ${\Omega }_c{\Omega }_{cc}(sscscc)$, ${\Omega }_b{\Omega }_{bb}(ssbsbb)$ and ${\Omega }_{ccb}{\Omega }_{cbb}(ccbcbb)$ are below their respective two-baryon thresholds, suggesting the presence of bound states which are stable under strong and electromagnetic interactions. We also predict their masses precisely. For dibaryons ${\Sigma }_c{\Xi }_{cc}(uucucc)$, and ${\Sigma }_b{\Xi }_{bb}(uububb)$, we could not reach to a definitive conclusion about the presence of any bound state due to large systematics associated with these states. We also find that the binding of these dibaryons becomes stronger as they become heavier in mass. This study also opens up the possibility of the existence of many other exotic nuclei, which can be formed through the fusion of heavy baryons, similar to the formation of nuclei of elements in the Periodic Table.

   ↳ hep-lathep-exhep-phnucl-ex+1PRL(2019)·73 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.