Mon·Sep 2, 2019Monday·September 2, 2019

1. 01*

   Impact of ${}^{16}$O($e,e^{\prime }\alpha$)${}^{12}$C measurements on the ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O astrophysical reaction rate

   R. J. Holt🇺🇸 · B. W. Filippone🇺🇸

   The ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O reaction, an important component of stellar helium burning, has a key role in nuclear astrophysics. It has direct impact on the evolution and final state of massive stars and also influences the elemental abundances resulting from nucleosynthesis in such stars. Providing a reliable estimate for the energy dependence of this reaction at stellar helium burning temperatures has been a longstanding and important goal. In this work, we study the role of potential new measurements of the reaction, ${}^{16}$O($e,e^{\prime }\alpha$)${}^{12}$C reaction, in reducing the overall uncertainty. A multilevel $R$-matrix analysis is used to make extrapolations of the astrophysical S factor for the ${}^{12}$C($\alpha ,\gamma$)${}^{16}$O reaction to the stellar energy of 300 keV. The statistical precision of the $S$-factor extrapolation is determined by performing multiple fits to existing $E1$ and $E2$ ground state capture data, including the impact of possible future measurements of the ${}^{16}$O($e,e^{\prime }\alpha$)${}^{12}$C reaction. In particular, we consider a proposed MIT experiment that would make use of a high-intensity low-energy electron beam that impinges on a windowless oxygen gas target as a means to determine the total $E1$ and $E2$ cross sections for this reaction.

   nucl-exPRC(2019)·7 citations
2. 02*

   Experimental searches for rare alpha and beta decays

   P. Belli🇮🇹 · R. Bernabei🇮🇹 · F.A. Danevich🇺🇦 · A. Incicchitti🇮🇹 · V.I. Tretyak🇺🇦

   The current status of the experimental searches for rare alpha and beta decays is reviewed. Several interesting observations of alpha and beta decays, previously unseen due to their large half-lives ($10^{15}-10^{20}$ yr), have been achieved during the last years thanks to the improvements in the experimental techniques and to the underground locations of experiments that allows to suppress backgrounds. In particular, the list includes first observations of alpha decays of ${}^{151}$Eu, ${}^{180}$W (both to the ground state of the daughter nuclei), ${}^{190}$Pt (to excited state of the daughter nucleus), ${}^{209}$Bi (to the ground and excited states of the daughter nucleus). The isotope ${}^{209}$Bi has the longest known half-life of $T_{1/2}\approx 10^{19}$ yr relatively to alpha decay. The beta decay of ${}^{115}$In to the first excited state of ${}^{115}$Sn (E${}_{exc}=497.334$ keV), recently observed for the first time, has the $Q_{\beta }$ value of only $(147\pm 10)$ eV, which is the lowest $Q_{\beta }$ value known to-date. Searches and investigations of other rare alpha and beta decays (${}^{48}$Ca, ${}^{50}$V, ${}^{96}$Zr, ${}^{113}$Cd, ${}^{123}$Te, ${}^{178m2}$Hf, ${}^{180m}$Ta and others) are also discussed.

   nucl-exphysics.ins-detEPJA(2019)·36 citations
3. 03*

   Normal and intruder configurations in ${}^{34}$Si populated in the ${\beta }^{-}$ decay of ${}^{34}$Mg and ${}^{34}$Al

   R. Lica🇷🇴 · F. Rotaru🇷🇴 · M.J.G. Borge🇨🇭 · S. Grevy🇫🇷 · F. Negoita🇷🇴 · A. Poves🇪🇸 · O. Sorlin🇫🇷 · A.N. Andreyev🇬🇧 · R. Borcea🇷🇴 · C. Costache🇷🇴 · H. De Witte🇧🇪 · L.M. Fraile🇪🇸 and 44 other authors

   The structure of ${}^{34}$Si was studied through $\gamma$ spectroscopy separately in the ${\beta }^{-}$ decays of ${}^{34}$Mg and ${}^{34}$Al at the ISOLDE facility of CERN. Different configurations in ${}^{34}$Si were populated independently from the two recently identified $\beta$-decaying states in ${}^{34}$Al having spin-parity assignments $J^{\pi }=4^{-}$ dominated by the normal configuration $\pi (d_{5/2}{)}^{-1}\otimes \nu (f_{7/2})$ and $J^{\pi }=1^{+}$ by the intruder configuration $\pi (d_{5/2}{)}^{-1}\otimes \nu (d_{3/2}{)}^{-1}(f_{7/2}{)}^2$. The paper reports on spectroscopic properties of ${}^{34}$Si such as an extended level scheme, spin and parity assignments based on log($ft$) values and $\gamma$-ray branching ratios, absolute $\beta$ feeding intensities and neutron emission probabilities. A total of 11 newly identified levels and 26 transitions were added to the previously known level scheme of ${}^{34}$Si. Large scale shell-model calculations using the {\sc sdpf-u-mix} interaction, able to treat higher order intruder configurations, are compared with the new results and conclusions are drawn concerning the predictive power of {\sc sdpf-u-mix}, the $N=20$ shell gap, the level of mixing between normal and intruder configurations for the 0${}_1^{+}$, 0${}_2^{+}$ and 2${}_1^{+}$ states and the absence of triaxial deformation in ${}^{34}$Si.

   nucl-exPRC(2019)·18 citations
4. 04*

   Search for exotic states in photoproduction at GlueX

   Abdennacer Hamdi🇩🇪

   Quantum Chromodynamics (QCD) is the theory that describes how hadrons are built from quarks and gluons via the strong interaction. Many predictions have been experimentally confirmed, but others remain under experimental investigation. Of particular interest is how gluonic excitations give rise to states with constituent glue. One class of such states are hybrid mesons that are predicted by theoretical models and Lattice QCD calculations. Searching for and understanding the nature of these states is a primary physics goal of the GlueX experiment at the CEBAF accelerator at Jefferson Lab in the US. We will give an overview of the experiment, and present the status of the search for a hybrid meson candidate, Y (2175). This work is supported by HGS-HIRe.

   nucl-exhep-exJ.Phys.Conf.Ser.(2020)·8 citations
5. 05*

   Review of predictions of hard probes in $p+$Pb collisions at $\sqrt{s_{NN}}=5.02$ and 8.16 TeV and comparison with data

   R. Vogt🇺🇸

   Predictions have been compiled for the $p+$Pb LHC runs, focusing on production of hard probes in cold nuclear matter. These predictions were first made for the $\sqrt{s_{{}_{NN}}}=5.02$ TeV $p+$Pb run and were later compared to the available data. A similar set of predictions were published for the 8.16~TeV $p+$Pb run. A selection of the predictions are reviewed here.

   ↳ hep-phnucl-exnucl-th1 citation
6. 06*

   Theoretical interpretation of the $D_s^{+}\to {\pi }^{+}{\pi }^0\eta$ decay and the nature of $a_0(980)$

   Raquel Molina🇧🇷 · Ju-Jun Xie🇨🇳 · Wei-Hong Liang🇨🇳 · Li-Sheng Geng🇨🇳 · Eulogio Oset🇪🇸

   In a recent paper \cite{Ablikim:2019pit}, the BESIII collaboration reported the so-called first observation of pure $W$-annihilation decays $D_s^{+}\to a_0^{+}(980){\pi }^0$ and $D_s^{+}\to a_0^0(980){\pi }^{+}$. The measured absolute branching fractions are, however, puzzlingly larger than those of other measured pure $W$-annihilation decays by at least one order of magnitude. In addition, the relative phase between the two decay modes is found to be about 180 degrees. In this letter, we show that all these can be easily understood if the $a_0(980)$ is a dynamically generated state from $\bar{K}K$ and $\pi \eta$ interactions in coupled channels. In such a scenario, the $D_s^{+}$ decay proceeds via internal $W$ emission instead of $W$-annihilation, which has a larger decay rate than $W$-annihilation. The proposed decay mechanism and the molecular nature of the $a_0(980)$ also provide a natural explanation to the measured negative interference between the two decay modes.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2020)·48 citations
7. 07*

   Charged-hadron suppression in Pb+Pb and Xe+Xe collisions measured with the ATLAS detector

   Petr Balek (for the ATLAS Collaboration)🇮🇱

   The ATLAS detector at the LHC recorded 0.49nb${}^{-1}$ of Pb+Pb collisions and 25pb${}^{-1}$ of $pp$ collisions, both at the center-of-mass energy 5.02TeV per nucleon pair. Recently, ATLAS also recorded 3$\mu$b${}^{-1}$ of Xe+Xe collisions at the center-of-mass energy 5.44TeV, which provides a new opportunity to study the system-size dependence of the charged-hadron production in heavy-ion collisions. The large acceptance of the ATLAS detector allows to measure the spectra of charged hadrons in a wide range of pseudorapidity and transverse momentum. The nuclear modification factors $R_{\mathrm{AA}}$ are constructed as a ratio of the spectra measured in Pb+Pb or Xe+Xe collisions to that measured in $pp$ collisions. The $R_{\mathrm{AA}}$ obtained in the two systems are presented for different centrality intervals and the results are discussed.

   ↳ hep-exnucl-exNPA(2019)·3 citations
8. 08*

   ${}^{12}\mathbf{C}+{}^{16}\mathbf{O}$ molecular resonances at deep sub-barrier energy

   Yasutaka Taniguchi🇯🇵 · Masaaki Kimura🇯🇵

   The existence of ${}^{12}\mathrm{C}+{}^{16}\mathrm{O}$ molecular resonances at sub-barrier energy has been a significant problem in nuclear astrophysics because they strongly affect the ${}^{12}\mathrm{C}+{}^{16}\mathrm{O}$ fusion reaction rate in type Ia supernovae and heavy stars. However, experimental surveys have been limited to 4~MeV and cannot access the deep sub-barrier energy due to a very small fusion cross section. Here we predict a couple of resonances with $J^{\pi }=0^{+}$, $2^{+}$, and $4^{+}$ in the deep sub-barrier energy based on the antisymmetrized molecular dynamics calculation that reproduces the known resonances and low-lying spectrum of ${}^{28}\mathrm{Si}$.

   ↳ nucl-thastro-ph.SRnucl-exPLB(2020)·11 citations
9. 09*

   Kinetic freeze-out temperature from yields of short-lived resonances

   Anton Motornenko🇩🇪 · Volodymyr Vovchenko🇩🇪 · Carsten Greiner🇩🇪 · Horst Stoecker🇩🇪

   A method to determine the kinetic freeze-out temperature in heavy-ion collisions from measured yields of short-lived resonances is presented. The resonance production is treated in the framework of thermal model with an evolution between chemical and kinetic freeze-outs. The yields of many short-lived resonances are suppressed at $T=T_{\mathrm{kin}}<T_{\mathrm{ch}}$. We determine the values of $T_{\mathrm{kin}}$ and $T_{\mathrm{ch}}$ for various centralities in Pb--Pb collisions at $\sqrt{s_{{}_{NN}}}=2.76$ TeV by fitting the abundances of both the stable hadrons and the short-lived resonances such as ${\rho }^0$ and ${\text{K}}^{\ast 0}$, that were measured by the ALICE collaboration. This allows to extract the kinetic freeze-out temperature from the measured hadron and resonance yields alone, independent of assumptions about the flow velocity profile and the freeze-out hypersurface. The extracted $T_{\mathrm{ch}}$ values exhibit a moderate multiplicity dependence whereas $T_{\mathrm{kin}}$ drops, from $T_{\mathrm{kin}}\simeq T_{\mathrm{ch}}\simeq 155$ MeV in peripheral collisions to $T_{\mathrm{kin}}\simeq 110$ MeV in 0-20% central collisions. Predictions for other short-lived resonances are presented. A potential (non-)observation of a suppressed $f_0(980)$ meson yield will allow to constrain the lifetime of that meson.

   ↳ hep-phnucl-exnucl-thPRC(2020)·51 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.